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Commit 41f2df62 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
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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: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 01b6b67e

fs/gfs2/log.c

+1 −1
Original line number Diff line number Diff line
@@ -595,7 +595,7 @@ static void log_write_header(struct gfs2_sbd *sdp, u32 flags, int pull) 
	if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags))

		goto skip_barrier;

	get_bh(bh);

	submit_bh(WRITE_SYNC | (1 << BIO_RW_BARRIER) | (1 << BIO_RW_META), bh);

	submit_bh(WRITE_BARRIER | (1 << BIO_RW_META), bh);

	wait_on_buffer(bh);

	if (buffer_eopnotsupp(bh)) {

		clear_buffer_eopnotsupp(bh);

include/linux/fs.h

+2 −2
Original line number Diff line number Diff line
@@ -136,7 +136,7 @@ struct inodes_stat_t { 
 * 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 @@ struct inodes_stat_t { 
#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