Re: [28/83] ext4: lock i_mutex when truncating orphan inodes

[Luis Henriques <luis.henriques@canonical.com>]

Ben Hutchings <ben@decadent.org.uk> writes:

> 3.2.47-rc1 review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: Theodore Ts'o <tytso@mit.edu>
>
> commit 721e3eba21e43532e438652dd8f1fcdfce3187e7 upstream.

I'm also queuing this commit as it looks like 3.5 is also missing it.

Cheers,
-- 
Luis

>
> Commit c278531d39 added a warning when ext4_flush_unwritten_io() is
> called without i_mutex being taken.  It had previously not been taken
> during orphan cleanup since races weren't possible at that point in
> the mount process, but as a result of this c278531d39, we will now see
> a kernel WARN_ON in this case.  Take the i_mutex in
> ext4_orphan_cleanup() to suppress this warning.
>
> Reported-by: Alexander Beregalov <a.beregalov@gmail.com>
> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
> Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> ---
>  fs/ext4/super.c |    2 ++
>  1 file changed, 2 insertions(+)
>
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -2260,7 +2260,9 @@ static void ext4_orphan_cleanup(struct s
>  				__func__, inode->i_ino, inode->i_size);
>  			jbd_debug(2, "truncating inode %lu to %lld bytes\n",
>  				  inode->i_ino, inode->i_size);
> +			mutex_lock(&inode->i_mutex);
>  			ext4_truncate(inode);
> +			mutex_unlock(&inode->i_mutex);
>  			nr_truncates++;
>  		} else {
>  			ext4_msg(sb, KERN_DEBUG,
>
> --
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