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[/] [or1k/] [tags/] [LINUX_2_4_26_OR32/] [linux/] [linux-2.4/] [fs/] [lockd/] [svclock.c] - Rev 1765
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/* * 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/config.h> #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_insert_block(struct nlm_block *block, unsigned long); static int nlmsvc_remove_block(struct nlm_block *block); static void nlmsvc_grant_callback(struct rpc_task *task); static void nlmsvc_notify_blocked(struct file_lock *); /* * The list of blocked locks to retry */ static struct nlm_block * 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 **bp, *b; dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when); if (block->b_queued) nlmsvc_remove_block(block); bp = &nlm_blocked; if (when != NLM_NEVER) { if ((when += jiffies) == NLM_NEVER) when ++; while ((b = *bp) && time_before_eq(b->b_when,when) && b->b_when != NLM_NEVER) bp = &b->b_next; } else while ((b = *bp)) bp = &b->b_next; block->b_queued = 1; block->b_when = when; block->b_next = b; *bp = block; } /* * Remove a block from the global list */ static int nlmsvc_remove_block(struct nlm_block *block) { struct nlm_block **bp, *b; if (!block->b_queued) return 1; for (bp = &nlm_blocked; (b = *bp); bp = &b->b_next) { if (b == block) { *bp = block->b_next; block->b_queued = 0; return 1; } } return 0; } /* * Find a block for a given lock and optionally remove it from * the list. */ static struct nlm_block * nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock, int remove) { struct nlm_block **head, *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); for (head = &nlm_blocked; (block = *head); head = &block->b_next) { 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)) { if (remove) { *head = block->b_next; block->b_queued = 0; } 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 sockaddr_in *sin) { struct nlm_block *block; for (block = nlm_blocked; block; block = block->b_next) { dprintk("cookie: head of blocked queue %p, block %p\n", nlm_blocked, block); if (nlm_cookie_match(&block->b_call.a_args.cookie,cookie) && nlm_cmp_addr(sin, &block->b_host->h_addr)) break; } 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. */ 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; /* Create host handle for callback */ host = nlmclnt_lookup_host(&rqstp->rq_addr, rqstp->rq_prot, rqstp->rq_vers); if (host == NULL) return NULL; /* Allocate memory for block, and initialize arguments */ if (!(block = (struct nlm_block *) kmalloc(sizeof(*block), GFP_KERNEL))) goto failed; memset(block, 0, sizeof(*block)); locks_init_lock(&block->b_call.a_args.lock.fl); locks_init_lock(&block->b_call.a_res.lock.fl); block->b_host = nlmsvc_lookup_host(rqstp); if (block->b_host == NULL) { goto failed_free; } if (!nlmclnt_setgrantargs(&block->b_call, lock)) goto failed_free; /* Set notifier function for VFS, and init args */ block->b_call.a_args.lock.fl.fl_notify = nlmsvc_notify_blocked; block->b_call.a_args.cookie = *cookie; /* see above */ dprintk("lockd: created block %p...\n", block); /* Create and initialize the block */ block->b_daemon = rqstp->rq_server; block->b_file = file; /* Add to file's list of blocks */ block->b_fnext = file->f_blocks; file->f_blocks = block; /* Set up RPC arguments for callback */ call = &block->b_call; call->a_host = host; call->a_flags = RPC_TASK_ASYNC; return block; failed_free: kfree(block); failed: nlm_release_host(host); 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 void nlmsvc_delete_block(struct nlm_block *block, int unlock) { struct file_lock *fl = &block->b_call.a_args.lock.fl; struct nlm_file *file = block->b_file; struct nlm_block **bp; dprintk("lockd: deleting block %p...\n", block); /* Remove block from list */ nlmsvc_remove_block(block); /* If granted, unlock it, else remove from inode block list */ if (unlock && block->b_granted) { dprintk("lockd: deleting granted lock\n"); fl->fl_type = F_UNLCK; posix_lock_file(&block->b_file->f_file, fl, 0); block->b_granted = 0; } else { dprintk("lockd: unblocking blocked lock\n"); posix_unblock_lock(fl); } /* If the block is in the middle of a GRANT callback, * don't kill it yet. */ if (block->b_incall) { nlmsvc_insert_block(block, NLM_NEVER); block->b_done = 1; return; } /* Remove block from file's list of blocks */ for (bp = &file->f_blocks; *bp; bp = &(*bp)->b_fnext) { if (*bp == block) { *bp = block->b_fnext; break; } } nlm_release_host(block->b_host); nlmclnt_freegrantargs(&block->b_call); kfree(block); } /* * Loop over all blocks and perform the action specified. * (NLM_ACT_CHECK handled by nlmsvc_inspect_file). */ int nlmsvc_traverse_blocks(struct nlm_host *host, struct nlm_file *file, int action) { struct nlm_block *block, *next; down(&file->f_sema); for (block = file->f_blocks; block; block = next) { next = block->b_fnext; if (action == NLM_ACT_MARK) block->b_host->h_inuse = 1; else if (action == NLM_ACT_UNLOCK) { if (host == NULL || host == block->b_host) nlmsvc_delete_block(block, 1); } } up(&file->f_sema); return 0; } /* * Attempt to establish a lock, and if it can't be granted, block it * if required. */ u32 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file, struct nlm_lock *lock, int wait, struct nlm_cookie *cookie) { struct file_lock *conflock; struct nlm_block *block; int error; dprintk("lockd: nlmsvc_lock(%04x/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n", file->f_file.f_dentry->d_inode->i_dev, 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); /* Get existing block (in case client is busy-waiting) */ block = nlmsvc_lookup_block(file, lock, 0); lock->fl.fl_flags |= FL_LOCKD; again: /* Lock file against concurrent access */ down(&file->f_sema); if (!(conflock = posix_test_lock(&file->f_file, &lock->fl))) { error = posix_lock_file(&file->f_file, &lock->fl, 0); if (block) nlmsvc_delete_block(block, 0); up(&file->f_sema); dprintk("lockd: posix_lock_file returned %d\n", -error); switch(-error) { case 0: return nlm_granted; case EDEADLK: return nlm_deadlock; case EAGAIN: return nlm_lck_denied; default: /* includes ENOLCK */ return nlm_lck_denied_nolocks; } } if (!wait) { up(&file->f_sema); return nlm_lck_denied; } if (posix_locks_deadlock(&lock->fl, conflock)) { up(&file->f_sema); return nlm_deadlock; } /* 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_sema as nlmsvc_create_block may try to * claim it while doing host garbage collection */ if (block == NULL) { up(&file->f_sema); dprintk("lockd: blocking on this lock (allocating).\n"); if (!(block = nlmsvc_create_block(rqstp, file, lock, cookie))) return nlm_lck_denied_nolocks; goto again; } /* Append to list of blocked */ nlmsvc_insert_block(block, NLM_NEVER); if (list_empty(&block->b_call.a_args.lock.fl.fl_block)) { /* Now add block to block list of the conflicting lock if we haven't done so. */ dprintk("lockd: blocking on this lock.\n"); posix_block_lock(conflock, &block->b_call.a_args.lock.fl); } up(&file->f_sema); return nlm_lck_blocked; } /* * Test for presence of a conflicting lock. */ u32 nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock, struct nlm_lock *conflock) { struct file_lock *fl; dprintk("lockd: nlmsvc_testlock(%04x/%ld, ty=%d, %Ld-%Ld)\n", file->f_file.f_dentry->d_inode->i_dev, 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 ((fl = posix_test_lock(&file->f_file, &lock->fl)) != NULL) { dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n", fl->fl_type, (long long)fl->fl_start, (long long)fl->fl_end); conflock->caller = "somehost"; /* FIXME */ conflock->oh.len = 0; /* don't return OH info */ conflock->fl = *fl; 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. */ u32 nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock) { int error; dprintk("lockd: nlmsvc_unlock(%04x/%ld, pi=%d, %Ld-%Ld)\n", file->f_file.f_dentry->d_inode->i_dev, 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, 0); 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. */ u32 nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock) { struct nlm_block *block; dprintk("lockd: nlmsvc_cancel(%04x/%ld, pi=%d, %Ld-%Ld)\n", file->f_file.f_dentry->d_inode->i_dev, 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); down(&file->f_sema); if ((block = nlmsvc_lookup_block(file, lock, 1)) != NULL) nlmsvc_delete_block(block, 1); up(&file->f_sema); return 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 **bp, *block; dprintk("lockd: VFS unblock notification for block %p\n", fl); posix_unblock_lock(fl); for (bp = &nlm_blocked; (block = *bp); bp = &block->b_next) { 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"); } /* * 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; struct file_lock *conflock; int error; dprintk("lockd: grant blocked lock %p\n", block); /* First thing is lock the file */ down(&file->f_sema); /* Unlink block request from list */ nlmsvc_remove_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_call.a_host); goto callback; } /* Try the lock operation again */ if ((conflock = posix_test_lock(&file->f_file, &lock->fl)) != NULL) { /* Bummer, we blocked again */ dprintk("lockd: lock still blocked\n"); nlmsvc_insert_block(block, NLM_NEVER); posix_block_lock(conflock, &lock->fl); up(&file->f_sema); return; } /* Alright, no conflicting lock. Now lock it for real. If the * following yields an error, this is most probably due to low * memory. Retry the lock in a few seconds. */ if ((error = posix_lock_file(&file->f_file, &lock->fl, 0)) < 0) { printk(KERN_WARNING "lockd: unexpected error %d in %s!\n", -error, __FUNCTION__); nlmsvc_insert_block(block, 10 * HZ); up(&file->f_sema); return; } callback: /* Lock was granted by VFS. */ dprintk("lockd: GRANTing blocked lock.\n"); block->b_granted = 1; block->b_incall = 1; /* Schedule next grant callback in 30 seconds */ nlmsvc_insert_block(block, 30 * HZ); /* Call the client */ nlm_get_host(block->b_call.a_host); if (nlmsvc_async_call(&block->b_call, NLMPROC_GRANTED_MSG, nlmsvc_grant_callback) < 0) nlm_release_host(block->b_call.a_host); up(&file->f_sema); } /* * 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) { struct nlm_rqst *call = (struct nlm_rqst *) task->tk_calldata; struct nlm_block *block; unsigned long timeout; struct sockaddr_in *peer_addr = RPC_PEERADDR(task->tk_client); dprintk("lockd: GRANT_MSG RPC callback\n"); dprintk("callback: looking for cookie %s, host %u.%u.%u.%u\n", nlmdbg_cookie2a(&call->a_args.cookie), NIPQUAD(peer_addr->sin_addr.s_addr)); if (!(block = nlmsvc_find_block(&call->a_args.cookie, peer_addr))) { dprintk("lockd: no block for cookie %s, host %u.%u.%u.%u\n", nlmdbg_cookie2a(&call->a_args.cookie), NIPQUAD(peer_addr->sin_addr.s_addr)); return; } /* 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 if (block->b_done) { /* Block already removed, kill it for real */ timeout = 0; } else { /* Call was successful, now wait for client callback */ timeout = 60 * HZ; } nlmsvc_insert_block(block, timeout); svc_wake_up(block->b_daemon); block->b_incall = 0; nlm_release_host(call->a_host); } /* * We received a GRANT_RES callback. Try to find the corresponding * block. */ void nlmsvc_grant_reply(struct svc_rqst *rqstp, struct nlm_cookie *cookie, u32 status) { struct nlm_block *block; struct nlm_file *file; dprintk("grant_reply: looking for cookie %x, host (%08x), s=%d \n", *(unsigned int *)(cookie->data), ntohl(rqstp->rq_addr.sin_addr.s_addr), status); if (!(block = nlmsvc_find_block(cookie, &rqstp->rq_addr))) return; file = block->b_file; file->f_count++; down(&file->f_sema); if ((block = nlmsvc_find_block(cookie,&rqstp->rq_addr)) != NULL) { if (status == NLM_LCK_DENIED_GRACE_PERIOD) { /* Try again in a couple of seconds */ nlmsvc_insert_block(block, 10 * HZ); block = NULL; } else { /* Lock is now held by client, or has been rejected. * In both cases, the block should be removed. */ file->f_count++; up(&file->f_sema); if (status == NLM_LCK_GRANTED) nlmsvc_delete_block(block, 0); else nlmsvc_delete_block(block, 1); } } if (!block) up(&file->f_sema); nlm_release_file(file); } /* * 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) { struct nlm_block *block; dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n", nlm_blocked, nlm_blocked? nlm_blocked->b_when : 0); while ((block = nlm_blocked)) { if (block->b_when == NLM_NEVER) break; if (time_after(block->b_when,jiffies)) break; dprintk("nlmsvc_retry_blocked(%p, when=%ld, done=%d)\n", block, block->b_when, block->b_done); if (block->b_done) nlmsvc_delete_block(block, 0); else nlmsvc_grant_blocked(block); } if ((block = nlm_blocked) && block->b_when != NLM_NEVER) return (block->b_when - jiffies); return MAX_SCHEDULE_TIMEOUT; }