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| author | Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> | 2010-07-22 14:17:00 -0700 |
|---|---|---|
| committer | Jens Axboe <jaxboe@fusionio.com> | 2010-08-07 18:52:53 +0200 |
| commit | 4dab46ff26c6003a13ec769312c50938b93c359d (patch) | |
| tree | 02d6f99222034dfeb73ccb388663570db883cb52 | |
| parent | e96f6abe02fc3320d669985443e8c68ff8e83294 (diff) | |
| download | linux-4dab46ff26c6003a13ec769312c50938b93c359d.tar.bz2 | |
xen/blkfront: use tagged queuing for barriers
When barriers are supported, then use QUEUE_ORDERED_TAG to tell the block
subsystem that it doesn't need to do anything else with the barriers.
Previously we used ORDERED_DRAIN which caused the block subsystem to
drain all pending IO before submitting the barrier, which would be
very expensive.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
| -rw-r--r-- | drivers/block/xen-blkfront.c | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index c6727b5cefd6..6d912ab47292 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -420,9 +420,19 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size) static int xlvbd_barrier(struct blkfront_info *info) { int err; + unsigned ordered = QUEUE_ORDERED_NONE; - err = blk_queue_ordered(info->rq, - info->feature_barrier ? QUEUE_ORDERED_DRAIN : QUEUE_ORDERED_NONE); + /* + * If we don't have barrier support, then there's really no + * way to guarantee write ordering, so we really just have to + * send writes to the backend and hope for the best. If + * barriers are supported then we can treat them as proper + * ordering tags. + */ + if (info->feature_barrier) + ordered = QUEUE_ORDERED_TAG; + + err = blk_queue_ordered(info->rq, ordered); if (err) return err; @@ -509,8 +519,7 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity, info->rq = gd->queue; info->gd = gd; - if (info->feature_barrier) - xlvbd_barrier(info); + xlvbd_barrier(info); if (vdisk_info & VDISK_READONLY) set_disk_ro(gd, 1); |