[PATCH] add bottom_half.h

[linux/fpc-iii.git] / fs / lockd / svclock.c

/*
 * linux/fs/lockd/svclock.c
 *
 * Handling of server-side locks, mostly of the blocked variety.
 * This is the ugliest part of lockd because we tread on very thin ice.
 * GRANT and CANCEL calls may get stuck, meet in mid-flight, etc.
 * IMNSHO introducing the grant callback into the NLM protocol was one
 * of the worst ideas Sun ever had. Except maybe for the idea of doing
 * NFS file locking at all.
 *
 * I'm trying hard to avoid race conditions by protecting most accesses
 * to a file's list of blocked locks through a semaphore. The global
 * list of blocked locks is not protected in this fashion however.
 * Therefore, some functions (such as the RPC callback for the async grant
 * call) move blocked locks towards the head of the list *while some other
 * process might be traversing it*. This should not be a problem in
 * practice, because this will only cause functions traversing the list
 * to visit some blocks twice.
 *
 * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/svc.h>
#include <linux/lockd/nlm.h>
#include <linux/lockd/lockd.h>

#define NLMDBG_FACILITY         NLMDBG_SVCLOCK

#ifdef CONFIG_LOCKD_V4
#define nlm_deadlock    nlm4_deadlock
#else
#define nlm_deadlock    nlm_lck_denied
#endif

static void nlmsvc_release_block(struct nlm_block *block);
static void     nlmsvc_insert_block(struct nlm_block *block, unsigned long);
static void     nlmsvc_remove_block(struct nlm_block *block);

static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock);
static void nlmsvc_freegrantargs(struct nlm_rqst *call);
static const struct rpc_call_ops nlmsvc_grant_ops;

/*
 * The list of blocked locks to retry
 */
static LIST_HEAD(nlm_blocked);

/*
 * Insert a blocked lock into the global list
 */
static void
nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
{
        struct nlm_block *b;
        struct list_head *pos;

        dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
        if (list_empty(&block->b_list)) {
                kref_get(&block->b_count);
        } else {
                list_del_init(&block->b_list);
        }

        pos = &nlm_blocked;
        if (when != NLM_NEVER) {
                if ((when += jiffies) == NLM_NEVER)
                        when ++;
                list_for_each(pos, &nlm_blocked) {
                        b = list_entry(pos, struct nlm_block, b_list);
                        if (time_after(b->b_when,when) || b->b_when == NLM_NEVER)
                                break;
                }
                /* On normal exit from the loop, pos == &nlm_blocked,
                 * so we will be adding to the end of the list - good
                 */
        }

        list_add_tail(&block->b_list, pos);
        block->b_when = when;
}

/*
 * Remove a block from the global list
 */
static inline void
nlmsvc_remove_block(struct nlm_block *block)
{
        if (!list_empty(&block->b_list)) {
                list_del_init(&block->b_list);
                nlmsvc_release_block(block);
        }
}

/*
 * Find a block for a given lock
 */
static struct nlm_block *
nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
{
        struct nlm_block        *block;
        struct file_lock        *fl;

        dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
                                file, lock->fl.fl_pid,
                                (long long)lock->fl.fl_start,
                                (long long)lock->fl.fl_end, lock->fl.fl_type);
        list_for_each_entry(block, &nlm_blocked, b_list) {
                fl = &block->b_call->a_args.lock.fl;
                dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
                                block->b_file, fl->fl_pid,
                                (long long)fl->fl_start,
                                (long long)fl->fl_end, fl->fl_type,
                                nlmdbg_cookie2a(&block->b_call->a_args.cookie));
                if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
                        kref_get(&block->b_count);
                        return block;
                }
        }

        return NULL;
}

static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
{
        if(a->len != b->len)
                return 0;
        if(memcmp(a->data,b->data,a->len))
                return 0;
        return 1;
}

/*
 * Find a block with a given NLM cookie.
 */
static inline struct nlm_block *
nlmsvc_find_block(struct nlm_cookie *cookie)
{
        struct nlm_block *block;

        list_for_each_entry(block, &nlm_blocked, b_list) {
                if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie))
                        goto found;
        }

        return NULL;

found:
        dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block);
        kref_get(&block->b_count);
        return block;
}

/*
 * Create a block and initialize it.
 *
 * Note: we explicitly set the cookie of the grant reply to that of
 * the blocked lock request. The spec explicitly mentions that the client
 * should _not_ rely on the callback containing the same cookie as the
 * request, but (as I found out later) that's because some implementations
 * do just this. Never mind the standards comittees, they support our
 * logging industries.
 *
 * 10 years later: I hope we can safely ignore these old and broken
 * clients by now. Let's fix this so we can uniquely identify an incoming
 * GRANTED_RES message by cookie, without having to rely on the client's IP
 * address. --okir
 */
static inline struct nlm_block *
nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
                                struct nlm_lock *lock, struct nlm_cookie *cookie)
{
        struct nlm_block        *block;
        struct nlm_host         *host;
        struct nlm_rqst         *call = NULL;

        /* Create host handle for callback */
        host = nlmsvc_lookup_host(rqstp, lock->caller, lock->len);
        if (host == NULL)
                return NULL;

        call = nlm_alloc_call(host);
        if (call == NULL)
                return NULL;

        /* Allocate memory for block, and initialize arguments */
        block = kzalloc(sizeof(*block), GFP_KERNEL);
        if (block == NULL)
                goto failed;
        kref_init(&block->b_count);
        INIT_LIST_HEAD(&block->b_list);
        INIT_LIST_HEAD(&block->b_flist);

        if (!nlmsvc_setgrantargs(call, lock))
                goto failed_free;

        /* Set notifier function for VFS, and init args */
        call->a_args.lock.fl.fl_flags |= FL_SLEEP;
        call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
        nlmclnt_next_cookie(&call->a_args.cookie);

        dprintk("lockd: created block %p...\n", block);

        /* Create and initialize the block */
        block->b_daemon = rqstp->rq_server;
        block->b_host   = host;
        block->b_file   = file;
        file->f_count++;

        /* Add to file's list of blocks */
        list_add(&block->b_flist, &file->f_blocks);

        /* Set up RPC arguments for callback */
        block->b_call = call;
        call->a_flags   = RPC_TASK_ASYNC;
        call->a_block = block;

        return block;

failed_free:
        kfree(block);
failed:
        nlm_release_call(call);
        return NULL;
}

/*
 * Delete a block. If the lock was cancelled or the grant callback
 * failed, unlock is set to 1.
 * It is the caller's responsibility to check whether the file
 * can be closed hereafter.
 */
static int nlmsvc_unlink_block(struct nlm_block *block)
{
        int status;
        dprintk("lockd: unlinking block %p...\n", block);

        /* Remove block from list */
        status = posix_unblock_lock(block->b_file->f_file, &block->b_call->a_args.lock.fl);
        nlmsvc_remove_block(block);
        return status;
}

static void nlmsvc_free_block(struct kref *kref)
{
        struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
        struct nlm_file         *file = block->b_file;

        dprintk("lockd: freeing block %p...\n", block);

        /* Remove block from file's list of blocks */
        mutex_lock(&file->f_mutex);
        list_del_init(&block->b_flist);
        mutex_unlock(&file->f_mutex);

        nlmsvc_freegrantargs(block->b_call);
        nlm_release_call(block->b_call);
        nlm_release_file(block->b_file);
        kfree(block);
}

static void nlmsvc_release_block(struct nlm_block *block)
{
        if (block != NULL)
                kref_put(&block->b_count, nlmsvc_free_block);
}

/*
 * Loop over all blocks and delete blocks held by
 * a matching host.
 */
void nlmsvc_traverse_blocks(struct nlm_host *host,
                        struct nlm_file *file,
                        nlm_host_match_fn_t match)
{
        struct nlm_block *block, *next;

restart:
        mutex_lock(&file->f_mutex);
        list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
                if (!match(block->b_host, host))
                        continue;
                /* Do not destroy blocks that are not on
                 * the global retry list - why? */
                if (list_empty(&block->b_list))
                        continue;
                kref_get(&block->b_count);
                mutex_unlock(&file->f_mutex);
                nlmsvc_unlink_block(block);
                nlmsvc_release_block(block);
                goto restart;
        }
        mutex_unlock(&file->f_mutex);
}

/*
 * Initialize arguments for GRANTED call. The nlm_rqst structure
 * has been cleared already.
 */
static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
{
        locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
        memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
        call->a_args.lock.caller = utsname()->nodename;
        call->a_args.lock.oh.len = lock->oh.len;

        /* set default data area */
        call->a_args.lock.oh.data = call->a_owner;
        call->a_args.lock.svid = lock->fl.fl_pid;

        if (lock->oh.len > NLMCLNT_OHSIZE) {
                void *data = kmalloc(lock->oh.len, GFP_KERNEL);
                if (!data)
                        return 0;
                call->a_args.lock.oh.data = (u8 *) data;
        }

        memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
        return 1;
}

static void nlmsvc_freegrantargs(struct nlm_rqst *call)
{
        if (call->a_args.lock.oh.data != call->a_owner)
                kfree(call->a_args.lock.oh.data);
}

/*
 * Attempt to establish a lock, and if it can't be granted, block it
 * if required.
 */
__be32
nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
                        struct nlm_lock *lock, int wait, struct nlm_cookie *cookie)
{
        struct nlm_block        *block, *newblock = NULL;
        int                     error;
        __be32                  ret;

        dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
                                file->f_file->f_dentry->d_inode->i_sb->s_id,
                                file->f_file->f_dentry->d_inode->i_ino,
                                lock->fl.fl_type, lock->fl.fl_pid,
                                (long long)lock->fl.fl_start,
                                (long long)lock->fl.fl_end,
                                wait);


        lock->fl.fl_flags &= ~FL_SLEEP;
again:
        /* Lock file against concurrent access */
        mutex_lock(&file->f_mutex);
        /* Get existing block (in case client is busy-waiting) */
        block = nlmsvc_lookup_block(file, lock);
        if (block == NULL) {
                if (newblock != NULL)
                        lock = &newblock->b_call->a_args.lock;
        } else
                lock = &block->b_call->a_args.lock;

        error = posix_lock_file(file->f_file, &lock->fl);
        lock->fl.fl_flags &= ~FL_SLEEP;

        dprintk("lockd: posix_lock_file returned %d\n", error);

        switch(error) {
                case 0:
                        ret = nlm_granted;
                        goto out;
                case -EAGAIN:
                        break;
                case -EDEADLK:
                        ret = nlm_deadlock;
                        goto out;
                default:                        /* includes ENOLCK */
                        ret = nlm_lck_denied_nolocks;
                        goto out;
        }

        ret = nlm_lck_denied;
        if (!wait)
                goto out;

        ret = nlm_lck_blocked;
        if (block != NULL)
                goto out;

        /* If we don't have a block, create and initialize it. Then
         * retry because we may have slept in kmalloc. */
        /* We have to release f_mutex as nlmsvc_create_block may try to
         * to claim it while doing host garbage collection */
        if (newblock == NULL) {
                mutex_unlock(&file->f_mutex);
                dprintk("lockd: blocking on this lock (allocating).\n");
                if (!(newblock = nlmsvc_create_block(rqstp, file, lock, cookie)))
                        return nlm_lck_denied_nolocks;
                goto again;
        }

        /* Append to list of blocked */
        nlmsvc_insert_block(newblock, NLM_NEVER);
out:
        mutex_unlock(&file->f_mutex);
        nlmsvc_release_block(newblock);
        nlmsvc_release_block(block);
        dprintk("lockd: nlmsvc_lock returned %u\n", ret);
        return ret;
}

/*
 * Test for presence of a conflicting lock.
 */
__be32
nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock,
                                       struct nlm_lock *conflock)
{
        dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
                                file->f_file->f_dentry->d_inode->i_sb->s_id,
                                file->f_file->f_dentry->d_inode->i_ino,
                                lock->fl.fl_type,
                                (long long)lock->fl.fl_start,
                                (long long)lock->fl.fl_end);

        if (posix_test_lock(file->f_file, &lock->fl, &conflock->fl)) {
                dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
                                conflock->fl.fl_type,
                                (long long)conflock->fl.fl_start,
                                (long long)conflock->fl.fl_end);
                conflock->caller = "somehost";  /* FIXME */
                conflock->len = strlen(conflock->caller);
                conflock->oh.len = 0;           /* don't return OH info */
                conflock->svid = conflock->fl.fl_pid;
                return nlm_lck_denied;
        }

        return nlm_granted;
}

/*
 * Remove a lock.
 * This implies a CANCEL call: We send a GRANT_MSG, the client replies
 * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
 * afterwards. In this case the block will still be there, and hence
 * must be removed.
 */
__be32
nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
{
        int     error;

        dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
                                file->f_file->f_dentry->d_inode->i_sb->s_id,
                                file->f_file->f_dentry->d_inode->i_ino,
                                lock->fl.fl_pid,
                                (long long)lock->fl.fl_start,
                                (long long)lock->fl.fl_end);

        /* First, cancel any lock that might be there */
        nlmsvc_cancel_blocked(file, lock);

        lock->fl.fl_type = F_UNLCK;
        error = posix_lock_file(file->f_file, &lock->fl);

        return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
}

/*
 * Cancel a previously blocked request.
 *
 * A cancel request always overrides any grant that may currently
 * be in progress.
 * The calling procedure must check whether the file can be closed.
 */
__be32
nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
{
        struct nlm_block        *block;
        int status = 0;

        dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
                                file->f_file->f_dentry->d_inode->i_sb->s_id,
                                file->f_file->f_dentry->d_inode->i_ino,
                                lock->fl.fl_pid,
                                (long long)lock->fl.fl_start,
                                (long long)lock->fl.fl_end);

        mutex_lock(&file->f_mutex);
        block = nlmsvc_lookup_block(file, lock);
        mutex_unlock(&file->f_mutex);
        if (block != NULL) {
                status = nlmsvc_unlink_block(block);
                nlmsvc_release_block(block);
        }
        return status ? nlm_lck_denied : nlm_granted;
}

/*
 * Unblock a blocked lock request. This is a callback invoked from the
 * VFS layer when a lock on which we blocked is removed.
 *
 * This function doesn't grant the blocked lock instantly, but rather moves
 * the block to the head of nlm_blocked where it can be picked up by lockd.
 */
static void
nlmsvc_notify_blocked(struct file_lock *fl)
{
        struct nlm_block        *block;

        dprintk("lockd: VFS unblock notification for block %p\n", fl);
        list_for_each_entry(block, &nlm_blocked, b_list) {
                if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
                        nlmsvc_insert_block(block, 0);
                        svc_wake_up(block->b_daemon);
                        return;
                }
        }

        printk(KERN_WARNING "lockd: notification for unknown block!\n");
}

static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
{
        return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
}

struct lock_manager_operations nlmsvc_lock_operations = {
        .fl_compare_owner = nlmsvc_same_owner,
        .fl_notify = nlmsvc_notify_blocked,
};

/*
 * Try to claim a lock that was previously blocked.
 *
 * Note that we use both the RPC_GRANTED_MSG call _and_ an async
 * RPC thread when notifying the client. This seems like overkill...
 * Here's why:
 *  -   we don't want to use a synchronous RPC thread, otherwise
 *      we might find ourselves hanging on a dead portmapper.
 *  -   Some lockd implementations (e.g. HP) don't react to
 *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
 */
static void
nlmsvc_grant_blocked(struct nlm_block *block)
{
        struct nlm_file         *file = block->b_file;
        struct nlm_lock         *lock = &block->b_call->a_args.lock;
        int                     error;

        dprintk("lockd: grant blocked lock %p\n", block);

        /* Unlink block request from list */
        nlmsvc_unlink_block(block);

        /* If b_granted is true this means we've been here before.
         * Just retry the grant callback, possibly refreshing the RPC
         * binding */
        if (block->b_granted) {
                nlm_rebind_host(block->b_host);
                goto callback;
        }

        /* Try the lock operation again */
        lock->fl.fl_flags |= FL_SLEEP;
        error = posix_lock_file(file->f_file, &lock->fl);
        lock->fl.fl_flags &= ~FL_SLEEP;

        switch (error) {
        case 0:
                break;
        case -EAGAIN:
                dprintk("lockd: lock still blocked\n");
                nlmsvc_insert_block(block, NLM_NEVER);
                return;
        default:
                printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
                                -error, __FUNCTION__);
                nlmsvc_insert_block(block, 10 * HZ);
                return;
        }

callback:
        /* Lock was granted by VFS. */
        dprintk("lockd: GRANTing blocked lock.\n");
        block->b_granted = 1;

        /* Schedule next grant callback in 30 seconds */
        nlmsvc_insert_block(block, 30 * HZ);

        /* Call the client */
        kref_get(&block->b_count);
        if (nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
                                                &nlmsvc_grant_ops) < 0)
                nlmsvc_release_block(block);
}

/*
 * This is the callback from the RPC layer when the NLM_GRANTED_MSG
 * RPC call has succeeded or timed out.
 * Like all RPC callbacks, it is invoked by the rpciod process, so it
 * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
 * chain once more in order to have it removed by lockd itself (which can
 * then sleep on the file semaphore without disrupting e.g. the nfs client).
 */
static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
{
        struct nlm_rqst         *call = data;
        struct nlm_block        *block = call->a_block;
        unsigned long           timeout;

        dprintk("lockd: GRANT_MSG RPC callback\n");

        /* Technically, we should down the file semaphore here. Since we
         * move the block towards the head of the queue only, no harm
         * can be done, though. */
        if (task->tk_status < 0) {
                /* RPC error: Re-insert for retransmission */
                timeout = 10 * HZ;
        } else {
                /* Call was successful, now wait for client callback */
                timeout = 60 * HZ;
        }
        nlmsvc_insert_block(block, timeout);
        svc_wake_up(block->b_daemon);
}

static void nlmsvc_grant_release(void *data)
{
        struct nlm_rqst         *call = data;

        nlmsvc_release_block(call->a_block);
}

static const struct rpc_call_ops nlmsvc_grant_ops = {
        .rpc_call_done = nlmsvc_grant_callback,
        .rpc_release = nlmsvc_grant_release,
};

/*
 * We received a GRANT_RES callback. Try to find the corresponding
 * block.
 */
void
nlmsvc_grant_reply(struct nlm_cookie *cookie, u32 status)
{
        struct nlm_block        *block;

        dprintk("grant_reply: looking for cookie %x, s=%d \n",
                *(unsigned int *)(cookie->data), status);
        if (!(block = nlmsvc_find_block(cookie)))
                return;

        if (block) {
                if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
                        /* Try again in a couple of seconds */
                        nlmsvc_insert_block(block, 10 * HZ);
                } else {
                        /* Lock is now held by client, or has been rejected.
                         * In both cases, the block should be removed. */
                        nlmsvc_unlink_block(block);
                }
        }
        nlmsvc_release_block(block);
}

/*
 * Retry all blocked locks that have been notified. This is where lockd
 * picks up locks that can be granted, or grant notifications that must
 * be retransmitted.
 */
unsigned long
nlmsvc_retry_blocked(void)
{
        unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
        struct nlm_block *block;

        while (!list_empty(&nlm_blocked)) {
                block = list_entry(nlm_blocked.next, struct nlm_block, b_list);

                if (block->b_when == NLM_NEVER)
                        break;
                if (time_after(block->b_when,jiffies)) {
                        timeout = block->b_when - jiffies;
                        break;
                }

                dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
                        block, block->b_when);
                kref_get(&block->b_count);
                nlmsvc_grant_blocked(block);
                nlmsvc_release_block(block);
        }

        return timeout;
}