Re: [patch, resend] ext4: fix race between unwritten extent conversion and truncate

[Ted Ts'o <tytso@mit.edu>]

On Thu, Feb 16, 2012 at 03:26:48PM -0500, Jeff Moyer wrote:
> Hi,
> 
> The following comment in ext4_end_io_dio caught my attention:
> 
> 	/* XXX: probably should move into the real I/O completion handler */
>         inode_dio_done(inode);
> 
> The truncate code takes i_mutex, then calls inode_dio_wait.  Because the
> ext4 code path above will end up dropping the mutex before it is
> reacquired by the worker thread that does the extent conversion, it
> seems to me that the truncate can happen out of order.  Jan Kara
> mentioned that this might result in error messages in the system logs,
> but that should be the extent of the "damage."
> 
> The fix is pretty straight-forward: don't call inode_dio_done until the
> extent conversion is complete.
> 
> Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
> Reviewed-by: Jan Kara <jack@suse.cz>

Thanks, applied.

						- Ted