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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 <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Christoph Hellwig 2010-06-17 09:54:32 +02:00 committed by Jens Axboe
parent 79600aadcf
commit fbbf055692
1 changed files with 2 additions and 5 deletions
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7
block/blk-core.c
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@ -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))