Commit 4b90de5b authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Carlos Maiolino
Browse files

xfs: reduce context switches for synchronous buffered I/O 



Currently all metadata I/O completions happen in the m_buf_workqueue
workqueue.  But for synchronous I/O (i.e. all buffer reads) there is no
need for that, as there always is a called in process context that is
waiting for the I/O.  Factor out the guts of xfs_buf_ioend into a
separate helper and call it from xfs_buf_iowait to avoid a double
an extra context switch to the workqueue.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Signed-off-by: default avatarCarlos Maiolino <cem@kernel.org>
parent 2d873efd

fs/xfs/xfs_buf.c

+27 −16
Original line number Diff line number Diff line
@@ -1345,6 +1345,7 @@ xfs_buf_ioend_handle_error( 
resubmit:

	xfs_buf_ioerror(bp, 0);

	bp->b_flags |= (XBF_DONE | XBF_WRITE_FAIL);

	reinit_completion(&bp->b_iowait);

	xfs_buf_submit(bp);

	return true;

out_stale:
@@ -1355,8 +1356,9 @@ xfs_buf_ioend_handle_error( 
	return false;

}



static void

xfs_buf_ioend(

/* returns false if the caller needs to resubmit the I/O, else true */

static bool

__xfs_buf_ioend(

	struct xfs_buf	*bp)

{

	trace_xfs_buf_iodone(bp, _RET_IP_);
@@ -1376,7 +1378,7 @@ xfs_buf_ioend( 
		}



		if (unlikely(bp->b_error) && xfs_buf_ioend_handle_error(bp))

			return;

			return false;



		/* clear the retry state */

		bp->b_last_error = 0;
@@ -1397,7 +1399,15 @@ xfs_buf_ioend( 


	bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD |

			 _XBF_LOGRECOVERY);

	return true;

}



static void

xfs_buf_ioend(

	struct xfs_buf	*bp)

{

	if (!__xfs_buf_ioend(bp))

		return;

	if (bp->b_flags & XBF_ASYNC)

		xfs_buf_relse(bp);

	else
@@ -1411,15 +1421,8 @@ xfs_buf_ioend_work( 
	struct xfs_buf		*bp =

		container_of(work, struct xfs_buf, b_ioend_work);



	xfs_buf_ioend(bp);

}



static void

xfs_buf_ioend_async(

	struct xfs_buf	*bp)

{

	INIT_WORK(&bp->b_ioend_work, xfs_buf_ioend_work);

	queue_work(bp->b_mount->m_buf_workqueue, &bp->b_ioend_work);

	if (__xfs_buf_ioend(bp))

		xfs_buf_relse(bp);

}



void
@@ -1491,7 +1494,13 @@ xfs_buf_bio_end_io( 
		 XFS_TEST_ERROR(false, bp->b_mount, XFS_ERRTAG_BUF_IOERROR))

		xfs_buf_ioerror(bp, -EIO);



	xfs_buf_ioend_async(bp);

	if (bp->b_flags & XBF_ASYNC) {

		INIT_WORK(&bp->b_ioend_work, xfs_buf_ioend_work);

		queue_work(bp->b_mount->m_buf_workqueue, &bp->b_ioend_work);

	} else {

		complete(&bp->b_iowait);

	}



	bio_put(bio);

}
@@ -1568,9 +1577,11 @@ xfs_buf_iowait( 
{

	ASSERT(!(bp->b_flags & XBF_ASYNC));



	do {

		trace_xfs_buf_iowait(bp, _RET_IP_);

		wait_for_completion(&bp->b_iowait);

		trace_xfs_buf_iowait_done(bp, _RET_IP_);

	} while (!__xfs_buf_ioend(bp));



	return bp->b_error;

}