Re: [PATCH v7 05/17] locks: eliminate BUG() call when there's an unexpected lock on file close

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Mar 19, 2014 at 04:45:49PM -0400, Jeff Layton wrote:
> A leftover lock on the list is surely a sign of a problem of some sort,
> but it's not necessarily a reason to panic the box. Instead, just log a
> warning with some info about the lock, and then delete it like we would
> any other lock.
> 
> In the event that the filesystem declares a ->lock f_op, we may end up
> leaking something, but that's generally preferable to an immediate
> panic.

Acked-by: J. Bruce Fields <bfields@redhat.com>

> 
> Signed-off-by: Jeff Layton <jlayton@redhat.com>
> ---
>  fs/locks.c | 24 ++++++++++++++++++------
>  1 file changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/locks.c b/fs/locks.c
> index 6084f5a32e9c..dd309333afc9 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -2281,16 +2281,28 @@ void locks_remove_flock(struct file *filp)
>  
>  	while ((fl = *before) != NULL) {
>  		if (fl->fl_file == filp) {
> -			if (IS_FLOCK(fl)) {
> -				locks_delete_lock(before);
> -				continue;
> -			}
>  			if (IS_LEASE(fl)) {
>  				lease_modify(before, F_UNLCK);
>  				continue;
>  			}
> -			/* What? */
> -			BUG();
> +
> +			/*
> +			 * There's a leftover lock on the list of a type that
> +			 * we didn't expect to see. Most likely a classic
> +			 * POSIX lock that ended up not getting released
> +			 * properly, or that raced onto the list somehow. Log
> +			 * some info about it and then just remove it from
> +			 * the list.
> +			 */
> +			WARN(!IS_FLOCK(fl),
> +				"leftover lock: dev=%u:%u ino=%lu type=%hhd flags=0x%x start=%lld end=%lld\n",
> +				MAJOR(inode->i_sb->s_dev),
> +				MINOR(inode->i_sb->s_dev), inode->i_ino,
> +				fl->fl_type, fl->fl_flags,
> +				fl->fl_start, fl->fl_end);
> +
> +			locks_delete_lock(before);
> +			continue;
>   		}
>  		before = &fl->fl_next;
>  	}
> -- 
> 1.8.5.3
>