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 <jlayton@kernel.org>

1 files changed, 1 insertions, 116 deletions

diff --git a/fs/locks.c b/fs/locks.c
index 74b2a1dfe8d8..3d6fb4ae847b 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1397,103 +1397,6 @@ static int posix_lock_inode_wait(struct inode *inode, struct file_lock *fl)
 	return error;
 }
 
-#ifdef CONFIG_MANDATORY_FILE_LOCKING
-/**
- * locks_mandatory_locked - Check for an active lock
- * @file: the file to check
- *
- * Searches the inode's list of locks to find any POSIX locks which conflict.
- * This function is called from locks_verify_locked() only.
- */
-int locks_mandatory_locked(struct file *file)
-{
-	int ret;
-	struct inode *inode = locks_inode(file);
-	struct file_lock_context *ctx;
-	struct file_lock *fl;
-
-	ctx = smp_load_acquire(&inode->i_flctx);
-	if (!ctx || list_empty_careful(&ctx->flc_posix))
-		return 0;
-
-	/*
-	 * Search the lock list for this inode for any POSIX locks.
-	 */
-	spin_lock(&ctx->flc_lock);
-	ret = 0;
-	list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
-		if (fl->fl_owner != current->files &&
-		    fl->fl_owner != file) {
-			ret = -EAGAIN;
-			break;
-		}
-	}
-	spin_unlock(&ctx->flc_lock);
-	return ret;
-}
-
-/**
- * locks_mandatory_area - Check for a conflicting lock
- * @inode:	the file to check
- * @filp:       how the file was opened (if it was)
- * @start:	first byte in the file to check
- * @end:	lastbyte in the file to check
- * @type:	%F_WRLCK for a write lock, else %F_RDLCK
- *
- * Searches the inode's list of locks to find any POSIX locks which conflict.
- */
-int locks_mandatory_area(struct inode *inode, struct file *filp, loff_t start,
-			 loff_t end, unsigned char type)
-{
-	struct file_lock fl;
-	int error;
-	bool sleep = false;
-
-	locks_init_lock(&fl);
-	fl.fl_pid = current->tgid;
-	fl.fl_file = filp;
-	fl.fl_flags = FL_POSIX | FL_ACCESS;
-	if (filp && !(filp->f_flags & O_NONBLOCK))
-		sleep = true;
-	fl.fl_type = type;
-	fl.fl_start = start;
-	fl.fl_end = end;
-
-	for (;;) {
-		if (filp) {
-			fl.fl_owner = filp;
-			fl.fl_flags &= ~FL_SLEEP;
-			error = posix_lock_inode(inode, &fl, NULL);
-			if (!error)
-				break;
-		}
-
-		if (sleep)
-			fl.fl_flags |= FL_SLEEP;
-		fl.fl_owner = current->files;
-		error = posix_lock_inode(inode, &fl, NULL);
-		if (error != FILE_LOCK_DEFERRED)
-			break;
-		error = wait_event_interruptible(fl.fl_wait,
-					list_empty(&fl.fl_blocked_member));
-		if (!error) {
-			/*
-			 * If we've been sleeping someone might have
-			 * changed the permissions behind our back.
-			 */
-			if (__mandatory_lock(inode))
-				continue;
-		}
-
-		break;
-	}
-	locks_delete_block(&fl);
-
-	return error;
-}
-EXPORT_SYMBOL(locks_mandatory_area);
-#endif /* CONFIG_MANDATORY_FILE_LOCKING */
-
 static void lease_clear_pending(struct file_lock *fl, int arg)
 {
 	switch (arg) {
@@ -2486,14 +2389,6 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
 	if (file_lock == NULL)
 		return -ENOLCK;
 
-	/* Don't allow mandatory locks on files that may be memory mapped
-	 * and shared.
-	 */
-	if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
-		error = -EAGAIN;
-		goto out;
-	}
-
 	error = flock_to_posix_lock(filp, file_lock, flock);
 	if (error)
 		goto out;
@@ -2611,21 +2506,12 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
 		struct flock64 *flock)
 {
 	struct file_lock *file_lock = locks_alloc_lock();
-	struct inode *inode = locks_inode(filp);
 	struct file *f;
 	int error;
 
 	if (file_lock == NULL)
 		return -ENOLCK;
 
-	/* Don't allow mandatory locks on files that may be memory mapped
-	 * and shared.
-	 */
-	if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
-		error = -EAGAIN;
-		goto out;
-	}
-
 	error = flock64_to_posix_lock(filp, file_lock, flock);
 	if (error)
 		goto out;
@@ -2857,8 +2743,7 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
 			seq_puts(f, "POSIX ");
 
 		seq_printf(f, " %s ",
-			     (inode == NULL) ? "*NOINODE*" :
-			     mandatory_lock(inode) ? "MANDATORY" : "ADVISORY ");
+			     (inode == NULL) ? "*NOINODE*" : "ADVISORY ");
 	} else if (IS_FLOCK(fl)) {
 		if (fl->fl_type & LOCK_MAND) {
 			seq_puts(f, "FLOCK  MSNFS     ");