block: add plug for blkdev_issue_discard
Last post of this patch appears lost, so I resend this.
Now discard merge works, add plug for blkdev_issue_discard. This will help
discard request merge especially for raid0 case. In raid0, a big discard
request is split to small requests, and if correct plug is added, such small
requests can be merged in low layer.
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 5677fd3..b3a1f2b7 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -48,6 +48,7 @@
struct bio_batch bb;
struct bio *bio;
int ret = 0;
+ struct blk_plug plug;
if (!q)
return -ENXIO;
@@ -82,6 +83,7 @@
bb.flags = 1 << BIO_UPTODATE;
bb.wait = &wait;
+ blk_start_plug(&plug);
while (nr_sects) {
unsigned int req_sects;
sector_t end_sect, tmp;
@@ -120,6 +122,7 @@
atomic_inc(&bb.done);
submit_bio(type, bio);
}
+ blk_finish_plug(&plug);
/* Wait for bios in-flight */
if (!atomic_dec_and_test(&bb.done))