/* * 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_path.dentry->d_inode->i_sb->s_id, file->f_file->f_path.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_path.dentry->d_inode->i_sb->s_id, file->f_file->f_path.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_path.dentry->d_inode->i_sb->s_id, file->f_file->f_path.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_path.dentry->d_inode->i_sb->s_id, file->f_file->f_path.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, __be32 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; }