diff options
Diffstat (limited to 'fs/locks.c')
| -rw-r--r-- | fs/locks.c | 114 |
1 files changed, 4 insertions, 110 deletions
diff --git a/fs/locks.c b/fs/locks.c index d397394633be..0fca9d680978 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -2,117 +2,11 @@ /* * 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 + * We implement four types of file locks: BSD locks, posix locks, open + * file description locks, and leases. For details about BSD locks, + * see the flock(2) man page; for details about the other three, see + * fcntl(2). * - * 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.rst' 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. * * Locking conflicts and dependencies: * If multiple threads attempt to lock the same byte (or flock the same file) |