Adding support for MOXA ART SoC. Testing port of linux-2.6.32.60-moxart.

[linux-3.6.7-moxart.git] / drivers / staging / ramster / zcache-main.c

/*
 * zcache.c
 *
 * Copyright (c) 2010-2012, Dan Magenheimer, Oracle Corp.
 * Copyright (c) 2010,2011, Nitin Gupta
 *
 * Zcache provides an in-kernel "host implementation" for transcendent memory
 * and, thus indirectly, for cleancache and frontswap.  Zcache includes two
 * page-accessible memory [1] interfaces, both utilizing lzo1x compression:
 * 1) "compression buddies" ("zbud") is used for ephemeral pages
 * 2) xvmalloc is used for persistent pages.
 * Xvmalloc (based on the TLSF allocator) has very low fragmentation
 * so maximizes space efficiency, while zbud allows pairs (and potentially,
 * in the future, more than a pair of) compressed pages to be closely linked
 * so that reclaiming can be done via the kernel's physical-page-oriented
 * "shrinker" interface.
 *
 * [1] For a definition of page-accessible memory (aka PAM), see:
 *   http://marc.info/?l=linux-mm&m=127811271605009
 *  RAMSTER TODO:
 *   - handle remotifying of buddied pages (see zbud_remotify_zbpg)
 *   - kernel boot params: nocleancache/nofrontswap don't always work?!?
 */

#include <linux/module.h>
#include <linux/cpu.h>
#include <linux/highmem.h>
#include <linux/list.h>
#include <linux/lzo.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/atomic.h>
#include <linux/math64.h>
#include "tmem.h"
#include "zcache.h"
#include "ramster.h"
#include "cluster/tcp.h"

#include "xvmalloc.h"   /* temporary until change to zsmalloc */

#define RAMSTER_TESTING

#if (!defined(CONFIG_CLEANCACHE) && !defined(CONFIG_FRONTSWAP))
#error "ramster is useless without CONFIG_CLEANCACHE or CONFIG_FRONTSWAP"
#endif
#ifdef CONFIG_CLEANCACHE
#include <linux/cleancache.h>
#endif
#ifdef CONFIG_FRONTSWAP
#include <linux/frontswap.h>
#endif

enum ramster_remotify_op {
        RAMSTER_REMOTIFY_EPH_PUT,
        RAMSTER_REMOTIFY_PERS_PUT,
        RAMSTER_REMOTIFY_FLUSH_PAGE,
        RAMSTER_REMOTIFY_FLUSH_OBJ,
        RAMSTER_INTRANSIT_PERS
};

struct ramster_remotify_hdr {
        enum ramster_remotify_op op;
        struct list_head list;
};

#define ZBH_SENTINEL  0x43214321
#define ZBPG_SENTINEL  0xdeadbeef

#define ZBUD_MAX_BUDS 2

struct zbud_hdr {
        struct ramster_remotify_hdr rem_op;
        uint16_t client_id;
        uint16_t pool_id;
        struct tmem_oid oid;
        uint32_t index;
        uint16_t size; /* compressed size in bytes, zero means unused */
        DECL_SENTINEL
};

#define ZVH_SENTINEL  0x43214321
static const int zv_max_page_size = (PAGE_SIZE / 8) * 7;

struct zv_hdr {
        struct ramster_remotify_hdr rem_op;
        uint16_t client_id;
        uint16_t pool_id;
        struct tmem_oid oid;
        uint32_t index;
        DECL_SENTINEL
};

struct flushlist_node {
        struct ramster_remotify_hdr rem_op;
        struct tmem_xhandle xh;
};

union {
        struct ramster_remotify_hdr rem_op;
        struct zv_hdr zv;
        struct zbud_hdr zbud;
        struct flushlist_node flist;
} remotify_list_node;

static LIST_HEAD(zcache_rem_op_list);
static DEFINE_SPINLOCK(zcache_rem_op_list_lock);

#if 0
/* this is more aggressive but may cause other problems? */
#define ZCACHE_GFP_MASK (GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN)
#else
#define ZCACHE_GFP_MASK \
        (__GFP_FS | __GFP_NORETRY | __GFP_NOWARN | __GFP_NOMEMALLOC)
#endif

#define MAX_POOLS_PER_CLIENT 16

#define MAX_CLIENTS 16
#define LOCAL_CLIENT ((uint16_t)-1)

MODULE_LICENSE("GPL");

struct zcache_client {
        struct tmem_pool *tmem_pools[MAX_POOLS_PER_CLIENT];
        struct xv_pool *xvpool;
        bool allocated;
        atomic_t refcount;
};

static struct zcache_client zcache_host;
static struct zcache_client zcache_clients[MAX_CLIENTS];

static inline uint16_t get_client_id_from_client(struct zcache_client *cli)
{
        BUG_ON(cli == NULL);
        if (cli == &zcache_host)
                return LOCAL_CLIENT;
        return cli - &zcache_clients[0];
}

static inline bool is_local_client(struct zcache_client *cli)
{
        return cli == &zcache_host;
}

/**********
 * Compression buddies ("zbud") provides for packing two (or, possibly
 * in the future, more) compressed ephemeral pages into a single "raw"
 * (physical) page and tracking them with data structures so that
 * the raw pages can be easily reclaimed.
 *
 * A zbud page ("zbpg") is an aligned page containing a list_head,
 * a lock, and two "zbud headers".  The remainder of the physical
 * page is divided up into aligned 64-byte "chunks" which contain
 * the compressed data for zero, one, or two zbuds.  Each zbpg
 * resides on: (1) an "unused list" if it has no zbuds; (2) a
 * "buddied" list if it is fully populated  with two zbuds; or
 * (3) one of PAGE_SIZE/64 "unbuddied" lists indexed by how many chunks
 * the one unbuddied zbud uses.  The data inside a zbpg cannot be
 * read or written unless the zbpg's lock is held.
 */

struct zbud_page {
        struct list_head bud_list;
        spinlock_t lock;
        struct zbud_hdr buddy[ZBUD_MAX_BUDS];
        DECL_SENTINEL
        /* followed by NUM_CHUNK aligned CHUNK_SIZE-byte chunks */
};

#define CHUNK_SHIFT     6
#define CHUNK_SIZE      (1 << CHUNK_SHIFT)
#define CHUNK_MASK      (~(CHUNK_SIZE-1))
#define NCHUNKS         (((PAGE_SIZE - sizeof(struct zbud_page)) & \
                                CHUNK_MASK) >> CHUNK_SHIFT)
#define MAX_CHUNK       (NCHUNKS-1)

static struct {
        struct list_head list;
        unsigned count;
} zbud_unbuddied[NCHUNKS];
/* list N contains pages with N chunks USED and NCHUNKS-N unused */
/* element 0 is never used but optimizing that isn't worth it */
static unsigned long zbud_cumul_chunk_counts[NCHUNKS];

struct list_head zbud_buddied_list;
static unsigned long zcache_zbud_buddied_count;

/* protects the buddied list and all unbuddied lists */
static DEFINE_SPINLOCK(zbud_budlists_spinlock);

static atomic_t zcache_zbud_curr_raw_pages;
static atomic_t zcache_zbud_curr_zpages;
static unsigned long zcache_zbud_curr_zbytes;
static unsigned long zcache_zbud_cumul_zpages;
static unsigned long zcache_zbud_cumul_zbytes;
static unsigned long zcache_compress_poor;
static unsigned long zcache_policy_percent_exceeded;
static unsigned long zcache_mean_compress_poor;

/*
 * RAMster counters
 * - Remote pages are pages with a local pampd but the data is remote
 * - Foreign pages are pages stored locally but belonging to another node
 */
static atomic_t ramster_remote_pers_pages = ATOMIC_INIT(0);
static unsigned long ramster_pers_remotify_enable;
static unsigned long ramster_eph_remotify_enable;
static unsigned long ramster_eph_pages_remoted;
static unsigned long ramster_eph_pages_remote_failed;
static unsigned long ramster_pers_pages_remoted;
static unsigned long ramster_pers_pages_remote_failed;
static unsigned long ramster_pers_pages_remote_nomem;
static unsigned long ramster_remote_objects_flushed;
static unsigned long ramster_remote_object_flushes_failed;
static unsigned long ramster_remote_pages_flushed;
static unsigned long ramster_remote_page_flushes_failed;
static unsigned long ramster_remote_eph_pages_succ_get;
static unsigned long ramster_remote_pers_pages_succ_get;
static unsigned long ramster_remote_eph_pages_unsucc_get;
static unsigned long ramster_remote_pers_pages_unsucc_get;
static atomic_t ramster_curr_flnode_count = ATOMIC_INIT(0);
static unsigned long ramster_curr_flnode_count_max;
static atomic_t ramster_foreign_eph_pampd_count = ATOMIC_INIT(0);
static unsigned long ramster_foreign_eph_pampd_count_max;
static atomic_t ramster_foreign_pers_pampd_count = ATOMIC_INIT(0);
static unsigned long ramster_foreign_pers_pampd_count_max;

/* forward references */
static void *zcache_get_free_page(void);
static void zcache_free_page(void *p);

/*
 * zbud helper functions
 */

static inline unsigned zbud_max_buddy_size(void)
{
        return MAX_CHUNK << CHUNK_SHIFT;
}

static inline unsigned zbud_size_to_chunks(unsigned size)
{
        BUG_ON(size == 0 || size > zbud_max_buddy_size());
        return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
}

static inline int zbud_budnum(struct zbud_hdr *zh)
{
        unsigned offset = (unsigned long)zh & (PAGE_SIZE - 1);
        struct zbud_page *zbpg = NULL;
        unsigned budnum = -1U;
        int i;

        for (i = 0; i < ZBUD_MAX_BUDS; i++)
                if (offset == offsetof(typeof(*zbpg), buddy[i])) {
                        budnum = i;
                        break;
                }
        BUG_ON(budnum == -1U);
        return budnum;
}

static char *zbud_data(struct zbud_hdr *zh, unsigned size)
{
        struct zbud_page *zbpg;
        char *p;
        unsigned budnum;

        ASSERT_SENTINEL(zh, ZBH);
        budnum = zbud_budnum(zh);
        BUG_ON(size == 0 || size > zbud_max_buddy_size());
        zbpg = container_of(zh, struct zbud_page, buddy[budnum]);
        ASSERT_SPINLOCK(&zbpg->lock);
        p = (char *)zbpg;
        if (budnum == 0)
                p += ((sizeof(struct zbud_page) + CHUNK_SIZE - 1) &
                                                        CHUNK_MASK);
        else if (budnum == 1)
                p += PAGE_SIZE - ((size + CHUNK_SIZE - 1) & CHUNK_MASK);
        return p;
}

static void zbud_copy_from_pampd(char *data, size_t *size, struct zbud_hdr *zh)
{
        struct zbud_page *zbpg;
        char *p;
        unsigned budnum;

        ASSERT_SENTINEL(zh, ZBH);
        budnum = zbud_budnum(zh);
        zbpg = container_of(zh, struct zbud_page, buddy[budnum]);
        spin_lock(&zbpg->lock);
        BUG_ON(zh->size > *size);
        p = (char *)zbpg;
        if (budnum == 0)
                p += ((sizeof(struct zbud_page) + CHUNK_SIZE - 1) &
                                                        CHUNK_MASK);
        else if (budnum == 1)
                p += PAGE_SIZE - ((zh->size + CHUNK_SIZE - 1) & CHUNK_MASK);
        /* client should be filled in by caller */
        memcpy(data, p, zh->size);
        *size = zh->size;
        spin_unlock(&zbpg->lock);
}

/*
 * zbud raw page management
 */

static struct zbud_page *zbud_alloc_raw_page(void)
{
        struct zbud_page *zbpg = NULL;
        struct zbud_hdr *zh0, *zh1;
                zbpg = zcache_get_free_page();
        if (likely(zbpg != NULL)) {
                INIT_LIST_HEAD(&zbpg->bud_list);
                zh0 = &zbpg->buddy[0]; zh1 = &zbpg->buddy[1];
                spin_lock_init(&zbpg->lock);
                atomic_inc(&zcache_zbud_curr_raw_pages);
                INIT_LIST_HEAD(&zbpg->bud_list);
                SET_SENTINEL(zbpg, ZBPG);
                zh0->size = 0; zh1->size = 0;
                tmem_oid_set_invalid(&zh0->oid);
                tmem_oid_set_invalid(&zh1->oid);
        }
        return zbpg;
}

static void zbud_free_raw_page(struct zbud_page *zbpg)
{
        struct zbud_hdr *zh0 = &zbpg->buddy[0], *zh1 = &zbpg->buddy[1];

        ASSERT_SENTINEL(zbpg, ZBPG);
        BUG_ON(!list_empty(&zbpg->bud_list));
        ASSERT_SPINLOCK(&zbpg->lock);
        BUG_ON(zh0->size != 0 || tmem_oid_valid(&zh0->oid));
        BUG_ON(zh1->size != 0 || tmem_oid_valid(&zh1->oid));
        INVERT_SENTINEL(zbpg, ZBPG);
        spin_unlock(&zbpg->lock);
        atomic_dec(&zcache_zbud_curr_raw_pages);
        zcache_free_page(zbpg);
}

/*
 * core zbud handling routines
 */

static unsigned zbud_free(struct zbud_hdr *zh)
{
        unsigned size;

        ASSERT_SENTINEL(zh, ZBH);
        BUG_ON(!tmem_oid_valid(&zh->oid));
        size = zh->size;
        BUG_ON(zh->size == 0 || zh->size > zbud_max_buddy_size());
        zh->size = 0;
        tmem_oid_set_invalid(&zh->oid);
        INVERT_SENTINEL(zh, ZBH);
        zcache_zbud_curr_zbytes -= size;
        atomic_dec(&zcache_zbud_curr_zpages);
        return size;
}

static void zbud_free_and_delist(struct zbud_hdr *zh)
{
        unsigned chunks;
        struct zbud_hdr *zh_other;
        unsigned budnum = zbud_budnum(zh), size;
        struct zbud_page *zbpg =
                container_of(zh, struct zbud_page, buddy[budnum]);

        /* FIXME, should be BUG_ON, pool destruction path doesn't disable
         * interrupts tmem_destroy_pool()->tmem_pampd_destroy_all_in_obj()->
         * tmem_objnode_node_destroy()-> zcache_pampd_free() */
        WARN_ON(!irqs_disabled());
        spin_lock(&zbpg->lock);
        if (list_empty(&zbpg->bud_list)) {
                /* ignore zombie page... see zbud_evict_pages() */
                spin_unlock(&zbpg->lock);
                return;
        }
        size = zbud_free(zh);
        ASSERT_SPINLOCK(&zbpg->lock);
        zh_other = &zbpg->buddy[(budnum == 0) ? 1 : 0];
        if (zh_other->size == 0) { /* was unbuddied: unlist and free */
                chunks = zbud_size_to_chunks(size) ;
                spin_lock(&zbud_budlists_spinlock);
                BUG_ON(list_empty(&zbud_unbuddied[chunks].list));
                list_del_init(&zbpg->bud_list);
                zbud_unbuddied[chunks].count--;
                spin_unlock(&zbud_budlists_spinlock);
                zbud_free_raw_page(zbpg);
        } else { /* was buddied: move remaining buddy to unbuddied list */
                chunks = zbud_size_to_chunks(zh_other->size) ;
                spin_lock(&zbud_budlists_spinlock);
                list_del_init(&zbpg->bud_list);
                zcache_zbud_buddied_count--;
                list_add_tail(&zbpg->bud_list, &zbud_unbuddied[chunks].list);
                zbud_unbuddied[chunks].count++;
                spin_unlock(&zbud_budlists_spinlock);
                spin_unlock(&zbpg->lock);
        }
}

static struct zbud_hdr *zbud_create(uint16_t client_id, uint16_t pool_id,
                                        struct tmem_oid *oid,
                                        uint32_t index, struct page *page,
                                        void *cdata, unsigned size)
{
        struct zbud_hdr *zh0, *zh1, *zh = NULL;
        struct zbud_page *zbpg = NULL, *ztmp;
        unsigned nchunks;
        char *to;
        int i, found_good_buddy = 0;

        nchunks = zbud_size_to_chunks(size) ;
        for (i = MAX_CHUNK - nchunks + 1; i > 0; i--) {
                spin_lock(&zbud_budlists_spinlock);
                if (!list_empty(&zbud_unbuddied[i].list)) {
                        list_for_each_entry_safe(zbpg, ztmp,
                                    &zbud_unbuddied[i].list, bud_list) {
                                if (spin_trylock(&zbpg->lock)) {
                                        found_good_buddy = i;
                                        goto found_unbuddied;
                                }
                        }
                }
                spin_unlock(&zbud_budlists_spinlock);
        }
        /* didn't find a good buddy, try allocating a new page */
        zbpg = zbud_alloc_raw_page();
        if (unlikely(zbpg == NULL))
                goto out;
        /* ok, have a page, now compress the data before taking locks */
        spin_lock(&zbud_budlists_spinlock);
        spin_lock(&zbpg->lock);
        list_add_tail(&zbpg->bud_list, &zbud_unbuddied[nchunks].list);
        zbud_unbuddied[nchunks].count++;
        zh = &zbpg->buddy[0];
        goto init_zh;

found_unbuddied:
        ASSERT_SPINLOCK(&zbpg->lock);
        zh0 = &zbpg->buddy[0]; zh1 = &zbpg->buddy[1];
        BUG_ON(!((zh0->size == 0) ^ (zh1->size == 0)));
        if (zh0->size != 0) { /* buddy0 in use, buddy1 is vacant */
                ASSERT_SENTINEL(zh0, ZBH);
                zh = zh1;
        } else if (zh1->size != 0) { /* buddy1 in use, buddy0 is vacant */
                ASSERT_SENTINEL(zh1, ZBH);
                zh = zh0;
        } else
                BUG();
        list_del_init(&zbpg->bud_list);
        zbud_unbuddied[found_good_buddy].count--;
        list_add_tail(&zbpg->bud_list, &zbud_buddied_list);
        zcache_zbud_buddied_count++;

init_zh:
        SET_SENTINEL(zh, ZBH);
        zh->size = size;
        zh->index = index;
        zh->oid = *oid;
        zh->pool_id = pool_id;
        zh->client_id = client_id;
        to = zbud_data(zh, size);
        memcpy(to, cdata, size);
        spin_unlock(&zbpg->lock);
        spin_unlock(&zbud_budlists_spinlock);
        zbud_cumul_chunk_counts[nchunks]++;
        atomic_inc(&zcache_zbud_curr_zpages);
        zcache_zbud_cumul_zpages++;
        zcache_zbud_curr_zbytes += size;
        zcache_zbud_cumul_zbytes += size;
out:
        return zh;
}

static int zbud_decompress(struct page *page, struct zbud_hdr *zh)
{
        struct zbud_page *zbpg;
        unsigned budnum = zbud_budnum(zh);
        size_t out_len = PAGE_SIZE;
        char *to_va, *from_va;
        unsigned size;
        int ret = 0;

        zbpg = container_of(zh, struct zbud_page, buddy[budnum]);
        spin_lock(&zbpg->lock);
        if (list_empty(&zbpg->bud_list)) {
                /* ignore zombie page... see zbud_evict_pages() */
                ret = -EINVAL;
                goto out;
        }
        ASSERT_SENTINEL(zh, ZBH);
        BUG_ON(zh->size == 0 || zh->size > zbud_max_buddy_size());
        to_va = kmap_atomic(page);
        size = zh->size;
        from_va = zbud_data(zh, size);
        ret = lzo1x_decompress_safe(from_va, size, to_va, &out_len);
        BUG_ON(ret != LZO_E_OK);
        BUG_ON(out_len != PAGE_SIZE);
        kunmap_atomic(to_va);
out:
        spin_unlock(&zbpg->lock);
        return ret;
}

/*
 * The following routines handle shrinking of ephemeral pages by evicting
 * pages "least valuable" first.
 */

static unsigned long zcache_evicted_raw_pages;
static unsigned long zcache_evicted_buddied_pages;
static unsigned long zcache_evicted_unbuddied_pages;

static struct tmem_pool *zcache_get_pool_by_id(uint16_t cli_id,
                                                uint16_t poolid);
static void zcache_put_pool(struct tmem_pool *pool);

/*
 * Flush and free all zbuds in a zbpg, then free the pageframe
 */
static void zbud_evict_zbpg(struct zbud_page *zbpg)
{
        struct zbud_hdr *zh;
        int i, j;
        uint32_t pool_id[ZBUD_MAX_BUDS], client_id[ZBUD_MAX_BUDS];
        uint32_t index[ZBUD_MAX_BUDS];
        struct tmem_oid oid[ZBUD_MAX_BUDS];
        struct tmem_pool *pool;
        unsigned long flags;

        ASSERT_SPINLOCK(&zbpg->lock);
        for (i = 0, j = 0; i < ZBUD_MAX_BUDS; i++) {
                zh = &zbpg->buddy[i];
                if (zh->size) {
                        client_id[j] = zh->client_id;
                        pool_id[j] = zh->pool_id;
                        oid[j] = zh->oid;
                        index[j] = zh->index;
                        j++;
                }
        }
        spin_unlock(&zbpg->lock);
        for (i = 0; i < j; i++) {
                pool = zcache_get_pool_by_id(client_id[i], pool_id[i]);
                BUG_ON(pool == NULL);
                local_irq_save(flags);
                /* these flushes should dispose of any local storage */
                tmem_flush_page(pool, &oid[i], index[i]);
                local_irq_restore(flags);
                zcache_put_pool(pool);
        }
}

/*
 * Free nr pages.  This code is funky because we want to hold the locks
 * protecting various lists for as short a time as possible, and in some
 * circumstances the list may change asynchronously when the list lock is
 * not held.  In some cases we also trylock not only to avoid waiting on a
 * page in use by another cpu, but also to avoid potential deadlock due to
 * lock inversion.
 */
static void zbud_evict_pages(int nr)
{
        struct zbud_page *zbpg;
        int i, newly_unused_pages = 0;


        /* now try freeing unbuddied pages, starting with least space avail */
        for (i = 0; i < MAX_CHUNK; i++) {
retry_unbud_list_i:
                spin_lock_bh(&zbud_budlists_spinlock);
                if (list_empty(&zbud_unbuddied[i].list)) {
                        spin_unlock_bh(&zbud_budlists_spinlock);
                        continue;
                }
                list_for_each_entry(zbpg, &zbud_unbuddied[i].list, bud_list) {
                        if (unlikely(!spin_trylock(&zbpg->lock)))
                                continue;
                        zbud_unbuddied[i].count--;
                        spin_unlock(&zbud_budlists_spinlock);
                        zcache_evicted_unbuddied_pages++;
                        /* want budlists unlocked when doing zbpg eviction */
                        zbud_evict_zbpg(zbpg);
                        newly_unused_pages++;
                        local_bh_enable();
                        if (--nr <= 0)
                                goto evict_unused;
                        goto retry_unbud_list_i;
                }
                spin_unlock_bh(&zbud_budlists_spinlock);
        }

        /* as a last resort, free buddied pages */
retry_bud_list:
        spin_lock_bh(&zbud_budlists_spinlock);
        if (list_empty(&zbud_buddied_list)) {
                spin_unlock_bh(&zbud_budlists_spinlock);
                goto evict_unused;
        }
        list_for_each_entry(zbpg, &zbud_buddied_list, bud_list) {
                if (unlikely(!spin_trylock(&zbpg->lock)))
                        continue;
                zcache_zbud_buddied_count--;
                spin_unlock(&zbud_budlists_spinlock);
                zcache_evicted_buddied_pages++;
                /* want budlists unlocked when doing zbpg eviction */
                zbud_evict_zbpg(zbpg);
                newly_unused_pages++;
                local_bh_enable();
                if (--nr <= 0)
                        goto evict_unused;
                goto retry_bud_list;
        }
        spin_unlock_bh(&zbud_budlists_spinlock);

evict_unused:
        return;
}

static DEFINE_PER_CPU(unsigned char *, zcache_remoteputmem);

static int zbud_remotify_zbud(struct tmem_xhandle *xh, char *data,
                                size_t size)
{
        struct tmem_pool *pool;
        int i, remotenode, ret = -1;
        unsigned char cksum, *p;
        unsigned long flags;

        for (p = data, cksum = 0, i = 0; i < size; i++)
                cksum += *p;
        ret = ramster_remote_put(xh, data, size, true, &remotenode);
        if (ret == 0) {
                /* data was successfully remoted so change the local version
                 * to point to the remote node where it landed */
                pool = zcache_get_pool_by_id(LOCAL_CLIENT, xh->pool_id);
                BUG_ON(pool == NULL);
                local_irq_save(flags);
                /* tmem_replace will also free up any local space */
                (void)tmem_replace(pool, &xh->oid, xh->index,
                        pampd_make_remote(remotenode, size, cksum));
                local_irq_restore(flags);
                zcache_put_pool(pool);
                ramster_eph_pages_remoted++;
                ret = 0;
        } else
                ramster_eph_pages_remote_failed++;
        return ret;
}

static int zbud_remotify_zbpg(struct zbud_page *zbpg)
{
        struct zbud_hdr *zh1, *zh2 = NULL;
        struct tmem_xhandle xh1, xh2 = { 0 };
        char *data1 = NULL, *data2 = NULL;
        size_t size1 = 0, size2 = 0;
        int ret = 0;
        unsigned char *tmpmem = __get_cpu_var(zcache_remoteputmem);

        ASSERT_SPINLOCK(&zbpg->lock);
        if (zbpg->buddy[0].size == 0)
                zh1 = &zbpg->buddy[1];
        else if (zbpg->buddy[1].size == 0)
                zh1 = &zbpg->buddy[0];
        else {
                zh1 = &zbpg->buddy[0];
                zh2 = &zbpg->buddy[1];
        }
        /* don't remotify pages that are already remotified */
        if (zh1->client_id != LOCAL_CLIENT)
                zh1 = NULL;
        if ((zh2 != NULL) && (zh2->client_id != LOCAL_CLIENT))
                zh2 = NULL;

        /* copy the data and metadata so can release lock */
        if (zh1 != NULL) {
                xh1.client_id = zh1->client_id;
                xh1.pool_id = zh1->pool_id;
                xh1.oid = zh1->oid;
                xh1.index = zh1->index;
                size1 = zh1->size;
                data1 = zbud_data(zh1, size1);
                memcpy(tmpmem, zbud_data(zh1, size1), size1);
                data1 = tmpmem;
                tmpmem += size1;
        }
        if (zh2 != NULL) {
                xh2.client_id = zh2->client_id;
                xh2.pool_id = zh2->pool_id;
                xh2.oid = zh2->oid;
                xh2.index = zh2->index;
                size2 = zh2->size;
                memcpy(tmpmem, zbud_data(zh2, size2), size2);
                data2 = tmpmem;
        }
        spin_unlock(&zbpg->lock);
        preempt_enable();

        /* OK, no locks held anymore, remotify one or both zbuds */
        if (zh1 != NULL)
                ret = zbud_remotify_zbud(&xh1, data1, size1);
        if (zh2 != NULL)
                ret |= zbud_remotify_zbud(&xh2, data2, size2);
        return ret;
}

void zbud_remotify_pages(int nr)
{
        struct zbud_page *zbpg;
        int i, ret;

        /*
         * for now just try remotifying unbuddied pages, starting with
         * least space avail
         */
        for (i = 0; i < MAX_CHUNK; i++) {
retry_unbud_list_i:
                preempt_disable();  /* enable in zbud_remotify_zbpg */
                spin_lock_bh(&zbud_budlists_spinlock);
                if (list_empty(&zbud_unbuddied[i].list)) {
                        spin_unlock_bh(&zbud_budlists_spinlock);
                        preempt_enable();
                        continue; /* next i in for loop */
                }
                list_for_each_entry(zbpg, &zbud_unbuddied[i].list, bud_list) {
                        if (unlikely(!spin_trylock(&zbpg->lock)))
                                continue; /* next list_for_each_entry */
                        zbud_unbuddied[i].count--;
                        /* want budlists unlocked when doing zbpg remotify */
                        spin_unlock_bh(&zbud_budlists_spinlock);
                        ret = zbud_remotify_zbpg(zbpg);
                        /* preemption is re-enabled in zbud_remotify_zbpg */
                        if (ret == 0) {
                                if (--nr <= 0)
                                        goto out;
                                goto retry_unbud_list_i;
                        }
                        /* if fail to remotify any page, quit */
                        pr_err("TESTING zbud_remotify_pages failed on page,"
                                " trying to re-add\n");
                        spin_lock_bh(&zbud_budlists_spinlock);
                        spin_lock(&zbpg->lock);
                        list_add_tail(&zbpg->bud_list, &zbud_unbuddied[i].list);
                        zbud_unbuddied[i].count++;
                        spin_unlock(&zbpg->lock);
                        spin_unlock_bh(&zbud_budlists_spinlock);
                        pr_err("TESTING zbud_remotify_pages failed on page,"
                                " finished re-add\n");
                        goto out;
                }
                spin_unlock_bh(&zbud_budlists_spinlock);
                preempt_enable();
        }

next_buddied_zbpg:
        preempt_disable();  /* enable in zbud_remotify_zbpg */
        spin_lock_bh(&zbud_budlists_spinlock);
        if (list_empty(&zbud_buddied_list))
                goto unlock_out;
        list_for_each_entry(zbpg, &zbud_buddied_list, bud_list) {
                if (unlikely(!spin_trylock(&zbpg->lock)))
                        continue; /* next list_for_each_entry */
                zcache_zbud_buddied_count--;
                /* want budlists unlocked when doing zbpg remotify */
                spin_unlock_bh(&zbud_budlists_spinlock);
                ret = zbud_remotify_zbpg(zbpg);
                /* preemption is re-enabled in zbud_remotify_zbpg */
                if (ret == 0) {
                        if (--nr <= 0)
                                goto out;
                        goto next_buddied_zbpg;
                }
                /* if fail to remotify any page, quit */
                pr_err("TESTING zbud_remotify_pages failed on BUDDIED page,"
                        " trying to re-add\n");
                spin_lock_bh(&zbud_budlists_spinlock);
                spin_lock(&zbpg->lock);
                list_add_tail(&zbpg->bud_list, &zbud_buddied_list);
                zcache_zbud_buddied_count++;
                spin_unlock(&zbpg->lock);
                spin_unlock_bh(&zbud_budlists_spinlock);
                pr_err("TESTING zbud_remotify_pages failed on BUDDIED page,"
                        " finished re-add\n");
                goto out;
        }
unlock_out:
        spin_unlock_bh(&zbud_budlists_spinlock);
        preempt_enable();
out:
        return;
}

/* the "flush list" asynchronously collects pages to remotely flush */
#define FLUSH_ENTIRE_OBJECT ((uint32_t)-1)
static void ramster_flnode_free(struct flushlist_node *,
                                struct tmem_pool *);

static void zcache_remote_flush_page(struct flushlist_node *flnode)
{
        struct tmem_xhandle *xh;
        int remotenode, ret;

        preempt_disable();
        xh = &flnode->xh;
        remotenode = flnode->xh.client_id;
        ret = ramster_remote_flush(xh, remotenode);
        if (ret >= 0)
                ramster_remote_pages_flushed++;
        else
                ramster_remote_page_flushes_failed++;
        preempt_enable_no_resched();
        ramster_flnode_free(flnode, NULL);
}

static void zcache_remote_flush_object(struct flushlist_node *flnode)
{
        struct tmem_xhandle *xh;
        int remotenode, ret;

        preempt_disable();
        xh = &flnode->xh;
        remotenode = flnode->xh.client_id;
        ret = ramster_remote_flush_object(xh, remotenode);
        if (ret >= 0)
                ramster_remote_objects_flushed++;
        else
                ramster_remote_object_flushes_failed++;
        preempt_enable_no_resched();
        ramster_flnode_free(flnode, NULL);
}

static void zcache_remote_eph_put(struct zbud_hdr *zbud)
{
        /* FIXME */
}

static void zcache_remote_pers_put(struct zv_hdr *zv)
{
        struct tmem_xhandle xh;
        uint16_t size;
        bool ephemeral;
        int remotenode, ret = -1;
        char *data;
        struct tmem_pool *pool;
        unsigned long flags;
        unsigned char cksum;
        char *p;
        int i;
        unsigned char *tmpmem = __get_cpu_var(zcache_remoteputmem);

        ASSERT_SENTINEL(zv, ZVH);
        BUG_ON(zv->client_id != LOCAL_CLIENT);
        local_bh_disable();
        xh.client_id = zv->client_id;
        xh.pool_id = zv->pool_id;
        xh.oid = zv->oid;
        xh.index = zv->index;
        size = xv_get_object_size(zv) - sizeof(*zv);
        BUG_ON(size == 0 || size > zv_max_page_size);
        data = (char *)zv + sizeof(*zv);
        for (p = data, cksum = 0, i = 0; i < size; i++)
                cksum += *p;
        memcpy(tmpmem, data, size);
        data = tmpmem;
        pool = zcache_get_pool_by_id(zv->client_id, zv->pool_id);
        ephemeral = is_ephemeral(pool);
        zcache_put_pool(pool);
        /* now OK to release lock set in caller */
        spin_unlock(&zcache_rem_op_list_lock);
        local_bh_enable();
        preempt_disable();
        ret = ramster_remote_put(&xh, data, size, ephemeral, &remotenode);
        preempt_enable_no_resched();
        if (ret != 0) {
                /*
                 * This is some form of a memory leak... if the remote put
                 * fails, there will never be another attempt to remotify
                 * this page.  But since we've dropped the zv pointer,
                 * the page may have been freed or the data replaced
                 * so we can't just "put it back" in the remote op list.
                 * Even if we could, not sure where to put it in the list
                 * because there may be flushes that must be strictly
                 * ordered vs the put.  So leave this as a FIXME for now.
                 * But count them so we know if it becomes a problem.
                 */
                ramster_pers_pages_remote_failed++;
                goto out;
        } else
                atomic_inc(&ramster_remote_pers_pages);
        ramster_pers_pages_remoted++;
        /*
         * data was successfully remoted so change the local version to
         * point to the remote node where it landed
         */
        local_bh_disable();
        pool = zcache_get_pool_by_id(LOCAL_CLIENT, xh.pool_id);
        local_irq_save(flags);
        (void)tmem_replace(pool, &xh.oid, xh.index,
                        pampd_make_remote(remotenode, size, cksum));
        local_irq_restore(flags);
        zcache_put_pool(pool);
        local_bh_enable();
out:
        return;
}

static void zcache_do_remotify_ops(int nr)
{
        struct ramster_remotify_hdr *rem_op;
        union remotify_list_node *u;

        while (1) {
                if (!nr)
                        goto out;
                spin_lock(&zcache_rem_op_list_lock);
                if (list_empty(&zcache_rem_op_list)) {
                        spin_unlock(&zcache_rem_op_list_lock);
                        goto out;
                }
                rem_op = list_first_entry(&zcache_rem_op_list,
                                struct ramster_remotify_hdr, list);
                list_del_init(&rem_op->list);
                if (rem_op->op != RAMSTER_REMOTIFY_PERS_PUT)
                        spin_unlock(&zcache_rem_op_list_lock);
                u = (union remotify_list_node *)rem_op;
                switch (rem_op->op) {
                case RAMSTER_REMOTIFY_EPH_PUT:
BUG();
                        zcache_remote_eph_put((struct zbud_hdr *)rem_op);
                        break;
                case RAMSTER_REMOTIFY_PERS_PUT:
                        zcache_remote_pers_put((struct zv_hdr *)rem_op);
                        break;
                case RAMSTER_REMOTIFY_FLUSH_PAGE:
                        zcache_remote_flush_page((struct flushlist_node *)u);
                        break;
                case RAMSTER_REMOTIFY_FLUSH_OBJ:
                        zcache_remote_flush_object((struct flushlist_node *)u);
                        break;
                default:
                        BUG();
                }
        }
out:
        return;
}

/*
 * Communicate interface revision with userspace
 */
#include "cluster/ramster_nodemanager.h"
static unsigned long ramster_interface_revision  = R2NM_API_VERSION;

/*
 * For now, just push over a few pages every few seconds to
 * ensure that it basically works
 */
static struct workqueue_struct *ramster_remotify_workqueue;
static void ramster_remotify_process(struct work_struct *work);
static DECLARE_DELAYED_WORK(ramster_remotify_worker,
                ramster_remotify_process);

static void ramster_remotify_queue_delayed_work(unsigned long delay)
{
        if (!queue_delayed_work(ramster_remotify_workqueue,
                                &ramster_remotify_worker, delay))
                pr_err("ramster_remotify: bad workqueue\n");
}


static int use_frontswap;
static int use_cleancache;
static int ramster_remote_target_nodenum = -1;
static void ramster_remotify_process(struct work_struct *work)
{
        static bool remotify_in_progress;

        BUG_ON(irqs_disabled());
        if (remotify_in_progress)
                ramster_remotify_queue_delayed_work(HZ);
        else if (ramster_remote_target_nodenum != -1) {
                remotify_in_progress = true;
#ifdef CONFIG_CLEANCACHE
        if (use_cleancache && ramster_eph_remotify_enable)
                zbud_remotify_pages(5000); /* FIXME is this a good number? */
#endif
#ifdef CONFIG_FRONTSWAP
        if (use_frontswap && ramster_pers_remotify_enable)
                zcache_do_remotify_ops(500); /* FIXME is this a good number? */
#endif
                remotify_in_progress = false;
                ramster_remotify_queue_delayed_work(HZ);
        }
}

static void ramster_remotify_init(void)
{
        unsigned long n = 60UL;
        ramster_remotify_workqueue =
                create_singlethread_workqueue("ramster_remotify");
        ramster_remotify_queue_delayed_work(n * HZ);
}


static void zbud_init(void)
{
        int i;

        INIT_LIST_HEAD(&zbud_buddied_list);
        zcache_zbud_buddied_count = 0;
        for (i = 0; i < NCHUNKS; i++) {
                INIT_LIST_HEAD(&zbud_unbuddied[i].list);
                zbud_unbuddied[i].count = 0;
        }
}

#ifdef CONFIG_SYSFS
/*
 * These sysfs routines show a nice distribution of how many zbpg's are
 * currently (and have ever been placed) in each unbuddied list.  It's fun
 * to watch but can probably go away before final merge.
 */
static int zbud_show_unbuddied_list_counts(char *buf)
{
        int i;
        char *p = buf;

        for (i = 0; i < NCHUNKS; i++)
                p += sprintf(p, "%u ", zbud_unbuddied[i].count);
        return p - buf;
}

static int zbud_show_cumul_chunk_counts(char *buf)
{
        unsigned long i, chunks = 0, total_chunks = 0, sum_total_chunks = 0;
        unsigned long total_chunks_lte_21 = 0, total_chunks_lte_32 = 0;
        unsigned long total_chunks_lte_42 = 0;
        char *p = buf;

        for (i = 0; i < NCHUNKS; i++) {
                p += sprintf(p, "%lu ", zbud_cumul_chunk_counts[i]);
                chunks += zbud_cumul_chunk_counts[i];
                total_chunks += zbud_cumul_chunk_counts[i];
                sum_total_chunks += i * zbud_cumul_chunk_counts[i];
                if (i == 21)
                        total_chunks_lte_21 = total_chunks;
                if (i == 32)
                        total_chunks_lte_32 = total_chunks;
                if (i == 42)
                        total_chunks_lte_42 = total_chunks;
        }
        p += sprintf(p, "<=21:%lu <=32:%lu <=42:%lu, mean:%lu\n",
                total_chunks_lte_21, total_chunks_lte_32, total_chunks_lte_42,
                chunks == 0 ? 0 : sum_total_chunks / chunks);
        return p - buf;
}
#endif

/**********
 * This "zv" PAM implementation combines the TLSF-based xvMalloc
 * with lzo1x compression to maximize the amount of data that can
 * be packed into a physical page.
 *
 * Zv represents a PAM page with the index and object (plus a "size" value
 * necessary for decompression) immediately preceding the compressed data.
 */

/* rudimentary policy limits */
/* total number of persistent pages may not exceed this percentage */
static unsigned int zv_page_count_policy_percent = 75;
/*
 * byte count defining poor compression; pages with greater zsize will be
 * rejected
 */
static unsigned int zv_max_zsize = (PAGE_SIZE / 8) * 7;
/*
 * byte count defining poor *mean* compression; pages with greater zsize
 * will be rejected until sufficient better-compressed pages are accepted
 * driving the mean below this threshold
 */
static unsigned int zv_max_mean_zsize = (PAGE_SIZE / 8) * 5;

static atomic_t zv_curr_dist_counts[NCHUNKS];
static atomic_t zv_cumul_dist_counts[NCHUNKS];


static struct zv_hdr *zv_create(struct zcache_client *cli, uint32_t pool_id,
                                struct tmem_oid *oid, uint32_t index,
                                void *cdata, unsigned clen)
{
        struct page *page;
        struct zv_hdr *zv = NULL;
        uint32_t offset;
        int alloc_size = clen + sizeof(struct zv_hdr);
        int chunks = (alloc_size + (CHUNK_SIZE - 1)) >> CHUNK_SHIFT;
        int ret;

        BUG_ON(!irqs_disabled());
        BUG_ON(chunks >= NCHUNKS);
        ret = xv_malloc(cli->xvpool, clen + sizeof(struct zv_hdr),
                        &page, &offset, ZCACHE_GFP_MASK);
        if (unlikely(ret))
                goto out;
        atomic_inc(&zv_curr_dist_counts[chunks]);
        atomic_inc(&zv_cumul_dist_counts[chunks]);
        zv = kmap_atomic(page) + offset;
        zv->index = index;
        zv->oid = *oid;
        zv->pool_id = pool_id;
        SET_SENTINEL(zv, ZVH);
        INIT_LIST_HEAD(&zv->rem_op.list);
        zv->client_id = get_client_id_from_client(cli);
        zv->rem_op.op = RAMSTER_REMOTIFY_PERS_PUT;
        if (zv->client_id == LOCAL_CLIENT) {
                spin_lock(&zcache_rem_op_list_lock);
                list_add_tail(&zv->rem_op.list, &zcache_rem_op_list);
                spin_unlock(&zcache_rem_op_list_lock);
        }
        memcpy((char *)zv + sizeof(struct zv_hdr), cdata, clen);
        kunmap_atomic(zv);
out:
        return zv;
}

/* similar to zv_create, but just reserve space, no data yet */
static struct zv_hdr *zv_alloc(struct tmem_pool *pool,
                                struct tmem_oid *oid, uint32_t index,
                                unsigned clen)
{
        struct zcache_client *cli = pool->client;
        struct page *page;
        struct zv_hdr *zv = NULL;
        uint32_t offset;
        int ret;

        BUG_ON(!irqs_disabled());
        BUG_ON(!is_local_client(pool->client));
        ret = xv_malloc(cli->xvpool, clen + sizeof(struct zv_hdr),
                        &page, &offset, ZCACHE_GFP_MASK);
        if (unlikely(ret))
                goto out;
        zv = kmap_atomic(page) + offset;
        SET_SENTINEL(zv, ZVH);
        INIT_LIST_HEAD(&zv->rem_op.list);
        zv->client_id = LOCAL_CLIENT;
        zv->rem_op.op = RAMSTER_INTRANSIT_PERS;
        zv->index = index;
        zv->oid = *oid;
        zv->pool_id = pool->pool_id;
        kunmap_atomic(zv);
out:
        return zv;
}

static void zv_free(struct xv_pool *xvpool, struct zv_hdr *zv)
{
        unsigned long flags;
        struct page *page;
        uint32_t offset;
        uint16_t size = xv_get_object_size(zv);
        int chunks = (size + (CHUNK_SIZE - 1)) >> CHUNK_SHIFT;

        ASSERT_SENTINEL(zv, ZVH);
        BUG_ON(chunks >= NCHUNKS);
        atomic_dec(&zv_curr_dist_counts[chunks]);
        size -= sizeof(*zv);
        spin_lock(&zcache_rem_op_list_lock);
        size = xv_get_object_size(zv) - sizeof(*zv);
        BUG_ON(size == 0);
        INVERT_SENTINEL(zv, ZVH);
        if (!list_empty(&zv->rem_op.list))
                list_del_init(&zv->rem_op.list);
        spin_unlock(&zcache_rem_op_list_lock);
        page = virt_to_page(zv);
        offset = (unsigned long)zv & ~PAGE_MASK;
        local_irq_save(flags);
        xv_free(xvpool, page, offset);
        local_irq_restore(flags);
}

static void zv_decompress(struct page *page, struct zv_hdr *zv)
{
        size_t clen = PAGE_SIZE;
        char *to_va;
        unsigned size;
        int ret;

        ASSERT_SENTINEL(zv, ZVH);
        size = xv_get_object_size(zv) - sizeof(*zv);
        BUG_ON(size == 0);
        to_va = kmap_atomic(page);
        ret = lzo1x_decompress_safe((char *)zv + sizeof(*zv),
                                        size, to_va, &clen);
        kunmap_atomic(to_va);
        BUG_ON(ret != LZO_E_OK);
        BUG_ON(clen != PAGE_SIZE);
}

static void zv_copy_from_pampd(char *data, size_t *bufsize, struct zv_hdr *zv)
{
        unsigned size;

        ASSERT_SENTINEL(zv, ZVH);
        size = xv_get_object_size(zv) - sizeof(*zv);
        BUG_ON(size == 0 || size > zv_max_page_size);
        BUG_ON(size > *bufsize);
        memcpy(data, (char *)zv + sizeof(*zv), size);
        *bufsize = size;
}

static void zv_copy_to_pampd(struct zv_hdr *zv, char *data, size_t size)
{
        unsigned zv_size;

        ASSERT_SENTINEL(zv, ZVH);
        zv_size = xv_get_object_size(zv) - sizeof(*zv);
        BUG_ON(zv_size != size);
        BUG_ON(zv_size == 0 || zv_size > zv_max_page_size);
        memcpy((char *)zv + sizeof(*zv), data, size);
}

#ifdef CONFIG_SYSFS
/*
 * show a distribution of compression stats for zv pages.
 */

static int zv_curr_dist_counts_show(char *buf)
{
        unsigned long i, n, chunks = 0, sum_total_chunks = 0;
        char *p = buf;

        for (i = 0; i < NCHUNKS; i++) {
                n = atomic_read(&zv_curr_dist_counts[i]);
                p += sprintf(p, "%lu ", n);
                chunks += n;
                sum_total_chunks += i * n;
        }
        p += sprintf(p, "mean:%lu\n",
                chunks == 0 ? 0 : sum_total_chunks / chunks);
        return p - buf;
}

static int zv_cumul_dist_counts_show(char *buf)
{
        unsigned long i, n, chunks = 0, sum_total_chunks = 0;
        char *p = buf;

        for (i = 0; i < NCHUNKS; i++) {
                n = atomic_read(&zv_cumul_dist_counts[i]);
                p += sprintf(p, "%lu ", n);
                chunks += n;
                sum_total_chunks += i * n;
        }
        p += sprintf(p, "mean:%lu\n",
                chunks == 0 ? 0 : sum_total_chunks / chunks);
        return p - buf;
}

/*
 * setting zv_max_zsize via sysfs causes all persistent (e.g. swap)
 * pages that don't compress to less than this value (including metadata
 * overhead) to be rejected.  We don't allow the value to get too close
 * to PAGE_SIZE.
 */
static ssize_t zv_max_zsize_show(struct kobject *kobj,
                                    struct kobj_attribute *attr,
                                    char *buf)
{
        return sprintf(buf, "%u\n", zv_max_zsize);
}

static ssize_t zv_max_zsize_store(struct kobject *kobj,
                                    struct kobj_attribute *attr,
                                    const char *buf, size_t count)
{
        unsigned long val;
        int err;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        err = kstrtoul(buf, 10, &val);
        if (err || (val == 0) || (val > (PAGE_SIZE / 8) * 7))
                return -EINVAL;
        zv_max_zsize = val;
        return count;
}

/*
 * setting zv_max_mean_zsize via sysfs causes all persistent (e.g. swap)
 * pages that don't compress to less than this value (including metadata
 * overhead) to be rejected UNLESS the mean compression is also smaller
 * than this value.  In other words, we are load-balancing-by-zsize the
 * accepted pages.  Again, we don't allow the value to get too close
 * to PAGE_SIZE.
 */
static ssize_t zv_max_mean_zsize_show(struct kobject *kobj,
                                    struct kobj_attribute *attr,
                                    char *buf)
{
        return sprintf(buf, "%u\n", zv_max_mean_zsize);
}

static ssize_t zv_max_mean_zsize_store(struct kobject *kobj,
                                    struct kobj_attribute *attr,
                                    const char *buf, size_t count)
{
        unsigned long val;
        int err;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        err = kstrtoul(buf, 10, &val);
        if (err || (val == 0) || (val > (PAGE_SIZE / 8) * 7))
                return -EINVAL;
        zv_max_mean_zsize = val;
        return count;
}

/*
 * setting zv_page_count_policy_percent via sysfs sets an upper bound of
 * persistent (e.g. swap) pages that will be retained according to:
 *     (zv_page_count_policy_percent * totalram_pages) / 100)
 * when that limit is reached, further puts will be rejected (until
 * some pages have been flushed).  Note that, due to compression,
 * this number may exceed 100; it defaults to 75 and we set an
 * arbitrary limit of 150.  A poor choice will almost certainly result
 * in OOM's, so this value should only be changed prudently.
 */
static ssize_t zv_page_count_policy_percent_show(struct kobject *kobj,
                                                 struct kobj_attribute *attr,
                                                 char *buf)
{
        return sprintf(buf, "%u\n", zv_page_count_policy_percent);
}

static ssize_t zv_page_count_policy_percent_store(struct kobject *kobj,
                                                  struct kobj_attribute *attr,
                                                  const char *buf, size_t count)
{
        unsigned long val;
        int err;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        err = kstrtoul(buf, 10, &val);
        if (err || (val == 0) || (val > 150))
                return -EINVAL;
        zv_page_count_policy_percent = val;
        return count;
}

static struct kobj_attribute zcache_zv_max_zsize_attr = {
                .attr = { .name = "zv_max_zsize", .mode = 0644 },
                .show = zv_max_zsize_show,
                .store = zv_max_zsize_store,
};

static struct kobj_attribute zcache_zv_max_mean_zsize_attr = {
                .attr = { .name = "zv_max_mean_zsize", .mode = 0644 },
                .show = zv_max_mean_zsize_show,
                .store = zv_max_mean_zsize_store,
};

static struct kobj_attribute zcache_zv_page_count_policy_percent_attr = {
                .attr = { .name = "zv_page_count_policy_percent",
                          .mode = 0644 },
                .show = zv_page_count_policy_percent_show,
                .store = zv_page_count_policy_percent_store,
};
#endif

/*
 * zcache core code starts here
 */

/* useful stats not collected by cleancache or frontswap */
static unsigned long zcache_flush_total;
static unsigned long zcache_flush_found;
static unsigned long zcache_flobj_total;
static unsigned long zcache_flobj_found;
static unsigned long zcache_failed_eph_puts;
static unsigned long zcache_nonactive_puts;
static unsigned long zcache_failed_pers_puts;

/*
 * Tmem operations assume the poolid implies the invoking client.
 * Zcache only has one client (the kernel itself): LOCAL_CLIENT.
 * RAMster has each client numbered by cluster node, and a KVM version
 * of zcache would have one client per guest and each client might
 * have a poolid==N.
 */
static struct tmem_pool *zcache_get_pool_by_id(uint16_t cli_id, uint16_t poolid)
{
        struct tmem_pool *pool = NULL;
        struct zcache_client *cli = NULL;

        if (cli_id == LOCAL_CLIENT)
                cli = &zcache_host;
        else {
                if (cli_id >= MAX_CLIENTS)
                        goto out;
                cli = &zcache_clients[cli_id];
                if (cli == NULL)
                        goto out;
                atomic_inc(&cli->refcount);
        }
        if (poolid < MAX_POOLS_PER_CLIENT) {
                pool = cli->tmem_pools[poolid];
                if (pool != NULL)
                        atomic_inc(&pool->refcount);
        }
out:
        return pool;
}

static void zcache_put_pool(struct tmem_pool *pool)
{
        struct zcache_client *cli = NULL;

        if (pool == NULL)
                BUG();
        cli = pool->client;
        atomic_dec(&pool->refcount);
        atomic_dec(&cli->refcount);
}

int zcache_new_client(uint16_t cli_id)
{
        struct zcache_client *cli = NULL;
        int ret = -1;

        if (cli_id == LOCAL_CLIENT)
                cli = &zcache_host;
        else if ((unsigned int)cli_id < MAX_CLIENTS)
                cli = &zcache_clients[cli_id];
        if (cli == NULL)
                goto out;
        if (cli->allocated)
                goto out;
        cli->allocated = 1;
#ifdef CONFIG_FRONTSWAP
        cli->xvpool = xv_create_pool();
        if (cli->xvpool == NULL)
                goto out;
#endif
        ret = 0;
out:
        return ret;
}

/* counters for debugging */
static unsigned long zcache_failed_get_free_pages;
static unsigned long zcache_failed_alloc;
static unsigned long zcache_put_to_flush;

/*
 * for now, used named slabs so can easily track usage; later can
 * either just use kmalloc, or perhaps add a slab-like allocator
 * to more carefully manage total memory utilization
 */
static struct kmem_cache *zcache_objnode_cache;
static struct kmem_cache *zcache_obj_cache;
static struct kmem_cache *ramster_flnode_cache;
static atomic_t zcache_curr_obj_count = ATOMIC_INIT(0);
static unsigned long zcache_curr_obj_count_max;
static atomic_t zcache_curr_objnode_count = ATOMIC_INIT(0);
static unsigned long zcache_curr_objnode_count_max;

/*
 * to avoid memory allocation recursion (e.g. due to direct reclaim), we
 * preload all necessary data structures so the hostops callbacks never
 * actually do a malloc
 */
struct zcache_preload {
        void *page;
        struct tmem_obj *obj;
        int nr;
        struct tmem_objnode *objnodes[OBJNODE_TREE_MAX_PATH];
        struct flushlist_node *flnode;
};
static DEFINE_PER_CPU(struct zcache_preload, zcache_preloads) = { 0, };

static int zcache_do_preload(struct tmem_pool *pool)
{
        struct zcache_preload *kp;
        struct tmem_objnode *objnode;
        struct tmem_obj *obj;
        struct flushlist_node *flnode;
        void *page;
        int ret = -ENOMEM;

        if (unlikely(zcache_objnode_cache == NULL))
                goto out;
        if (unlikely(zcache_obj_cache == NULL))
                goto out;
        preempt_disable();
        kp = &__get_cpu_var(zcache_preloads);
        while (kp->nr < ARRAY_SIZE(kp->objnodes)) {
                preempt_enable_no_resched();
                objnode = kmem_cache_alloc(zcache_objnode_cache,
                                ZCACHE_GFP_MASK);
                if (unlikely(objnode == NULL)) {
                        zcache_failed_alloc++;
                        goto out;
                }
                preempt_disable();
                kp = &__get_cpu_var(zcache_preloads);
                if (kp->nr < ARRAY_SIZE(kp->objnodes))
                        kp->objnodes[kp->nr++] = objnode;
                else
                        kmem_cache_free(zcache_objnode_cache, objnode);
        }
        preempt_enable_no_resched();
        obj = kmem_cache_alloc(zcache_obj_cache, ZCACHE_GFP_MASK);
        if (unlikely(obj == NULL)) {
                zcache_failed_alloc++;
                goto out;
        }
        flnode = kmem_cache_alloc(ramster_flnode_cache, ZCACHE_GFP_MASK);
        if (unlikely(flnode == NULL)) {
                zcache_failed_alloc++;
                goto out;
        }
        if (is_ephemeral(pool)) {
                page = (void *)__get_free_page(ZCACHE_GFP_MASK);
                if (unlikely(page == NULL)) {
                        zcache_failed_get_free_pages++;
                        kmem_cache_free(zcache_obj_cache, obj);
                        kmem_cache_free(ramster_flnode_cache, flnode);
                        goto out;
                }
        }
        preempt_disable();
        kp = &__get_cpu_var(zcache_preloads);
        if (kp->obj == NULL)
                kp->obj = obj;
        else
                kmem_cache_free(zcache_obj_cache, obj);
        if (kp->flnode == NULL)
                kp->flnode = flnode;
        else
                kmem_cache_free(ramster_flnode_cache, flnode);
        if (is_ephemeral(pool)) {
                if (kp->page == NULL)
                        kp->page = page;
                else
                        free_page((unsigned long)page);
        }
        ret = 0;
out:
        return ret;
}

static int ramster_do_preload_flnode_only(struct tmem_pool *pool)
{
        struct zcache_preload *kp;
        struct flushlist_node *flnode;
        int ret = -ENOMEM;

        BUG_ON(!irqs_disabled());
        if (unlikely(ramster_flnode_cache == NULL))
                BUG();
        kp = &__get_cpu_var(zcache_preloads);
        flnode = kmem_cache_alloc(ramster_flnode_cache, GFP_ATOMIC);
        if (unlikely(flnode == NULL) && kp->flnode == NULL)
                BUG();  /* FIXME handle more gracefully, but how??? */
        else if (kp->flnode == NULL)
                kp->flnode = flnode;
        else
                kmem_cache_free(ramster_flnode_cache, flnode);
        return ret;
}

static void *zcache_get_free_page(void)
{
        struct zcache_preload *kp;
        void *page;

        kp = &__get_cpu_var(zcache_preloads);
        page = kp->page;
        BUG_ON(page == NULL);
        kp->page = NULL;
        return page;
}

static void zcache_free_page(void *p)
{
        free_page((unsigned long)p);
}

/*
 * zcache implementation for tmem host ops
 */

static struct tmem_objnode *zcache_objnode_alloc(struct tmem_pool *pool)
{
        struct tmem_objnode *objnode = NULL;
        unsigned long count;
        struct zcache_preload *kp;

        kp = &__get_cpu_var(zcache_preloads);
        if (kp->nr <= 0)
                goto out;
        objnode = kp->objnodes[kp->nr - 1];
        BUG_ON(objnode == NULL);
        kp->objnodes[kp->nr - 1] = NULL;
        kp->nr--;
        count = atomic_inc_return(&zcache_curr_objnode_count);
        if (count > zcache_curr_objnode_count_max)
                zcache_curr_objnode_count_max = count;
out:
        return objnode;
}

static void zcache_objnode_free(struct tmem_objnode *objnode,
                                        struct tmem_pool *pool)
{
        atomic_dec(&zcache_curr_objnode_count);
        BUG_ON(atomic_read(&zcache_curr_objnode_count) < 0);
        kmem_cache_free(zcache_objnode_cache, objnode);
}

static struct tmem_obj *zcache_obj_alloc(struct tmem_pool *pool)
{
        struct tmem_obj *obj = NULL;
        unsigned long count;
        struct zcache_preload *kp;

        kp = &__get_cpu_var(zcache_preloads);
        obj = kp->obj;
        BUG_ON(obj == NULL);
        kp->obj = NULL;
        count = atomic_inc_return(&zcache_curr_obj_count);
        if (count > zcache_curr_obj_count_max)
                zcache_curr_obj_count_max = count;
        return obj;
}

static void zcache_obj_free(struct tmem_obj *obj, struct tmem_pool *pool)
{
        atomic_dec(&zcache_curr_obj_count);
        BUG_ON(atomic_read(&zcache_curr_obj_count) < 0);
        kmem_cache_free(zcache_obj_cache, obj);
}

static struct flushlist_node *ramster_flnode_alloc(struct tmem_pool *pool)
{
        struct flushlist_node *flnode = NULL;
        struct zcache_preload *kp;
        int count;

        kp = &__get_cpu_var(zcache_preloads);
        flnode = kp->flnode;
        BUG_ON(flnode == NULL);
        kp->flnode = NULL;
        count = atomic_inc_return(&ramster_curr_flnode_count);
        if (count > ramster_curr_flnode_count_max)
                ramster_curr_flnode_count_max = count;
        return flnode;
}

static void ramster_flnode_free(struct flushlist_node *flnode,
                                struct tmem_pool *pool)
{
        atomic_dec(&ramster_curr_flnode_count);
        BUG_ON(atomic_read(&ramster_curr_flnode_count) < 0);
        kmem_cache_free(ramster_flnode_cache, flnode);
}

static struct tmem_hostops zcache_hostops = {
        .obj_alloc = zcache_obj_alloc,
        .obj_free = zcache_obj_free,
        .objnode_alloc = zcache_objnode_alloc,
        .objnode_free = zcache_objnode_free,
};

/*
 * zcache implementations for PAM page descriptor ops
 */


static inline void dec_and_check(atomic_t *pvar)
{
        atomic_dec(pvar);
        /* later when all accounting is fixed, make this a BUG */
        WARN_ON_ONCE(atomic_read(pvar) < 0);
}

static atomic_t zcache_curr_eph_pampd_count = ATOMIC_INIT(0);
static unsigned long zcache_curr_eph_pampd_count_max;
static atomic_t zcache_curr_pers_pampd_count = ATOMIC_INIT(0);
static unsigned long zcache_curr_pers_pampd_count_max;

/* forward reference */
static int zcache_compress(struct page *from, void **out_va, size_t *out_len);

static int zcache_pampd_eph_create(char *data, size_t size, bool raw,
                                struct tmem_pool *pool, struct tmem_oid *oid,
                                uint32_t index, void **pampd)
{
        int ret = -1;
        void *cdata = data;
        size_t clen = size;
        struct zcache_client *cli = pool->client;
        uint16_t client_id = get_client_id_from_client(cli);
        struct page *page = NULL;
        unsigned long count;

        if (!raw) {
                page = virt_to_page(data);
                ret = zcache_compress(page, &cdata, &clen);
                if (ret == 0)
                        goto out;
                if (clen == 0 || clen > zbud_max_buddy_size()) {
                        zcache_compress_poor++;
                        goto out;
                }
        }
        *pampd = (void *)zbud_create(client_id, pool->pool_id, oid,
                                        index, page, cdata, clen);
        if (*pampd == NULL) {
                ret = -ENOMEM;
                goto out;
        }
        ret = 0;
        count = atomic_inc_return(&zcache_curr_eph_pampd_count);
        if (count > zcache_curr_eph_pampd_count_max)
                zcache_curr_eph_pampd_count_max = count;
        if (client_id != LOCAL_CLIENT) {
                count = atomic_inc_return(&ramster_foreign_eph_pampd_count);
                if (count > ramster_foreign_eph_pampd_count_max)
                        ramster_foreign_eph_pampd_count_max = count;
        }
out:
        return ret;
}

static int zcache_pampd_pers_create(char *data, size_t size, bool raw,
                                struct tmem_pool *pool, struct tmem_oid *oid,
                                uint32_t index, void **pampd)
{
        int ret = -1;
        void *cdata = data;
        size_t clen = size;
        struct zcache_client *cli = pool->client;
        struct page *page;
        unsigned long count;
        unsigned long zv_mean_zsize;
        struct zv_hdr *zv;
        long curr_pers_pampd_count;
        u64 total_zsize;
#ifdef RAMSTER_TESTING
        static bool pampd_neg_warned;
#endif

        curr_pers_pampd_count = atomic_read(&zcache_curr_pers_pampd_count) -
                        atomic_read(&ramster_remote_pers_pages);
#ifdef RAMSTER_TESTING
        /* should always be positive, but warn if accounting is off */
        if (!pampd_neg_warned) {
                pr_warn("ramster: bad accounting for curr_pers_pampd_count\n");
                pampd_neg_warned = true;
        }
#endif
        if (curr_pers_pampd_count >
                    (zv_page_count_policy_percent * totalram_pages) / 100) {
                zcache_policy_percent_exceeded++;
                goto out;
        }
        if (raw)
                goto ok_to_create;
        page = virt_to_page(data);
        if (zcache_compress(page, &cdata, &clen) == 0)
                goto out;
        /* reject if compression is too poor */
        if (clen > zv_max_zsize) {
                zcache_compress_poor++;
                goto out;
        }
        /* reject if mean compression is too poor */
        if ((clen > zv_max_mean_zsize) && (curr_pers_pampd_count > 0)) {
                total_zsize = xv_get_total_size_bytes(cli->xvpool);
                zv_mean_zsize = div_u64(total_zsize, curr_pers_pampd_count);
                if (zv_mean_zsize > zv_max_mean_zsize) {
                        zcache_mean_compress_poor++;
                        goto out;
                }
        }
ok_to_create:
        *pampd = (void *)zv_create(cli, pool->pool_id, oid, index, cdata, clen);
        if (*pampd == NULL) {
                ret = -ENOMEM;
                goto out;
        }
        ret = 0;
        count = atomic_inc_return(&zcache_curr_pers_pampd_count);
        if (count > zcache_curr_pers_pampd_count_max)
                zcache_curr_pers_pampd_count_max = count;
        if (is_local_client(cli))
                goto out;
        zv = *(struct zv_hdr **)pampd;
        count = atomic_inc_return(&ramster_foreign_pers_pampd_count);
        if (count > ramster_foreign_pers_pampd_count_max)
                ramster_foreign_pers_pampd_count_max = count;
out:
        return ret;
}

static void *zcache_pampd_create(char *data, size_t size, bool raw, int eph,
                                struct tmem_pool *pool, struct tmem_oid *oid,
                                uint32_t index)
{
        void *pampd = NULL;
        int ret;
        bool ephemeral;

        BUG_ON(preemptible());
        ephemeral = (eph == 1) || ((eph == 0) && is_ephemeral(pool));
        if (ephemeral)
                ret = zcache_pampd_eph_create(data, size, raw, pool,
                                                oid, index, &pampd);
        else
                ret = zcache_pampd_pers_create(data, size, raw, pool,
                                                oid, index, &pampd);
        /* FIXME add some counters here for failed creates? */
        return pampd;
}

/*
 * fill the pageframe corresponding to the struct page with the data
 * from the passed pampd
 */
static int zcache_pampd_get_data(char *data, size_t *bufsize, bool raw,
                                        void *pampd, struct tmem_pool *pool,
                                        struct tmem_oid *oid, uint32_t index)
{
        int ret = 0;

        BUG_ON(preemptible());
        BUG_ON(is_ephemeral(pool)); /* Fix later for shared pools? */
        BUG_ON(pampd_is_remote(pampd));
        if (raw)
                zv_copy_from_pampd(data, bufsize, pampd);
        else
                zv_decompress(virt_to_page(data), pampd);
        return ret;
}

static int zcache_pampd_get_data_and_free(char *data, size_t *bufsize, bool raw,
                                        void *pampd, struct tmem_pool *pool,
                                        struct tmem_oid *oid, uint32_t index)
{
        int ret = 0;
        unsigned long flags;
        struct zcache_client *cli = pool->client;

        BUG_ON(preemptible());
        BUG_ON(pampd_is_remote(pampd));
        if (is_ephemeral(pool)) {
                local_irq_save(flags);
                if (raw)
                        zbud_copy_from_pampd(data, bufsize, pampd);
                else
                        ret = zbud_decompress(virt_to_page(data), pampd);
                zbud_free_and_delist((struct zbud_hdr *)pampd);
                local_irq_restore(flags);
                if (!is_local_client(cli))
                        dec_and_check(&ramster_foreign_eph_pampd_count);
                dec_and_check(&zcache_curr_eph_pampd_count);
        } else {
                if (is_local_client(cli))
                        BUG();
                if (raw)
                        zv_copy_from_pampd(data, bufsize, pampd);
                else
                        zv_decompress(virt_to_page(data), pampd);
                zv_free(cli->xvpool, pampd);
                if (!is_local_client(cli))
                        dec_and_check(&ramster_foreign_pers_pampd_count);
                dec_and_check(&zcache_curr_pers_pampd_count);
                ret = 0;
        }
        return ret;
}

static bool zcache_pampd_is_remote(void *pampd)
{
        return pampd_is_remote(pampd);
}

/*
 * free the pampd and remove it from any zcache lists
 * pampd must no longer be pointed to from any tmem data structures!
 */
static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
                              struct tmem_oid *oid, uint32_t index, bool acct)
{
        struct zcache_client *cli = pool->client;
        bool eph = is_ephemeral(pool);
        struct zv_hdr *zv;

        BUG_ON(preemptible());
        if (pampd_is_remote(pampd)) {
                WARN_ON(acct == false);
                if (oid == NULL) {
                        /*
                         * a NULL oid means to ignore this pampd free
                         * as the remote freeing will be handled elsewhere
                         */
                } else if (eph) {
                        /* FIXME remote flush optional but probably good idea */
                        /* FIXME get these working properly again */
                        dec_and_check(&zcache_curr_eph_pampd_count);
                } else if (pampd_is_intransit(pampd)) {
                        /* did a pers remote get_and_free, so just free local */
                        pampd = pampd_mask_intransit_and_remote(pampd);
                        goto local_pers;
                } else {
                        struct flushlist_node *flnode =
                                ramster_flnode_alloc(pool);

                        flnode->xh.client_id = pampd_remote_node(pampd);
                        flnode->xh.pool_id = pool->pool_id;
                        flnode->xh.oid = *oid;
                        flnode->xh.index = index;
                        flnode->rem_op.op = RAMSTER_REMOTIFY_FLUSH_PAGE;
                        spin_lock(&zcache_rem_op_list_lock);
                        list_add(&flnode->rem_op.list, &zcache_rem_op_list);
                        spin_unlock(&zcache_rem_op_list_lock);
                        dec_and_check(&zcache_curr_pers_pampd_count);
                        dec_and_check(&ramster_remote_pers_pages);
                }
        } else if (eph) {
                zbud_free_and_delist((struct zbud_hdr *)pampd);
                if (!is_local_client(pool->client))
                        dec_and_check(&ramster_foreign_eph_pampd_count);
                if (acct)
                        /* FIXME get these working properly again */
                        dec_and_check(&zcache_curr_eph_pampd_count);
        } else {
local_pers:
                zv = (struct zv_hdr *)pampd;
                if (!is_local_client(pool->client))
                        dec_and_check(&ramster_foreign_pers_pampd_count);
                zv_free(cli->xvpool, zv);
                if (acct)
                        /* FIXME get these working properly again */
                        dec_and_check(&zcache_curr_pers_pampd_count);
        }
}

static void zcache_pampd_free_obj(struct tmem_pool *pool,
                                        struct tmem_obj *obj)
{
        struct flushlist_node *flnode;

        BUG_ON(preemptible());
        if (obj->extra == NULL)
                return;
        BUG_ON(!pampd_is_remote(obj->extra));
        flnode = ramster_flnode_alloc(pool);
        flnode->xh.client_id = pampd_remote_node(obj->extra);
        flnode->xh.pool_id = pool->pool_id;
        flnode->xh.oid = obj->oid;
        flnode->xh.index = FLUSH_ENTIRE_OBJECT;
        flnode->rem_op.op = RAMSTER_REMOTIFY_FLUSH_OBJ;
        spin_lock(&zcache_rem_op_list_lock);
        list_add(&flnode->rem_op.list, &zcache_rem_op_list);
        spin_unlock(&zcache_rem_op_list_lock);
}

void zcache_pampd_new_obj(struct tmem_obj *obj)
{
        obj->extra = NULL;
}

int zcache_pampd_replace_in_obj(void *new_pampd, struct tmem_obj *obj)
{
        int ret = -1;

        if (new_pampd != NULL) {
                if (obj->extra == NULL)
                        obj->extra = new_pampd;
                /* enforce that all remote pages in an object reside
                 * in the same node! */
                else if (pampd_remote_node(new_pampd) !=
                                pampd_remote_node((void *)(obj->extra)))
                        BUG();
                ret = 0;
        }
        return ret;
}

/*
 * Called by the message handler after a (still compressed) page has been
 * fetched from the remote machine in response to an "is_remote" tmem_get
 * or persistent tmem_localify.  For a tmem_get, "extra" is the address of
 * the page that is to be filled to successfully resolve the tmem_get; for
 * a (persistent) tmem_localify, "extra" is NULL (as the data is placed only
 * in the local zcache).  "data" points to "size" bytes of (compressed) data
 * passed in the message.  In the case of a persistent remote get, if
 * pre-allocation was successful (see zcache_repatriate_preload), the page
 * is placed into both local zcache and at "extra".
 */
int zcache_localify(int pool_id, struct tmem_oid *oidp,
                        uint32_t index, char *data, size_t size,
                        void *extra)
{
        int ret = -ENOENT;
        unsigned long flags;
        struct tmem_pool *pool;
        bool ephemeral, delete = false;
        size_t clen = PAGE_SIZE;
        void *pampd, *saved_hb;
        struct tmem_obj *obj;

        pool = zcache_get_pool_by_id(LOCAL_CLIENT, pool_id);
        if (unlikely(pool == NULL))
                /* pool doesn't exist anymore */
                goto out;
        ephemeral = is_ephemeral(pool);
        local_irq_save(flags);  /* FIXME: maybe only disable softirqs? */
        pampd = tmem_localify_get_pampd(pool, oidp, index, &obj, &saved_hb);
        if (pampd == NULL) {
                /* hmmm... must have been a flush while waiting */
#ifdef RAMSTER_TESTING
                pr_err("UNTESTED pampd==NULL in zcache_localify\n");
#endif
                if (ephemeral)
                        ramster_remote_eph_pages_unsucc_get++;
                else
                        ramster_remote_pers_pages_unsucc_get++;
                obj = NULL;
                goto finish;
        } else if (unlikely(!pampd_is_remote(pampd))) {
                /* hmmm... must have been a dup put while waiting */
#ifdef RAMSTER_TESTING
                pr_err("UNTESTED dup while waiting in zcache_localify\n");
#endif
                if (ephemeral)
                        ramster_remote_eph_pages_unsucc_get++;
                else
                        ramster_remote_pers_pages_unsucc_get++;
                obj = NULL;
                pampd = NULL;
                ret = -EEXIST;
                goto finish;
        } else if (size == 0) {
                /* no remote data, delete the local is_remote pampd */
                pampd = NULL;
                if (ephemeral)
                        ramster_remote_eph_pages_unsucc_get++;
                else
                        BUG();
                delete = true;
                goto finish;
        }
        if (!ephemeral && pampd_is_intransit(pampd)) {
                /* localify to zcache */
                pampd = pampd_mask_intransit_and_remote(pampd);
                zv_copy_to_pampd(pampd, data, size);
        } else {
                pampd = NULL;
                obj = NULL;
        }
        if (extra != NULL) {
                /* decompress direct-to-memory to complete remotify */
                ret = lzo1x_decompress_safe((char *)data, size,
                                                (char *)extra, &clen);
                BUG_ON(ret != LZO_E_OK);
                BUG_ON(clen != PAGE_SIZE);
        }
        if (ephemeral)
                ramster_remote_eph_pages_succ_get++;
        else
                ramster_remote_pers_pages_succ_get++;
        ret = 0;
finish:
        tmem_localify_finish(obj, index, pampd, saved_hb, delete);
        zcache_put_pool(pool);
        local_irq_restore(flags);
out:
        return ret;
}

/*
 * Called on a remote persistent tmem_get to attempt to preallocate
 * local storage for the data contained in the remote persistent page.
 * If successfully preallocated, returns the pampd, marked as remote and
 * in_transit.  Else returns NULL.  Note that the appropriate tmem data
 * structure must be locked.
 */
static void *zcache_pampd_repatriate_preload(void *pampd,
                                                struct tmem_pool *pool,
                                                struct tmem_oid *oid,
                                                uint32_t index,
                                                bool *intransit)
{
        int clen = pampd_remote_size(pampd);
        void *ret_pampd = NULL;
        unsigned long flags;

        if (!pampd_is_remote(pampd))
                BUG();
        if (is_ephemeral(pool))
                BUG();
        if (pampd_is_intransit(pampd)) {
                /*
                 * to avoid multiple allocations (and maybe a memory leak)
                 * don't preallocate if already in the process of being
                 * repatriated
                 */
                *intransit = true;
                goto out;
        }
        *intransit = false;
        local_irq_save(flags);
        ret_pampd = (void *)zv_alloc(pool, oid, index, clen);
        if (ret_pampd != NULL) {
                /*
                 *  a pampd is marked intransit if it is remote and space has
                 *  been allocated for it locally (note, only happens for
                 *  persistent pages, in which case the remote copy is freed)
                 */
                ret_pampd = pampd_mark_intransit(ret_pampd);
                dec_and_check(&ramster_remote_pers_pages);
        } else
                ramster_pers_pages_remote_nomem++;
        local_irq_restore(flags);
out:
        return ret_pampd;
}

/*
 * Called on a remote tmem_get to invoke a message to fetch the page.
 * Might sleep so no tmem locks can be held.  "extra" is passed
 * all the way through the round-trip messaging to zcache_localify.
 */
static int zcache_pampd_repatriate(void *fake_pampd, void *real_pampd,
                                   struct tmem_pool *pool,
                                   struct tmem_oid *oid, uint32_t index,
                                   bool free, void *extra)
{
        struct tmem_xhandle xh;
        int ret;

        if (pampd_is_intransit(real_pampd))
                /* have local space pre-reserved, so free remote copy */
                free = true;
        xh = tmem_xhandle_fill(LOCAL_CLIENT, pool, oid, index);
        /* unreliable request/response for now */
        ret = ramster_remote_async_get(&xh, free,
                                        pampd_remote_node(fake_pampd),
                                        pampd_remote_size(fake_pampd),
                                        pampd_remote_cksum(fake_pampd),
                                        extra);
#ifdef RAMSTER_TESTING
        if (ret != 0 && ret != -ENOENT)
                pr_err("TESTING zcache_pampd_repatriate returns, ret=%d\n",
                        ret);
#endif
        return ret;
}

static struct tmem_pamops zcache_pamops = {
        .create = zcache_pampd_create,
        .get_data = zcache_pampd_get_data,
        .free = zcache_pampd_free,
        .get_data_and_free = zcache_pampd_get_data_and_free,
        .free_obj = zcache_pampd_free_obj,
        .is_remote = zcache_pampd_is_remote,
        .repatriate_preload = zcache_pampd_repatriate_preload,
        .repatriate = zcache_pampd_repatriate,
        .new_obj = zcache_pampd_new_obj,
        .replace_in_obj = zcache_pampd_replace_in_obj,
};

/*
 * zcache compression/decompression and related per-cpu stuff
 */

#define LZO_WORKMEM_BYTES LZO1X_1_MEM_COMPRESS
#define LZO_DSTMEM_PAGE_ORDER 1
static DEFINE_PER_CPU(unsigned char *, zcache_workmem);
static DEFINE_PER_CPU(unsigned char *, zcache_dstmem);

static int zcache_compress(struct page *from, void **out_va, size_t *out_len)
{
        int ret = 0;
        unsigned char *dmem = __get_cpu_var(zcache_dstmem);
        unsigned char *wmem = __get_cpu_var(zcache_workmem);
        char *from_va;

        BUG_ON(!irqs_disabled());
        if (unlikely(dmem == NULL || wmem == NULL))
                goto out;  /* no buffer, so can't compress */
        from_va = kmap_atomic(from);
        mb();
        ret = lzo1x_1_compress(from_va, PAGE_SIZE, dmem, out_len, wmem);
        BUG_ON(ret != LZO_E_OK);
        *out_va = dmem;
        kunmap_atomic(from_va);
        ret = 1;
out:
        return ret;
}


static int zcache_cpu_notifier(struct notifier_block *nb,
                                unsigned long action, void *pcpu)
{
        int cpu = (long)pcpu;
        struct zcache_preload *kp;

        switch (action) {
        case CPU_UP_PREPARE:
                per_cpu(zcache_dstmem, cpu) = (void *)__get_free_pages(
                        GFP_KERNEL | __GFP_REPEAT,
                        LZO_DSTMEM_PAGE_ORDER),
                per_cpu(zcache_workmem, cpu) =
                        kzalloc(LZO1X_MEM_COMPRESS,
                                GFP_KERNEL | __GFP_REPEAT);
                per_cpu(zcache_remoteputmem, cpu) =
                        kzalloc(PAGE_SIZE, GFP_KERNEL | __GFP_REPEAT);
                break;
        case CPU_DEAD:
        case CPU_UP_CANCELED:
                kfree(per_cpu(zcache_remoteputmem, cpu));
                per_cpu(zcache_remoteputmem, cpu) = NULL;
                free_pages((unsigned long)per_cpu(zcache_dstmem, cpu),
                                LZO_DSTMEM_PAGE_ORDER);
                per_cpu(zcache_dstmem, cpu) = NULL;
                kfree(per_cpu(zcache_workmem, cpu));
                per_cpu(zcache_workmem, cpu) = NULL;
                kp = &per_cpu(zcache_preloads, cpu);
                while (kp->nr) {
                        kmem_cache_free(zcache_objnode_cache,
                                        kp->objnodes[kp->nr - 1]);
                        kp->objnodes[kp->nr - 1] = NULL;
                        kp->nr--;
                }
                if (kp->obj) {
                        kmem_cache_free(zcache_obj_cache, kp->obj);
                        kp->obj = NULL;
                }
                if (kp->flnode) {
                        kmem_cache_free(ramster_flnode_cache, kp->flnode);
                        kp->flnode = NULL;
                }
                if (kp->page) {
                        free_page((unsigned long)kp->page);
                        kp->page = NULL;
                }
                break;
        default:
                break;
        }
        return NOTIFY_OK;
}

static struct notifier_block zcache_cpu_notifier_block = {
        .notifier_call = zcache_cpu_notifier
};

#ifdef CONFIG_SYSFS
#define ZCACHE_SYSFS_RO(_name) \
        static ssize_t zcache_##_name##_show(struct kobject *kobj, \
                                struct kobj_attribute *attr, char *buf) \
        { \
                return sprintf(buf, "%lu\n", zcache_##_name); \
        } \
        static struct kobj_attribute zcache_##_name##_attr = { \
                .attr = { .name = __stringify(_name), .mode = 0444 }, \
                .show = zcache_##_name##_show, \
        }

#define ZCACHE_SYSFS_RO_ATOMIC(_name) \
        static ssize_t zcache_##_name##_show(struct kobject *kobj, \
                                struct kobj_attribute *attr, char *buf) \
        { \
            return sprintf(buf, "%d\n", atomic_read(&zcache_##_name)); \
        } \
        static struct kobj_attribute zcache_##_name##_attr = { \
                .attr = { .name = __stringify(_name), .mode = 0444 }, \
                .show = zcache_##_name##_show, \
        }

#define ZCACHE_SYSFS_RO_CUSTOM(_name, _func) \
        static ssize_t zcache_##_name##_show(struct kobject *kobj, \
                                struct kobj_attribute *attr, char *buf) \
        { \
            return _func(buf); \
        } \
        static struct kobj_attribute zcache_##_name##_attr = { \
                .attr = { .name = __stringify(_name), .mode = 0444 }, \
                .show = zcache_##_name##_show, \
        }

ZCACHE_SYSFS_RO(curr_obj_count_max);
ZCACHE_SYSFS_RO(curr_objnode_count_max);
ZCACHE_SYSFS_RO(flush_total);
ZCACHE_SYSFS_RO(flush_found);
ZCACHE_SYSFS_RO(flobj_total);
ZCACHE_SYSFS_RO(flobj_found);
ZCACHE_SYSFS_RO(failed_eph_puts);
ZCACHE_SYSFS_RO(nonactive_puts);
ZCACHE_SYSFS_RO(failed_pers_puts);
ZCACHE_SYSFS_RO(zbud_curr_zbytes);
ZCACHE_SYSFS_RO(zbud_cumul_zpages);
ZCACHE_SYSFS_RO(zbud_cumul_zbytes);
ZCACHE_SYSFS_RO(zbud_buddied_count);
ZCACHE_SYSFS_RO(evicted_raw_pages);
ZCACHE_SYSFS_RO(evicted_unbuddied_pages);
ZCACHE_SYSFS_RO(evicted_buddied_pages);
ZCACHE_SYSFS_RO(failed_get_free_pages);
ZCACHE_SYSFS_RO(failed_alloc);
ZCACHE_SYSFS_RO(put_to_flush);
ZCACHE_SYSFS_RO(compress_poor);
ZCACHE_SYSFS_RO(mean_compress_poor);
ZCACHE_SYSFS_RO(policy_percent_exceeded);
ZCACHE_SYSFS_RO_ATOMIC(zbud_curr_raw_pages);
ZCACHE_SYSFS_RO_ATOMIC(zbud_curr_zpages);
ZCACHE_SYSFS_RO_ATOMIC(curr_obj_count);
ZCACHE_SYSFS_RO_ATOMIC(curr_objnode_count);
ZCACHE_SYSFS_RO_CUSTOM(zbud_unbuddied_list_counts,
                        zbud_show_unbuddied_list_counts);
ZCACHE_SYSFS_RO_CUSTOM(zbud_cumul_chunk_counts,
                        zbud_show_cumul_chunk_counts);
ZCACHE_SYSFS_RO_CUSTOM(zv_curr_dist_counts,
                        zv_curr_dist_counts_show);
ZCACHE_SYSFS_RO_CUSTOM(zv_cumul_dist_counts,
                        zv_cumul_dist_counts_show);

static struct attribute *zcache_attrs[] = {
        &zcache_curr_obj_count_attr.attr,
        &zcache_curr_obj_count_max_attr.attr,
        &zcache_curr_objnode_count_attr.attr,
        &zcache_curr_objnode_count_max_attr.attr,
        &zcache_flush_total_attr.attr,
        &zcache_flobj_total_attr.attr,
        &zcache_flush_found_attr.attr,
        &zcache_flobj_found_attr.attr,
        &zcache_failed_eph_puts_attr.attr,
        &zcache_nonactive_puts_attr.attr,
        &zcache_failed_pers_puts_attr.attr,
        &zcache_policy_percent_exceeded_attr.attr,
        &zcache_compress_poor_attr.attr,
        &zcache_mean_compress_poor_attr.attr,
        &zcache_zbud_curr_raw_pages_attr.attr,
        &zcache_zbud_curr_zpages_attr.attr,
        &zcache_zbud_curr_zbytes_attr.attr,
        &zcache_zbud_cumul_zpages_attr.attr,
        &zcache_zbud_cumul_zbytes_attr.attr,
        &zcache_zbud_buddied_count_attr.attr,
        &zcache_evicted_raw_pages_attr.attr,
        &zcache_evicted_unbuddied_pages_attr.attr,
        &zcache_evicted_buddied_pages_attr.attr,
        &zcache_failed_get_free_pages_attr.attr,
        &zcache_failed_alloc_attr.attr,
        &zcache_put_to_flush_attr.attr,
        &zcache_zbud_unbuddied_list_counts_attr.attr,
        &zcache_zbud_cumul_chunk_counts_attr.attr,
        &zcache_zv_curr_dist_counts_attr.attr,
        &zcache_zv_cumul_dist_counts_attr.attr,
        &zcache_zv_max_zsize_attr.attr,
        &zcache_zv_max_mean_zsize_attr.attr,
        &zcache_zv_page_count_policy_percent_attr.attr,
        NULL,
};

static struct attribute_group zcache_attr_group = {
        .attrs = zcache_attrs,
        .name = "zcache",
};

#define RAMSTER_SYSFS_RO(_name) \
        static ssize_t ramster_##_name##_show(struct kobject *kobj, \
                                struct kobj_attribute *attr, char *buf) \
        { \
                return sprintf(buf, "%lu\n", ramster_##_name); \
        } \
        static struct kobj_attribute ramster_##_name##_attr = { \
                .attr = { .name = __stringify(_name), .mode = 0444 }, \
                .show = ramster_##_name##_show, \
        }

#define RAMSTER_SYSFS_RW(_name) \
        static ssize_t ramster_##_name##_show(struct kobject *kobj, \
                                struct kobj_attribute *attr, char *buf) \
        { \
                return sprintf(buf, "%lu\n", ramster_##_name); \
        } \
        static ssize_t ramster_##_name##_store(struct kobject *kobj, \
                struct kobj_attribute *attr, const char *buf, size_t count) \
        { \
                int err; \
                unsigned long enable; \
                err = kstrtoul(buf, 10, &enable); \
                if (err) \
                        return -EINVAL; \
                ramster_##_name = enable; \
                return count; \
        } \
        static struct kobj_attribute ramster_##_name##_attr = { \
                .attr = { .name = __stringify(_name), .mode = 0644 }, \
                .show = ramster_##_name##_show, \
                .store = ramster_##_name##_store, \
        }

#define RAMSTER_SYSFS_RO_ATOMIC(_name) \
        static ssize_t ramster_##_name##_show(struct kobject *kobj, \
                                struct kobj_attribute *attr, char *buf) \
        { \
            return sprintf(buf, "%d\n", atomic_read(&ramster_##_name)); \
        } \
        static struct kobj_attribute ramster_##_name##_attr = { \
                .attr = { .name = __stringify(_name), .mode = 0444 }, \
                .show = ramster_##_name##_show, \
        }

RAMSTER_SYSFS_RO(interface_revision);
RAMSTER_SYSFS_RO_ATOMIC(remote_pers_pages);
RAMSTER_SYSFS_RW(pers_remotify_enable);
RAMSTER_SYSFS_RW(eph_remotify_enable);
RAMSTER_SYSFS_RO(eph_pages_remoted);
RAMSTER_SYSFS_RO(eph_pages_remote_failed);
RAMSTER_SYSFS_RO(pers_pages_remoted);
RAMSTER_SYSFS_RO(pers_pages_remote_failed);
RAMSTER_SYSFS_RO(pers_pages_remote_nomem);
RAMSTER_SYSFS_RO(remote_pages_flushed);
RAMSTER_SYSFS_RO(remote_page_flushes_failed);
RAMSTER_SYSFS_RO(remote_objects_flushed);
RAMSTER_SYSFS_RO(remote_object_flushes_failed);
RAMSTER_SYSFS_RO(remote_eph_pages_succ_get);
RAMSTER_SYSFS_RO(remote_eph_pages_unsucc_get);
RAMSTER_SYSFS_RO(remote_pers_pages_succ_get);
RAMSTER_SYSFS_RO(remote_pers_pages_unsucc_get);
RAMSTER_SYSFS_RO_ATOMIC(foreign_eph_pampd_count);
RAMSTER_SYSFS_RO(foreign_eph_pampd_count_max);
RAMSTER_SYSFS_RO_ATOMIC(foreign_pers_pampd_count);
RAMSTER_SYSFS_RO(foreign_pers_pampd_count_max);
RAMSTER_SYSFS_RO_ATOMIC(curr_flnode_count);
RAMSTER_SYSFS_RO(curr_flnode_count_max);

#define MANUAL_NODES 8
static bool ramster_nodes_manual_up[MANUAL_NODES];
static ssize_t ramster_manual_node_up_show(struct kobject *kobj,
                                struct kobj_attribute *attr, char *buf)
{
        int i;
        char *p = buf;
        for (i = 0; i < MANUAL_NODES; i++)
                if (ramster_nodes_manual_up[i])
                        p += sprintf(p, "%d ", i);
        p += sprintf(p, "\n");
        return p - buf;
}

static ssize_t ramster_manual_node_up_store(struct kobject *kobj,
                struct kobj_attribute *attr, const char *buf, size_t count)
{
        int err;
        unsigned long node_num;

        err = kstrtoul(buf, 10, &node_num);
        if (err) {
                pr_err("ramster: bad strtoul?\n");
                return -EINVAL;
        }
        if (node_num >= MANUAL_NODES) {
                pr_err("ramster: bad node_num=%lu?\n", node_num);
                return -EINVAL;
        }
        if (ramster_nodes_manual_up[node_num]) {
                pr_err("ramster: node %d already up, ignoring\n",
                                                        (int)node_num);
        } else {
                ramster_nodes_manual_up[node_num] = true;
                r2net_hb_node_up_manual((int)node_num);
        }
        return count;
}

static struct kobj_attribute ramster_manual_node_up_attr = {
        .attr = { .name = "manual_node_up", .mode = 0644 },
        .show = ramster_manual_node_up_show,
        .store = ramster_manual_node_up_store,
};

static ssize_t ramster_remote_target_nodenum_show(struct kobject *kobj,
                                struct kobj_attribute *attr, char *buf)
{
        if (ramster_remote_target_nodenum == -1UL)
                return sprintf(buf, "unset\n");
        else
                return sprintf(buf, "%d\n", ramster_remote_target_nodenum);
}

static ssize_t ramster_remote_target_nodenum_store(struct kobject *kobj,
                struct kobj_attribute *attr, const char *buf, size_t count)
{
        int err;
        unsigned long node_num;

        err = kstrtoul(buf, 10, &node_num);
        if (err) {
                pr_err("ramster: bad strtoul?\n");
                return -EINVAL;
        } else if (node_num == -1UL) {
                pr_err("ramster: disabling all remotification, "
                        "data may still reside on remote nodes however\n");
                return -EINVAL;
        } else if (node_num >= MANUAL_NODES) {
                pr_err("ramster: bad node_num=%lu?\n", node_num);
                return -EINVAL;
        } else if (!ramster_nodes_manual_up[node_num]) {
                pr_err("ramster: node %d not up, ignoring setting "
                        "of remotification target\n", (int)node_num);
        } else if (r2net_remote_target_node_set((int)node_num) >= 0) {
                pr_info("ramster: node %d set as remotification target\n",
                                (int)node_num);
                ramster_remote_target_nodenum = (int)node_num;
        } else {
                pr_err("ramster: bad num to node node_num=%d?\n",
                                (int)node_num);
                return -EINVAL;
        }
        return count;
}

static struct kobj_attribute ramster_remote_target_nodenum_attr = {
        .attr = { .name = "remote_target_nodenum", .mode = 0644 },
        .show = ramster_remote_target_nodenum_show,
        .store = ramster_remote_target_nodenum_store,
};


static struct attribute *ramster_attrs[] = {
        &ramster_interface_revision_attr.attr,
        &ramster_pers_remotify_enable_attr.attr,
        &ramster_eph_remotify_enable_attr.attr,
        &ramster_remote_pers_pages_attr.attr,
        &ramster_eph_pages_remoted_attr.attr,
        &ramster_eph_pages_remote_failed_attr.attr,
        &ramster_pers_pages_remoted_attr.attr,
        &ramster_pers_pages_remote_failed_attr.attr,
        &ramster_pers_pages_remote_nomem_attr.attr,
        &ramster_remote_pages_flushed_attr.attr,
        &ramster_remote_page_flushes_failed_attr.attr,
        &ramster_remote_objects_flushed_attr.attr,
        &ramster_remote_object_flushes_failed_attr.attr,
        &ramster_remote_eph_pages_succ_get_attr.attr,
        &ramster_remote_eph_pages_unsucc_get_attr.attr,
        &ramster_remote_pers_pages_succ_get_attr.attr,
        &ramster_remote_pers_pages_unsucc_get_attr.attr,
        &ramster_foreign_eph_pampd_count_attr.attr,
        &ramster_foreign_eph_pampd_count_max_attr.attr,
        &ramster_foreign_pers_pampd_count_attr.attr,
        &ramster_foreign_pers_pampd_count_max_attr.attr,
        &ramster_curr_flnode_count_attr.attr,
        &ramster_curr_flnode_count_max_attr.attr,
        &ramster_manual_node_up_attr.attr,
        &ramster_remote_target_nodenum_attr.attr,
        NULL,
};

static struct attribute_group ramster_attr_group = {
        .attrs = ramster_attrs,
        .name = "ramster",
};

#endif /* CONFIG_SYSFS */
/*
 * When zcache is disabled ("frozen"), pools can be created and destroyed,
 * but all puts (and thus all other operations that require memory allocation)
 * must fail.  If zcache is unfrozen, accepts puts, then frozen again,
 * data consistency requires all puts while frozen to be converted into
 * flushes.
 */
static bool zcache_freeze;

/*
 * zcache shrinker interface (only useful for ephemeral pages, so zbud only)
 */
static int shrink_zcache_memory(struct shrinker *shrink,
                                struct shrink_control *sc)
{
        int ret = -1;
        int nr = sc->nr_to_scan;
        gfp_t gfp_mask = sc->gfp_mask;

        if (nr >= 0) {
                if (!(gfp_mask & __GFP_FS))
                        /* does this case really need to be skipped? */
                        goto out;
                zbud_evict_pages(nr);
        }
        ret = (int)atomic_read(&zcache_zbud_curr_raw_pages);
out:
        return ret;
}

static struct shrinker zcache_shrinker = {
        .shrink = shrink_zcache_memory,
        .seeks = DEFAULT_SEEKS,
};

/*
 * zcache shims between cleancache/frontswap ops and tmem
 */

int zcache_put(int cli_id, int pool_id, struct tmem_oid *oidp,
                        uint32_t index, char *data, size_t size,
                        bool raw, int ephemeral)
{
        struct tmem_pool *pool;
        int ret = -1;

        BUG_ON(!irqs_disabled());
        pool = zcache_get_pool_by_id(cli_id, pool_id);
        if (unlikely(pool == NULL))
                goto out;
        if (!zcache_freeze && zcache_do_preload(pool) == 0) {
                /* preload does preempt_disable on success */
                ret = tmem_put(pool, oidp, index, data, size, raw, ephemeral);
                if (ret < 0) {
                        if (is_ephemeral(pool))
                                zcache_failed_eph_puts++;
                        else
                                zcache_failed_pers_puts++;
                }
                zcache_put_pool(pool);
                preempt_enable_no_resched();
        } else {
                zcache_put_to_flush++;
                if (atomic_read(&pool->obj_count) > 0)
                        /* the put fails whether the flush succeeds or not */
                        (void)tmem_flush_page(pool, oidp, index);
                zcache_put_pool(pool);
        }
out:
        return ret;
}

int zcache_get(int cli_id, int pool_id, struct tmem_oid *oidp,
                        uint32_t index, char *data, size_t *sizep,
                        bool raw, int get_and_free)
{
        struct tmem_pool *pool;
        int ret = -1;
        bool eph;

        if (!raw) {
                BUG_ON(irqs_disabled());
                BUG_ON(in_softirq());
        }
        pool = zcache_get_pool_by_id(cli_id, pool_id);
        eph = is_ephemeral(pool);
        if (likely(pool != NULL)) {
                if (atomic_read(&pool->obj_count) > 0)
                        ret = tmem_get(pool, oidp, index, data, sizep,
                                        raw, get_and_free);
                zcache_put_pool(pool);
        }
        WARN_ONCE((!eph && (ret != 0)), "zcache_get fails on persistent pool, "
                          "bad things are very likely to happen soon\n");
#ifdef RAMSTER_TESTING
        if (ret != 0 && ret != -1 && !(ret == -EINVAL && is_ephemeral(pool)))
                pr_err("TESTING zcache_get tmem_get returns ret=%d\n", ret);
#endif
        if (ret == -EAGAIN)
                BUG(); /* FIXME... don't need this anymore??? let's ensure */
        return ret;
}

int zcache_flush(int cli_id, int pool_id,
                                struct tmem_oid *oidp, uint32_t index)
{
        struct tmem_pool *pool;
        int ret = -1;
        unsigned long flags;

        local_irq_save(flags);
        zcache_flush_total++;
        pool = zcache_get_pool_by_id(cli_id, pool_id);
        ramster_do_preload_flnode_only(pool);
        if (likely(pool != NULL)) {
                if (atomic_read(&pool->obj_count) > 0)
                        ret = tmem_flush_page(pool, oidp, index);
                zcache_put_pool(pool);
        }
        if (ret >= 0)
                zcache_flush_found++;
        local_irq_restore(flags);
        return ret;
}

int zcache_flush_object(int cli_id, int pool_id, struct tmem_oid *oidp)
{
        struct tmem_pool *pool;
        int ret = -1;
        unsigned long flags;

        local_irq_save(flags);
        zcache_flobj_total++;
        pool = zcache_get_pool_by_id(cli_id, pool_id);
        ramster_do_preload_flnode_only(pool);
        if (likely(pool != NULL)) {
                if (atomic_read(&pool->obj_count) > 0)
                        ret = tmem_flush_object(pool, oidp);
                zcache_put_pool(pool);
        }
        if (ret >= 0)
                zcache_flobj_found++;
        local_irq_restore(flags);
        return ret;
}

int zcache_client_destroy_pool(int cli_id, int pool_id)
{
        struct tmem_pool *pool = NULL;
        struct zcache_client *cli = NULL;
        int ret = -1;

        if (pool_id < 0)
                goto out;
        if (cli_id == LOCAL_CLIENT)
                cli = &zcache_host;
        else if ((unsigned int)cli_id < MAX_CLIENTS)
                cli = &zcache_clients[cli_id];
        if (cli == NULL)
                goto out;
        atomic_inc(&cli->refcount);
        pool = cli->tmem_pools[pool_id];
        if (pool == NULL)
                goto out;
        cli->tmem_pools[pool_id] = NULL;
        /* wait for pool activity on other cpus to quiesce */
        while (atomic_read(&pool->refcount) != 0)
                ;
        atomic_dec(&cli->refcount);
        local_bh_disable();
        ret = tmem_destroy_pool(pool);
        local_bh_enable();
        kfree(pool);
        pr_info("ramster: destroyed pool id=%d cli_id=%d\n", pool_id, cli_id);
out:
        return ret;
}

static int zcache_destroy_pool(int pool_id)
{
        return zcache_client_destroy_pool(LOCAL_CLIENT, pool_id);
}

int zcache_new_pool(uint16_t cli_id, uint32_t flags)
{
        int poolid = -1;
        struct tmem_pool *pool;
        struct zcache_client *cli = NULL;

        if (cli_id == LOCAL_CLIENT)
                cli = &zcache_host;
        else if ((unsigned int)cli_id < MAX_CLIENTS)
                cli = &zcache_clients[cli_id];
        if (cli == NULL)
                goto out;
        atomic_inc(&cli->refcount);
        pool = kmalloc(sizeof(struct tmem_pool), GFP_ATOMIC);
        if (pool == NULL) {
                pr_info("ramster: pool creation failed: out of memory\n");
                goto out;
        }

        for (poolid = 0; poolid < MAX_POOLS_PER_CLIENT; poolid++)
                if (cli->tmem_pools[poolid] == NULL)
                        break;
        if (poolid >= MAX_POOLS_PER_CLIENT) {
                pr_info("ramster: pool creation failed: max exceeded\n");
                kfree(pool);
                poolid = -1;
                goto out;
        }
        atomic_set(&pool->refcount, 0);
        pool->client = cli;
        pool->pool_id = poolid;
        tmem_new_pool(pool, flags);
        cli->tmem_pools[poolid] = pool;
        if (cli_id == LOCAL_CLIENT)
                pr_info("ramster: created %s tmem pool, id=%d, local client\n",
                        flags & TMEM_POOL_PERSIST ? "persistent" : "ephemeral",
                        poolid);
        else
                pr_info("ramster: created %s tmem pool, id=%d, client=%d\n",
                        flags & TMEM_POOL_PERSIST ? "persistent" : "ephemeral",
                        poolid, cli_id);
out:
        if (cli != NULL)
                atomic_dec(&cli->refcount);
        return poolid;
}

static int zcache_local_new_pool(uint32_t flags)
{
        return zcache_new_pool(LOCAL_CLIENT, flags);
}

int zcache_autocreate_pool(int cli_id, int pool_id, bool ephemeral)
{
        struct tmem_pool *pool;
        struct zcache_client *cli = NULL;
        uint32_t flags = ephemeral ? 0 : TMEM_POOL_PERSIST;
        int ret = -1;

        if (cli_id == LOCAL_CLIENT)
                goto out;
        if (pool_id >= MAX_POOLS_PER_CLIENT)
                goto out;
        else if ((unsigned int)cli_id < MAX_CLIENTS)
                cli = &zcache_clients[cli_id];
        if ((ephemeral && !use_cleancache) || (!ephemeral && !use_frontswap))
                BUG(); /* FIXME, handle more gracefully later */
        if (!cli->allocated) {
                if (zcache_new_client(cli_id))
                        BUG(); /* FIXME, handle more gracefully later */
                cli = &zcache_clients[cli_id];
        }
        atomic_inc(&cli->refcount);
        pool = cli->tmem_pools[pool_id];
        if (pool != NULL) {
                if (pool->persistent && ephemeral) {
                        pr_err("zcache_autocreate_pool: type mismatch\n");
                        goto out;
                }
                ret = 0;
                goto out;
        }
        pool = kmalloc(sizeof(struct tmem_pool), GFP_KERNEL);
        if (pool == NULL) {
                pr_info("ramster: pool creation failed: out of memory\n");
                goto out;
        }
        atomic_set(&pool->refcount, 0);
        pool->client = cli;
        pool->pool_id = pool_id;
        tmem_new_pool(pool, flags);
        cli->tmem_pools[pool_id] = pool;
        pr_info("ramster: AUTOcreated %s tmem poolid=%d, for remote client=%d\n",
                flags & TMEM_POOL_PERSIST ? "persistent" : "ephemeral",
                pool_id, cli_id);
        ret = 0;
out:
        if (cli == NULL)
                BUG(); /* FIXME, handle more gracefully later */
                /* pr_err("zcache_autocreate_pool: failed\n"); */
        if (cli != NULL)
                atomic_dec(&cli->refcount);
        return ret;
}

/**********
 * Two kernel functionalities currently can be layered on top of tmem.
 * These are "cleancache" which is used as a second-chance cache for clean
 * page cache pages; and "frontswap" which is used for swap pages
 * to avoid writes to disk.  A generic "shim" is provided here for each
 * to translate in-kernel semantics to zcache semantics.
 */

#ifdef CONFIG_CLEANCACHE
static void zcache_cleancache_put_page(int pool_id,
                                        struct cleancache_filekey key,
                                        pgoff_t index, struct page *page)
{
        u32 ind = (u32) index;
        struct tmem_oid oid = *(struct tmem_oid *)&key;

#ifdef __PG_WAS_ACTIVE
        if (!PageWasActive(page)) {
                zcache_nonactive_puts++;
                return;
        }
#endif
        if (likely(ind == index)) {
                char *kva = page_address(page);

                (void)zcache_put(LOCAL_CLIENT, pool_id, &oid, index,
                        kva, PAGE_SIZE, 0, 1);
        }
}

static int zcache_cleancache_get_page(int pool_id,
                                        struct cleancache_filekey key,
                                        pgoff_t index, struct page *page)
{
        u32 ind = (u32) index;
        struct tmem_oid oid = *(struct tmem_oid *)&key;
        int ret = -1;

        preempt_disable();
        if (likely(ind == index)) {
                char *kva = page_address(page);
                size_t size = PAGE_SIZE;

                ret = zcache_get(LOCAL_CLIENT, pool_id, &oid, index,
                        kva, &size, 0, 0);
#ifdef __PG_WAS_ACTIVE
                if (ret == 0)
                        SetPageWasActive(page);
#endif
        }
        preempt_enable();
        return ret;
}

static void zcache_cleancache_flush_page(int pool_id,
                                        struct cleancache_filekey key,
                                        pgoff_t index)
{
        u32 ind = (u32) index;
        struct tmem_oid oid = *(struct tmem_oid *)&key;

        if (likely(ind == index))
                (void)zcache_flush(LOCAL_CLIENT, pool_id, &oid, ind);
}

static void zcache_cleancache_flush_inode(int pool_id,
                                        struct cleancache_filekey key)
{
        struct tmem_oid oid = *(struct tmem_oid *)&key;

        (void)zcache_flush_object(LOCAL_CLIENT, pool_id, &oid);
}

static void zcache_cleancache_flush_fs(int pool_id)
{
        if (pool_id >= 0)
                (void)zcache_destroy_pool(pool_id);
}

static int zcache_cleancache_init_fs(size_t pagesize)
{
        BUG_ON(sizeof(struct cleancache_filekey) !=
                                sizeof(struct tmem_oid));
        BUG_ON(pagesize != PAGE_SIZE);
        return zcache_local_new_pool(0);
}

static int zcache_cleancache_init_shared_fs(char *uuid, size_t pagesize)
{
        /* shared pools are unsupported and map to private */
        BUG_ON(sizeof(struct cleancache_filekey) !=
                                sizeof(struct tmem_oid));
        BUG_ON(pagesize != PAGE_SIZE);
        return zcache_local_new_pool(0);
}

static struct cleancache_ops zcache_cleancache_ops = {
        .put_page = zcache_cleancache_put_page,
        .get_page = zcache_cleancache_get_page,
        .invalidate_page = zcache_cleancache_flush_page,
        .invalidate_inode = zcache_cleancache_flush_inode,
        .invalidate_fs = zcache_cleancache_flush_fs,
        .init_shared_fs = zcache_cleancache_init_shared_fs,
        .init_fs = zcache_cleancache_init_fs
};

struct cleancache_ops zcache_cleancache_register_ops(void)
{
        struct cleancache_ops old_ops =
                cleancache_register_ops(&zcache_cleancache_ops);

        return old_ops;
}
#endif

#ifdef CONFIG_FRONTSWAP
/* a single tmem poolid is used for all frontswap "types" (swapfiles) */
static int zcache_frontswap_poolid = -1;

/*
 * Swizzling increases objects per swaptype, increasing tmem concurrency
 * for heavy swaploads.  Later, larger nr_cpus -> larger SWIZ_BITS
 */
#define SWIZ_BITS               8
#define SWIZ_MASK               ((1 << SWIZ_BITS) - 1)
#define _oswiz(_type, _ind)     ((_type << SWIZ_BITS) | (_ind & SWIZ_MASK))
#define iswiz(_ind)             (_ind >> SWIZ_BITS)

static inline struct tmem_oid oswiz(unsigned type, u32 ind)
{
        struct tmem_oid oid = { .oid = { 0 } };
        oid.oid[0] = _oswiz(type, ind);
        return oid;
}

static int zcache_frontswap_store(unsigned type, pgoff_t offset,
                                   struct page *page)
{
        u64 ind64 = (u64)offset;
        u32 ind = (u32)offset;
        struct tmem_oid oid = oswiz(type, ind);
        int ret = -1;
        unsigned long flags;
        char *kva;

        BUG_ON(!PageLocked(page));
        if (likely(ind64 == ind)) {
                local_irq_save(flags);
                kva = page_address(page);
                ret = zcache_put(LOCAL_CLIENT, zcache_frontswap_poolid,
                                &oid, iswiz(ind), kva, PAGE_SIZE, 0, 0);
                local_irq_restore(flags);
        }
        return ret;
}

/* returns 0 if the page was successfully gotten from frontswap, -1 if
 * was not present (should never happen!) */
static int zcache_frontswap_load(unsigned type, pgoff_t offset,
                                   struct page *page)
{
        u64 ind64 = (u64)offset;
        u32 ind = (u32)offset;
        struct tmem_oid oid = oswiz(type, ind);
        int ret = -1;

        preempt_disable(); /* FIXME, remove this? */
        BUG_ON(!PageLocked(page));
        if (likely(ind64 == ind)) {
                char *kva = page_address(page);
                size_t size = PAGE_SIZE;

                ret = zcache_get(LOCAL_CLIENT, zcache_frontswap_poolid,
                                        &oid, iswiz(ind), kva, &size, 0, -1);
        }
        preempt_enable(); /* FIXME, remove this? */
        return ret;
}

/* flush a single page from frontswap */
static void zcache_frontswap_flush_page(unsigned type, pgoff_t offset)
{
        u64 ind64 = (u64)offset;
        u32 ind = (u32)offset;
        struct tmem_oid oid = oswiz(type, ind);

        if (likely(ind64 == ind))
                (void)zcache_flush(LOCAL_CLIENT, zcache_frontswap_poolid,
                                        &oid, iswiz(ind));
}

/* flush all pages from the passed swaptype */
static void zcache_frontswap_flush_area(unsigned type)
{
        struct tmem_oid oid;
        int ind;

        for (ind = SWIZ_MASK; ind >= 0; ind--) {
                oid = oswiz(type, ind);
                (void)zcache_flush_object(LOCAL_CLIENT,
                                                zcache_frontswap_poolid, &oid);
        }
}

static void zcache_frontswap_init(unsigned ignored)
{
        /* a single tmem poolid is used for all frontswap "types" (swapfiles) */
        if (zcache_frontswap_poolid < 0)
                zcache_frontswap_poolid =
                                zcache_local_new_pool(TMEM_POOL_PERSIST);
}

static struct frontswap_ops zcache_frontswap_ops = {
        .store = zcache_frontswap_store,
        .load = zcache_frontswap_load,
        .invalidate_page = zcache_frontswap_flush_page,
        .invalidate_area = zcache_frontswap_flush_area,
        .init = zcache_frontswap_init
};

struct frontswap_ops zcache_frontswap_register_ops(void)
{
        struct frontswap_ops old_ops =
                frontswap_register_ops(&zcache_frontswap_ops);

        return old_ops;
}
#endif

/*
 * frontswap selfshrinking
 */

#ifdef CONFIG_FRONTSWAP
/* In HZ, controls frequency of worker invocation. */
static unsigned int selfshrink_interval __read_mostly = 5;

static void selfshrink_process(struct work_struct *work);
static DECLARE_DELAYED_WORK(selfshrink_worker, selfshrink_process);

/* Enable/disable with sysfs. */
static bool frontswap_selfshrinking __read_mostly;

/* Enable/disable with kernel boot option. */
static bool use_frontswap_selfshrink __initdata = true;

/*
 * The default values for the following parameters were deemed reasonable
 * by experimentation, may be workload-dependent, and can all be
 * adjusted via sysfs.
 */

/* Control rate for frontswap shrinking. Higher hysteresis is slower. */
static unsigned int frontswap_hysteresis __read_mostly = 20;

/*
 * Number of selfshrink worker invocations to wait before observing that
 * frontswap selfshrinking should commence. Note that selfshrinking does
 * not use a separate worker thread.
 */
static unsigned int frontswap_inertia __read_mostly = 3;

/* Countdown to next invocation of frontswap_shrink() */
static unsigned long frontswap_inertia_counter;

/*
 * Invoked by the selfshrink worker thread, uses current number of pages
 * in frontswap (frontswap_curr_pages()), previous status, and control
 * values (hysteresis and inertia) to determine if frontswap should be
 * shrunk and what the new frontswap size should be.  Note that
 * frontswap_shrink is essentially a partial swapoff that immediately
 * transfers pages from the "swap device" (frontswap) back into kernel
 * RAM; despite the name, frontswap "shrinking" is very different from
 * the "shrinker" interface used by the kernel MM subsystem to reclaim
 * memory.
 */
static void frontswap_selfshrink(void)
{
        static unsigned long cur_frontswap_pages;
        static unsigned long last_frontswap_pages;
        static unsigned long tgt_frontswap_pages;

        last_frontswap_pages = cur_frontswap_pages;
        cur_frontswap_pages = frontswap_curr_pages();
        if (!cur_frontswap_pages ||
                        (cur_frontswap_pages > last_frontswap_pages)) {
                frontswap_inertia_counter = frontswap_inertia;
                return;
        }
        if (frontswap_inertia_counter && --frontswap_inertia_counter)
                return;
        if (cur_frontswap_pages <= frontswap_hysteresis)
                tgt_frontswap_pages = 0;
        else
                tgt_frontswap_pages = cur_frontswap_pages -
                        (cur_frontswap_pages / frontswap_hysteresis);
        frontswap_shrink(tgt_frontswap_pages);
}

static int __init ramster_nofrontswap_selfshrink_setup(char *s)
{
        use_frontswap_selfshrink = false;
        return 1;
}

__setup("noselfshrink", ramster_nofrontswap_selfshrink_setup);

static void selfshrink_process(struct work_struct *work)
{
        if (frontswap_selfshrinking && frontswap_enabled) {
                frontswap_selfshrink();
                schedule_delayed_work(&selfshrink_worker,
                        selfshrink_interval * HZ);
        }
}

static int ramster_enabled;

static int __init ramster_selfshrink_init(void)
{
        frontswap_selfshrinking = ramster_enabled && use_frontswap_selfshrink;
        if (frontswap_selfshrinking)
                pr_info("ramster: Initializing frontswap "
                                        "selfshrinking driver.\n");
        else
                return -ENODEV;

        schedule_delayed_work(&selfshrink_worker, selfshrink_interval * HZ);

        return 0;
}

subsys_initcall(ramster_selfshrink_init);
#endif

/*
 * zcache initialization
 * NOTE FOR NOW ramster MUST BE PROVIDED AS A KERNEL BOOT PARAMETER OR
 * NOTHING HAPPENS!
 */

static int ramster_enabled;

static int __init enable_ramster(char *s)
{
        ramster_enabled = 1;
        return 1;
}
__setup("ramster", enable_ramster);

/* allow independent dynamic disabling of cleancache and frontswap */

static int use_cleancache = 1;

static int __init no_cleancache(char *s)
{
        pr_info("INIT no_cleancache called\n");
        use_cleancache = 0;
        return 1;
}

/*
 * FIXME: need to guarantee this gets checked before zcache_init is called
 * What is the correct way to achieve this?
 */
early_param("nocleancache", no_cleancache);

static int use_frontswap = 1;

static int __init no_frontswap(char *s)
{
        pr_info("INIT no_frontswap called\n");
        use_frontswap = 0;
        return 1;
}

__setup("nofrontswap", no_frontswap);

static int __init zcache_init(void)
{
        int ret = 0;

#ifdef CONFIG_SYSFS
        ret = sysfs_create_group(mm_kobj, &zcache_attr_group);
        ret = sysfs_create_group(mm_kobj, &ramster_attr_group);
        if (ret) {
                pr_err("ramster: can't create sysfs\n");
                goto out;
        }
#endif /* CONFIG_SYSFS */
#if defined(CONFIG_CLEANCACHE) || defined(CONFIG_FRONTSWAP)
        if (ramster_enabled) {
                unsigned int cpu;

                (void)r2net_register_handlers();
                tmem_register_hostops(&zcache_hostops);
                tmem_register_pamops(&zcache_pamops);
                ret = register_cpu_notifier(&zcache_cpu_notifier_block);
                if (ret) {
                        pr_err("ramster: can't register cpu notifier\n");
                        goto out;
                }
                for_each_online_cpu(cpu) {
                        void *pcpu = (void *)(long)cpu;
                        zcache_cpu_notifier(&zcache_cpu_notifier_block,
                                CPU_UP_PREPARE, pcpu);
                }
        }
        zcache_objnode_cache = kmem_cache_create("zcache_objnode",
                                sizeof(struct tmem_objnode), 0, 0, NULL);
        zcache_obj_cache = kmem_cache_create("zcache_obj",
                                sizeof(struct tmem_obj), 0, 0, NULL);
        ramster_flnode_cache = kmem_cache_create("ramster_flnode",
                                sizeof(struct flushlist_node), 0, 0, NULL);
#endif
#ifdef CONFIG_CLEANCACHE
        pr_info("INIT ramster_enabled=%d use_cleancache=%d\n",
                                        ramster_enabled, use_cleancache);
        if (ramster_enabled && use_cleancache) {
                struct cleancache_ops old_ops;

                zbud_init();
                register_shrinker(&zcache_shrinker);
                old_ops = zcache_cleancache_register_ops();
                pr_info("ramster: cleancache enabled using kernel "
                        "transcendent memory and compression buddies\n");
                if (old_ops.init_fs != NULL)
                        pr_warning("ramster: cleancache_ops overridden");
        }
#endif
#ifdef CONFIG_FRONTSWAP
        pr_info("INIT ramster_enabled=%d use_frontswap=%d\n",
                                        ramster_enabled, use_frontswap);
        if (ramster_enabled && use_frontswap) {
                struct frontswap_ops old_ops;

                zcache_new_client(LOCAL_CLIENT);
                old_ops = zcache_frontswap_register_ops();
                pr_info("ramster: frontswap enabled using kernel "
                        "transcendent memory and xvmalloc\n");
                if (old_ops.init != NULL)
                        pr_warning("ramster: frontswap_ops overridden");
        }
        if (ramster_enabled && (use_frontswap || use_cleancache))
                ramster_remotify_init();
#endif
out:
        return ret;
}

module_init(zcache_init)