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File locking changes for v5.16 

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Merge tag 'locks-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux

Pull file locking updates from Jeff Layton:
 "Most of this is just follow-on cleanup work of documentation and
  comments from the mandatory locking removal in v5.15.

  The only real functional change is that LOCK_MAND flock() support is
  also being removed, as it has basically been non-functional since the
  v2.5 days"

* tag 'locks-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
  fs: remove leftover comments from mandatory locking removal
  locks: remove changelog comments
  docs: fs: locks.rst: update comment about mandatory file locking
  Documentation: remove reference to now removed mandatory-locking doc
  locks: remove LOCK_MAND flock lock support
This commit is contained in:
Linus Torvalds 2021-11-01 09:06:53 -07:00
parent ad98a92466 482e00075d
commit 9ac211426f
9 changed files with 36 additions and 169 deletions
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1
Documentation/filesystems/index.rst
View File

@ -29,7 +29,6 @@ algorithms work.
fiemap
files
locks
mandatory-locking
mount_api
quota
seq_file

17
Documentation/filesystems/locks.rst
View File

@ -57,16 +57,9 @@ fcntl(), with all the problems that implies.
1.3 Mandatory Locking As A Mount Option
---------------------------------------
Mandatory locking, as described in
'Documentation/filesystems/mandatory-locking.rst' was prior to this release a
general configuration option that was valid for all mounted filesystems. This
had a number of inherent dangers, not the least of which was the ability to
freeze an NFS server by asking it to read a file for which a mandatory lock
existed.
From this release of the kernel, mandatory locking can be turned on and off
on a per-filesystem basis, using the mount options 'mand' and 'nomand'.
The default is to disallow mandatory locking. The intention is that
mandatory locking only be enabled on a local filesystem as the specific need
arises.
Mandatory locking was prior to this release a general configuration option
that was valid for all mounted filesystems. This had a number of inherent
dangers, not the least of which was the ability to freeze an NFS server by
asking it to read a file for which a mandatory lock existed.
Such option was dropped in Kernel v5.14.

3
fs/ceph/locks.c
View File

@ -302,9 +302,6 @@ int ceph_flock(struct file *file, int cmd, struct file_lock *fl)
if (!(fl->fl_flags & FL_FLOCK))
return -ENOLCK;
/* No mandatory locks */
if (fl->fl_type & LOCK_MAND)
return -EOPNOTSUPP;
dout("ceph_flock, fl_file: %p\n", fl->fl_file);

2
fs/gfs2/file.c
View File

@ -1338,8 +1338,6 @@ static int gfs2_flock(struct file *file, int cmd, struct file_lock *fl)
{
if (!(fl->fl_flags & FL_FLOCK))
return -ENOLCK;
if (fl->fl_type & LOCK_MAND)
return -EOPNOTSUPP;
if (fl->fl_type == F_UNLCK) {
do_unflock(file, fl);

161
fs/locks.c
View File

@ -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)
@ -461,8 +355,6 @@ static void locks_move_blocks(struct file_lock *new, struct file_lock *fl)
}
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;
@ -942,8 +834,6 @@ static bool flock_locks_conflict(struct file_lock *caller_fl,
*/
if (caller_fl->fl_file == sys_fl->fl_file)
return false;
if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
return false;
return locks_conflict(caller_fl, sys_fl);
}
@ -2116,11 +2006,9 @@ EXPORT_SYMBOL(locks_lock_inode_wait);
* - %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 -- a 'mandatory' flock. (DEPRECATED)
*
* %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
* processes read and write access respectively.
* %LOCK_MAND support has been removed from the kernel.
*/
SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
{
@ -2137,10 +2025,23 @@ SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
cmd &= ~LOCK_NB;
unlock = (cmd == LOCK_UN);
if (!unlock && !(cmd & LOCK_MAND) &&
!(f.file->f_mode & (FMODE_READ|FMODE_WRITE)))
if (!unlock && !(f.file->f_mode & (FMODE_READ|FMODE_WRITE)))
goto out_putf;
/*
* LOCK_MAND locks were broken for a long time in that they never
* conflicted with one another and didn't prevent any sort of open,
* read or write activity.
*
* Just ignore these requests now, to preserve legacy behavior, but
* throw a warning to let people know that they don't actually work.
*/
if (cmd & LOCK_MAND) {
pr_warn_once("Attempt to set a LOCK_MAND lock via flock(2). This support has been removed and the request ignored.\n");
error = 0;
goto out_putf;
}
lock = flock_make_lock(f.file, cmd, NULL);
if (IS_ERR(lock)) {
error = PTR_ERR(lock);
@ -2718,6 +2619,7 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
struct inode *inode = NULL;
unsigned int fl_pid;
struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file)->i_sb);
int type;
fl_pid = locks_translate_pid(fl, proc_pidns);
/*
@ -2745,11 +2647,7 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
seq_printf(f, " %s ",
(inode == NULL) ? "*NOINODE*" : "ADVISORY ");
} else if (IS_FLOCK(fl)) {
if (fl->fl_type & LOCK_MAND) {
seq_puts(f, "FLOCK MSNFS ");
} else {
seq_puts(f, "FLOCK ADVISORY ");
}
seq_puts(f, "FLOCK ADVISORY ");
} else if (IS_LEASE(fl)) {
if (fl->fl_flags & FL_DELEG)
seq_puts(f, "DELEG ");
@ -2765,17 +2663,10 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
} 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 {
int type = IS_LEASE(fl) ? target_leasetype(fl) : fl->fl_type;
type = IS_LEASE(fl) ? target_leasetype(fl) : fl->fl_type;
seq_printf(f, "%s ", (type == F_WRLCK) ? "WRITE" :
(type == F_RDLCK) ? "READ" : "UNLCK");
}
seq_printf(f, "%s ", (type == F_WRLCK) ? "WRITE" :
(type == F_RDLCK) ? "READ" : "UNLCK");
if (inode) {
/* userspace relies on this representation of dev_t */
seq_printf(f, "%d %02x:%02x:%lu ", fl_pid,

4
fs/namei.c
View File

@ -3076,9 +3076,7 @@ static int handle_truncate(struct user_namespace *mnt_userns, struct file *filp)
int error = get_write_access(inode);
if (error)
return error;
/*
* Refuse to truncate files with mandatory locks held on them.
*/
error = security_path_truncate(path);
if (!error) {
error = do_truncate(mnt_userns, path->dentry, 0,

9
fs/nfs/file.c
View File

@ -843,15 +843,6 @@ int nfs_flock(struct file *filp, int cmd, struct file_lock *fl)
if (!(fl->fl_flags & FL_FLOCK))
return -ENOLCK;
/*
* The NFSv4 protocol doesn't support LOCK_MAND, which is not part of
* any standard. In principle we might be able to support LOCK_MAND
* on NFSv2/3 since NLMv3/4 support DOS share modes, but for now the
* NFS code is not set up for it.
*/
if (fl->fl_type & LOCK_MAND)
return -EINVAL;
if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FLOCK)
is_local = 1;

4
fs/read_write.c
View File

@ -368,10 +368,6 @@ int rw_verify_area(int read_write, struct file *file, const loff_t *ppos, size_t
if (unlikely((ssize_t) count < 0))
return -EINVAL;
/*
* ranged mandatory locking does not apply to streams - it makes sense
* only for files where position has a meaning.
*/
if (ppos) {
loff_t pos = *ppos;

4
include/uapi/asm-generic/fcntl.h
View File

@ -181,6 +181,10 @@ struct f_owner_ex {
blocking */
#define LOCK_UN 8 /* remove lock */
/*
* LOCK_MAND support has been removed from the kernel. We leave the symbols
* here to not break legacy builds, but these should not be used in new code.
*/
#define LOCK_MAND 32 /* This is a mandatory flock ... */
#define LOCK_READ 64 /* which allows concurrent read operations */
#define LOCK_WRITE 128 /* which allows concurrent write operations */