[PATCH 004/102] xfs: reduce ioend latency

Dave Chinner
2012-08-23T05:02:40Z

From: Christoph Hellwig <hch@infradead.org>

Upstream commit: fc0063c4474599b7a066ba76b90902abe21bc675

There is no reason to queue up ioends for processing in user context
unless we actually need it. Just complete ioends that do not convert
unwritten extents or need a size update from the end_io context.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Alex Elder <aelder@sgi.com>
---
fs/xfs/linux-2.6/xfs_aops.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index 68ac1ce..20f356d 100644
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -149,6 +149,15 @@ xfs_ioend_new_eof(
}

/*
+ * Fast and loose check if this write could update the on-disk inode size.
+ */
+static inline bool xfs_ioend_is_append(struct xfs_ioend *ioend)
+{
+ return ioend->io_offset + ioend->io_size >
+ XFS_I(ioend->io_inode)->i_d.di_size;
+}
+
+/*
* Update on-disk file size now that data has been written to disk. The
* current in-memory file size is i_size. If a write is beyond eof i_new_size
* will be the intended file size until i_size is updated. If this write does
@@ -184,6 +193,9 @@ xfs_setfilesize(

/*
* Schedule IO completion handling on the final put of an ioend.
+ *
+ * If there is no work to do we might as well call it a day and free the
+ * ioend right now.
*/
STATIC void
xfs_finish_ioend(
@@ -192,8 +204,10 @@ xfs_finish_ioend(
if (atomic_dec_and_test(&ioend->io_remaining)) {
if (ioend->io_type == IO_UNWRITTEN)
queue_work(xfsconvertd_workqueue, &ioend->io_work);
- else
+ else if (xfs_ioend_is_append(ioend))
queue_work(xfsdatad_workqueue, &ioend->io_work);
+ else
+ xfs_destroy_ioend(ioend);