block: respect virtual boundary mask in bvecs

Johannes Thumshirn · axboe · commit df376b2ed51a · 2018-11-07T13:04:22.000-07:00
With drivers that are settting a virtual boundary constrain, we are
seeing a lot of bio splitting and smaller I/Os being submitted to the
driver.

This happens because the bio gap detection code does not account cases
where PAGE_SIZE - 1 is bigger than queue_virt_boundary() and thus will
split the bio unnecessarily.

Cc: Jan Kara &lt;jack@suse.cz&gt;
Cc: Bart Van Assche &lt;bvanassche@acm.org&gt;
Cc: Ming Lei &lt;ming.lei@redhat.com&gt;
Reviewed-by: Sagi Grimberg &lt;sagi@grimberg.me&gt;
Signed-off-by: Johannes Thumshirn &lt;jthumshirn@suse.de&gt;
Acked-by: Keith Busch &lt;keith.busch@intel.com&gt;
Reviewed-by: Ming Lei &lt;ming.lei@redhat.com&gt;
Signed-off-by: Jens Axboe &lt;axboe@kernel.dk&gt;
diff --git a/block/blk-merge.c b/block/blk-merge.c
@@ -46,7 +46,7 @@ static inline bool bio_will_gap(struct request_queue *q,
 		bio_get_first_bvec(prev_rq->bio, &pb);
 	else
 		bio_get_first_bvec(prev, &pb);
-	if (pb.bv_offset)
+	if (pb.bv_offset & queue_virt_boundary(q))
 		return true;
 
 	/*
diff --git a/block/blk.h b/block/blk.h
@@ -169,7 +169,7 @@ static inline bool biovec_phys_mergeable(struct request_queue *q,
 static inline bool __bvec_gap_to_prev(struct request_queue *q,
 		struct bio_vec *bprv, unsigned int offset)
 {
-	return offset ||
+	return (offset & queue_virt_boundary(q)) ||
 		((bprv->bv_offset + bprv->bv_len) & queue_virt_boundary(q));
 }
 

Original file line number	Diff line number	Diff line change
`@@ -169,7 +169,7 @@ static inline bool biovec_phys_mergeable(struct request_queue *q,`
`169`	`169`	`static inline bool __bvec_gap_to_prev(struct request_queue *q,`
`170`	`170`	`struct bio_vec *bprv, unsigned int offset)`
`171`	`171`	`{`
`172`		`- return offset \|\|`
	`172`	`+ return (offset & queue_virt_boundary(q)) \|\|`
`173`	`173`	`((bprv->bv_offset + bprv->bv_len) & queue_virt_boundary(q));`
`174`	`174`	`}`
`175`	`175`