block: BARRIER request should imply SYNC
A barrier request should by defintion have priority in get_request
and let the queue be unplugged immediately as it's blocking all forward
progress due to the queue draining.
Most filesystems already get this implicitly by the way how submit_bh
treats the buffer_ordered flag, and gfs2 sets it explicitly. But btrfs
and XFS are still forgetting to set the flag, as is blkdev_issue_flush
and some places in DM/MD.
For XFS on metadata heavy workloads this gives a consistent speedup
in the 2-3% range.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 68ca1b0..5988788 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -136,7 +136,7 @@
* SWRITE_SYNC
* SWRITE_SYNC_PLUG Like WRITE_SYNC/WRITE_SYNC_PLUG, but locks the buffer.
* See SWRITE.
- * WRITE_BARRIER Like WRITE, but tells the block layer that all
+ * WRITE_BARRIER Like WRITE_SYNC, but tells the block layer that all
* previously submitted writes must be safely on storage
* before this one is started. Also guarantees that when
* this write is complete, it itself is also safely on
@@ -159,7 +159,7 @@
#define SWRITE_SYNC_PLUG \
(SWRITE | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_NOIDLE))
#define SWRITE_SYNC (SWRITE_SYNC_PLUG | (1 << BIO_RW_UNPLUG))
-#define WRITE_BARRIER (WRITE | (1 << BIO_RW_BARRIER))
+#define WRITE_BARRIER (WRITE_SYNC | (1 << BIO_RW_BARRIER))
/*
* These aren't really reads or writes, they pass down information about