Re: [PATCH 4/4] xfs: remove the XBF_STALE check from xfs_buf_rele_cached

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Feb 17, 2025 at 10:31:29AM +0100, Christoph Hellwig wrote:
> xfs_buf_stale already set b_lru_ref to 0, and thus prevents the buffer
> from moving to the LRU.  Remove the duplicate check.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

I'd long wondered why that was necessary...
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/xfs/xfs_buf.c | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index f8efdee3c8b4..cf88b25fe3c5 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -99,12 +99,6 @@ xfs_buf_stale(
>  	 */
>  	bp->b_flags &= ~_XBF_DELWRI_Q;
>  
> -	/*
> -	 * Once the buffer is marked stale and unlocked, a subsequent lookup
> -	 * could reset b_flags. There is no guarantee that the buffer is
> -	 * unaccounted (released to LRU) before that occurs. Drop in-flight
> -	 * status now to preserve accounting consistency.
> -	 */
>  	spin_lock(&bp->b_lock);
>  	atomic_set(&bp->b_lru_ref, 0);
>  	if (!(bp->b_state & XFS_BSTATE_DISPOSE) &&
> @@ -1033,7 +1027,7 @@ xfs_buf_rele_cached(
>  	}
>  
>  	/* we are asked to drop the last reference */
> -	if (!(bp->b_flags & XBF_STALE) && atomic_read(&bp->b_lru_ref)) {
> +	if (atomic_read(&bp->b_lru_ref)) {
>  		/*
>  		 * If the buffer is added to the LRU, keep the reference to the
>  		 * buffer for the LRU and clear the (now stale) dispose list
> -- 
> 2.45.2
> 
>