Re: [PATCH v3] xfs: restore nofs context unconditionally in xfs_trans_roll

[Darrick J. Wong]

On Thu, Jul 30, 2026 at 05:30:02PM +0800, Yun Zhou wrote:
> When __xfs_trans_commit() fails in xfs_trans_roll(), the NOFS context
> is cleared but only restored in the success path.  This leaves the
> error path without nofs protection, causing a circular lock dependency
> between xfs_nondir_ilock_class and fs_reclaim:
> 
>        CPU0                    CPU1
>        ----                    ----
>   lock(&xfs_nondir_ilock_class);
>                                lock(fs_reclaim);
>                                lock(&xfs_nondir_ilock_class);
>   lock(fs_reclaim);
> 
> Fix this by moving xfs_trans_set_context() before the error check so
> that nofs context is always restored on the new transaction.
> 
> Reported-by: syzbot+59178abfeb0ea3f0ab20@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=59178abfeb0ea3f0ab20
> Fixes: a1ca658d649a ("xfs: fix incorrect context handling in xfs_trans_roll")
> Cc: stable@xxxxxxxxxxxxxxx
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Signed-off-by: Yun Zhou <yun.zhou@xxxxxxxxxxxxx>

Looks good to me,
Reviewed-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>

--D

> ---
> v3:
>   - Change back to v1
> 
> v2:
>   - Instead of moving xfs_trans_set_context() before the error check,
>     transfer the nofs context in xfs_trans_dup() via a new
>     memalloc_flags_move() helper, as suggested by Darrick.
>   - Change t_pflags from unsigned long to unsigned int to match mm API.
> 
> v1: https://lore.kernel.org/all/20260713035505.1635191-1-yun.zhou@xxxxxxxxxxxxx/T/
> 
>  fs/xfs/xfs_trans.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> index 7bfbd9f6f0df..1b36cf12d4e3 100644
> --- a/fs/xfs/xfs_trans.c
> +++ b/fs/xfs/xfs_trans.c
> @@ -1029,6 +1029,15 @@ xfs_trans_roll(
>  	 * duplicate transaction that gets returned.
>  	 */
>  	error = __xfs_trans_commit(tp, true);
> +
> +	tp = *tpp;
> +	/*
> +	 * __xfs_trans_commit cleared the NOFS flag by calling into
> +	 * xfs_trans_free.  Set it again here before doing memory
> +	 * allocations.
> +	 */
> +	xfs_trans_set_context(tp);
> +
>  	if (error)
>  		return error;
>  
> @@ -1040,13 +1049,6 @@ xfs_trans_roll(
>  	 * either nothing be locked across this call, or that anything that is
>  	 * locked be logged in the prior and the next transactions.
>  	 */
> -	tp = *tpp;
> -	/*
> -	 * __xfs_trans_commit cleared the NOFS flag by calling into
> -	 * xfs_trans_free.  Set it again here before doing memory
> -	 * allocations.
> -	 */
> -	xfs_trans_set_context(tp);
>  	error = xfs_log_regrant(tp->t_mountp, tp->t_ticket);
>  	if (error)
>  		return error;
> -- 
> 2.43.0
> 
>