On Tue, 2021-10-19 at 12:16 -0400, J. Bruce Fields wrote: > On Tue, Oct 19, 2021 at 11:46:51AM -0400, Jeff Layton wrote: > > IDK...Do we want to "erase history" selectively like that? > > Seems like pretty spotty history anyway, so I don't think it's a > problem, but... > > > Maybe we should just get rid of the whole pile of "changelog" comments > > in fs/locks.c? They aren't terribly useful these days anyhow. > > ... that'd be fine with me. > > I didn't mainly because I thought it'd be good to read through it and > see if there's anything that should be salvaged. > > Reading through it now: > > The last few paragraphs (under "Locking conflicts and dependencies" were > added more recently by Neil and are still useful. > > I'd be OK losing the rest. > > It might still be good to have some basic introduction; maybe something > like this?: > > --b. > > diff --git a/fs/locks.c b/fs/locks.c > index 3d6fb4ae847b..b54813eae44f 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@xxxxxxxxxx), 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@xxxxxxxxxxxxxxxxxxxxxxxxx), 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@xxxxxxxxxx), 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@xxxxxxxxxxxxxxxxxxx), February 14, 1995 > - * > - * Scrapped free list which is redundant now that we allocate locks > - * dynamically with kmalloc()/kfree(). > - * Andy Walker (andy@xxxxxxxxxxxxxxxxxxx), 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@xxxxxxxxxxxxxxxxxxx), 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@xxxxxxx), 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@xxxxxxxxxxxxxxxxxxx), 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@xxxxxxxxxxxxxxxxxxx), 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@xxxxxxxxxxxxxxxxxxx), April 09, 1996. > - * > - * Tidied up block list handling. Added '/proc/locks' interface. > - * Andy Walker (andy@xxxxxxxxxxxxxxxxxxx), April 24, 1996. > - * > - * Fixed deadlock condition for pathological code that mixes calls to > - * flock() and fcntl(). > - * Andy Walker (andy@xxxxxxxxxxxxxxxxxxx), 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@xxxxxxxxxxxxxxxxxxx), May 15, 1996. > - * > - * Added a couple of missing wake_up() calls. Thanks to Thomas Meckel > - * (Thomas.Meckel@xxxxxxxxxxxxxxxxx) for spotting this. > - * Andy Walker (andy@xxxxxxxxxxxxxxxxxxx), 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@xxxxxxxxxxxxxxxxxxx), Sep 21, 1996. > - * > - * Made the block list a circular list to minimise searching in the list. > - * Andy Walker (andy@xxxxxxxxxxxxxxxxxxx), Sep 25, 1996. > - * > - * Made mandatory locking a mount option. Default is not to allow mandatory > - * locking. > - * Andy Walker (andy@xxxxxxxxxxxxxxxxxxx), Oct 04, 1996. > - * > - * Some adaptations for NFS support. > - * Olaf Kirch (okir@xxxxxxxxxxxx), Dec 1996, > - * > - * Fixed /proc/locks interface so that we can't overrun the buffer we are handed. > - * Andy Walker (andy@xxxxxxxxxxxxxxxxxxx), 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@xxxxxxxxxx>, March, 2000. > - * > - * Leases and LOCK_MAND > - * Matthew Wilcox <willy@xxxxxxxxxx>, June, 2000. > - * Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>, June, 2000. > * > * Locking conflicts and dependencies: > * If multiple threads attempt to lock the same byte (or flock the same file) Yeah, I think that looks great. Send it with a changelog and I'll pull it into the branch I have feeding into -next. Thanks, -- Jeff Layton <jlayton@xxxxxxxxxx>
