diff options
Diffstat (limited to 'fs/lockd/svclock.c')
| -rw-r--r-- | fs/lockd/svclock.c | 1054 |
1 files changed, 1054 insertions, 0 deletions
diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c new file mode 100644 index 0000000000..43aeba9de5 --- /dev/null +++ b/fs/lockd/svclock.c @@ -0,0 +1,1054 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * 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/slab.h> +#include <linux/errno.h> +#include <linux/kernel.h> +#include <linux/sched.h> +#include <linux/sunrpc/clnt.h> +#include <linux/sunrpc/svc_xprt.h> +#include <linux/lockd/nlm.h> +#include <linux/lockd/lockd.h> +#include <linux/kthread.h> +#include <linux/exportfs.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); +static DEFINE_SPINLOCK(nlm_blocked_lock); + +#if IS_ENABLED(CONFIG_SUNRPC_DEBUG) +static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie) +{ + /* + * We can get away with a static buffer because this is only called + * from lockd, which is single-threaded. + */ + static char buf[2*NLM_MAXCOOKIELEN+1]; + unsigned int i, len = sizeof(buf); + char *p = buf; + + len--; /* allow for trailing \0 */ + if (len < 3) + return "???"; + for (i = 0 ; i < cookie->len ; i++) { + if (len < 2) { + strcpy(p-3, "..."); + break; + } + sprintf(p, "%02x", cookie->data[i]); + p += 2; + len -= 2; + } + *p = '\0'; + + return buf; +} +#endif + +/* + * Insert a blocked lock into the global list + */ +static void +nlmsvc_insert_block_locked(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; +} + +static void nlmsvc_insert_block(struct nlm_block *block, unsigned long when) +{ + spin_lock(&nlm_blocked_lock); + nlmsvc_insert_block_locked(block, when); + spin_unlock(&nlm_blocked_lock); +} + +/* + * Remove a block from the global list + */ +static inline void +nlmsvc_remove_block(struct nlm_block *block) +{ + spin_lock(&nlm_blocked_lock); + if (!list_empty(&block->b_list)) { + list_del_init(&block->b_list); + spin_unlock(&nlm_blocked_lock); + nlmsvc_release_block(block); + return; + } + spin_unlock(&nlm_blocked_lock); +} + +/* + * 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); + spin_lock(&nlm_blocked_lock); + 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); + spin_unlock(&nlm_blocked_lock); + return block; + } + } + spin_unlock(&nlm_blocked_lock); + + 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; + + spin_lock(&nlm_blocked_lock); + list_for_each_entry(block, &nlm_blocked, b_list) { + if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie)) + goto found; + } + spin_unlock(&nlm_blocked_lock); + + return NULL; + +found: + dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block); + kref_get(&block->b_count); + spin_unlock(&nlm_blocked_lock); + 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 struct nlm_block * +nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host, + struct nlm_file *file, struct nlm_lock *lock, + struct nlm_cookie *cookie) +{ + struct nlm_block *block; + struct nlm_rqst *call = 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: + nlmsvc_release_call(call); + return NULL; +} + +/* + * Delete a block. + * 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 = locks_delete_block(&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 */ + list_del_init(&block->b_flist); + mutex_unlock(&file->f_mutex); + + nlmsvc_freegrantargs(block->b_call); + nlmsvc_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_mutex(&block->b_count, nlmsvc_free_block, &block->b_file->f_mutex); +} + +/* + * 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); + spin_lock(&nlm_blocked_lock); + 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); + spin_unlock(&nlm_blocked_lock); + mutex_unlock(&file->f_mutex); + nlmsvc_unlink_block(block); + nlmsvc_release_block(block); + goto restart; + } + spin_unlock(&nlm_blocked_lock); + mutex_unlock(&file->f_mutex); +} + +static struct nlm_lockowner * +nlmsvc_get_lockowner(struct nlm_lockowner *lockowner) +{ + refcount_inc(&lockowner->count); + return lockowner; +} + +void nlmsvc_put_lockowner(struct nlm_lockowner *lockowner) +{ + if (!refcount_dec_and_lock(&lockowner->count, &lockowner->host->h_lock)) + return; + list_del(&lockowner->list); + spin_unlock(&lockowner->host->h_lock); + nlmsvc_release_host(lockowner->host); + kfree(lockowner); +} + +static struct nlm_lockowner *__nlmsvc_find_lockowner(struct nlm_host *host, pid_t pid) +{ + struct nlm_lockowner *lockowner; + list_for_each_entry(lockowner, &host->h_lockowners, list) { + if (lockowner->pid != pid) + continue; + return nlmsvc_get_lockowner(lockowner); + } + return NULL; +} + +static struct nlm_lockowner *nlmsvc_find_lockowner(struct nlm_host *host, pid_t pid) +{ + struct nlm_lockowner *res, *new = NULL; + + spin_lock(&host->h_lock); + res = __nlmsvc_find_lockowner(host, pid); + + if (res == NULL) { + spin_unlock(&host->h_lock); + new = kmalloc(sizeof(*res), GFP_KERNEL); + spin_lock(&host->h_lock); + res = __nlmsvc_find_lockowner(host, pid); + if (res == NULL && new != NULL) { + res = new; + /* fs/locks.c will manage the refcount through lock_ops */ + refcount_set(&new->count, 1); + new->pid = pid; + new->host = nlm_get_host(host); + list_add(&new->list, &host->h_lockowners); + new = NULL; + } + } + + spin_unlock(&host->h_lock); + kfree(new); + return res; +} + +void +nlmsvc_release_lockowner(struct nlm_lock *lock) +{ + if (lock->fl.fl_owner) + nlmsvc_put_lockowner(lock->fl.fl_owner); +} + +void nlmsvc_locks_init_private(struct file_lock *fl, struct nlm_host *host, + pid_t pid) +{ + fl->fl_owner = nlmsvc_find_lockowner(host, pid); +} + +/* + * 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 = ((struct nlm_lockowner *)lock->fl.fl_owner)->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); + + locks_release_private(&call->a_args.lock.fl); +} + +/* + * Deferred lock request handling for non-blocking lock + */ +static __be32 +nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block) +{ + __be32 status = nlm_lck_denied_nolocks; + + block->b_flags |= B_QUEUED; + + nlmsvc_insert_block(block, NLM_TIMEOUT); + + block->b_cache_req = &rqstp->rq_chandle; + if (rqstp->rq_chandle.defer) { + block->b_deferred_req = + rqstp->rq_chandle.defer(block->b_cache_req); + if (block->b_deferred_req != NULL) + status = nlm_drop_reply; + } + dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n", + block, block->b_flags, ntohl(status)); + + return status; +} + +/* + * 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_host *host, struct nlm_lock *lock, int wait, + struct nlm_cookie *cookie, int reclaim) +{ +#if IS_ENABLED(CONFIG_SUNRPC_DEBUG) + struct inode *inode = nlmsvc_file_inode(file); +#endif + struct nlm_block *block = NULL; + int error; + int mode; + int async_block = 0; + __be32 ret; + + dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n", + inode->i_sb->s_id, inode->i_ino, + lock->fl.fl_type, lock->fl.fl_pid, + (long long)lock->fl.fl_start, + (long long)lock->fl.fl_end, + wait); + + if (nlmsvc_file_file(file)->f_op->lock) { + async_block = wait; + wait = 0; + } + + /* Lock file against concurrent access */ + mutex_lock(&file->f_mutex); + /* Get existing block (in case client is busy-waiting) + * or create new block + */ + block = nlmsvc_lookup_block(file, lock); + if (block == NULL) { + block = nlmsvc_create_block(rqstp, host, file, lock, cookie); + ret = nlm_lck_denied_nolocks; + if (block == NULL) + goto out; + lock = &block->b_call->a_args.lock; + } else + lock->fl.fl_flags &= ~FL_SLEEP; + + if (block->b_flags & B_QUEUED) { + dprintk("lockd: nlmsvc_lock deferred block %p flags %d\n", + block, block->b_flags); + if (block->b_granted) { + nlmsvc_unlink_block(block); + ret = nlm_granted; + goto out; + } + if (block->b_flags & B_TIMED_OUT) { + nlmsvc_unlink_block(block); + ret = nlm_lck_denied; + goto out; + } + ret = nlm_drop_reply; + goto out; + } + + if (locks_in_grace(SVC_NET(rqstp)) && !reclaim) { + ret = nlm_lck_denied_grace_period; + goto out; + } + if (reclaim && !locks_in_grace(SVC_NET(rqstp))) { + ret = nlm_lck_denied_grace_period; + goto out; + } + + if (!wait) + lock->fl.fl_flags &= ~FL_SLEEP; + mode = lock_to_openmode(&lock->fl); + error = vfs_lock_file(file->f_file[mode], F_SETLK, &lock->fl, NULL); + lock->fl.fl_flags &= ~FL_SLEEP; + + dprintk("lockd: vfs_lock_file returned %d\n", error); + switch (error) { + case 0: + ret = nlm_granted; + goto out; + case -EAGAIN: + /* + * If this is a blocking request for an + * already pending lock request then we need + * to put it back on lockd's block list + */ + if (wait) + break; + ret = async_block ? nlm_lck_blocked : nlm_lck_denied; + goto out; + case FILE_LOCK_DEFERRED: + if (wait) + break; + /* Filesystem lock operation is in progress + Add it to the queue waiting for callback */ + ret = nlmsvc_defer_lock_rqst(rqstp, block); + goto out; + case -EDEADLK: + ret = nlm_deadlock; + goto out; + default: /* includes ENOLCK */ + ret = nlm_lck_denied_nolocks; + goto out; + } + + ret = nlm_lck_blocked; + + /* Append to list of blocked */ + nlmsvc_insert_block(block, NLM_NEVER); +out: + mutex_unlock(&file->f_mutex); + 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 svc_rqst *rqstp, struct nlm_file *file, + struct nlm_host *host, struct nlm_lock *lock, + struct nlm_lock *conflock, struct nlm_cookie *cookie) +{ + int error; + int mode; + __be32 ret; + + dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n", + nlmsvc_file_inode(file)->i_sb->s_id, + nlmsvc_file_inode(file)->i_ino, + lock->fl.fl_type, + (long long)lock->fl.fl_start, + (long long)lock->fl.fl_end); + + if (locks_in_grace(SVC_NET(rqstp))) { + ret = nlm_lck_denied_grace_period; + goto out; + } + + mode = lock_to_openmode(&lock->fl); + error = vfs_test_lock(file->f_file[mode], &lock->fl); + if (error) { + /* We can't currently deal with deferred test requests */ + if (error == FILE_LOCK_DEFERRED) + WARN_ON_ONCE(1); + + ret = nlm_lck_denied_nolocks; + goto out; + } + + if (lock->fl.fl_type == F_UNLCK) { + ret = nlm_granted; + goto out; + } + + dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n", + lock->fl.fl_type, (long long)lock->fl.fl_start, + (long long)lock->fl.fl_end); + conflock->caller = "somehost"; /* FIXME */ + conflock->len = strlen(conflock->caller); + conflock->oh.len = 0; /* don't return OH info */ + conflock->svid = lock->fl.fl_pid; + conflock->fl.fl_type = lock->fl.fl_type; + conflock->fl.fl_start = lock->fl.fl_start; + conflock->fl.fl_end = lock->fl.fl_end; + locks_release_private(&lock->fl); + + ret = nlm_lck_denied; +out: + return ret; +} + +/* + * 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 net *net, struct nlm_file *file, struct nlm_lock *lock) +{ + int error = 0; + + dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n", + nlmsvc_file_inode(file)->i_sb->s_id, + nlmsvc_file_inode(file)->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(net, file, lock); + + lock->fl.fl_type = F_UNLCK; + lock->fl.fl_file = file->f_file[O_RDONLY]; + if (lock->fl.fl_file) + error = vfs_lock_file(lock->fl.fl_file, F_SETLK, + &lock->fl, NULL); + lock->fl.fl_file = file->f_file[O_WRONLY]; + if (lock->fl.fl_file) + error |= vfs_lock_file(lock->fl.fl_file, F_SETLK, + &lock->fl, NULL); + + 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 net *net, struct nlm_file *file, struct nlm_lock *lock) +{ + struct nlm_block *block; + int status = 0; + int mode; + + dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n", + nlmsvc_file_inode(file)->i_sb->s_id, + nlmsvc_file_inode(file)->i_ino, + lock->fl.fl_pid, + (long long)lock->fl.fl_start, + (long long)lock->fl.fl_end); + + if (locks_in_grace(net)) + return nlm_lck_denied_grace_period; + + mutex_lock(&file->f_mutex); + block = nlmsvc_lookup_block(file, lock); + mutex_unlock(&file->f_mutex); + if (block != NULL) { + struct file_lock *fl = &block->b_call->a_args.lock.fl; + + mode = lock_to_openmode(fl); + vfs_cancel_lock(block->b_file->f_file[mode], fl); + status = nlmsvc_unlink_block(block); + nlmsvc_release_block(block); + } + return status ? nlm_lck_denied : nlm_granted; +} + +/* + * This is a callback from the filesystem for VFS file lock requests. + * It will be used if lm_grant is defined and the filesystem can not + * respond to the request immediately. + * For SETLK or SETLKW request it will get the local posix lock. + * In all cases it will move the block to the head of nlm_blocked q where + * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the + * deferred rpc for GETLK and SETLK. + */ +static void +nlmsvc_update_deferred_block(struct nlm_block *block, int result) +{ + block->b_flags |= B_GOT_CALLBACK; + if (result == 0) + block->b_granted = 1; + else + block->b_flags |= B_TIMED_OUT; +} + +static int nlmsvc_grant_deferred(struct file_lock *fl, int result) +{ + struct nlm_block *block; + int rc = -ENOENT; + + spin_lock(&nlm_blocked_lock); + list_for_each_entry(block, &nlm_blocked, b_list) { + if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) { + dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n", + block, block->b_flags); + if (block->b_flags & B_QUEUED) { + if (block->b_flags & B_TIMED_OUT) { + rc = -ENOLCK; + break; + } + nlmsvc_update_deferred_block(block, result); + } else if (result == 0) + block->b_granted = 1; + + nlmsvc_insert_block_locked(block, 0); + svc_wake_up(block->b_daemon); + rc = 0; + break; + } + } + spin_unlock(&nlm_blocked_lock); + if (rc == -ENOENT) + printk(KERN_WARNING "lockd: grant for unknown block\n"); + return rc; +} + +/* + * 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); + spin_lock(&nlm_blocked_lock); + list_for_each_entry(block, &nlm_blocked, b_list) { + if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) { + nlmsvc_insert_block_locked(block, 0); + spin_unlock(&nlm_blocked_lock); + svc_wake_up(block->b_daemon); + return; + } + } + spin_unlock(&nlm_blocked_lock); + printk(KERN_WARNING "lockd: notification for unknown block!\n"); +} + +static fl_owner_t nlmsvc_get_owner(fl_owner_t owner) +{ + return nlmsvc_get_lockowner(owner); +} + +static void nlmsvc_put_owner(fl_owner_t owner) +{ + nlmsvc_put_lockowner(owner); +} + +const struct lock_manager_operations nlmsvc_lock_operations = { + .lm_notify = nlmsvc_notify_blocked, + .lm_grant = nlmsvc_grant_deferred, + .lm_get_owner = nlmsvc_get_owner, + .lm_put_owner = nlmsvc_put_owner, +}; + +/* + * 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 mode; + int error; + loff_t fl_start, fl_end; + + dprintk("lockd: grant blocked lock %p\n", block); + + kref_get(&block->b_count); + + /* 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 */ + /* vfs_lock_file() can mangle fl_start and fl_end, but we need + * them unchanged for the GRANT_MSG + */ + lock->fl.fl_flags |= FL_SLEEP; + fl_start = lock->fl.fl_start; + fl_end = lock->fl.fl_end; + mode = lock_to_openmode(&lock->fl); + error = vfs_lock_file(file->f_file[mode], F_SETLK, &lock->fl, NULL); + lock->fl.fl_flags &= ~FL_SLEEP; + lock->fl.fl_start = fl_start; + lock->fl.fl_end = fl_end; + + switch (error) { + case 0: + break; + case FILE_LOCK_DEFERRED: + dprintk("lockd: lock still blocked error %d\n", error); + nlmsvc_insert_block(block, NLM_NEVER); + nlmsvc_release_block(block); + return; + default: + printk(KERN_WARNING "lockd: unexpected error %d in %s!\n", + -error, __func__); + nlmsvc_insert_block(block, 10 * HZ); + nlmsvc_release_block(block); + return; + } + +callback: + /* Lock was granted by VFS. */ + dprintk("lockd: GRANTing blocked lock.\n"); + block->b_granted = 1; + + /* keep block on the list, but don't reattempt until the RPC + * completes or the submission fails + */ + nlmsvc_insert_block(block, NLM_NEVER); + + /* Call the client -- use a soft RPC task since nlmsvc_retry_blocked + * will queue up a new one if this one times out + */ + error = nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG, + &nlmsvc_grant_ops); + + /* RPC submission failed, wait a bit and retry */ + if (error < 0) + nlmsvc_insert_block(block, 10 * HZ); +} + +/* + * 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"); + + spin_lock(&nlm_blocked_lock); + /* if the block is not on a list at this point then it has + * been invalidated. Don't try to requeue it. + * + * FIXME: it's possible that the block is removed from the list + * after this check but before the nlmsvc_insert_block. In that + * case it will be added back. Perhaps we need better locking + * for nlm_blocked? + */ + if (list_empty(&block->b_list)) + goto out; + + /* 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_locked(block, timeout); + svc_wake_up(block->b_daemon); +out: + spin_unlock(&nlm_blocked_lock); +} + +/* + * FIXME: nlmsvc_release_block() grabs a mutex. This is not allowed for an + * .rpc_release rpc_call_op + */ +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, __be32 status) +{ + struct nlm_block *block; + struct file_lock *fl; + int error; + + dprintk("grant_reply: looking for cookie %x, s=%d \n", + *(unsigned int *)(cookie->data), status); + if (!(block = nlmsvc_find_block(cookie))) + return; + + switch (status) { + case nlm_lck_denied_grace_period: + /* Try again in a couple of seconds */ + nlmsvc_insert_block(block, 10 * HZ); + break; + case nlm_lck_denied: + /* Client doesn't want it, just unlock it */ + nlmsvc_unlink_block(block); + fl = &block->b_call->a_args.lock.fl; + fl->fl_type = F_UNLCK; + error = vfs_lock_file(fl->fl_file, F_SETLK, fl, NULL); + if (error) + pr_warn("lockd: unable to unlock lock rejected by client!\n"); + break; + default: + /* + * Either it was accepted or the status makes no sense + * just unlink it either way. + */ + nlmsvc_unlink_block(block); + } + nlmsvc_release_block(block); +} + +/* Helper function to handle retry of a deferred block. + * If it is a blocking lock, call grant_blocked. + * For a non-blocking lock or test lock, revisit the request. + */ +static void +retry_deferred_block(struct nlm_block *block) +{ + if (!(block->b_flags & B_GOT_CALLBACK)) + block->b_flags |= B_TIMED_OUT; + nlmsvc_insert_block(block, NLM_TIMEOUT); + dprintk("revisit block %p flags %d\n", block, block->b_flags); + if (block->b_deferred_req) { + block->b_deferred_req->revisit(block->b_deferred_req, 0); + block->b_deferred_req = NULL; + } +} + +/* + * 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. + */ +void +nlmsvc_retry_blocked(void) +{ + unsigned long timeout = MAX_SCHEDULE_TIMEOUT; + struct nlm_block *block; + + spin_lock(&nlm_blocked_lock); + while (!list_empty(&nlm_blocked) && !kthread_should_stop()) { + 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; + } + spin_unlock(&nlm_blocked_lock); + + dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n", + block, block->b_when); + if (block->b_flags & B_QUEUED) { + dprintk("nlmsvc_retry_blocked delete block (%p, granted=%d, flags=%d)\n", + block, block->b_granted, block->b_flags); + retry_deferred_block(block); + } else + nlmsvc_grant_blocked(block); + spin_lock(&nlm_blocked_lock); + } + spin_unlock(&nlm_blocked_lock); + + if (timeout < MAX_SCHEDULE_TIMEOUT) + mod_timer(&nlmsvc_retry, jiffies + timeout); +} |