/* * linux/fs/locks.c * * Provide support for fcntl()'s F_GETLK, F_SETLK, and F_SETLKW calls. * Doug Evans (dje@spiff.uucp), August 07, 1992 * * Deadlock detection added. * FIXME: one thing isn't handled yet: * - mandatory locks (requires lots of changes elsewhere) * Kelly Carmichael (kelly@[142.24.8.65]), September 17, 1994. * * Miscellaneous edits, and a total rewrite of posix_lock_file() code. * Kai Petzke (wpp@marie.physik.tu-berlin.de), 1994 * * Converted file_lock_table to a linked list from an array, which eliminates * the limits on how many active file locks are open. * Chad Page (pageone@netcom.com), November 27, 1994 * * Removed dependency on file descriptors. dup()'ed file descriptors now * get the same locks as the original file descriptors, and a close() on * any file descriptor removes ALL the locks on the file for the current * process. Since locks still depend on the process id, locks are inherited * after an exec() but not after a fork(). This agrees with POSIX, and both * BSD and SVR4 practice. * Andy Walker (andy@lysaker.kvaerner.no), February 14, 1995 * * Scrapped free list which is redundant now that we allocate locks * dynamically with kmalloc()/kfree(). * Andy Walker (andy@lysaker.kvaerner.no), February 21, 1995 * * Implemented two lock personalities - FL_FLOCK and FL_POSIX. * * FL_POSIX locks are created with calls to fcntl() and lockf() through the * fcntl() system call. They have the semantics described above. * * FL_FLOCK locks are created with calls to flock(), through the flock() * system call, which is new. Old C libraries implement flock() via fcntl() * and will continue to use the old, broken implementation. * * FL_FLOCK locks follow the 4.4 BSD flock() semantics. They are associated * with a file pointer (filp). As a result they can be shared by a parent * process and its children after a fork(). They are removed when the last * file descriptor referring to the file pointer is closed (unless explicitly * unlocked). * * FL_FLOCK locks never deadlock, an existing lock is always removed before * upgrading from shared to exclusive (or vice versa). When this happens * any processes blocked by the current lock are woken up and allowed to * run before the new lock is applied. * Andy Walker (andy@lysaker.kvaerner.no), June 09, 1995 * * Removed some race conditions in flock_lock_file(), marked other possible * races. Just grep for FIXME to see them. * Dmitry Gorodchanin (pgmdsg@ibi.com), February 09, 1996. * * Addressed Dmitry's concerns. Deadlock checking no longer recursive. * Lock allocation changed to GFP_ATOMIC as we can't afford to sleep * once we've checked for blocking and deadlocking. * Andy Walker (andy@lysaker.kvaerner.no), April 03, 1996. * * Initial implementation of mandatory locks. SunOS turned out to be * a rotten model, so I implemented the "obvious" semantics. * See 'Documentation/filesystems/mandatory-locking.txt' for details. * Andy Walker (andy@lysaker.kvaerner.no), April 06, 1996. * * Don't allow mandatory locks on mmap()'ed files. Added simple functions to * check if a file has mandatory locks, used by mmap(), open() and creat() to * see if system call should be rejected. Ref. HP-UX/SunOS/Solaris Reference * Manual, Section 2. * Andy Walker (andy@lysaker.kvaerner.no), April 09, 1996. * * Tidied up block list handling. Added '/proc/locks' interface. * Andy Walker (andy@lysaker.kvaerner.no), April 24, 1996. * * Fixed deadlock condition for pathological code that mixes calls to * flock() and fcntl(). * Andy Walker (andy@lysaker.kvaerner.no), April 29, 1996. * * Allow only one type of locking scheme (FL_POSIX or FL_FLOCK) to be in use * for a given file at a time. Changed the CONFIG_LOCK_MANDATORY scheme to * guarantee sensible behaviour in the case where file system modules might * be compiled with different options than the kernel itself. * Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996. * * Added a couple of missing wake_up() calls. Thanks to Thomas Meckel * (Thomas.Meckel@mni.fh-giessen.de) for spotting this. * Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996. * * Changed FL_POSIX locks to use the block list in the same way as FL_FLOCK * locks. Changed process synchronisation to avoid dereferencing locks that * have already been freed. * Andy Walker (andy@lysaker.kvaerner.no), Sep 21, 1996. * * Made the block list a circular list to minimise searching in the list. * Andy Walker (andy@lysaker.kvaerner.no), Sep 25, 1996. * * Made mandatory locking a mount option. Default is not to allow mandatory * locking. * Andy Walker (andy@lysaker.kvaerner.no), Oct 04, 1996. * * Some adaptations for NFS support. * Olaf Kirch (okir@monad.swb.de), Dec 1996, * * Fixed /proc/locks interface so that we can't overrun the buffer we are handed. * Andy Walker (andy@lysaker.kvaerner.no), May 12, 1997. * * Use slab allocator instead of kmalloc/kfree. * Use generic list implementation from . * Sped up posix_locks_deadlock by only considering blocked locks. * Matthew Wilcox , March, 2000. * * Leases and LOCK_MAND * Matthew Wilcox , June, 2000. * Stephen Rothwell , June, 2000. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define CREATE_TRACE_POINTS #include #include #define IS_POSIX(fl) (fl->fl_flags & FL_POSIX) #define IS_FLOCK(fl) (fl->fl_flags & FL_FLOCK) #define IS_LEASE(fl) (fl->fl_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT)) #define IS_OFDLCK(fl) (fl->fl_flags & FL_OFDLCK) static bool lease_breaking(struct file_lock *fl) { return fl->fl_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING); } static int target_leasetype(struct file_lock *fl) { if (fl->fl_flags & FL_UNLOCK_PENDING) return F_UNLCK; if (fl->fl_flags & FL_DOWNGRADE_PENDING) return F_RDLCK; return fl->fl_type; } int leases_enable = 1; int lease_break_time = 45; /* * The global file_lock_list is only used for displaying /proc/locks, so we * keep a list on each CPU, with each list protected by its own spinlock via * the file_lock_lglock. Note that alterations to the list also require that * the relevant flc_lock is held. */ DEFINE_STATIC_LGLOCK(file_lock_lglock); static DEFINE_PER_CPU(struct hlist_head, file_lock_list); /* * The blocked_hash is used to find POSIX lock loops for deadlock detection. * It is protected by blocked_lock_lock. * * We hash locks by lockowner in order to optimize searching for the lock a * particular lockowner is waiting on. * * FIXME: make this value scale via some heuristic? We generally will want more * buckets when we have more lockowners holding locks, but that's a little * difficult to determine without knowing what the workload will look like. */ #define BLOCKED_HASH_BITS 7 static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS); /* * This lock protects the blocked_hash. Generally, if you're accessing it, you * want to be holding this lock. * * In addition, it also protects the fl->fl_block list, and the fl->fl_next * pointer for file_lock structures that are acting as lock requests (in * contrast to those that are acting as records of acquired locks). * * Note that when we acquire this lock in order to change the above fields, * we often hold the flc_lock as well. In certain cases, when reading the fields * protected by this lock, we can skip acquiring it iff we already hold the * flc_lock. * * In particular, adding an entry to the fl_block list requires that you hold * both the flc_lock and the blocked_lock_lock (acquired in that order). * Deleting an entry from the list however only requires the file_lock_lock. */ static DEFINE_SPINLOCK(blocked_lock_lock); static struct kmem_cache *flctx_cache __read_mostly; static struct kmem_cache *filelock_cache __read_mostly; static struct file_lock_context * locks_get_lock_context(struct inode *inode) { struct file_lock_context *new; if (likely(inode->i_flctx)) goto out; new = kmem_cache_alloc(flctx_cache, GFP_KERNEL); if (!new) goto out; spin_lock_init(&new->flc_lock); INIT_LIST_HEAD(&new->flc_flock); INIT_LIST_HEAD(&new->flc_posix); INIT_LIST_HEAD(&new->flc_lease); /* * Assign the pointer if it's not already assigned. If it is, then * free the context we just allocated. */ spin_lock(&inode->i_lock); if (likely(!inode->i_flctx)) { inode->i_flctx = new; new = NULL; } spin_unlock(&inode->i_lock); if (new) kmem_cache_free(flctx_cache, new); out: return inode->i_flctx; } void locks_free_lock_context(struct file_lock_context *ctx) { if (ctx) { WARN_ON_ONCE(!list_empty(&ctx->flc_flock)); WARN_ON_ONCE(!list_empty(&ctx->flc_posix)); WARN_ON_ONCE(!list_empty(&ctx->flc_lease)); kmem_cache_free(flctx_cache, ctx); } } static void locks_init_lock_heads(struct file_lock *fl) { INIT_HLIST_NODE(&fl->fl_link); INIT_LIST_HEAD(&fl->fl_list); INIT_LIST_HEAD(&fl->fl_block); init_waitqueue_head(&fl->fl_wait); } /* Allocate an empty lock structure. */ struct file_lock *locks_alloc_lock(void) { struct file_lock *fl = kmem_cache_zalloc(filelock_cache, GFP_KERNEL); if (fl) locks_init_lock_heads(fl); return fl; } EXPORT_SYMBOL_GPL(locks_alloc_lock); void locks_release_private(struct file_lock *fl) { if (fl->fl_ops) { if (fl->fl_ops->fl_release_private) fl->fl_ops->fl_release_private(fl); fl->fl_ops = NULL; } if (fl->fl_lmops) { if (fl->fl_lmops->lm_put_owner) fl->fl_lmops->lm_put_owner(fl); fl->fl_lmops = NULL; } } EXPORT_SYMBOL_GPL(locks_release_private); /* Free a lock which is not in use. */ void locks_free_lock(struct file_lock *fl) { BUG_ON(waitqueue_active(&fl->fl_wait)); BUG_ON(!list_empty(&fl->fl_list)); BUG_ON(!list_empty(&fl->fl_block)); BUG_ON(!hlist_unhashed(&fl->fl_link)); locks_release_private(fl); kmem_cache_free(filelock_cache, fl); } EXPORT_SYMBOL(locks_free_lock); static void locks_dispose_list(struct list_head *dispose) { struct file_lock *fl; while (!list_empty(dispose)) { fl = list_first_entry(dispose, struct file_lock, fl_list); list_del_init(&fl->fl_list); locks_free_lock(fl); } } void locks_init_lock(struct file_lock *fl) { memset(fl, 0, sizeof(struct file_lock)); locks_init_lock_heads(fl); } EXPORT_SYMBOL(locks_init_lock); /* * Initialize a new lock from an existing file_lock structure. */ void locks_copy_conflock(struct file_lock *new, struct file_lock *fl) { new->fl_owner = fl->fl_owner; new->fl_pid = fl->fl_pid; new->fl_file = NULL; new->fl_flags = fl->fl_flags; new->fl_type = fl->fl_type; new->fl_start = fl->fl_start; new->fl_end = fl->fl_end; new->fl_lmops = fl->fl_lmops; new->fl_ops = NULL; if (fl->fl_lmops) { if (fl->fl_lmops->lm_get_owner) fl->fl_lmops->lm_get_owner(new, fl); } } EXPORT_SYMBOL(locks_copy_conflock); void locks_copy_lock(struct file_lock *new, struct file_lock *fl) { /* "new" must be a freshly-initialized lock */ WARN_ON_ONCE(new->fl_ops); locks_copy_conflock(new, fl); new->fl_file = fl->fl_file; new->fl_ops = fl->fl_ops; if (fl->fl_ops) { if (fl->fl_ops->fl_copy_lock) fl->fl_ops->fl_copy_lock(new, fl); } } EXPORT_SYMBOL(locks_copy_lock); static inline int flock_translate_cmd(int cmd) { if (cmd & LOCK_MAND) return cmd & (LOCK_MAND | LOCK_RW); switch (cmd) { case LOCK_SH: return F_RDLCK; case LOCK_EX: return F_WRLCK; case LOCK_UN: return F_UNLCK; } return -EINVAL; } /* Fill in a file_lock structure with an appropriate FLOCK lock. */ static struct file_lock * flock_make_lock(struct file *filp, unsigned int cmd) { struct file_lock *fl; int type = flock_translate_cmd(cmd); if (type < 0) return ERR_PTR(type); fl = locks_alloc_lock(); if (fl == NULL) return ERR_PTR(-ENOMEM); fl->fl_file = filp; fl->fl_owner = filp; fl->fl_pid = current->tgid; fl->fl_flags = FL_FLOCK; fl->fl_type = type; fl->fl_end = OFFSET_MAX; return fl; } static int assign_type(struct file_lock *fl, long type) { switch (type) { case F_RDLCK: case F_WRLCK: case F_UNLCK: fl->fl_type = type; break; default: return -EINVAL; } return 0; } static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl, struct flock64 *l) { switch (l->l_whence) { case SEEK_SET: fl->fl_start = 0; break; case SEEK_CUR: fl->fl_start = filp->f_pos; break; case SEEK_END: fl->fl_start = i_size_read(file_inode(filp)); break; default: return -EINVAL; } if (l->l_start > OFFSET_MAX - fl->fl_start) return -EOVERFLOW; fl->fl_start += l->l_start; if (fl->fl_start < 0) return -EINVAL; /* POSIX-1996 leaves the case l->l_len < 0 undefined; POSIX-2001 defines it. */ if (l->l_len > 0) { if (l->l_len - 1 > OFFSET_MAX - fl->fl_start) return -EOVERFLOW; fl->fl_end = fl->fl_start + l->l_len - 1; } else if (l->l_len < 0) { if (fl->fl_start + l->l_len < 0) return -EINVAL; fl->fl_end = fl->fl_start - 1; fl->fl_start += l->l_len; } else fl->fl_end = OFFSET_MAX; fl->fl_owner = current->files; fl->fl_pid = current->tgid; fl->fl_file = filp; fl->fl_flags = FL_POSIX; fl->fl_ops = NULL; fl->fl_lmops = NULL; return assign_type(fl, l->l_type); } /* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX * style lock. */ static int flock_to_posix_lock(struct file *filp, struct file_lock *fl, struct flock *l) { struct flock64 ll = { .l_type = l->l_type, .l_whence = l->l_whence, .l_start = l->l_start, .l_len = l->l_len, }; return flock64_to_posix_lock(filp, fl, &ll); } /* default lease lock manager operations */ static bool lease_break_callback(struct file_lock *fl) { kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG); return false; } static void lease_setup(struct file_lock *fl, void **priv) { struct file *filp = fl->fl_file; struct fasync_struct *fa = *priv; /* * fasync_insert_entry() returns the old entry if any. If there was no * old entry, then it used "priv" and inserted it into the fasync list. * Clear the pointer to indicate that it shouldn't be freed. */ if (!fasync_insert_entry(fa->fa_fd, filp, &fl->fl_fasync, fa)) *priv = NULL; __f_setown(filp, task_pid(current), PIDTYPE_PID, 0); } static const struct lock_manager_operations lease_manager_ops = { .lm_break = lease_break_callback, .lm_change = lease_modify, .lm_setup = lease_setup, }; /* * Initialize a lease, use the default lock manager operations */ static int lease_init(struct file *filp, long type, struct file_lock *fl) { if (assign_type(fl, type) != 0) return -EINVAL; fl->fl_owner = filp; fl->fl_pid = current->tgid; fl->fl_file = filp; fl->fl_flags = FL_LEASE; fl->fl_start = 0; fl->fl_end = OFFSET_MAX; fl->fl_ops = NULL; fl->fl_lmops = &lease_manager_ops; return 0; } /* Allocate a file_lock initialised to this type of lease */ static struct file_lock *lease_alloc(struct file *filp, long type) { struct file_lock *fl = locks_alloc_lock(); int error = -ENOMEM; if (fl == NULL) return ERR_PTR(error); error = lease_init(filp, type, fl); if (error) { locks_free_lock(fl); return ERR_PTR(error); } return fl; } /* Check if two locks overlap each other. */ static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2) { return ((fl1->fl_end >= fl2->fl_start) && (fl2->fl_end >= fl1->fl_start)); } /* * Check whether two locks have the same owner. */ static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2) { if (fl1->fl_lmops && fl1->fl_lmops->lm_compare_owner) return fl2->fl_lmops == fl1->fl_lmops && fl1->fl_lmops->lm_compare_owner(fl1, fl2); return fl1->fl_owner == fl2->fl_owner; } /* Must be called with the flc_lock held! */ static void locks_insert_global_locks(struct file_lock *fl) { lg_local_lock(&file_lock_lglock); fl->fl_link_cpu = smp_processor_id(); hlist_add_head(&fl->fl_link, this_cpu_ptr(&file_lock_list)); lg_local_unlock(&file_lock_lglock); } /* Must be called with the flc_lock held! */ static void locks_delete_global_locks(struct file_lock *fl) { /* * Avoid taking lock if already unhashed. This is safe since this check * is done while holding the flc_lock, and new insertions into the list * also require that it be held. */ if (hlist_unhashed(&fl->fl_link)) return; lg_local_lock_cpu(&file_lock_lglock, fl->fl_link_cpu); hlist_del_init(&fl->fl_link); lg_local_unlock_cpu(&file_lock_lglock, fl->fl_link_cpu); } static unsigned long posix_owner_key(struct file_lock *fl) { if (fl->fl_lmops && fl->fl_lmops->lm_owner_key) return fl->fl_lmops->lm_owner_key(fl); return (unsigned long)fl->fl_owner; } static void locks_insert_global_blocked(struct file_lock *waiter) { hash_add(blocked_hash, &waiter->fl_link, posix_owner_key(waiter)); } static void locks_delete_global_blocked(struct file_lock *waiter) { hash_del(&waiter->fl_link); } /* Remove waiter from blocker's block list. * When blocker ends up pointing to itself then the list is empty. * * Must be called with blocked_lock_lock held. */ static void __locks_delete_block(struct file_lock *waiter) { locks_delete_global_blocked(waiter); list_del_init(&waiter->fl_block); waiter->fl_next = NULL; } static void locks_delete_block(struct file_lock *waiter) { spin_lock(&blocked_lock_lock); __locks_delete_block(waiter); spin_unlock(&blocked_lock_lock); } /* Insert waiter into blocker's block list. * We use a circular list so that processes can be easily woken up in * the order they blocked. The documentation doesn't require this but * it seems like the reasonable thing to do. * * Must be called with both the flc_lock and blocked_lock_lock held. The * fl_block list itself is protected by the blocked_lock_lock, but by ensuring * that the flc_lock is also held on insertions we can avoid taking the * blocked_lock_lock in some cases when we see that the fl_block list is empty. */ static void __locks_insert_block(struct file_lock *blocker, struct file_lock *waiter) { BUG_ON(!list_empty(&waiter->fl_block)); waiter->fl_next = blocker; list_add_tail(&waiter->fl_block, &blocker->fl_block); if (IS_POSIX(blocker) && !IS_OFDLCK(blocker)) locks_insert_global_blocked(waiter); } /* Must be called with flc_lock held. */ static void locks_insert_block(struct file_lock *blocker, struct file_lock *waiter) { spin_lock(&blocked_lock_lock); __locks_insert_block(blocker, waiter); spin_unlock(&blocked_lock_lock); } /* * Wake up processes blocked waiting for blocker. * * Must be called with the inode->flc_lock held! */ static void locks_wake_up_blocks(struct file_lock *blocker) { /* * Avoid taking global lock if list is empty. This is safe since new * blocked requests are only added to the list under the flc_lock, and * the flc_lock is always held here. Note that removal from the fl_block * list does not require the flc_lock, so we must recheck list_empty() * after acquiring the blocked_lock_lock. */ if (list_empty(&blocker->fl_block)) return; spin_lock(&blocked_lock_lock); while (!list_empty(&blocker->fl_block)) { struct file_lock *waiter; waiter = list_first_entry(&blocker->fl_block, struct file_lock, fl_block); __locks_delete_block(waiter); if (waiter->fl_lmops && waiter->fl_lmops->lm_notify) waiter->fl_lmops->lm_notify(waiter); else wake_up(&waiter->fl_wait); } spin_unlock(&blocked_lock_lock); } static void locks_insert_lock_ctx(struct file_lock *fl, struct list_head *before) { fl->fl_nspid = get_pid(task_tgid(current)); list_add_tail(&fl->fl_list, before); locks_insert_global_locks(fl); } static void locks_unlink_lock_ctx(struct file_lock *fl) { locks_delete_global_locks(fl); list_del_init(&fl->fl_list); if (fl->fl_nspid) { put_pid(fl->fl_nspid); fl->fl_nspid = NULL; } locks_wake_up_blocks(fl); } static void locks_delete_lock_ctx(struct file_lock *fl, struct list_head *dispose) { locks_unlink_lock_ctx(fl); if (dispose) list_add(&fl->fl_list, dispose); else locks_free_lock(fl); } /* Determine if lock sys_fl blocks lock caller_fl. Common functionality * checks for shared/exclusive status of overlapping locks. */ static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl) { if (sys_fl->fl_type == F_WRLCK) return 1; if (caller_fl->fl_type == F_WRLCK) return 1; return 0; } /* Determine if lock sys_fl blocks lock caller_fl. POSIX specific * checking before calling the locks_conflict(). */ static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl) { /* POSIX locks owned by the same process do not conflict with * each other. */ if (!IS_POSIX(sys_fl) || posix_same_owner(caller_fl, sys_fl)) return (0); /* Check whether they overlap */ if (!locks_overlap(caller_fl, sys_fl)) return 0; return (locks_conflict(caller_fl, sys_fl)); } /* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific * checking before calling the locks_conflict(). */ static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl) { /* FLOCK locks referring to the same filp do not conflict with * each other. */ if (!IS_FLOCK(sys_fl) || (caller_fl->fl_file == sys_fl->fl_file)) return (0); if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND)) return 0; return (locks_conflict(caller_fl, sys_fl)); } void posix_test_lock(struct file *filp, struct file_lock *fl) { struct file_lock *cfl; struct file_lock_context *ctx; struct inode *inode = file_inode(filp); ctx = inode->i_flctx; if (!ctx || list_empty_careful(&ctx->flc_posix)) { fl->fl_type = F_UNLCK; return; } spin_lock(&ctx->flc_lock); list_for_each_entry(cfl, &ctx->flc_posix, fl_list) { if (posix_locks_conflict(fl, cfl)) { locks_copy_conflock(fl, cfl); if (cfl->fl_nspid) fl->fl_pid = pid_vnr(cfl->fl_nspid); goto out; } } fl->fl_type = F_UNLCK; out: spin_unlock(&ctx->flc_lock); return; } EXPORT_SYMBOL(posix_test_lock); /* * Deadlock detection: * * We attempt to detect deadlocks that are due purely to posix file * locks. * * We assume that a task can be waiting for at most one lock at a time. * So for any acquired lock, the process holding that lock may be * waiting on at most one other lock. That lock in turns may be held by * someone waiting for at most one other lock. Given a requested lock * caller_fl which is about to wait for a conflicting lock block_fl, we * follow this chain of waiters to ensure we are not about to create a * cycle. * * Since we do this before we ever put a process to sleep on a lock, we * are ensured that there is never a cycle; that is what guarantees that * the while() loop in posix_locks_deadlock() eventually completes. * * Note: the above assumption may not be true when handling lock * requests from a broken NFS client. It may also fail in the presence * of tasks (such as posix threads) sharing the same open file table. * To handle those cases, we just bail out after a few iterations. * * For FL_OFDLCK locks, the owner is the filp, not the files_struct. * Because the owner is not even nominally tied to a thread of * execution, the deadlock detection below can't reasonably work well. Just * skip it for those. * * In principle, we could do a more limited deadlock detection on FL_OFDLCK * locks that just checks for the case where two tasks are attempting to * upgrade from read to write locks on the same inode. */ #define MAX_DEADLK_ITERATIONS 10 /* Find a lock that the owner of the given block_fl is blocking on. */ static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl) { struct file_lock *fl; hash_for_each_possible(blocked_hash, fl, fl_link, posix_owner_key(block_fl)) { if (posix_same_owner(fl, block_fl)) return fl->fl_next; } return NULL; } /* Must be called with the blocked_lock_lock held! */ static int posix_locks_deadlock(struct file_lock *caller_fl, struct file_lock *block_fl) { int i = 0; /* * This deadlock detector can't reasonably detect deadlocks with * FL_OFDLCK locks, since they aren't owned by a process, per-se. */ if (IS_OFDLCK(caller_fl)) return 0; while ((block_fl = what_owner_is_waiting_for(block_fl))) { if (i++ > MAX_DEADLK_ITERATIONS) return 0; if (posix_same_owner(caller_fl, block_fl)) return 1; } return 0; } /* Try to create a FLOCK lock on filp. We always insert new FLOCK locks * after any leases, but before any posix locks. * * Note that if called with an FL_EXISTS argument, the caller may determine * whether or not a lock was successfully freed by testing the return * value for -ENOENT. */ static int flock_lock_file(struct file *filp, struct file_lock *request) { struct file_lock *new_fl = NULL; struct file_lock *fl; struct file_lock_context *ctx; struct inode *inode = file_inode(filp); int error = 0; bool found = false; LIST_HEAD(dispose); ctx = locks_get_lock_context(inode); if (!ctx) return -ENOMEM; if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) { new_fl = locks_alloc_lock(); if (!new_fl) return -ENOMEM; } spin_lock(&ctx->flc_lock); if (request->fl_flags & FL_ACCESS) goto find_conflict; list_for_each_entry(fl, &ctx->flc_flock, fl_list) { if (filp != fl->fl_file) continue; if (request->fl_type == fl->fl_type) goto out; found = true; locks_delete_lock_ctx(fl, &dispose); break; } if (request->fl_type == F_UNLCK) { if ((request->fl_flags & FL_EXISTS) && !found) error = -ENOENT; goto out; } find_conflict: list_for_each_entry(fl, &ctx->flc_flock, fl_list) { if (!flock_locks_conflict(request, fl)) continue; error = -EAGAIN; if (!(request->fl_flags & FL_SLEEP)) goto out; error = FILE_LOCK_DEFERRED; locks_insert_block(fl, request); goto out; } if (request->fl_flags & FL_ACCESS) goto out; locks_copy_lock(new_fl, request); locks_insert_lock_ctx(new_fl, &ctx->flc_flock); new_fl = NULL; error = 0; out: spin_unlock(&ctx->flc_lock); if (new_fl) locks_free_lock(new_fl); locks_dispose_list(&dispose); return error; } static int __posix_lock_file(struct inode *inode, struct file_lock *request, struct file_lock *conflock) { struct file_lock *fl, *tmp; struct file_lock *new_fl = NULL; struct file_lock *new_fl2 = NULL; struct file_lock *left = NULL; struct file_lock *right = NULL; struct file_lock_context *ctx; int error; bool added = false; LIST_HEAD(dispose); ctx = locks_get_lock_context(inode); if (!ctx) return -ENOMEM; /* * We may need two file_lock structures for this operation, * so we get them in advance to avoid races. * * In some cases we can be sure, that no new locks will be needed */ if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK || request->fl_start != 0 || request->fl_end != OFFSET_MAX)) { new_fl = locks_alloc_lock(); new_fl2 = locks_alloc_lock(); } spin_lock(&ctx->flc_lock); /* * New lock request. Walk all POSIX locks and look for conflicts. If * there are any, either return error or put the request on the * blocker's list of waiters and the global blocked_hash. */ if (request->fl_type != F_UNLCK) { list_for_each_entry(fl, &ctx->flc_posix, fl_list) { if (!posix_locks_conflict(request, fl)) continue; if (conflock) locks_copy_conflock(conflock, fl); error = -EAGAIN; if (!(request->fl_flags & FL_SLEEP)) goto out; /* * Deadlock detection and insertion into the blocked * locks list must be done while holding the same lock! */ error = -EDEADLK; spin_lock(&blocked_lock_lock); if (likely(!posix_locks_deadlock(request, fl))) { error = FILE_LOCK_DEFERRED; __locks_insert_block(fl, request); } spin_unlock(&blocked_lock_lock); goto out; } } /* If we're just looking for a conflict, we're done. */ error = 0; if (request->fl_flags & FL_ACCESS) goto out; /* Find the first old lock with the same owner as the new lock */ list_for_each_entry(fl, &ctx->flc_posix, fl_list) { if (posix_same_owner(request, fl)) break; } /* Process locks with this owner. */ list_for_each_entry_safe_from(fl, tmp, &ctx->flc_posix, fl_list) { if (!posix_same_owner(request, fl)) break; /* Detect adjacent or overlapping regions (if same lock type) */ if (request->fl_type == fl->fl_type) { /* In all comparisons of start vs end, use * "start - 1" rather than "end + 1". If end * is OFFSET_MAX, end + 1 will become negative. */ if (fl->fl_end < request->fl_start - 1) continue; /* If the next lock in the list has entirely bigger * addresses than the new one, insert the lock here. */ if (fl->fl_start - 1 > request->fl_end) break; /* If we come here, the new and old lock are of the * same type and adjacent or overlapping. Make one * lock yielding from the lower start address of both * locks to the higher end address. */ if (fl->fl_start > request->fl_start) fl->fl_start = request->fl_start; else request->fl_start = fl->fl_start; if (fl->fl_end < request->fl_end) fl->fl_end = request->fl_end; else request->fl_end = fl->fl_end; if (added) { locks_delete_lock_ctx(fl, &dispose); continue; } request = fl; added = true; } else { /* Processing for different lock types is a bit * more complex. */ if (fl->fl_end < request->fl_start) continue; if (fl->fl_start > request->fl_end) break; if (request->fl_type == F_UNLCK) added = true; if (fl->fl_start < request->fl_start) left = fl; /* If the next lock in the list has a higher end * address than the new one, insert the new one here. */ if (fl->fl_end > request->fl_end) { right = fl; break; } if (fl->fl_start >= request->fl_start) { /* The new lock completely replaces an old * one (This may happen several times). */ if (added) { locks_delete_lock_ctx(fl, &dispose); continue; } /* * Replace the old lock with new_fl, and * remove the old one. It's safe to do the * insert here since we know that we won't be * using new_fl later, and that the lock is * just replacing an existing lock. */ error = -ENOLCK; if (!new_fl) goto out; locks_copy_lock(new_fl, request); request = new_fl; new_fl = NULL; locks_insert_lock_ctx(request, &fl->fl_list); locks_delete_lock_ctx(fl, &dispose); added = true; } } } /* * The above code only modifies existing locks in case of merging or * replacing. If new lock(s) need to be inserted all modifications are * done below this, so it's safe yet to bail out. */ error = -ENOLCK; /* "no luck" */ if (right && left == right && !new_fl2) goto out; error = 0; if (!added) { if (request->fl_type == F_UNLCK) { if (request->fl_flags & FL_EXISTS) error = -ENOENT; goto out; } if (!new_fl) { error = -ENOLCK; goto out; } locks_copy_lock(new_fl, request); locks_insert_lock_ctx(new_fl, &fl->fl_list); fl = new_fl; new_fl = NULL; } if (right) { if (left == right) { /* The new lock breaks the old one in two pieces, * so we have to use the second new lock. */ left = new_fl2; new_fl2 = NULL; locks_copy_lock(left, right); locks_insert_lock_ctx(left, &fl->fl_list); } right->fl_start = request->fl_end + 1; locks_wake_up_blocks(right); } if (left) { left->fl_end = request->fl_start - 1; locks_wake_up_blocks(left); } out: spin_unlock(&ctx->flc_lock); /* * Free any unused locks. */ if (new_fl) locks_free_lock(new_fl); if (new_fl2) locks_free_lock(new_fl2); locks_dispose_list(&dispose); return error; } /** * posix_lock_file - Apply a POSIX-style lock to a file * @filp: The file to apply the lock to * @fl: The lock to be applied * @conflock: Place to return a copy of the conflicting lock, if found. * * Add a POSIX style lock to a file. * We merge adjacent & overlapping locks whenever possible. * POSIX locks are sorted by owner task, then by starting address * * Note that if called with an FL_EXISTS argument, the caller may determine * whether or not a lock was successfully freed by testing the return * value for -ENOENT. */ int posix_lock_file(struct file *filp, struct file_lock *fl, struct file_lock *conflock) { return __posix_lock_file(file_inode(filp), fl, conflock); } EXPORT_SYMBOL(posix_lock_file); /** * posix_lock_file_wait - Apply a POSIX-style lock to a file * @filp: The file to apply the lock to * @fl: The lock to be applied * * Add a POSIX style lock to a file. * We merge adjacent & overlapping locks whenever possible. * POSIX locks are sorted by owner task, then by starting address */ int posix_lock_file_wait(struct file *filp, struct file_lock *fl) { int error; might_sleep (); for (;;) { error = posix_lock_file(filp, fl, NULL); if (error != FILE_LOCK_DEFERRED) break; error = wait_event_interruptible(fl->fl_wait, !fl->fl_next); if (!error) continue; locks_delete_block(fl); break; } return error; } EXPORT_SYMBOL(posix_lock_file_wait); /** * locks_mandatory_locked - Check for an active lock * @file: the file to check * * Searches the inode's list of locks to find any POSIX locks which conflict. * This function is called from locks_verify_locked() only. */ int locks_mandatory_locked(struct file *file) { int ret; struct inode *inode = file_inode(file); struct file_lock_context *ctx; struct file_lock *fl; ctx = inode->i_flctx; if (!ctx || list_empty_careful(&ctx->flc_posix)) return 0; /* * Search the lock list for this inode for any POSIX locks. */ spin_lock(&ctx->flc_lock); ret = 0; list_for_each_entry(fl, &ctx->flc_posix, fl_list) { if (fl->fl_owner != current->files && fl->fl_owner != file) { ret = -EAGAIN; break; } } spin_unlock(&ctx->flc_lock); return ret; } /** * locks_mandatory_area - Check for a conflicting lock * @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ * for shared * @inode: the file to check * @filp: how the file was opened (if it was) * @offset: start of area to check * @count: length of area to check * * Searches the inode's list of locks to find any POSIX locks which conflict. * This function is called from rw_verify_area() and * locks_verify_truncate(). */ int locks_mandatory_area(int read_write, struct inode *inode, struct file *filp, loff_t offset, size_t count) { struct file_lock fl; int error; bool sleep = false; locks_init_lock(&fl); fl.fl_pid = current->tgid; fl.fl_file = filp; fl.fl_flags = FL_POSIX | FL_ACCESS; if (filp && !(filp->f_flags & O_NONBLOCK)) sleep = true; fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK; fl.fl_start = offset; fl.fl_end = offset + count - 1; for (;;) { if (filp) { fl.fl_owner = filp; fl.fl_flags &= ~FL_SLEEP; error = __posix_lock_file(inode, &fl, NULL); if (!error) break; } if (sleep) fl.fl_flags |= FL_SLEEP; fl.fl_owner = current->files; error = __posix_lock_file(inode, &fl, NULL); if (error != FILE_LOCK_DEFERRED) break; error = wait_event_interruptible(fl.fl_wait, !fl.fl_next); if (!error) { /* * If we've been sleeping someone might have * changed the permissions behind our back. */ if (__mandatory_lock(inode)) continue; } locks_delete_block(&fl); break; } return error; } EXPORT_SYMBOL(locks_mandatory_area); static void lease_clear_pending(struct file_lock *fl, int arg) { switch (arg) { case F_UNLCK: fl->fl_flags &= ~FL_UNLOCK_PENDING; /* fall through: */ case F_RDLCK: fl->fl_flags &= ~FL_DOWNGRADE_PENDING; } } /* We already had a lease on this file; just change its type */ int lease_modify(struct file_lock *fl, int arg, struct list_head *dispose) { int error = assign_type(fl, arg); if (error) return error; lease_clear_pending(fl, arg); locks_wake_up_blocks(fl); if (arg == F_UNLCK) { struct file *filp = fl->fl_file; f_delown(filp); filp->f_owner.signum = 0; fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync); if (fl->fl_fasync != NULL) { printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync); fl->fl_fasync = NULL; } locks_delete_lock_ctx(fl, dispose); } return 0; } EXPORT_SYMBOL(lease_modify); static bool past_time(unsigned long then) { if (!then) /* 0 is a special value meaning "this never expires": */ return false; return time_after(jiffies, then); } static void time_out_leases(struct inode *inode, struct list_head *dispose) { struct file_lock_context *ctx = inode->i_flctx; struct file_lock *fl, *tmp; lockdep_assert_held(&ctx->flc_lock); list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) { trace_time_out_leases(inode, fl); if (past_time(fl->fl_downgrade_time)) lease_modify(fl, F_RDLCK, dispose); if (past_time(fl->fl_break_time)) lease_modify(fl, F_UNLCK, dispose); } } static bool leases_conflict(struct file_lock *lease, struct file_lock *breaker) { if ((breaker->fl_flags & FL_LAYOUT) != (lease->fl_flags & FL_LAYOUT)) return false; if ((breaker->fl_flags & FL_DELEG) && (lease->fl_flags & FL_LEASE)) return false; return locks_conflict(breaker, lease); } static bool any_leases_conflict(struct inode *inode, struct file_lock *breaker) { struct file_lock_context *ctx = inode->i_flctx; struct file_lock *fl; lockdep_assert_held(&ctx->flc_lock); list_for_each_entry(fl, &ctx->flc_lease, fl_list) { if (leases_conflict(fl, breaker)) return true; } return false; } /** * __break_lease - revoke all outstanding leases on file * @inode: the inode of the file to return * @mode: O_RDONLY: break only write leases; O_WRONLY or O_RDWR: * break all leases * @type: FL_LEASE: break leases and delegations; FL_DELEG: break * only delegations * * break_lease (inlined for speed) has checked there already is at least * some kind of lock (maybe a lease) on this file. Leases are broken on * a call to open() or truncate(). This function can sleep unless you * specified %O_NONBLOCK to your open(). */ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type) { int error = 0; struct file_lock_context *ctx = inode->i_flctx; struct file_lock *new_fl, *fl, *tmp; unsigned long break_time; int want_write = (mode & O_ACCMODE) != O_RDONLY; LIST_HEAD(dispose); new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK); if (IS_ERR(new_fl)) return PTR_ERR(new_fl); new_fl->fl_flags = type; /* typically we will check that ctx is non-NULL before calling */ if (!ctx) { WARN_ON_ONCE(1); return error; } spin_lock(&ctx->flc_lock); time_out_leases(inode, &dispose); if (!any_leases_conflict(inode, new_fl)) goto out; break_time = 0; if (lease_break_time > 0) { break_time = jiffies + lease_break_time * HZ; if (break_time == 0) break_time++; /* so that 0 means no break time */ } list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) { if (!leases_conflict(fl, new_fl)) continue; if (want_write) { if (fl->fl_flags & FL_UNLOCK_PENDING) continue; fl->fl_flags |= FL_UNLOCK_PENDING; fl->fl_break_time = break_time; } else { if (lease_breaking(fl)) continue; fl->fl_flags |= FL_DOWNGRADE_PENDING; fl->fl_downgrade_time = break_time; } if (fl->fl_lmops->lm_break(fl)) locks_delete_lock_ctx(fl, &dispose); } if (list_empty(&ctx->flc_lease)) goto out; if (mode & O_NONBLOCK) { trace_break_lease_noblock(inode, new_fl); error = -EWOULDBLOCK; goto out; } restart: fl = list_first_entry(&ctx->flc_lease, struct file_lock, fl_list); break_time = fl->fl_break_time; if (break_time != 0) break_time -= jiffies; if (break_time == 0) break_time++; locks_insert_block(fl, new_fl); trace_break_lease_block(inode, new_fl); spin_unlock(&ctx->flc_lock); locks_dispose_list(&dispose); error = wait_event_interruptible_timeout(new_fl->fl_wait, !new_fl->fl_next, break_time); spin_lock(&ctx->flc_lock); trace_break_lease_unblock(inode, new_fl); locks_delete_block(new_fl); if (error >= 0) { /* * Wait for the next conflicting lease that has not been * broken yet */ if (error == 0) time_out_leases(inode, &dispose); if (any_leases_conflict(inode, new_fl)) goto restart; error = 0; } out: spin_unlock(&ctx->flc_lock); locks_dispose_list(&dispose); locks_free_lock(new_fl); return error; } EXPORT_SYMBOL(__break_lease); /** * lease_get_mtime - get the last modified time of an inode * @inode: the inode * @time: pointer to a timespec which will contain the last modified time * * This is to force NFS clients to flush their caches for files with * exclusive leases. The justification is that if someone has an * exclusive lease, then they could be modifying it. */ void lease_get_mtime(struct inode *inode, struct timespec *time) { bool has_lease = false; struct file_lock_context *ctx = inode->i_flctx; struct file_lock *fl; if (ctx && !list_empty_careful(&ctx->flc_lease)) { spin_lock(&ctx->flc_lock); if (!list_empty(&ctx->flc_lease)) { fl = list_first_entry(&ctx->flc_lease, struct file_lock, fl_list); if (fl->fl_type == F_WRLCK) has_lease = true; } spin_unlock(&ctx->flc_lock); } if (has_lease) *time = current_fs_time(inode->i_sb); else *time = inode->i_mtime; } EXPORT_SYMBOL(lease_get_mtime); /** * fcntl_getlease - Enquire what lease is currently active * @filp: the file * * The value returned by this function will be one of * (if no lease break is pending): * * %F_RDLCK to indicate a shared lease is held. * * %F_WRLCK to indicate an exclusive lease is held. * * %F_UNLCK to indicate no lease is held. * * (if a lease break is pending): * * %F_RDLCK to indicate an exclusive lease needs to be * changed to a shared lease (or removed). * * %F_UNLCK to indicate the lease needs to be removed. * * XXX: sfr & willy disagree over whether F_INPROGRESS * should be returned to userspace. */ int fcntl_getlease(struct file *filp) { struct file_lock *fl; struct inode *inode = file_inode(filp); struct file_lock_context *ctx = inode->i_flctx; int type = F_UNLCK; LIST_HEAD(dispose); if (ctx && !list_empty_careful(&ctx->flc_lease)) { spin_lock(&ctx->flc_lock); time_out_leases(file_inode(filp), &dispose); list_for_each_entry(fl, &ctx->flc_lease, fl_list) { if (fl->fl_file != filp) continue; type = target_leasetype(fl); break; } spin_unlock(&ctx->flc_lock); locks_dispose_list(&dispose); } return type; } /** * check_conflicting_open - see if the given dentry points to a file that has * an existing open that would conflict with the * desired lease. * @dentry: dentry to check * @arg: type of lease that we're trying to acquire * * Check to see if there's an existing open fd on this file that would * conflict with the lease we're trying to set. */ static int check_conflicting_open(const struct dentry *dentry, const long arg, int flags) { int ret = 0; struct inode *inode = dentry->d_inode; if (flags & FL_LAYOUT) return 0; if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0)) return -EAGAIN; if ((arg == F_WRLCK) && ((d_count(dentry) > 1) || (atomic_read(&inode->i_count) > 1))) ret = -EAGAIN; return ret; } static int generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **priv) { struct file_lock *fl, *my_fl = NULL, *lease; struct dentry *dentry = filp->f_path.dentry; struct inode *inode = dentry->d_inode; struct file_lock_context *ctx; bool is_deleg = (*flp)->fl_flags & FL_DELEG; int error; LIST_HEAD(dispose); lease = *flp; trace_generic_add_lease(inode, lease); ctx = locks_get_lock_context(inode); if (!ctx) return -ENOMEM; /* * In the delegation case we need mutual exclusion with * a number of operations that take the i_mutex. We trylock * because delegations are an optional optimization, and if * there's some chance of a conflict--we'd rather not * bother, maybe that's a sign this just isn't a good file to * hand out a delegation on. */ if (is_deleg && !mutex_trylock(&inode->i_mutex)) return -EAGAIN; if (is_deleg && arg == F_WRLCK) { /* Write delegations are not currently supported: */ mutex_unlock(&inode->i_mutex); WARN_ON_ONCE(1); return -EINVAL; } spin_lock(&ctx->flc_lock); time_out_leases(inode, &dispose); error = check_conflicting_open(dentry, arg, lease->fl_flags); if (error) goto out; /* * At this point, we know that if there is an exclusive * lease on this file, then we hold it on this filp * (otherwise our open of this file would have blocked). * And if we are trying to acquire an exclusive lease, * then the file is not open by anyone (including us) * except for this filp. */ error = -EAGAIN; list_for_each_entry(fl, &ctx->flc_lease, fl_list) { if (fl->fl_file == filp && fl->fl_owner == lease->fl_owner) { my_fl = fl; continue; } /* * No exclusive leases if someone else has a lease on * this file: */ if (arg == F_WRLCK) goto out; /* * Modifying our existing lease is OK, but no getting a * new lease if someone else is opening for write: */ if (fl->fl_flags & FL_UNLOCK_PENDING) goto out; } if (my_fl != NULL) { lease = my_fl; error = lease->fl_lmops->lm_change(lease, arg, &dispose); if (error) goto out; goto out_setup; } error = -EINVAL; if (!leases_enable) goto out; locks_insert_lock_ctx(lease, &ctx->flc_lease); /* * The check in break_lease() is lockless. It's possible for another * open to race in after we did the earlier check for a conflicting * open but before the lease was inserted. Check again for a * conflicting open and cancel the lease if there is one. * * We also add a barrier here to ensure that the insertion of the lock * precedes these checks. */ smp_mb(); error = check_conflicting_open(dentry, arg, lease->fl_flags); if (error) { locks_unlink_lock_ctx(lease); goto out; } out_setup: if (lease->fl_lmops->lm_setup) lease->fl_lmops->lm_setup(lease, priv); out: spin_unlock(&ctx->flc_lock); locks_dispose_list(&dispose); if (is_deleg) mutex_unlock(&inode->i_mutex); if (!error && !my_fl) *flp = NULL; return error; } static int generic_delete_lease(struct file *filp, void *owner) { int error = -EAGAIN; struct file_lock *fl, *victim = NULL; struct dentry *dentry = filp->f_path.dentry; struct inode *inode = dentry->d_inode; struct file_lock_context *ctx = inode->i_flctx; LIST_HEAD(dispose); if (!ctx) { trace_generic_delete_lease(inode, NULL); return error; } spin_lock(&ctx->flc_lock); list_for_each_entry(fl, &ctx->flc_lease, fl_list) { if (fl->fl_file == filp && fl->fl_owner == owner) { victim = fl; break; } } trace_generic_delete_lease(inode, victim); if (victim) error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose); spin_unlock(&ctx->flc_lock); locks_dispose_list(&dispose); return error; } /** * generic_setlease - sets a lease on an open file * @filp: file pointer * @arg: type of lease to obtain * @flp: input - file_lock to use, output - file_lock inserted * @priv: private data for lm_setup (may be NULL if lm_setup * doesn't require it) * * The (input) flp->fl_lmops->lm_break function is required * by break_lease(). */ int generic_setlease(struct file *filp, long arg, struct file_lock **flp, void **priv) { struct dentry *dentry = filp->f_path.dentry; struct inode *inode = dentry->d_inode; int error; if ((!uid_eq(current_fsuid(), inode->i_uid)) && !capable(CAP_LEASE)) return -EACCES; if (!S_ISREG(inode->i_mode)) return -EINVAL; error = security_file_lock(filp, arg); if (error) return error; switch (arg) { case F_UNLCK: return generic_delete_lease(filp, *priv); case F_RDLCK: case F_WRLCK: if (!(*flp)->fl_lmops->lm_break) { WARN_ON_ONCE(1); return -ENOLCK; } return generic_add_lease(filp, arg, flp, priv); default: return -EINVAL; } } EXPORT_SYMBOL(generic_setlease); /** * vfs_setlease - sets a lease on an open file * @filp: file pointer * @arg: type of lease to obtain * @lease: file_lock to use when adding a lease * @priv: private info for lm_setup when adding a lease (may be * NULL if lm_setup doesn't require it) * * Call this to establish a lease on the file. The "lease" argument is not * used for F_UNLCK requests and may be NULL. For commands that set or alter * an existing lease, the (*lease)->fl_lmops->lm_break operation must be set; * if not, this function will return -ENOLCK (and generate a scary-looking * stack trace). * * The "priv" pointer is passed directly to the lm_setup function as-is. It * may be NULL if the lm_setup operation doesn't require it. */ int vfs_setlease(struct file *filp, long arg, struct file_lock **lease, void **priv) { if (filp->f_op->setlease) return filp->f_op->setlease(filp, arg, lease, priv); else return generic_setlease(filp, arg, lease, priv); } EXPORT_SYMBOL_GPL(vfs_setlease); static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg) { struct file_lock *fl; struct fasync_struct *new; int error; fl = lease_alloc(filp, arg); if (IS_ERR(fl)) return PTR_ERR(fl); new = fasync_alloc(); if (!new) { locks_free_lock(fl); return -ENOMEM; } new->fa_fd = fd; error = vfs_setlease(filp, arg, &fl, (void **)&new); if (fl) locks_free_lock(fl); if (new) fasync_free(new); return error; } /** * fcntl_setlease - sets a lease on an open file * @fd: open file descriptor * @filp: file pointer * @arg: type of lease to obtain * * Call this fcntl to establish a lease on the file. * Note that you also need to call %F_SETSIG to * receive a signal when the lease is broken. */ int fcntl_setlease(unsigned int fd, struct file *filp, long arg) { if (arg == F_UNLCK) return vfs_setlease(filp, F_UNLCK, NULL, (void **)&filp); return do_fcntl_add_lease(fd, filp, arg); } /** * flock_lock_file_wait - Apply a FLOCK-style lock to a file * @filp: The file to apply the lock to * @fl: The lock to be applied * * Add a FLOCK style lock to a file. */ int flock_lock_file_wait(struct file *filp, struct file_lock *fl) { int error; might_sleep(); for (;;) { error = flock_lock_file(filp, fl); if (error != FILE_LOCK_DEFERRED) break; error = wait_event_interruptible(fl->fl_wait, !fl->fl_next); if (!error) continue; locks_delete_block(fl); break; } return error; } EXPORT_SYMBOL(flock_lock_file_wait); /** * sys_flock: - flock() system call. * @fd: the file descriptor to lock. * @cmd: the type of lock to apply. * * Apply a %FL_FLOCK style lock to an open file descriptor. * The @cmd can be one of * * %LOCK_SH -- a shared lock. * * %LOCK_EX -- an exclusive lock. * * %LOCK_UN -- remove an existing lock. * * %LOCK_MAND -- a `mandatory' flock. This exists to emulate Windows Share Modes. * * %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other * processes read and write access respectively. */ SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd) { struct fd f = fdget(fd); struct file_lock *lock; int can_sleep, unlock; int error; error = -EBADF; if (!f.file) goto out; can_sleep = !(cmd & LOCK_NB); cmd &= ~LOCK_NB; unlock = (cmd == LOCK_UN); if (!unlock && !(cmd & LOCK_MAND) && !(f.file->f_mode & (FMODE_READ|FMODE_WRITE))) goto out_putf; lock = flock_make_lock(f.file, cmd); if (IS_ERR(lock)) { error = PTR_ERR(lock); goto out_putf; } if (can_sleep) lock->fl_flags |= FL_SLEEP; error = security_file_lock(f.file, lock->fl_type); if (error) goto out_free; if (f.file->f_op->flock) error = f.file->f_op->flock(f.file, (can_sleep) ? F_SETLKW : F_SETLK, lock); else error = flock_lock_file_wait(f.file, lock); out_free: locks_free_lock(lock); out_putf: fdput(f); out: return error; } /** * vfs_test_lock - test file byte range lock * @filp: The file to test lock for * @fl: The lock to test; also used to hold result * * Returns -ERRNO on failure. Indicates presence of conflicting lock by * setting conf->fl_type to something other than F_UNLCK. */ int vfs_test_lock(struct file *filp, struct file_lock *fl) { if (filp->f_op->lock) return filp->f_op->lock(filp, F_GETLK, fl); posix_test_lock(filp, fl); return 0; } EXPORT_SYMBOL_GPL(vfs_test_lock); static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl) { flock->l_pid = IS_OFDLCK(fl) ? -1 : fl->fl_pid; #if BITS_PER_LONG == 32 /* * Make sure we can represent the posix lock via * legacy 32bit flock. */ if (fl->fl_start > OFFT_OFFSET_MAX) return -EOVERFLOW; if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX) return -EOVERFLOW; #endif flock->l_start = fl->fl_start; flock->l_len = fl->fl_end == OFFSET_MAX ? 0 : fl->fl_end - fl->fl_start + 1; flock->l_whence = 0; flock->l_type = fl->fl_type; return 0; } #if BITS_PER_LONG == 32 static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl) { flock->l_pid = IS_OFDLCK(fl) ? -1 : fl->fl_pid; flock->l_start = fl->fl_start; flock->l_len = fl->fl_end == OFFSET_MAX ? 0 : fl->fl_end - fl->fl_start + 1; flock->l_whence = 0; flock->l_type = fl->fl_type; } #endif /* Report the first existing lock that would conflict with l. * This implements the F_GETLK command of fcntl(). */ int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock __user *l) { struct file_lock file_lock; struct flock flock; int error; error = -EFAULT; if (copy_from_user(&flock, l, sizeof(flock))) goto out; error = -EINVAL; if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK)) goto out; error = flock_to_posix_lock(filp, &file_lock, &flock); if (error) goto out; if (cmd == F_OFD_GETLK) { error = -EINVAL; if (flock.l_pid != 0) goto out; cmd = F_GETLK; file_lock.fl_flags |= FL_OFDLCK; file_lock.fl_owner = filp; } error = vfs_test_lock(filp, &file_lock); if (error) goto out; flock.l_type = file_lock.fl_type; if (file_lock.fl_type != F_UNLCK) { error = posix_lock_to_flock(&flock, &file_lock); if (error) goto rel_priv; } error = -EFAULT; if (!copy_to_user(l, &flock, sizeof(flock))) error = 0; rel_priv: locks_release_private(&file_lock); out: return error; } /** * vfs_lock_file - file byte range lock * @filp: The file to apply the lock to * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.) * @fl: The lock to be applied * @conf: Place to return a copy of the conflicting lock, if found. * * A caller that doesn't care about the conflicting lock may pass NULL * as the final argument. * * If the filesystem defines a private ->lock() method, then @conf will * be left unchanged; so a caller that cares should initialize it to * some acceptable default. * * To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX * locks, the ->lock() interface may return asynchronously, before the lock has * been granted or denied by the underlying filesystem, if (and only if) * lm_grant is set. Callers expecting ->lock() to return asynchronously * will only use F_SETLK, not F_SETLKW; they will set FL_SLEEP if (and only if) * the request is for a blocking lock. When ->lock() does return asynchronously, * it must return FILE_LOCK_DEFERRED, and call ->lm_grant() when the lock * request completes. * If the request is for non-blocking lock the file system should return * FILE_LOCK_DEFERRED then try to get the lock and call the callback routine * with the result. If the request timed out the callback routine will return a * nonzero return code and the file system should release the lock. The file * system is also responsible to keep a corresponding posix lock when it * grants a lock so the VFS can find out which locks are locally held and do * the correct lock cleanup when required. * The underlying filesystem must not drop the kernel lock or call * ->lm_grant() before returning to the caller with a FILE_LOCK_DEFERRED * return code. */ int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf) { if (filp->f_op->lock) return filp->f_op->lock(filp, cmd, fl); else return posix_lock_file(filp, fl, conf); } EXPORT_SYMBOL_GPL(vfs_lock_file); static int do_lock_file_wait(struct file *filp, unsigned int cmd, struct file_lock *fl) { int error; error = security_file_lock(filp, fl->fl_type); if (error) return error; for (;;) { error = vfs_lock_file(filp, cmd, fl, NULL); if (error != FILE_LOCK_DEFERRED) break; error = wait_event_interruptible(fl->fl_wait, !fl->fl_next); if (!error) continue; locks_delete_block(fl); break; } return error; } /* Ensure that fl->fl_filp has compatible f_mode for F_SETLK calls */ static int check_fmode_for_setlk(struct file_lock *fl) { switch (fl->fl_type) { case F_RDLCK: if (!(fl->fl_file->f_mode & FMODE_READ)) return -EBADF; break; case F_WRLCK: if (!(fl->fl_file->f_mode & FMODE_WRITE)) return -EBADF; } return 0; } /* Apply the lock described by l to an open file descriptor. * This implements both the F_SETLK and F_SETLKW commands of fcntl(). */ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd, struct flock __user *l) { struct file_lock *file_lock = locks_alloc_lock(); struct flock flock; struct inode *inode; struct file *f; int error; if (file_lock == NULL) return -ENOLCK; /* * This might block, so we do it before checking the inode. */ error = -EFAULT; if (copy_from_user(&flock, l, sizeof(flock))) goto out; inode = file_inode(filp); /* Don't allow mandatory locks on files that may be memory mapped * and shared. */ if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) { error = -EAGAIN; goto out; } again: error = flock_to_posix_lock(filp, file_lock, &flock); if (error) goto out; error = check_fmode_for_setlk(file_lock); if (error) goto out; /* * If the cmd is requesting file-private locks, then set the * FL_OFDLCK flag and override the owner. */ switch (cmd) { case F_OFD_SETLK: error = -EINVAL; if (flock.l_pid != 0) goto out; cmd = F_SETLK; file_lock->fl_flags |= FL_OFDLCK; file_lock->fl_owner = filp; break; case F_OFD_SETLKW: error = -EINVAL; if (flock.l_pid != 0) goto out; cmd = F_SETLKW; file_lock->fl_flags |= FL_OFDLCK; file_lock->fl_owner = filp; /* Fallthrough */ case F_SETLKW: file_lock->fl_flags |= FL_SLEEP; } error = do_lock_file_wait(filp, cmd, file_lock); /* * Attempt to detect a close/fcntl race and recover by * releasing the lock that was just acquired. */ /* * we need that spin_lock here - it prevents reordering between * update of i_flctx->flc_posix and check for it done in close(). * rcu_read_lock() wouldn't do. */ spin_lock(¤t->files->file_lock); f = fcheck(fd); spin_unlock(¤t->files->file_lock); if (!error && f != filp && flock.l_type != F_UNLCK) { flock.l_type = F_UNLCK; goto again; } out: locks_free_lock(file_lock); return error; } #if BITS_PER_LONG == 32 /* Report the first existing lock that would conflict with l. * This implements the F_GETLK command of fcntl(). */ int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 __user *l) { struct file_lock file_lock; struct flock64 flock; int error; error = -EFAULT; if (copy_from_user(&flock, l, sizeof(flock))) goto out; error = -EINVAL; if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK)) goto out; error = flock64_to_posix_lock(filp, &file_lock, &flock); if (error) goto out; if (cmd == F_OFD_GETLK) { error = -EINVAL; if (flock.l_pid != 0) goto out; cmd = F_GETLK64; file_lock.fl_flags |= FL_OFDLCK; file_lock.fl_owner = filp; } error = vfs_test_lock(filp, &file_lock); if (error) goto out; flock.l_type = file_lock.fl_type; if (file_lock.fl_type != F_UNLCK) posix_lock_to_flock64(&flock, &file_lock); error = -EFAULT; if (!copy_to_user(l, &flock, sizeof(flock))) error = 0; locks_release_private(&file_lock); out: return error; } /* Apply the lock described by l to an open file descriptor. * This implements both the F_SETLK and F_SETLKW commands of fcntl(). */ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd, struct flock64 __user *l) { struct file_lock *file_lock = locks_alloc_lock(); struct flock64 flock; struct inode *inode; struct file *f; int error; if (file_lock == NULL) return -ENOLCK; /* * This might block, so we do it before checking the inode. */ error = -EFAULT; if (copy_from_user(&flock, l, sizeof(flock))) goto out; inode = file_inode(filp); /* Don't allow mandatory locks on files that may be memory mapped * and shared. */ if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) { error = -EAGAIN; goto out; } again: error = flock64_to_posix_lock(filp, file_lock, &flock); if (error) goto out; error = check_fmode_for_setlk(file_lock); if (error) goto out; /* * If the cmd is requesting file-private locks, then set the * FL_OFDLCK flag and override the owner. */ switch (cmd) { case F_OFD_SETLK: error = -EINVAL; if (flock.l_pid != 0) goto out; cmd = F_SETLK64; file_lock->fl_flags |= FL_OFDLCK; file_lock->fl_owner = filp; break; case F_OFD_SETLKW: error = -EINVAL; if (flock.l_pid != 0) goto out; cmd = F_SETLKW64; file_lock->fl_flags |= FL_OFDLCK; file_lock->fl_owner = filp; /* Fallthrough */ case F_SETLKW64: file_lock->fl_flags |= FL_SLEEP; } error = do_lock_file_wait(filp, cmd, file_lock); /* * Attempt to detect a close/fcntl race and recover by * releasing the lock that was just acquired. */ spin_lock(¤t->files->file_lock); f = fcheck(fd); spin_unlock(¤t->files->file_lock); if (!error && f != filp && flock.l_type != F_UNLCK) { flock.l_type = F_UNLCK; goto again; } out: locks_free_lock(file_lock); return error; } #endif /* BITS_PER_LONG == 32 */ /* * This function is called when the file is being removed * from the task's fd array. POSIX locks belonging to this task * are deleted at this time. */ void locks_remove_posix(struct file *filp, fl_owner_t owner) { struct file_lock lock; struct file_lock_context *ctx = file_inode(filp)->i_flctx; /* * If there are no locks held on this file, we don't need to call * posix_lock_file(). Another process could be setting a lock on this * file at the same time, but we wouldn't remove that lock anyway. */ if (!ctx || list_empty(&ctx->flc_posix)) return; lock.fl_type = F_UNLCK; lock.fl_flags = FL_POSIX | FL_CLOSE; lock.fl_start = 0; lock.fl_end = OFFSET_MAX; lock.fl_owner = owner; lock.fl_pid = current->tgid; lock.fl_file = filp; lock.fl_ops = NULL; lock.fl_lmops = NULL; vfs_lock_file(filp, F_SETLK, &lock, NULL); if (lock.fl_ops && lock.fl_ops->fl_release_private) lock.fl_ops->fl_release_private(&lock); } EXPORT_SYMBOL(locks_remove_posix); /* The i_flctx must be valid when calling into here */ static void locks_remove_flock(struct file *filp) { struct file_lock fl = { .fl_owner = filp, .fl_pid = current->tgid, .fl_file = filp, .fl_flags = FL_FLOCK, .fl_type = F_UNLCK, .fl_end = OFFSET_MAX, }; struct file_lock_context *flctx = file_inode(filp)->i_flctx; if (list_empty(&flctx->flc_flock)) return; if (filp->f_op->flock) filp->f_op->flock(filp, F_SETLKW, &fl); else flock_lock_file(filp, &fl); if (fl.fl_ops && fl.fl_ops->fl_release_private) fl.fl_ops->fl_release_private(&fl); } /* The i_flctx must be valid when calling into here */ static void locks_remove_lease(struct file *filp) { struct inode *inode = file_inode(filp); struct file_lock_context *ctx = inode->i_flctx; struct file_lock *fl, *tmp; LIST_HEAD(dispose); if (list_empty(&ctx->flc_lease)) return; spin_lock(&ctx->flc_lock); list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) if (filp == fl->fl_file) lease_modify(fl, F_UNLCK, &dispose); spin_unlock(&ctx->flc_lock); locks_dispose_list(&dispose); } /* * This function is called on the last close of an open file. */ void locks_remove_file(struct file *filp) { if (!file_inode(filp)->i_flctx) return; /* remove any OFD locks */ locks_remove_posix(filp, filp); /* remove flock locks */ locks_remove_flock(filp); /* remove any leases */ locks_remove_lease(filp); } /** * posix_unblock_lock - stop waiting for a file lock * @waiter: the lock which was waiting * * lockd needs to block waiting for locks. */ int posix_unblock_lock(struct file_lock *waiter) { int status = 0; spin_lock(&blocked_lock_lock); if (waiter->fl_next) __locks_delete_block(waiter); else status = -ENOENT; spin_unlock(&blocked_lock_lock); return status; } EXPORT_SYMBOL(posix_unblock_lock); /** * vfs_cancel_lock - file byte range unblock lock * @filp: The file to apply the unblock to * @fl: The lock to be unblocked * * Used by lock managers to cancel blocked requests */ int vfs_cancel_lock(struct file *filp, struct file_lock *fl) { if (filp->f_op->lock) return filp->f_op->lock(filp, F_CANCELLK, fl); return 0; } EXPORT_SYMBOL_GPL(vfs_cancel_lock); #ifdef CONFIG_PROC_FS #include #include struct locks_iterator { int li_cpu; loff_t li_pos; }; static void lock_get_status(struct seq_file *f, struct file_lock *fl, loff_t id, char *pfx) { struct inode *inode = NULL; unsigned int fl_pid; if (fl->fl_nspid) fl_pid = pid_vnr(fl->fl_nspid); else fl_pid = fl->fl_pid; if (fl->fl_file != NULL) inode = file_inode(fl->fl_file); seq_printf(f, "%lld:%s ", id, pfx); if (IS_POSIX(fl)) { if (fl->fl_flags & FL_ACCESS) seq_puts(f, "ACCESS"); else if (IS_OFDLCK(fl)) seq_puts(f, "OFDLCK"); else seq_puts(f, "POSIX "); seq_printf(f, " %s ", (inode == NULL) ? "*NOINODE*" : mandatory_lock(inode) ? "MANDATORY" : "ADVISORY "); } else if (IS_FLOCK(fl)) { if (fl->fl_type & LOCK_MAND) { seq_puts(f, "FLOCK MSNFS "); } else { seq_puts(f, "FLOCK ADVISORY "); } } else if (IS_LEASE(fl)) { if (fl->fl_flags & FL_DELEG) seq_puts(f, "DELEG "); else seq_puts(f, "LEASE "); if (lease_breaking(fl)) seq_puts(f, "BREAKING "); else if (fl->fl_file) seq_puts(f, "ACTIVE "); else seq_puts(f, "BREAKER "); } else { seq_puts(f, "UNKNOWN UNKNOWN "); } if (fl->fl_type & LOCK_MAND) { seq_printf(f, "%s ", (fl->fl_type & LOCK_READ) ? (fl->fl_type & LOCK_WRITE) ? "RW " : "READ " : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE "); } else { seq_printf(f, "%s ", (lease_breaking(fl)) ? (fl->fl_type == F_UNLCK) ? "UNLCK" : "READ " : (fl->fl_type == F_WRLCK) ? "WRITE" : "READ "); } if (inode) { #ifdef WE_CAN_BREAK_LSLK_NOW seq_printf(f, "%d %s:%ld ", fl_pid, inode->i_sb->s_id, inode->i_ino); #else /* userspace relies on this representation of dev_t ;-( */ seq_printf(f, "%d %02x:%02x:%ld ", fl_pid, MAJOR(inode->i_sb->s_dev), MINOR(inode->i_sb->s_dev), inode->i_ino); #endif } else { seq_printf(f, "%d :0 ", fl_pid); } if (IS_POSIX(fl)) { if (fl->fl_end == OFFSET_MAX) seq_printf(f, "%Ld EOF\n", fl->fl_start); else seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end); } else { seq_puts(f, "0 EOF\n"); } } static int locks_show(struct seq_file *f, void *v) { struct locks_iterator *iter = f->private; struct file_lock *fl, *bfl; fl = hlist_entry(v, struct file_lock, fl_link); lock_get_status(f, fl, iter->li_pos, ""); list_for_each_entry(bfl, &fl->fl_block, fl_block) lock_get_status(f, bfl, iter->li_pos, " ->"); return 0; } static void *locks_start(struct seq_file *f, loff_t *pos) __acquires(&blocked_lock_lock) { struct locks_iterator *iter = f->private; iter->li_pos = *pos + 1; lg_global_lock(&file_lock_lglock); spin_lock(&blocked_lock_lock); return seq_hlist_start_percpu(&file_lock_list, &iter->li_cpu, *pos); } static void *locks_next(struct seq_file *f, void *v, loff_t *pos) { struct locks_iterator *iter = f->private; ++iter->li_pos; return seq_hlist_next_percpu(v, &file_lock_list, &iter->li_cpu, pos); } static void locks_stop(struct seq_file *f, void *v) __releases(&blocked_lock_lock) { spin_unlock(&blocked_lock_lock); lg_global_unlock(&file_lock_lglock); } static const struct seq_operations locks_seq_operations = { .start = locks_start, .next = locks_next, .stop = locks_stop, .show = locks_show, }; static int locks_open(struct inode *inode, struct file *filp) { return seq_open_private(filp, &locks_seq_operations, sizeof(struct locks_iterator)); } static const struct file_operations proc_locks_operations = { .open = locks_open, .read = seq_read, .llseek = seq_lseek, .release = seq_release_private, }; static int __init proc_locks_init(void) { proc_create("locks", 0, NULL, &proc_locks_operations); return 0; } module_init(proc_locks_init); #endif static int __init filelock_init(void) { int i; flctx_cache = kmem_cache_create("file_lock_ctx", sizeof(struct file_lock_context), 0, SLAB_PANIC, NULL); filelock_cache = kmem_cache_create("file_lock_cache", sizeof(struct file_lock), 0, SLAB_PANIC, NULL); lg_lock_init(&file_lock_lglock, "file_lock_lglock"); for_each_possible_cpu(i) INIT_HLIST_HEAD(per_cpu_ptr(&file_lock_list, i)); return 0; } core_initcall(filelock_init);