cregit-Linux how code gets into the kernel

Release 4.10 fs/lockd/svclock.c

Directory: fs/lockd
 * 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 <>

#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>



#define nlm_deadlock	nlm4_deadlock

#define nlm_deadlock	nlm_lck_denied

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);


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; }


trond myklebusttrond myklebust12099.17%150.00%
jeff laytonjeff layton10.83%150.00%

#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; }


olaf kircholaf kirch5638.36%116.67%
trond myklebusttrond myklebust128.22%233.33%
bryan schumakerbryan schumaker10.68%116.67%

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); }


bryan schumakerbryan schumaker34100.00%1100.00%

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


olaf kircholaf kirch1224.00%125.00%
bryan schumakerbryan schumaker1224.00%125.00%
trond myklebusttrond myklebust510.00%125.00%

/* * 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; }


trond myklebusttrond myklebust105.92%228.57%
olaf kircholaf kirch84.73%114.29%
ed schoutened schouten52.96%114.29%

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; }


olaf kircholaf kirch2431.58%228.57%
trond myklebusttrond myklebust1013.16%228.57%

/* * 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; }


trond myklebusttrond myklebust7330.04%750.00%
olaf kircholaf kirch2711.11%214.29%
chuck leverchuck lever10.41%17.14%

/* * 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 = posix_unblock_lock(&block->b_call->a_args.lock.fl); nlmsvc_remove_block(block); return status; }


trond myklebusttrond myklebust2860.87%250.00%
j. bruce fieldsj. bruce fields12.17%125.00%

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); }


trond myklebusttrond myklebust4148.24%342.86%
olaf kircholaf kirch55.88%114.29%
neil brownneil brown22.35%114.29%
chuck leverchuck lever11.18%114.29%

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); }


trond myklebusttrond myklebust2573.53%133.33%
al viroal viro823.53%133.33%

/* * 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); }


trond myklebusttrond myklebust4843.64%233.33%
olaf kircholaf kirch2825.45%233.33%
neil brownneil brown65.45%116.67%

/* * 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-> = 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-> = (u8 *) data; } memcpy(call->, lock->, lock->oh.len); return 1; }


trond myklebusttrond myklebust19598.48%150.00%
serge hallynserge hallyn31.52%150.00%

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


trond myklebusttrond myklebust4076.92%150.00%
felix blyakherfelix blyakher1223.08%150.00%

/* * 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; }


marc eshelmarc eshel9494.95%150.00%
al viroal viro55.05%150.00%

/* * 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) { struct nlm_block *block = NULL; int error; __be32 ret; dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n", file_inode(file->f_file)->i_sb->s_id, file_inode(file->f_file)->i_ino, lock->fl.fl_type, lock->fl.fl_pid, (long long)lock->fl.fl_start, (long long)lock->fl.fl_end, wait); /* 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; error = vfs_lock_file(file->f_file, 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 = 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; }


marc eshelmarc eshel14331.29%311.54%
trond myklebusttrond myklebust5912.91%415.38%
j. bruce fieldsj. bruce fields357.66%27.69%
andy adamsonandy adamson347.44%27.69%
stanislav kinsburskystanislav kinsbursky122.63%13.85%
al viroal viro112.41%311.54%
miklos szeredimiklos szeredi102.19%27.69%
neil brownneil brown71.53%27.69%
linus torvaldslinus torvalds51.09%27.69%
jeff laytonjeff layton51.09%13.85%

/* * 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; __be32 ret; dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n", file_inode(file->f_file)->i_sb->s_id, file_inode(file->f_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; } error = vfs_test_lock(file->f_file, &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; }


marc eshelmarc eshel9934.14%315.79%
j. bruce fieldsj. bruce fields134.48%15.26%
jeff laytonjeff layton134.48%210.53%
olaf kircholaf kirch113.79%15.26%
al viroal viro103.45%315.79%
kinglong meekinglong mee82.76%15.26%
andy adamsonandy adamson82.76%15.26%
stanislav kinsburskystanislav kinsbursky62.07%15.26%
linus torvaldslinus torvalds41.38%15.26%
trond myklebusttrond myklebust31.03%15.26%
oleg drokinoleg drokin10.34%15.26%

/* * 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; dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n", file_inode(file->f_file)->i_sb->s_id, file_inode(file->f_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; error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL); return (error < 0)? nlm_lck_denied_nolocks : nlm_granted; }


al viroal viro108.26%330.00%
stanislav kinsburskystanislav kinsbursky75.79%110.00%
marc eshelmarc eshel54.13%220.00%
linus torvaldslinus torvalds43.31%110.00%

/* * 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; dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n", file_inode(file->f_file)->i_sb->s_id, file_inode(file->f_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) { vfs_cancel_lock(block->b_file->f_file, &block->b_call->a_args.lock.fl); status = nlmsvc_unlink_block(block); nlmsvc_release_block(block); } return status ? nlm_lck_denied : nlm_granted; }


marc eshelmarc eshel2012.27%17.14%
j. bruce fieldsj. bruce fields1811.04%214.29%
trond myklebusttrond myklebust1811.04%214.29%
al viroal viro106.13%321.43%
stanislav kinsburskystanislav kinsbursky84.91%17.14%
neil brownneil brown42.45%17.14%
linus torvaldslinus torvalds42.45%17.14%

/* * 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; }


marc eshelmarc eshel39100.00%1100.00%

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; }


marc eshelmarc eshel14893.08%150.00%
bryan schumakerbryan schumaker116.92%150.00%

/* * 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"); }


j. bruce fieldsj. bruce fields1920.65%116.67%
olaf kircholaf kirch88.70%116.67%
trond myklebusttrond myklebust11.09%116.67%

static int nlmsvc_same_owner(struct file_lock *fl1, struct