fs: remove mandatory file locking support

We added CONFIG_MANDATORY_FILE_LOCKING in 2015, and soon after turned it
off in Fedora and RHEL8. Several other distros have followed suit.

I've heard of one problem in all that time: Someone migrated from an
older distro that supported "-o mand" to one that didn't, and the host
had a fstab entry with "mand" in it which broke on reboot. They didn't
actually _use_ mandatory locking so they just removed the mount option
and moved on.

This patch rips out mandatory locking support wholesale from the kernel,
along with the Kconfig option and the Documentation file. It also
changes the mount code to ignore the "mand" mount option instead of
erroring out, and to throw a big, ugly warning.

Signed-off-by: Jeff Layton <[email protected]>

fs/9p/vfs_file.c

@@ -121,10 +121,6 @@ static int v9fs_file_lock(struct file *filp, int cmd, struct file_lock *fl)
 
 	p9_debug(P9_DEBUG_VFS, "filp: %p lock: %p\n", filp, fl);
 
-	/* No mandatory locks */
-	if (__mandatory_lock(inode) && fl->fl_type != F_UNLCK)
-		return -ENOLCK;
-
 	if ((IS_SETLK(cmd) || IS_SETLKW(cmd)) && fl->fl_type != F_UNLCK) {
 		filemap_write_and_wait(inode->i_mapping);
 		invalidate_mapping_pages(&inode->i_data, 0, -1);
@@ -312,10 +308,6 @@ static int v9fs_file_lock_dotl(struct file *filp, int cmd, struct file_lock *fl)
 	p9_debug(P9_DEBUG_VFS, "filp: %p cmd:%d lock: %p name: %pD\n",
 		 filp, cmd, fl, filp);
 
-	/* No mandatory locks */
-	if (__mandatory_lock(inode) && fl->fl_type != F_UNLCK)
-		goto out_err;
-
 	if ((IS_SETLK(cmd) || IS_SETLKW(cmd)) && fl->fl_type != F_UNLCK) {
 		filemap_write_and_wait(inode->i_mapping);
 		invalidate_mapping_pages(&inode->i_data, 0, -1);
@@ -327,7 +319,6 @@ static int v9fs_file_lock_dotl(struct file *filp, int cmd, struct file_lock *fl)
 		ret = v9fs_file_getlock(filp, fl);
 	else
 		ret = -EINVAL;
-out_err:
 	return ret;
 }
 
@@ -348,10 +339,6 @@ static int v9fs_file_flock_dotl(struct file *filp, int cmd,
 	p9_debug(P9_DEBUG_VFS, "filp: %p cmd:%d lock: %p name: %pD\n",
 		 filp, cmd, fl, filp);
 
-	/* No mandatory locks */
-	if (__mandatory_lock(inode) && fl->fl_type != F_UNLCK)
-		goto out_err;
-
 	if (!(fl->fl_flags & FL_FLOCK))
 		goto out_err;
 

fs/Kconfig

@@ -101,16 +101,6 @@ config FILE_LOCKING
           for filesystems like NFS and for the flock() system
           call. Disabling this option saves about 11k.
 
-config MANDATORY_FILE_LOCKING
-	bool "Enable Mandatory file locking"
-	depends on FILE_LOCKING
-	default y
-	help
-	  This option enables files appropriately marked files on appropriely
-	  mounted filesystems to support mandatory locking.
-
-	  To the best of my knowledge this is dead code that no one cares about.
-
 source "fs/crypto/Kconfig"
 
 source "fs/verity/Kconfig"

fs/afs/flock.c

@@ -772,10 +772,6 @@ int afs_lock(struct file *file, int cmd, struct file_lock *fl)
 	       fl->fl_type, fl->fl_flags,
 	       (long long) fl->fl_start, (long long) fl->fl_end);
 
-	/* AFS doesn't support mandatory locks */
-	if (__mandatory_lock(&vnode->vfs_inode) && fl->fl_type != F_UNLCK)
-		return -ENOLCK;
-
 	if (IS_GETLK(cmd))
 		return afs_do_getlk(file, fl);
 

fs/ceph/locks.c

@@ -240,9 +240,6 @@ int ceph_lock(struct file *file, int cmd, struct file_lock *fl)
 
 	if (!(fl->fl_flags & FL_POSIX))
 		return -ENOLCK;
-	/* No mandatory locks */
-	if (__mandatory_lock(file->f_mapping->host) && fl->fl_type != F_UNLCK)
-		return -ENOLCK;
 
 	dout("ceph_lock, fl_owner: %p\n", fl->fl_owner);
 

fs/gfs2/file.c

@@ -1237,9 +1237,6 @@ static int gfs2_lock(struct file *file, int cmd, struct file_lock *fl)
 
 	if (!(fl->fl_flags & FL_POSIX))
 		return -ENOLCK;
-	if (__mandatory_lock(&ip->i_inode) && fl->fl_type != F_UNLCK)
-		return -ENOLCK;
-
 	if (cmd == F_CANCELLK) {
 		/* Hack: */
 		cmd = F_SETLK;