Re: [PATCH 2/8] xfs: don't commit the first deferred transaction without intents

[Christoph Hellwig <hch@infradead.org>]

On Wed, Apr 27, 2022 at 12:22:53PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> If the first operation in a string of defer ops has no intents,
> then there is no reason to commit it before running the first call
> to xfs_defer_finish_one(). This allows the defer ops to be used
> effectively for non-intent based operations without requiring an
> unnecessary extra transaction commit when first called.
> 
> This fixes a regression in per-attribute modification transaction
> count when delayed attributes are not being used.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
>  fs/xfs/libxfs/xfs_defer.c | 29 +++++++++++++++++------------
>  1 file changed, 17 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_defer.c b/fs/xfs/libxfs/xfs_defer.c
> index 0805ade2d300..66b4555bda8e 100644
> --- a/fs/xfs/libxfs/xfs_defer.c
> +++ b/fs/xfs/libxfs/xfs_defer.c
> @@ -186,7 +186,7 @@ static const struct xfs_defer_op_type *defer_op_types[] = {
>  	[XFS_DEFER_OPS_TYPE_AGFL_FREE]	= &xfs_agfl_free_defer_type,
>  };
>  
> -static void
> +static bool
>  xfs_defer_create_intent(
>  	struct xfs_trans		*tp,
>  	struct xfs_defer_pending	*dfp,
> @@ -197,6 +197,7 @@ xfs_defer_create_intent(
>  	if (!dfp->dfp_intent)
>  		dfp->dfp_intent = ops->create_intent(tp, &dfp->dfp_work,
>  						     dfp->dfp_count, sort);
> +	return dfp->dfp_intent;
>  }
>  
>  /*
> @@ -204,16 +205,18 @@ xfs_defer_create_intent(
>   * associated extents, then add the entire intake list to the end of
>   * the pending list.
>   */
> -STATIC void
> +static bool
>  xfs_defer_create_intents(
>  	struct xfs_trans		*tp)
>  {
>  	struct xfs_defer_pending	*dfp;
> +	bool				ret = false;
>  
>  	list_for_each_entry(dfp, &tp->t_dfops, dfp_list) {
>  		trace_xfs_defer_create_intent(tp->t_mountp, dfp);
> -		xfs_defer_create_intent(tp, dfp, true);
> +		ret |= xfs_defer_create_intent(tp, dfp, true);
>  	}
> +	return ret;
>  }
>  
>  /* Abort all the intents that were committed. */
> @@ -487,7 +490,7 @@ int
>  xfs_defer_finish_noroll(
>  	struct xfs_trans		**tp)
>  {
> -	struct xfs_defer_pending	*dfp;
> +	struct xfs_defer_pending	*dfp = NULL;
>  	int				error = 0;
>  	LIST_HEAD(dop_pending);
>  
> @@ -506,17 +509,19 @@ xfs_defer_finish_noroll(
>  		 * of time that any one intent item can stick around in memory,
>  		 * pinning the log tail.
>  		 */
> -		xfs_defer_create_intents(*tp);
> +		bool has_intents = xfs_defer_create_intents(*tp);
>  		list_splice_init(&(*tp)->t_dfops, &dop_pending);

While we're nitpicking:  an emptry line under the variable declaration
would be nice to have.

> +			/* Possibly relog intent items to keep the log moving. */

And a really annoying 81 character line that just wraps around here.

But except for the nitpicks this looks good to me:

Reviewed-by: Christoph Hellwig <hch@lst.de>