Re: [PATCH 2/2] xfs: don't check for AG deadlock for realtime files in bunmapi

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Tue, Nov 26, 2019 at 12:13:29PM -0800, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> Commit 5b094d6dac04 ("xfs: fix multi-AG deadlock in xfs_bunmapi") added
> a check in __xfs_bunmapi() to stop early if we would touch multiple AGs
> in the wrong order. However, this check isn't applicable for realtime
> files. In most cases, it just makes us do unnecessary commits. However,
> without the fix from the previous commit ("xfs: fix realtime file data
> space leak"), if the last and second-to-last extents also happen to have
> different "AG numbers", then the break actually causes __xfs_bunmapi()
> to return without making any progress, which sends
> xfs_itruncate_extents_flags() into an infinite loop.
> 
> Fixes: 5b094d6dac04 ("xfs: fix multi-AG deadlock in xfs_bunmapi")
> Signed-off-by: Omar Sandoval <osandov@fb.com>

Looks pretty straightforward,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/xfs/libxfs/xfs_bmap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 6f8791a1e460..a11b6e7cb35f 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -5300,7 +5300,7 @@ __xfs_bunmapi(
>  		 * Make sure we don't touch multiple AGF headers out of order
>  		 * in a single transaction, as that could cause AB-BA deadlocks.
>  		 */
> -		if (!wasdel) {
> +		if (!wasdel && !isrt) {
>  			agno = XFS_FSB_TO_AGNO(mp, del.br_startblock);
>  			if (prev_agno != NULLAGNUMBER && prev_agno > agno)
>  				break;
> -- 
> 2.24.0
>