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Subject[PATCH v1 22/54] block: bounce: convert multipage bvecs into singlepage
Date
This patch trys to split the incoming multipage bvecs bio, so
that the splitted bio can be held into one singlepage bvecs bio.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
block/bounce.c | 41 +++++++++++++++++++++++++++++++++--------
1 file changed, 33 insertions(+), 8 deletions(-)

diff --git a/block/bounce.c b/block/bounce.c
index a42f7b98b7e6..08841ed4cdae 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -187,22 +187,33 @@ static void bounce_end_io_read_isa(struct bio *bio)
__bounce_end_io_read(bio, isa_page_pool);
}

+static inline bool need_bounce(struct request_queue *q, struct bio *bio)
+{
+ struct bvec_iter iter;
+ struct bio_vec bv;
+
+ bio_for_each_segment_mp(bv, bio, iter) {
+ unsigned nr = (bv.bv_offset + bv.bv_len - 1) >>
+ PAGE_SHIFT;
+
+ if (page_to_pfn(bv.bv_page) + nr > queue_bounce_pfn(q))
+ return true;
+ }
+ return false;
+}
+
static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
mempool_t *pool)
{
struct bio *bio;
int rw = bio_data_dir(*bio_orig);
- struct bio_vec *to, from;
- struct bvec_iter iter;
+ struct bio_vec *to;
unsigned i;

- bio_for_each_segment(from, *bio_orig, iter)
- if (page_to_pfn(from.bv_page) > queue_bounce_pfn(q))
- goto bounce;
+ if (!need_bounce(q, *bio_orig))
+ return;

- return;
-bounce:
- bio = bio_clone_bioset(*bio_orig, GFP_NOIO, fs_bio_set);
+ bio = bio_clone_bioset_sp(*bio_orig, GFP_NOIO, fs_bio_set);

bio_for_each_segment_all(to, bio, i) {
struct page *page = to->bv_page;
@@ -246,6 +257,7 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
{
mempool_t *pool;
+ unsigned sectors;

/*
* Data-less bio, nothing to bounce
@@ -267,9 +279,22 @@ void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
pool = isa_page_pool;
}

+ if (!need_bounce(q, *bio_orig))
+ return;
+
/*
* slow path
+ *
+ * REQ_PC bio won't reach splitting because multipage bvec
+ * isn't enabled for REQ_PC.
*/
+ if (!bio_can_convert_to_sp(*bio_orig, &sectors)) {
+ struct bio *split = bio_split(*bio_orig, sectors,
+ GFP_NOIO, q->bio_split);
+ bio_chain(split, *bio_orig);
+ generic_make_request(*bio_orig);
+ *bio_orig = split;
+ }
__blk_queue_bounce(q, bio_orig, pool);
}

--
2.7.4
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