block: fix DISCARD_BARRIER requests

Filesystems assume that DISCARD_BARRIER are full barriers, so that they don't have to track in-progress discard operation when submitting new I/O. But currently we only treat them as elevator barriers, which don't actually do the nessecary queue drains. Also remove the unlikely around both the DISCARD and BARRIER requests - the happen far too often for a static mispredict. Signed-off-by: Christoph Hellwig <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
iegor · Jun 17, 2010 · fbbf055 · fbbf055
1 parent 79600aa
commit fbbf055
Showing 1 changed file with 2 additions and 5 deletions.
diff --git a/block/blk-core.c b/block/blk-core.c
@@ -1149,13 +1149,10 @@ void init_request_from_bio(struct request *req, struct bio *bio)
 	else
 		req->cmd_flags |= bio->bi_rw & REQ_FAILFAST_MASK;
 
-	if (unlikely(bio_rw_flagged(bio, BIO_RW_DISCARD))) {
+	if (bio_rw_flagged(bio, BIO_RW_DISCARD))
 		req->cmd_flags |= REQ_DISCARD;
-		if (bio_rw_flagged(bio, BIO_RW_BARRIER))
-			req->cmd_flags |= REQ_SOFTBARRIER;
-	} else if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER)))
+	if (bio_rw_flagged(bio, BIO_RW_BARRIER))
 		req->cmd_flags |= REQ_HARDBARRIER;
-
 	if (bio_rw_flagged(bio, BIO_RW_SYNCIO))
 		req->cmd_flags |= REQ_RW_SYNC;
 	if (bio_rw_flagged(bio, BIO_RW_META))