| /* |
| * 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/mandatory.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 <linux/list.h>. |
| * Sped up posix_locks_deadlock by only considering blocked locks. |
| * Matthew Wilcox <willy@debian.org>, March, 2000. |
| * |
| * Leases and LOCK_MAND |
| * Matthew Wilcox <willy@debian.org>, June, 2000. |
| * Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000. |
| */ |
| |
| #include <linux/capability.h> |
| #include <linux/file.h> |
| #include <linux/fs.h> |
| #include <linux/init.h> |
| #include <linux/module.h> |
| #include <linux/security.h> |
| #include <linux/slab.h> |
| #include <linux/smp_lock.h> |
| #include <linux/syscalls.h> |
| #include <linux/time.h> |
| #include <linux/rcupdate.h> |
| |
| #include <asm/semaphore.h> |
| #include <asm/uaccess.h> |
| |
| #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) |
| |
| int leases_enable = 1; |
| int lease_break_time = 45; |
| |
| #define for_each_lock(inode, lockp) \ |
| for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next) |
| |
| static LIST_HEAD(file_lock_list); |
| static LIST_HEAD(blocked_list); |
| |
| static struct kmem_cache *filelock_cache __read_mostly; |
| |
| /* Allocate an empty lock structure. */ |
| static struct file_lock *locks_alloc_lock(void) |
| { |
| return kmem_cache_alloc(filelock_cache, GFP_KERNEL); |
| } |
| |
| static 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->fl_release_private) |
| fl->fl_lmops->fl_release_private(fl); |
| fl->fl_lmops = NULL; |
| } |
| |
| } |
| |
| /* Free a lock which is not in use. */ |
| static void locks_free_lock(struct file_lock *fl) |
| { |
| BUG_ON(waitqueue_active(&fl->fl_wait)); |
| BUG_ON(!list_empty(&fl->fl_block)); |
| BUG_ON(!list_empty(&fl->fl_link)); |
| |
| locks_release_private(fl); |
| kmem_cache_free(filelock_cache, fl); |
| } |
| |
| void locks_init_lock(struct file_lock *fl) |
| { |
| INIT_LIST_HEAD(&fl->fl_link); |
| INIT_LIST_HEAD(&fl->fl_block); |
| init_waitqueue_head(&fl->fl_wait); |
| fl->fl_next = NULL; |
| fl->fl_fasync = NULL; |
| fl->fl_owner = NULL; |
| fl->fl_pid = 0; |
| fl->fl_file = NULL; |
| fl->fl_flags = 0; |
| fl->fl_type = 0; |
| fl->fl_start = fl->fl_end = 0; |
| fl->fl_ops = NULL; |
| fl->fl_lmops = NULL; |
| } |
| |
| EXPORT_SYMBOL(locks_init_lock); |
| |
| /* |
| * Initialises the fields of the file lock which are invariant for |
| * free file_locks. |
| */ |
| static void init_once(void *foo, struct kmem_cache *cache, unsigned long flags) |
| { |
| struct file_lock *lock = (struct file_lock *) foo; |
| |
| locks_init_lock(lock); |
| } |
| |
| static void locks_copy_private(struct file_lock *new, struct file_lock *fl) |
| { |
| if (fl->fl_ops) { |
| if (fl->fl_ops->fl_copy_lock) |
| fl->fl_ops->fl_copy_lock(new, fl); |
| new->fl_ops = fl->fl_ops; |
| } |
| if (fl->fl_lmops) { |
| if (fl->fl_lmops->fl_copy_lock) |
| fl->fl_lmops->fl_copy_lock(new, fl); |
| new->fl_lmops = fl->fl_lmops; |
| } |
| } |
| |
| /* |
| * Initialize a new lock from an existing file_lock structure. |
| */ |
| static void __locks_copy_lock(struct file_lock *new, const 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_ops = NULL; |
| new->fl_lmops = NULL; |
| } |
| |
| void locks_copy_lock(struct file_lock *new, struct file_lock *fl) |
| { |
| locks_release_private(new); |
| |
| __locks_copy_lock(new, fl); |
| new->fl_file = fl->fl_file; |
| new->fl_ops = fl->fl_ops; |
| new->fl_lmops = fl->fl_lmops; |
| |
| locks_copy_private(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 int flock_make_lock(struct file *filp, struct file_lock **lock, |
| unsigned int cmd) |
| { |
| struct file_lock *fl; |
| int type = flock_translate_cmd(cmd); |
| if (type < 0) |
| return type; |
| |
| fl = locks_alloc_lock(); |
| if (fl == NULL) |
| return -ENOMEM; |
| |
| fl->fl_file = filp; |
| fl->fl_pid = current->tgid; |
| fl->fl_flags = FL_FLOCK; |
| fl->fl_type = type; |
| fl->fl_end = OFFSET_MAX; |
| |
| *lock = fl; |
| return 0; |
| } |
| |
| static int assign_type(struct file_lock *fl, int type) |
| { |
| switch (type) { |
| case F_RDLCK: |
| case F_WRLCK: |
| case F_UNLCK: |
| fl->fl_type = type; |
| break; |
| default: |
| return -EINVAL; |
| } |
| return 0; |
| } |
| |
| /* 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) |
| { |
| off_t start, end; |
| |
| switch (l->l_whence) { |
| case SEEK_SET: |
| start = 0; |
| break; |
| case SEEK_CUR: |
| start = filp->f_pos; |
| break; |
| case SEEK_END: |
| start = i_size_read(filp->f_path.dentry->d_inode); |
| break; |
| default: |
| return -EINVAL; |
| } |
| |
| /* POSIX-1996 leaves the case l->l_len < 0 undefined; |
| POSIX-2001 defines it. */ |
| start += l->l_start; |
| if (start < 0) |
| return -EINVAL; |
| fl->fl_end = OFFSET_MAX; |
| if (l->l_len > 0) { |
| end = start + l->l_len - 1; |
| fl->fl_end = end; |
| } else if (l->l_len < 0) { |
| end = start - 1; |
| fl->fl_end = end; |
| start += l->l_len; |
| if (start < 0) |
| return -EINVAL; |
| } |
| fl->fl_start = start; /* we record the absolute position */ |
| if (fl->fl_end < fl->fl_start) |
| return -EOVERFLOW; |
| |
| 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); |
| } |
| |
| #if BITS_PER_LONG == 32 |
| static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl, |
| struct flock64 *l) |
| { |
| loff_t start; |
| |
| switch (l->l_whence) { |
| case SEEK_SET: |
| start = 0; |
| break; |
| case SEEK_CUR: |
| start = filp->f_pos; |
| break; |
| case SEEK_END: |
| start = i_size_read(filp->f_path.dentry->d_inode); |
| break; |
| default: |
| return -EINVAL; |
| } |
| |
| start += l->l_start; |
| if (start < 0) |
| return -EINVAL; |
| fl->fl_end = OFFSET_MAX; |
| if (l->l_len > 0) { |
| fl->fl_end = start + l->l_len - 1; |
| } else if (l->l_len < 0) { |
| fl->fl_end = start - 1; |
| start += l->l_len; |
| if (start < 0) |
| return -EINVAL; |
| } |
| fl->fl_start = start; /* we record the absolute position */ |
| if (fl->fl_end < fl->fl_start) |
| return -EOVERFLOW; |
| |
| 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; |
| |
| switch (l->l_type) { |
| case F_RDLCK: |
| case F_WRLCK: |
| case F_UNLCK: |
| fl->fl_type = l->l_type; |
| break; |
| default: |
| return -EINVAL; |
| } |
| |
| return (0); |
| } |
| #endif |
| |
| /* default lease lock manager operations */ |
| static void lease_break_callback(struct file_lock *fl) |
| { |
| kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG); |
| } |
| |
| static void lease_release_private_callback(struct file_lock *fl) |
| { |
| if (!fl->fl_file) |
| return; |
| |
| f_delown(fl->fl_file); |
| fl->fl_file->f_owner.signum = 0; |
| } |
| |
| static int lease_mylease_callback(struct file_lock *fl, struct file_lock *try) |
| { |
| return fl->fl_file == try->fl_file; |
| } |
| |
| static struct lock_manager_operations lease_manager_ops = { |
| .fl_break = lease_break_callback, |
| .fl_release_private = lease_release_private_callback, |
| .fl_mylease = lease_mylease_callback, |
| .fl_change = lease_modify, |
| }; |
| |
| /* |
| * Initialize a lease, use the default lock manager operations |
| */ |
| static int lease_init(struct file *filp, int type, struct file_lock *fl) |
| { |
| if (assign_type(fl, type) != 0) |
| return -EINVAL; |
| |
| fl->fl_owner = current->files; |
| 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, int 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->fl_compare_owner) |
| return fl2->fl_lmops == fl1->fl_lmops && |
| fl1->fl_lmops->fl_compare_owner(fl1, fl2); |
| return fl1->fl_owner == fl2->fl_owner; |
| } |
| |
| /* Remove waiter from blocker's block list. |
| * When blocker ends up pointing to itself then the list is empty. |
| */ |
| static void __locks_delete_block(struct file_lock *waiter) |
| { |
| list_del_init(&waiter->fl_block); |
| list_del_init(&waiter->fl_link); |
| waiter->fl_next = NULL; |
| } |
| |
| /* |
| */ |
| static void locks_delete_block(struct file_lock *waiter) |
| { |
| lock_kernel(); |
| __locks_delete_block(waiter); |
| unlock_kernel(); |
| } |
| |
| /* 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. |
| */ |
| static void locks_insert_block(struct file_lock *blocker, |
| struct file_lock *waiter) |
| { |
| BUG_ON(!list_empty(&waiter->fl_block)); |
| list_add_tail(&waiter->fl_block, &blocker->fl_block); |
| waiter->fl_next = blocker; |
| if (IS_POSIX(blocker)) |
| list_add(&waiter->fl_link, &blocked_list); |
| } |
| |
| /* Wake up processes blocked waiting for blocker. |
| * If told to wait then schedule the processes until the block list |
| * is empty, otherwise empty the block list ourselves. |
| */ |
| static void locks_wake_up_blocks(struct file_lock *blocker) |
| { |
| while (!list_empty(&blocker->fl_block)) { |
| struct file_lock *waiter = list_entry(blocker->fl_block.next, |
| struct file_lock, fl_block); |
| __locks_delete_block(waiter); |
| if (waiter->fl_lmops && waiter->fl_lmops->fl_notify) |
| waiter->fl_lmops->fl_notify(waiter); |
| else |
| wake_up(&waiter->fl_wait); |
| } |
| } |
| |
| /* Insert file lock fl into an inode's lock list at the position indicated |
| * by pos. At the same time add the lock to the global file lock list. |
| */ |
| static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl) |
| { |
| list_add(&fl->fl_link, &file_lock_list); |
| |
| /* insert into file's list */ |
| fl->fl_next = *pos; |
| *pos = fl; |
| |
| if (fl->fl_ops && fl->fl_ops->fl_insert) |
| fl->fl_ops->fl_insert(fl); |
| } |
| |
| /* |
| * Delete a lock and then free it. |
| * Wake up processes that are blocked waiting for this lock, |
| * notify the FS that the lock has been cleared and |
| * finally free the lock. |
| */ |
| static void locks_delete_lock(struct file_lock **thisfl_p) |
| { |
| struct file_lock *fl = *thisfl_p; |
| |
| *thisfl_p = fl->fl_next; |
| fl->fl_next = NULL; |
| list_del_init(&fl->fl_link); |
| |
| 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; |
| } |
| |
| if (fl->fl_ops && fl->fl_ops->fl_remove) |
| fl->fl_ops->fl_remove(fl); |
| |
| locks_wake_up_blocks(fl); |
| 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)); |
| } |
| |
| static int interruptible_sleep_on_locked(wait_queue_head_t *fl_wait, int timeout) |
| { |
| int result = 0; |
| DECLARE_WAITQUEUE(wait, current); |
| |
| __set_current_state(TASK_INTERRUPTIBLE); |
| add_wait_queue(fl_wait, &wait); |
| if (timeout == 0) |
| schedule(); |
| else |
| result = schedule_timeout(timeout); |
| if (signal_pending(current)) |
| result = -ERESTARTSYS; |
| remove_wait_queue(fl_wait, &wait); |
| __set_current_state(TASK_RUNNING); |
| return result; |
| } |
| |
| static int locks_block_on_timeout(struct file_lock *blocker, struct file_lock *waiter, int time) |
| { |
| int result; |
| locks_insert_block(blocker, waiter); |
| result = interruptible_sleep_on_locked(&waiter->fl_wait, time); |
| __locks_delete_block(waiter); |
| return result; |
| } |
| |
| int |
| posix_test_lock(struct file *filp, struct file_lock *fl) |
| { |
| struct file_lock *cfl; |
| |
| lock_kernel(); |
| for (cfl = filp->f_path.dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) { |
| if (!IS_POSIX(cfl)) |
| continue; |
| if (posix_locks_conflict(cfl, fl)) |
| break; |
| } |
| if (cfl) { |
| __locks_copy_lock(fl, cfl); |
| unlock_kernel(); |
| return 1; |
| } else |
| fl->fl_type = F_UNLCK; |
| unlock_kernel(); |
| return 0; |
| } |
| |
| EXPORT_SYMBOL(posix_test_lock); |
| |
| /* This function tests for deadlock condition before putting a process to |
| * sleep. The detection scheme is no longer recursive. Recursive was neat, |
| * but dangerous - we risked stack corruption if the lock data was bad, or |
| * if the recursion was too deep for any other reason. |
| * |
| * We rely on the fact that a task can only be on one lock's wait queue |
| * at a time. When we find blocked_task on a wait queue we can re-search |
| * with blocked_task equal to that queue's owner, until either blocked_task |
| * isn't found, or blocked_task is found on a queue owned by my_task. |
| * |
| * Note: the above assumption may not be true when handling lock requests |
| * from a broken NFS client. But broken NFS clients have a lot more to |
| * worry about than proper deadlock detection anyway... --okir |
| */ |
| static int posix_locks_deadlock(struct file_lock *caller_fl, |
| struct file_lock *block_fl) |
| { |
| struct list_head *tmp; |
| |
| next_task: |
| if (posix_same_owner(caller_fl, block_fl)) |
| return 1; |
| list_for_each(tmp, &blocked_list) { |
| struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link); |
| if (posix_same_owner(fl, block_fl)) { |
| fl = fl->fl_next; |
| block_fl = fl; |
| goto next_task; |
| } |
| } |
| return 0; |
| } |
| |
| /* Try to create a FLOCK lock on filp. We always insert new FLOCK locks |
| * at the head of the list, but that's secret knowledge known only to |
| * flock_lock_file and posix_lock_file. |
| * |
| * 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 **before; |
| struct inode * inode = filp->f_path.dentry->d_inode; |
| int error = 0; |
| int found = 0; |
| |
| lock_kernel(); |
| if (request->fl_flags & FL_ACCESS) |
| goto find_conflict; |
| for_each_lock(inode, before) { |
| struct file_lock *fl = *before; |
| if (IS_POSIX(fl)) |
| break; |
| if (IS_LEASE(fl)) |
| continue; |
| if (filp != fl->fl_file) |
| continue; |
| if (request->fl_type == fl->fl_type) |
| goto out; |
| found = 1; |
| locks_delete_lock(before); |
| break; |
| } |
| |
| if (request->fl_type == F_UNLCK) { |
| if ((request->fl_flags & FL_EXISTS) && !found) |
| error = -ENOENT; |
| goto out; |
| } |
| |
| error = -ENOMEM; |
| new_fl = locks_alloc_lock(); |
| if (new_fl == NULL) |
| goto out; |
| /* |
| * If a higher-priority process was blocked on the old file lock, |
| * give it the opportunity to lock the file. |
| */ |
| if (found) |
| cond_resched(); |
| |
| find_conflict: |
| for_each_lock(inode, before) { |
| struct file_lock *fl = *before; |
| if (IS_POSIX(fl)) |
| break; |
| if (IS_LEASE(fl)) |
| continue; |
| if (!flock_locks_conflict(request, fl)) |
| continue; |
| error = -EAGAIN; |
| if (request->fl_flags & FL_SLEEP) |
| locks_insert_block(fl, request); |
| goto out; |
| } |
| if (request->fl_flags & FL_ACCESS) |
| goto out; |
| locks_copy_lock(new_fl, request); |
| locks_insert_lock(&inode->i_flock, new_fl); |
| new_fl = NULL; |
| error = 0; |
| |
| out: |
| unlock_kernel(); |
| if (new_fl) |
| locks_free_lock(new_fl); |
| return error; |
| } |
| |
| static int __posix_lock_file(struct inode *inode, struct file_lock *request, struct file_lock *conflock) |
| { |
| struct file_lock *fl; |
| 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 **before; |
| int error, added = 0; |
| |
| /* |
| * 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(); |
| } |
| |
| lock_kernel(); |
| if (request->fl_type != F_UNLCK) { |
| for_each_lock(inode, before) { |
| struct file_lock *fl = *before; |
| if (!IS_POSIX(fl)) |
| continue; |
| if (!posix_locks_conflict(request, fl)) |
| continue; |
| if (conflock) |
| locks_copy_lock(conflock, fl); |
| error = -EAGAIN; |
| if (!(request->fl_flags & FL_SLEEP)) |
| goto out; |
| error = -EDEADLK; |
| if (posix_locks_deadlock(request, fl)) |
| goto out; |
| error = -EAGAIN; |
| locks_insert_block(fl, request); |
| 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. |
| */ |
| |
| before = &inode->i_flock; |
| |
| /* First skip locks owned by other processes. */ |
| while ((fl = *before) && (!IS_POSIX(fl) || |
| !posix_same_owner(request, fl))) { |
| before = &fl->fl_next; |
| } |
| |
| /* Process locks with this owner. */ |
| while ((fl = *before) && posix_same_owner(request, fl)) { |
| /* 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) |
| goto next_lock; |
| /* 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(before); |
| continue; |
| } |
| request = fl; |
| added = 1; |
| } |
| else { |
| /* Processing for different lock types is a bit |
| * more complex. |
| */ |
| if (fl->fl_end < request->fl_start) |
| goto next_lock; |
| if (fl->fl_start > request->fl_end) |
| break; |
| if (request->fl_type == F_UNLCK) |
| added = 1; |
| 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(before); |
| continue; |
| } |
| /* Replace the old lock with the new one. |
| * Wake up anybody waiting for the old one, |
| * as the change in lock type might satisfy |
| * their needs. |
| */ |
| locks_wake_up_blocks(fl); |
| fl->fl_start = request->fl_start; |
| fl->fl_end = request->fl_end; |
| fl->fl_type = request->fl_type; |
| locks_release_private(fl); |
| locks_copy_private(fl, request); |
| request = fl; |
| added = 1; |
| } |
| } |
| /* Go on to next lock. |
| */ |
| next_lock: |
| before = &fl->fl_next; |
| } |
| |
| /* |
| * 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 bellow 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(before, 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(before, left); |
| } |
| 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: |
| unlock_kernel(); |
| /* |
| * Free any unused locks. |
| */ |
| if (new_fl) |
| locks_free_lock(new_fl); |
| if (new_fl2) |
| locks_free_lock(new_fl2); |
| 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(filp->f_path.dentry->d_inode, 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 != -EAGAIN) || !(fl->fl_flags & FL_SLEEP)) |
| 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 |
| * @inode: 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 inode *inode) |
| { |
| fl_owner_t owner = current->files; |
| struct file_lock *fl; |
| |
| /* |
| * Search the lock list for this inode for any POSIX locks. |
| */ |
| lock_kernel(); |
| for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) { |
| if (!IS_POSIX(fl)) |
| continue; |
| if (fl->fl_owner != owner) |
| break; |
| } |
| unlock_kernel(); |
| return fl ? -EAGAIN : 0; |
| } |
| |
| /** |
| * 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; |
| |
| locks_init_lock(&fl); |
| fl.fl_owner = current->files; |
| fl.fl_pid = current->tgid; |
| fl.fl_file = filp; |
| fl.fl_flags = FL_POSIX | FL_ACCESS; |
| if (filp && !(filp->f_flags & O_NONBLOCK)) |
| fl.fl_flags |= FL_SLEEP; |
| fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK; |
| fl.fl_start = offset; |
| fl.fl_end = offset + count - 1; |
| |
| for (;;) { |
| error = __posix_lock_file(inode, &fl, NULL); |
| if (error != -EAGAIN) |
| break; |
| if (!(fl.fl_flags & FL_SLEEP)) |
| 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 ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID) |
| continue; |
| } |
| |
| locks_delete_block(&fl); |
| break; |
| } |
| |
| return error; |
| } |
| |
| EXPORT_SYMBOL(locks_mandatory_area); |
| |
| /* We already had a lease on this file; just change its type */ |
| int lease_modify(struct file_lock **before, int arg) |
| { |
| struct file_lock *fl = *before; |
| int error = assign_type(fl, arg); |
| |
| if (error) |
| return error; |
| locks_wake_up_blocks(fl); |
| if (arg == F_UNLCK) |
| locks_delete_lock(before); |
| return 0; |
| } |
| |
| EXPORT_SYMBOL(lease_modify); |
| |
| static void time_out_leases(struct inode *inode) |
| { |
| struct file_lock **before; |
| struct file_lock *fl; |
| |
| before = &inode->i_flock; |
| while ((fl = *before) && IS_LEASE(fl) && (fl->fl_type & F_INPROGRESS)) { |
| if ((fl->fl_break_time == 0) |
| || time_before(jiffies, fl->fl_break_time)) { |
| before = &fl->fl_next; |
| continue; |
| } |
| lease_modify(before, fl->fl_type & ~F_INPROGRESS); |
| if (fl == *before) /* lease_modify may have freed fl */ |
| before = &fl->fl_next; |
| } |
| } |
| |
| /** |
| * __break_lease - revoke all outstanding leases on file |
| * @inode: the inode of the file to return |
| * @mode: the open mode (read or write) |
| * |
| * 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) |
| { |
| int error = 0, future; |
| struct file_lock *new_fl, *flock; |
| struct file_lock *fl; |
| unsigned long break_time; |
| int i_have_this_lease = 0; |
| |
| new_fl = lease_alloc(NULL, mode & FMODE_WRITE ? F_WRLCK : F_RDLCK); |
| |
| lock_kernel(); |
| |
| time_out_leases(inode); |
| |
| flock = inode->i_flock; |
| if ((flock == NULL) || !IS_LEASE(flock)) |
| goto out; |
| |
| for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) |
| if (fl->fl_owner == current->files) |
| i_have_this_lease = 1; |
| |
| if (mode & FMODE_WRITE) { |
| /* If we want write access, we have to revoke any lease. */ |
| future = F_UNLCK | F_INPROGRESS; |
| } else if (flock->fl_type & F_INPROGRESS) { |
| /* If the lease is already being broken, we just leave it */ |
| future = flock->fl_type; |
| } else if (flock->fl_type & F_WRLCK) { |
| /* Downgrade the exclusive lease to a read-only lease. */ |
| future = F_RDLCK | F_INPROGRESS; |
| } else { |
| /* the existing lease was read-only, so we can read too. */ |
| goto out; |
| } |
| |
| if (IS_ERR(new_fl) && !i_have_this_lease |
| && ((mode & O_NONBLOCK) == 0)) { |
| error = PTR_ERR(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 */ |
| } |
| |
| for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) { |
| if (fl->fl_type != future) { |
| fl->fl_type = future; |
| fl->fl_break_time = break_time; |
| /* lease must have lmops break callback */ |
| fl->fl_lmops->fl_break(fl); |
| } |
| } |
| |
| if (i_have_this_lease || (mode & O_NONBLOCK)) { |
| error = -EWOULDBLOCK; |
| goto out; |
| } |
| |
| restart: |
| break_time = flock->fl_break_time; |
| if (break_time != 0) { |
| break_time -= jiffies; |
| if (break_time == 0) |
| break_time++; |
| } |
| error = locks_block_on_timeout(flock, new_fl, break_time); |
| if (error >= 0) { |
| if (error == 0) |
| time_out_leases(inode); |
| /* Wait for the next lease that has not been broken yet */ |
| for (flock = inode->i_flock; flock && IS_LEASE(flock); |
| flock = flock->fl_next) { |
| if (flock->fl_type & F_INPROGRESS) |
| goto restart; |
| } |
| error = 0; |
| } |
| |
| out: |
| unlock_kernel(); |
| if (!IS_ERR(new_fl)) |
| locks_free_lock(new_fl); |
| return error; |
| } |
| |
| EXPORT_SYMBOL(__break_lease); |
| |
| /** |
| * lease_get_mtime |
| * @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 modifiying it. |
| */ |
| void lease_get_mtime(struct inode *inode, struct timespec *time) |
| { |
| struct file_lock *flock = inode->i_flock; |
| if (flock && IS_LEASE(flock) && (flock->fl_type & F_WRLCK)) |
| *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; |
| int type = F_UNLCK; |
| |
| lock_kernel(); |
| time_out_leases(filp->f_path.dentry->d_inode); |
| for (fl = filp->f_path.dentry->d_inode->i_flock; fl && IS_LEASE(fl); |
| fl = fl->fl_next) { |
| if (fl->fl_file == filp) { |
| type = fl->fl_type & ~F_INPROGRESS; |
| break; |
| } |
| } |
| unlock_kernel(); |
| return type; |
| } |
| |
| /** |
| * __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 |
| * |
| * The (input) flp->fl_lmops->fl_break function is required |
| * by break_lease(). |
| * |
| * Called with kernel lock held. |
| */ |
| static int __setlease(struct file *filp, long arg, struct file_lock **flp) |
| { |
| struct file_lock *fl, **before, **my_before = NULL, *lease; |
| struct dentry *dentry = filp->f_path.dentry; |
| struct inode *inode = dentry->d_inode; |
| int error, rdlease_count = 0, wrlease_count = 0; |
| |
| time_out_leases(inode); |
| |
| BUG_ON(!(*flp)->fl_lmops->fl_break); |
| |
| lease = *flp; |
| |
| error = -EAGAIN; |
| if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0)) |
| goto out; |
| if ((arg == F_WRLCK) |
| && ((atomic_read(&dentry->d_count) > 1) |
| || (atomic_read(&inode->i_count) > 1))) |
| 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. |
| */ |
| for (before = &inode->i_flock; |
| ((fl = *before) != NULL) && IS_LEASE(fl); |
| before = &fl->fl_next) { |
| if (lease->fl_lmops->fl_mylease(fl, lease)) |
| my_before = before; |
| else if (fl->fl_type == (F_INPROGRESS | F_UNLCK)) |
| /* |
| * Someone is in the process of opening this |
| * file for writing so we may not take an |
| * exclusive lease on it. |
| */ |
| wrlease_count++; |
| else |
| rdlease_count++; |
| } |
| |
| if ((arg == F_RDLCK && (wrlease_count > 0)) || |
| (arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0))) |
| goto out; |
| |
| if (my_before != NULL) { |
| *flp = *my_before; |
| error = lease->fl_lmops->fl_change(my_before, arg); |
| goto out; |
| } |
| |
| error = 0; |
| if (arg == F_UNLCK) |
| goto out; |
| |
| error = -EINVAL; |
| if (!leases_enable) |
| goto out; |
| |
| error = -ENOMEM; |
| fl = locks_alloc_lock(); |
| if (fl == NULL) |
| goto out; |
| |
| locks_copy_lock(fl, lease); |
| |
| locks_insert_lock(before, fl); |
| |
| *flp = fl; |
| error = 0; |
| out: |
| return error; |
| } |
| |
| /** |
| * setlease - sets a lease on an open file |
| * @filp: file pointer |
| * @arg: type of lease to obtain |
| * @lease: file_lock to use |
| * |
| * Call this to establish a lease on the file. |
| * The fl_lmops fl_break function is required by break_lease |
| */ |
| |
| int setlease(struct file *filp, long arg, struct file_lock **lease) |
| { |
| struct dentry *dentry = filp->f_path.dentry; |
| struct inode *inode = dentry->d_inode; |
| int error; |
| |
| if ((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; |
| |
| lock_kernel(); |
| error = __setlease(filp, arg, lease); |
| unlock_kernel(); |
| |
| return error; |
| } |
| |
| EXPORT_SYMBOL(setlease); |
| |
| /** |
| * 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) |
| { |
| struct file_lock fl, *flp = &fl; |
| struct dentry *dentry = filp->f_path.dentry; |
| struct inode *inode = dentry->d_inode; |
| int error; |
| |
| if ((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; |
| |
| locks_init_lock(&fl); |
| error = lease_init(filp, arg, &fl); |
| if (error) |
| return error; |
| |
| lock_kernel(); |
| |
| error = __setlease(filp, arg, &flp); |
| if (error || arg == F_UNLCK) |
| goto out_unlock; |
| |
| error = fasync_helper(fd, filp, 1, &flp->fl_fasync); |
| if (error < 0) { |
| /* remove lease just inserted by __setlease */ |
| flp->fl_type = F_UNLCK | F_INPROGRESS; |
| flp->fl_break_time = jiffies- 10; |
| time_out_leases(inode); |
| goto out_unlock; |
| } |
| |
| error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0); |
| out_unlock: |
| unlock_kernel(); |
| return error; |
| } |
| |
| /** |
| * 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 != -EAGAIN) || !(fl->fl_flags & FL_SLEEP)) |
| 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. |
| */ |
| asmlinkage long sys_flock(unsigned int fd, unsigned int cmd) |
| { |
| struct file *filp; |
| struct file_lock *lock; |
| int can_sleep, unlock; |
| int error; |
| |
| error = -EBADF; |
| filp = fget(fd); |
| if (!filp) |
| goto out; |
| |
| can_sleep = !(cmd & LOCK_NB); |
| cmd &= ~LOCK_NB; |
| unlock = (cmd == LOCK_UN); |
| |
| if (!unlock && !(cmd & LOCK_MAND) && !(filp->f_mode & 3)) |
| goto out_putf; |
| |
| error = flock_make_lock(filp, &lock, cmd); |
| if (error) |
| goto out_putf; |
| if (can_sleep) |
| lock->fl_flags |= FL_SLEEP; |
| |
| error = security_file_lock(filp, cmd); |
| if (error) |
| goto out_free; |
| |
| if (filp->f_op && filp->f_op->flock) |
| error = filp->f_op->flock(filp, |
| (can_sleep) ? F_SETLKW : F_SETLK, |
| lock); |
| else |
| error = flock_lock_file_wait(filp, lock); |
| |
| out_free: |
| locks_free_lock(lock); |
| |
| out_putf: |
| fput(filp); |
| out: |
| return error; |
| } |
| |
| /** |
| * vfs_test_lock - test file byte range lock |
| * @filp: The file to test lock for |
| * @fl: The lock to test |
| * @conf: Place to return a copy of the conflicting lock, if found |
| * |
| * 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 && 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 = 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 = 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, 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; |
| |
| 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 out; |
| } |
| error = -EFAULT; |
| if (!copy_to_user(l, &flock, sizeof(flock))) |
| error = 0; |
| 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) |
| * fl_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 -EINPROGRESS, and call ->fl_grant() when the lock |
| * request completes. |
| * If the request is for non-blocking lock the file system should return |
| * -EINPROGRESS 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 |
| * ->fl_grant() before returning to the caller with a -EINPROGRESS |
| * return code. |
| */ |
| int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf) |
| { |
| if (filp->f_op && 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); |
| |
| /* 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; |
| 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 = filp->f_path.dentry->d_inode; |
| |
| /* Don't allow mandatory locks on files that may be memory mapped |
| * and shared. |
| */ |
| if (IS_MANDLOCK(inode) && |
| (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID && |
| mapping_writably_mapped(filp->f_mapping)) { |
| error = -EAGAIN; |
| goto out; |
| } |
| |
| again: |
| error = flock_to_posix_lock(filp, file_lock, &flock); |
| if (error) |
| goto out; |
| if (cmd == F_SETLKW) { |
| file_lock->fl_flags |= FL_SLEEP; |
| } |
| |
| error = -EBADF; |
| switch (flock.l_type) { |
| case F_RDLCK: |
| if (!(filp->f_mode & FMODE_READ)) |
| goto out; |
| break; |
| case F_WRLCK: |
| if (!(filp->f_mode & FMODE_WRITE)) |
| goto out; |
| break; |
| case F_UNLCK: |
| break; |
| default: |
| error = -EINVAL; |
| goto out; |
| } |
| |
| error = security_file_lock(filp, file_lock->fl_type); |
| if (error) |
| goto out; |
| |
| for (;;) { |
| error = vfs_lock_file(filp, cmd, file_lock, NULL); |
| if (error != -EAGAIN || cmd == F_SETLK) |
| break; |
| error = wait_event_interruptible(file_lock->fl_wait, |
| !file_lock->fl_next); |
| if (!error) |
| continue; |
| |
| locks_delete_block(file_lock); |
| break; |
| } |
| |
| /* |
| * Attempt to detect a close/fcntl race and recover by |
| * releasing the lock that was just acquired. |
| */ |
| if (!error && fcheck(fd) != 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, 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; |
| |
| 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; |
| |
| 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; |
| 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 = filp->f_path.dentry->d_inode; |
| |
| /* Don't allow mandatory locks on files that may be memory mapped |
| * and shared. |
| */ |
| if (IS_MANDLOCK(inode) && |
| (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID && |
| mapping_writably_mapped(filp->f_mapping)) { |
| error = -EAGAIN; |
| goto out; |
| } |
| |
| again: |
| error = flock64_to_posix_lock(filp, file_lock, &flock); |
| if (error) |
| goto out; |
| if (cmd == F_SETLKW64) { |
| file_lock->fl_flags |= FL_SLEEP; |
| } |
| |
| error = -EBADF; |
| switch (flock.l_type) { |
| case F_RDLCK: |
| if (!(filp->f_mode & FMODE_READ)) |
| goto out; |
| break; |
| case F_WRLCK: |
| if (!(filp->f_mode & FMODE_WRITE)) |
| goto out; |
| break; |
| case F_UNLCK: |
| break; |
| default: |
| error = -EINVAL; |
| goto out; |
| } |
| |
| error = security_file_lock(filp, file_lock->fl_type); |
| if (error) |
| goto out; |
| |
| for (;;) { |
| error = vfs_lock_file(filp, cmd, file_lock, NULL); |
| if (error != -EAGAIN || cmd == F_SETLK64) |
| break; |
| error = wait_event_interruptible(file_lock->fl_wait, |
| !file_lock->fl_next); |
| if (!error) |
| continue; |
| |
| locks_delete_block(file_lock); |
| break; |
| } |
| |
| /* |
| * Attempt to detect a close/fcntl race and recover by |
| * releasing the lock that was just acquired. |
| */ |
| if (!error && fcheck(fd) != 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; |
| |
| /* |
| * 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 (!filp->f_path.dentry->d_inode->i_flock) |
| 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); |
| |
| /* |
| * This function is called on the last close of an open file. |
| */ |
| void locks_remove_flock(struct file *filp) |
| { |
| struct inode * inode = filp->f_path.dentry->d_inode; |
| struct file_lock *fl; |
| struct file_lock **before; |
| |
| if (!inode->i_flock) |
| return; |
| |
| if (filp->f_op && filp->f_op->flock) { |
| struct file_lock fl = { |
| .fl_pid = current->tgid, |
| .fl_file = filp, |
| .fl_flags = FL_FLOCK, |
| .fl_type = F_UNLCK, |
| .fl_end = OFFSET_MAX, |
| }; |
| filp->f_op->flock(filp, F_SETLKW, &fl); |
| if (fl.fl_ops && fl.fl_ops->fl_release_private) |
| fl.fl_ops->fl_release_private(&fl); |
| } |
| |
| lock_kernel(); |
| before = &inode->i_flock; |
| |
| while ((fl = *before) != NULL) { |
| if (fl->fl_file == filp) { |
| if (IS_FLOCK(fl)) { |
| locks_delete_lock(before); |
| continue; |
| } |
| if (IS_LEASE(fl)) { |
| lease_modify(before, F_UNLCK); |
| continue; |
| } |
| /* What? */ |
| BUG(); |
| } |
| before = &fl->fl_next; |
| } |
| unlock_kernel(); |
| } |
| |
| /** |
| * posix_unblock_lock - stop waiting for a file lock |
| * @filp: how the file was opened |
| * @waiter: the lock which was waiting |
| * |
| * lockd needs to block waiting for locks. |
| */ |
| int |
| posix_unblock_lock(struct file *filp, struct file_lock *waiter) |
| { |
| int status = 0; |
| |
| lock_kernel(); |
| if (waiter->fl_next) |
| __locks_delete_block(waiter); |
| else |
| status = -ENOENT; |
| unlock_kernel(); |
| 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 && filp->f_op->lock) |
| return filp->f_op->lock(filp, F_CANCELLK, fl); |
| return 0; |
| } |
| |
| EXPORT_SYMBOL_GPL(vfs_cancel_lock); |
| |
| static void lock_get_status(char* out, struct file_lock *fl, int id, char *pfx) |
| { |
| struct inode *inode = NULL; |
| |
| if (fl->fl_file != NULL) |
| inode = fl->fl_file->f_path.dentry->d_inode; |
| |
| out += sprintf(out, "%d:%s ", id, pfx); |
| if (IS_POSIX(fl)) { |
| out += sprintf(out, "%6s %s ", |
| (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ", |
| (inode == NULL) ? "*NOINODE*" : |
| (IS_MANDLOCK(inode) && |
| (inode->i_mode & (S_IXGRP | S_ISGID)) == S_ISGID) ? |
| "MANDATORY" : "ADVISORY "); |
| } else if (IS_FLOCK(fl)) { |
| if (fl->fl_type & LOCK_MAND) { |
| out += sprintf(out, "FLOCK MSNFS "); |
| } else { |
| out += sprintf(out, "FLOCK ADVISORY "); |
| } |
| } else if (IS_LEASE(fl)) { |
| out += sprintf(out, "LEASE "); |
| if (fl->fl_type & F_INPROGRESS) |
| out += sprintf(out, "BREAKING "); |
| else if (fl->fl_file) |
| out += sprintf(out, "ACTIVE "); |
| else |
| out += sprintf(out, "BREAKER "); |
| } else { |
| out += sprintf(out, "UNKNOWN UNKNOWN "); |
| } |
| if (fl->fl_type & LOCK_MAND) { |
| out += sprintf(out, "%s ", |
| (fl->fl_type & LOCK_READ) |
| ? (fl->fl_type & LOCK_WRITE) ? "RW " : "READ " |
| : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE "); |
| } else { |
| out += sprintf(out, "%s ", |
| (fl->fl_type & F_INPROGRESS) |
| ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ " |
| : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ "); |
| } |
| if (inode) { |
| #ifdef WE_CAN_BREAK_LSLK_NOW |
| out += sprintf(out, "%d %s:%ld ", fl->fl_pid, |
| inode->i_sb->s_id, inode->i_ino); |
| #else |
| /* userspace relies on this representation of dev_t ;-( */ |
| out += sprintf(out, "%d %02x:%02x:%ld ", fl->fl_pid, |
| MAJOR(inode->i_sb->s_dev), |
| MINOR(inode->i_sb->s_dev), inode->i_ino); |
| #endif |
| } else { |
| out += sprintf(out, "%d <none>:0 ", fl->fl_pid); |
| } |
| if (IS_POSIX(fl)) { |
| if (fl->fl_end == OFFSET_MAX) |
| out += sprintf(out, "%Ld EOF\n", fl->fl_start); |
| else |
| out += sprintf(out, "%Ld %Ld\n", fl->fl_start, |
| fl->fl_end); |
| } else { |
| out += sprintf(out, "0 EOF\n"); |
| } |
| } |
| |
| static void move_lock_status(char **p, off_t* pos, off_t offset) |
| { |
| int len; |
| len = strlen(*p); |
| if(*pos >= offset) { |
| /* the complete line is valid */ |
| *p += len; |
| *pos += len; |
| return; |
| } |
| if(*pos+len > offset) { |
| /* use the second part of the line */ |
| int i = offset-*pos; |
| memmove(*p,*p+i,len-i); |
| *p += len-i; |
| *pos += len; |
| return; |
| } |
| /* discard the complete line */ |
| *pos += len; |
| } |
| |
| /** |
| * get_locks_status - reports lock usage in /proc/locks |
| * @buffer: address in userspace to write into |
| * @start: ? |
| * @offset: how far we are through the buffer |
| * @length: how much to read |
| */ |
| |
| int get_locks_status(char *buffer, char **start, off_t offset, int length) |
| { |
| struct list_head *tmp; |
| char *q = buffer; |
| off_t pos = 0; |
| int i = 0; |
| |
| lock_kernel(); |
| list_for_each(tmp, &file_lock_list) { |
| struct list_head *btmp; |
| struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link); |
| lock_get_status(q, fl, ++i, ""); |
| move_lock_status(&q, &pos, offset); |
| |
| if(pos >= offset+length) |
| goto done; |
| |
| list_for_each(btmp, &fl->fl_block) { |
| struct file_lock *bfl = list_entry(btmp, |
| struct file_lock, fl_block); |
| lock_get_status(q, bfl, i, " ->"); |
| move_lock_status(&q, &pos, offset); |
| |
| if(pos >= offset+length) |
| goto done; |
| } |
| } |
| done: |
| unlock_kernel(); |
| *start = buffer; |
| if(q-buffer < length) |
| return (q-buffer); |
| return length; |
| } |
| |
| /** |
| * lock_may_read - checks that the region is free of locks |
| * @inode: the inode that is being read |
| * @start: the first byte to read |
| * @len: the number of bytes to read |
| * |
| * Emulates Windows locking requirements. Whole-file |
| * mandatory locks (share modes) can prohibit a read and |
| * byte-range POSIX locks can prohibit a read if they overlap. |
| * |
| * N.B. this function is only ever called |
| * from knfsd and ownership of locks is never checked. |
| */ |
| int lock_may_read(struct inode *inode, loff_t start, unsigned long len) |
| { |
| struct file_lock *fl; |
| int result = 1; |
| lock_kernel(); |
| for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) { |
| if (IS_POSIX(fl)) { |
| if (fl->fl_type == F_RDLCK) |
| continue; |
| if ((fl->fl_end < start) || (fl->fl_start > (start + len))) |
| continue; |
| } else if (IS_FLOCK(fl)) { |
| if (!(fl->fl_type & LOCK_MAND)) |
| continue; |
| if (fl->fl_type & LOCK_READ) |
| continue; |
| } else |
| continue; |
| result = 0; |
| break; |
| } |
| unlock_kernel(); |
| return result; |
| } |
| |
| EXPORT_SYMBOL(lock_may_read); |
| |
| /** |
| * lock_may_write - checks that the region is free of locks |
| * @inode: the inode that is being written |
| * @start: the first byte to write |
| * @len: the number of bytes to write |
| * |
| * Emulates Windows locking requirements. Whole-file |
| * mandatory locks (share modes) can prohibit a write and |
| * byte-range POSIX locks can prohibit a write if they overlap. |
| * |
| * N.B. this function is only ever called |
| * from knfsd and ownership of locks is never checked. |
| */ |
| int lock_may_write(struct inode *inode, loff_t start, unsigned long len) |
| { |
| struct file_lock *fl; |
| int result = 1; |
| lock_kernel(); |
| for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) { |
| if (IS_POSIX(fl)) { |
| if ((fl->fl_end < start) || (fl->fl_start > (start + len))) |
| continue; |
| } else if (IS_FLOCK(fl)) { |
| if (!(fl->fl_type & LOCK_MAND)) |
| continue; |
| if (fl->fl_type & LOCK_WRITE) |
| continue; |
| } else |
| continue; |
| result = 0; |
| break; |
| } |
| unlock_kernel(); |
| return result; |
| } |
| |
| EXPORT_SYMBOL(lock_may_write); |
| |
| static int __init filelock_init(void) |
| { |
| filelock_cache = kmem_cache_create("file_lock_cache", |
| sizeof(struct file_lock), 0, SLAB_PANIC, |
| init_once, NULL); |
| return 0; |
| } |
| |
| core_initcall(filelock_init); |