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authorTejun Heo <htejun@gmail.com>2007-06-19 09:18:13 +0200
committerJens Axboe <jens.axboe@oracle.com>2007-07-10 08:03:33 +0200
commitf4b09303d00212ead0619db58d8ec8a0a7a94882 (patch)
tree43f37ba1c6afe058eac7cdd345cea04ff7b1a851 /block
parent554988d6fe369719ae5b41255c577569ecf47c30 (diff)
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[BLOCK] drop unnecessary bvec rewinding from flush_dry_bio_endio
Barrier bios are completed twice - once after the barrier write itself is done and again after the whole sequence is complete. flush_dry_bio_endio() is for the first completion. It doesn't really complete the bio. It rewinds bvec and resets bio so that it can be completed again when the whole barrier sequence is complete. The bvec rewinding code has the following problems. 1. The rewinding code is wrong because filesystems may pass bvec with non zero bv_offset. 2. The block layer doesn't guarantee anything about the state of bvec array on request completion. bv_offset and len are updated iff __end_that_request_first() completes the bvec partially. Because of #2, #1 doesn't really matter (nobody cares whether bvec is re-wound correctly or not) but then again by not doing unwinding at all, we'll always give back the same bvec to the caller as full bvec completion doesn't alter bvecs and the final completion is always full completion. Drop unnecessary rewinding code. This is spotted by Neil Brown. Signed-off-by: Tejun Heo <htejun@gmail.com> Cc: Neil Brown <neilb@suse.de> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block')
-rw-r--r--block/ll_rw_blk.c9
1 files changed, 0 insertions, 9 deletions
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 3e7801e4903..ef42bb2b12b 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -527,8 +527,6 @@ int blk_do_ordered(request_queue_t *q, struct request **rqp)
static int flush_dry_bio_endio(struct bio *bio, unsigned int bytes, int error)
{
request_queue_t *q = bio->bi_private;
- struct bio_vec *bvec;
- int i;
/*
* This is dry run, restore bio_sector and size. We'll finish
@@ -540,13 +538,6 @@ static int flush_dry_bio_endio(struct bio *bio, unsigned int bytes, int error)
if (bio->bi_size)
return 1;
- /* Rewind bvec's */
- bio->bi_idx = 0;
- bio_for_each_segment(bvec, bio, i) {
- bvec->bv_len += bvec->bv_offset;
- bvec->bv_offset = 0;
- }
-
/* Reset bio */
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio->bi_size = q->bi_size;