Linux v2.6.13

[linux-2.6/next.git] / fs / nfs / pagelist.c

/*
 * linux/fs/nfs/pagelist.c
 *
 * A set of helper functions for managing NFS read and write requests.
 * The main purpose of these routines is to provide support for the
 * coalescing of several requests into a single RPC call.
 *
 * Copyright 2000, 2001 (c) Trond Myklebust <trond.myklebust@fys.uio.no>
 *
 */

#include <linux/config.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfs3.h>
#include <linux/nfs4.h>
#include <linux/nfs_page.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>

#define NFS_PARANOIA 1

static kmem_cache_t *nfs_page_cachep;

static inline struct nfs_page *
nfs_page_alloc(void)
{
        struct nfs_page *p;
        p = kmem_cache_alloc(nfs_page_cachep, SLAB_KERNEL);
        if (p) {
                memset(p, 0, sizeof(*p));
                INIT_LIST_HEAD(&p->wb_list);
        }
        return p;
}

static inline void
nfs_page_free(struct nfs_page *p)
{
        kmem_cache_free(nfs_page_cachep, p);
}

/**
 * nfs_create_request - Create an NFS read/write request.
 * @file: file descriptor to use
 * @inode: inode to which the request is attached
 * @page: page to write
 * @offset: starting offset within the page for the write
 * @count: number of bytes to read/write
 *
 * The page must be locked by the caller. This makes sure we never
 * create two different requests for the same page, and avoids
 * a possible deadlock when we reach the hard limit on the number
 * of dirty pages.
 * User should ensure it is safe to sleep in this function.
 */
struct nfs_page *
nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
                   struct page *page,
                   unsigned int offset, unsigned int count)
{
        struct nfs_server *server = NFS_SERVER(inode);
        struct nfs_page         *req;

        /* Deal with hard limits.  */
        for (;;) {
                /* try to allocate the request struct */
                req = nfs_page_alloc();
                if (req != NULL)
                        break;

                /* Try to free up at least one request in order to stay
                 * below the hard limit
                 */
                if (signalled() && (server->flags & NFS_MOUNT_INTR))
                        return ERR_PTR(-ERESTARTSYS);
                yield();
        }

        /* Initialize the request struct. Initially, we assume a
         * long write-back delay. This will be adjusted in
         * update_nfs_request below if the region is not locked. */
        req->wb_page    = page;
        atomic_set(&req->wb_complete, 0);
        req->wb_index   = page->index;
        page_cache_get(page);
        req->wb_offset  = offset;
        req->wb_pgbase  = offset;
        req->wb_bytes   = count;
        atomic_set(&req->wb_count, 1);
        req->wb_context = get_nfs_open_context(ctx);

        return req;
}

/**
 * nfs_unlock_request - Unlock request and wake up sleepers.
 * @req:
 */
void nfs_unlock_request(struct nfs_page *req)
{
        if (!NFS_WBACK_BUSY(req)) {
                printk(KERN_ERR "NFS: Invalid unlock attempted\n");
                BUG();
        }
        smp_mb__before_clear_bit();
        clear_bit(PG_BUSY, &req->wb_flags);
        smp_mb__after_clear_bit();
        wake_up_bit(&req->wb_flags, PG_BUSY);
        nfs_release_request(req);
}

/**
 * nfs_set_page_writeback_locked - Lock a request for writeback
 * @req:
 */
int nfs_set_page_writeback_locked(struct nfs_page *req)
{
        struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);

        if (!nfs_lock_request(req))
                return 0;
        radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
        return 1;
}

/**
 * nfs_clear_page_writeback - Unlock request and wake up sleepers
 */
void nfs_clear_page_writeback(struct nfs_page *req)
{
        struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);

        spin_lock(&nfsi->req_lock);
        radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
        spin_unlock(&nfsi->req_lock);
        nfs_unlock_request(req);
}

/**
 * nfs_clear_request - Free up all resources allocated to the request
 * @req:
 *
 * Release page resources associated with a write request after it
 * has completed.
 */
void nfs_clear_request(struct nfs_page *req)
{
        if (req->wb_page) {
                page_cache_release(req->wb_page);
                req->wb_page = NULL;
        }
}


/**
 * nfs_release_request - Release the count on an NFS read/write request
 * @req: request to release
 *
 * Note: Should never be called with the spinlock held!
 */
void
nfs_release_request(struct nfs_page *req)
{
        if (!atomic_dec_and_test(&req->wb_count))
                return;

#ifdef NFS_PARANOIA
        BUG_ON (!list_empty(&req->wb_list));
        BUG_ON (NFS_WBACK_BUSY(req));
#endif

        /* Release struct file or cached credential */
        nfs_clear_request(req);
        put_nfs_open_context(req->wb_context);
        nfs_page_free(req);
}

static int nfs_wait_bit_interruptible(void *word)
{
        int ret = 0;

        if (signal_pending(current))
                ret = -ERESTARTSYS;
        else
                schedule();
        return ret;
}

/**
 * nfs_wait_on_request - Wait for a request to complete.
 * @req: request to wait upon.
 *
 * Interruptible by signals only if mounted with intr flag.
 * The user is responsible for holding a count on the request.
 */
int
nfs_wait_on_request(struct nfs_page *req)
{
        struct rpc_clnt *clnt = NFS_CLIENT(req->wb_context->dentry->d_inode);
        sigset_t oldmask;
        int ret = 0;

        if (!test_bit(PG_BUSY, &req->wb_flags))
                goto out;
        /*
         * Note: the call to rpc_clnt_sigmask() suffices to ensure that we
         *       are not interrupted if intr flag is not set
         */
        rpc_clnt_sigmask(clnt, &oldmask);
        ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY,
                        nfs_wait_bit_interruptible, TASK_INTERRUPTIBLE);
        rpc_clnt_sigunmask(clnt, &oldmask);
out:
        return ret;
}

/**
 * nfs_coalesce_requests - Split coalesced requests out from a list.
 * @head: source list
 * @dst: destination list
 * @nmax: maximum number of requests to coalesce
 *
 * Moves a maximum of 'nmax' elements from one list to another.
 * The elements are checked to ensure that they form a contiguous set
 * of pages, and that the RPC credentials are the same.
 */
int
nfs_coalesce_requests(struct list_head *head, struct list_head *dst,
                      unsigned int nmax)
{
        struct nfs_page         *req = NULL;
        unsigned int            npages = 0;

        while (!list_empty(head)) {
                struct nfs_page *prev = req;

                req = nfs_list_entry(head->next);
                if (prev) {
                        if (req->wb_context->cred != prev->wb_context->cred)
                                break;
                        if (req->wb_context->lockowner != prev->wb_context->lockowner)
                                break;
                        if (req->wb_context->state != prev->wb_context->state)
                                break;
                        if (req->wb_index != (prev->wb_index + 1))
                                break;

                        if (req->wb_pgbase != 0)
                                break;
                }
                nfs_list_remove_request(req);
                nfs_list_add_request(req, dst);
                npages++;
                if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE)
                        break;
                if (npages >= nmax)
                        break;
        }
        return npages;
}

#define NFS_SCAN_MAXENTRIES 16
/**
 * nfs_scan_lock_dirty - Scan the radix tree for dirty requests
 * @nfsi: NFS inode
 * @dst: Destination list
 * @idx_start: lower bound of page->index to scan
 * @npages: idx_start + npages sets the upper bound to scan.
 *
 * Moves elements from one of the inode request lists.
 * If the number of requests is set to 0, the entire address_space
 * starting at index idx_start, is scanned.
 * The requests are *not* checked to ensure that they form a contiguous set.
 * You must be holding the inode's req_lock when calling this function
 */
int
nfs_scan_lock_dirty(struct nfs_inode *nfsi, struct list_head *dst,
              unsigned long idx_start, unsigned int npages)
{
        struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
        struct nfs_page *req;
        unsigned long idx_end;
        int found, i;
        int res;

        res = 0;
        if (npages == 0)
                idx_end = ~0;
        else
                idx_end = idx_start + npages - 1;

        for (;;) {
                found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
                                (void **)&pgvec[0], idx_start, NFS_SCAN_MAXENTRIES,
                                NFS_PAGE_TAG_DIRTY);
                if (found <= 0)
                        break;
                for (i = 0; i < found; i++) {
                        req = pgvec[i];
                        if (req->wb_index > idx_end)
                                goto out;

                        idx_start = req->wb_index + 1;

                        if (nfs_set_page_writeback_locked(req)) {
                                radix_tree_tag_clear(&nfsi->nfs_page_tree,
                                                req->wb_index, NFS_PAGE_TAG_DIRTY);
                                nfs_list_remove_request(req);
                                nfs_list_add_request(req, dst);
                                res++;
                        }
                }
        }
out:
        return res;
}

/**
 * nfs_scan_list - Scan a list for matching requests
 * @head: One of the NFS inode request lists
 * @dst: Destination list
 * @idx_start: lower bound of page->index to scan
 * @npages: idx_start + npages sets the upper bound to scan.
 *
 * Moves elements from one of the inode request lists.
 * If the number of requests is set to 0, the entire address_space
 * starting at index idx_start, is scanned.
 * The requests are *not* checked to ensure that they form a contiguous set.
 * You must be holding the inode's req_lock when calling this function
 */
int
nfs_scan_list(struct list_head *head, struct list_head *dst,
              unsigned long idx_start, unsigned int npages)
{
        struct list_head        *pos, *tmp;
        struct nfs_page         *req;
        unsigned long           idx_end;
        int                     res;

        res = 0;
        if (npages == 0)
                idx_end = ~0;
        else
                idx_end = idx_start + npages - 1;

        list_for_each_safe(pos, tmp, head) {

                req = nfs_list_entry(pos);

                if (req->wb_index < idx_start)
                        continue;
                if (req->wb_index > idx_end)
                        break;

                if (!nfs_set_page_writeback_locked(req))
                        continue;
                nfs_list_remove_request(req);
                nfs_list_add_request(req, dst);
                res++;
        }
        return res;
}

int nfs_init_nfspagecache(void)
{
        nfs_page_cachep = kmem_cache_create("nfs_page",
                                            sizeof(struct nfs_page),
                                            0, SLAB_HWCACHE_ALIGN,
                                            NULL, NULL);
        if (nfs_page_cachep == NULL)
                return -ENOMEM;

        return 0;
}

void nfs_destroy_nfspagecache(void)
{
        if (kmem_cache_destroy(nfs_page_cachep))
                printk(KERN_INFO "nfs_page: not all structures were freed\n");
}