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 <hch@xxxxxx>
Index: linux-2.6/block/blk-core.c
===================================================================
--- linux-2.6.orig/block/blk-core.c 2010-06-17 09:42:23.924004448 +0200
+++ linux-2.6/block/blk-core.c 2010-06-17 09:45:46.727004030 +0200
@@ -1149,13 +1149,10 @@ void init_request_from_bio(struct reques
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))
--
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