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

Documentation/filesystems/index.rst

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

Documentation/filesystems/locks.rst

@@ -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.

fs/ceph/locks.c

@@ -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);
 

fs/gfs2/file.c

@@ -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);

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)
@@ -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)
 {
@@ -2137,9 +2025,22 @@ 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)) {
@@ -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,

fs/namei.c

@@ -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,

fs/nfs/file.c

@@ -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;
 

fs/read_write.c

@@ -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;
 

include/uapi/asm-generic/fcntl.h

@@ -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 */