On Mon, Jan 06, 2025 at 10:54:42AM +0100, Christoph Hellwig wrote:
> xfs_buf_delwri_pushbuf synchronously writes a buffer that is on a delwri
> list already. Instead of doing a complicated dance with the delwri
> and wait list, just leave them alone and open code the actual buffer
> write.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/xfs/xfs_buf.c | 33 ++++++++-------------------------
> 1 file changed, 8 insertions(+), 25 deletions(-)
>
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index a3484421a6d8..7edd7a1e9dae 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -2391,14 +2391,9 @@ xfs_buf_delwri_submit(
> * Push a single buffer on a delwri queue.
> *
> * The purpose of this function is to submit a single buffer of a delwri queue
> - * and return with the buffer still on the original queue. The waiting delwri
> - * buffer submission infrastructure guarantees transfer of the delwri queue
> - * buffer reference to a temporary wait list. We reuse this infrastructure to
> - * transfer the buffer back to the original queue.
> + * and return with the buffer still on the original queue.
> *
> - * Note the buffer transitions from the queued state, to the submitted and wait
> - * listed state and back to the queued state during this call. The buffer
> - * locking and queue management logic between _delwri_pushbuf() and
> + * The buffer locking and queue management logic between _delwri_pushbuf() and
> * _delwri_queue() guarantee that the buffer cannot be queued to another list
> * before returning.
> */
> @@ -2407,33 +2402,21 @@ xfs_buf_delwri_pushbuf(
> struct xfs_buf *bp,
> struct list_head *buffer_list)
> {
> - LIST_HEAD (submit_list);
> int error;
>
> ASSERT(bp->b_flags & _XBF_DELWRI_Q);
>
> trace_xfs_buf_delwri_pushbuf(bp, _RET_IP_);
>
> - /*
> - * Isolate the buffer to a new local list so we can submit it for I/O
> - * independently from the rest of the original list.
> - */
> xfs_buf_lock(bp);
> - list_move(&bp->b_list, &submit_list);
> - xfs_buf_unlock(bp);
> -
> - /*
> - * Delwri submission clears the DELWRI_Q buffer flag and returns with
> - * the buffer on the wait list with the original reference. Rather than
> - * bounce the buffer from a local wait list back to the original list
> - * after I/O completion, reuse the original list as the wait list.
> - */
> - xfs_buf_delwri_submit_buffers(&submit_list, buffer_list);
> + bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_ASYNC);
> + bp->b_flags |= XBF_WRITE;
> + xfs_buf_submit(bp);
Why is it ok to ignore the return value here? Is it because the only
error path in xfs_buf_submit is the xlog_is_shutdown case, in which case
the buffer ioend will have been called already and the EIO will be
returned by xfs_buf_iowait?
--D
>
> /*
> - * The buffer is now locked, under I/O and wait listed on the original
> - * delwri queue. Wait for I/O completion, restore the DELWRI_Q flag and
> - * return with the buffer unlocked and on the original queue.
> + * The buffer is now locked, under I/O but still on the original delwri
> + * queue. Wait for I/O completion, restore the DELWRI_Q flag and
> + * return with the buffer unlocked and still on the original queue.
> */
> error = xfs_buf_iowait(bp);
> bp->b_flags |= _XBF_DELWRI_Q;
> --
> 2.45.2
>
>
