[PATCH v1 2/4] block: check virt boundary in bio_will_gap()

Ming Lei
2016-02-19T03:21:15Z

In the following patch, the way for figuring out
the last bvec will be changed with a bit cost introduced,
so return immediately if the queue doesn't have virt
boundary limit. Actually most of devices have not
this limit.

Cc: Sagi Grimberg <sagig@dev.mellanox.co.il>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
include/linux/blkdev.h | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 4571ef1..5023401 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1372,6 +1372,13 @@ static inline void put_dev_sector(Sector p)
page_cache_release(p.v);
}

+static inline bool __bvec_gap_to_prev(struct request_queue *q,
+ struct bio_vec *bprv, unsigned int offset)
+{
+ return offset ||
+ ((bprv->bv_offset + bprv->bv_len) & queue_virt_boundary(q));
+}
+
/*
* Check if adding a bio_vec after bprv with offset would create a gap in
* the SG list. Most drivers don't care about this, but some do.
@@ -1381,14 +1388,13 @@ static inline bool bvec_gap_to_prev(struct request_queue *q,
{
if (!queue_virt_boundary(q))
return false;
- return offset ||
- ((bprv->bv_offset + bprv->bv_len) & queue_virt_boundary(q));
+ return __bvec_gap_to_prev(q, bprv, offset);
}

static inline bool bio_will_gap(struct request_queue *q, struct bio *prev,
struct bio *next)
{
- if (!bio_has_data(prev))
+ if (!bio_has_data(prev) || !queue_virt_boundary(q))
return false;

return bvec_gap_to_prev(q, &prev->bi_io_vec[prev->bi_vcnt - 1],
--
1.9.1