[PATCH 13/13] block: don't check for BIO_MAX_PAGES in blk_bio_segment_split()

NeilBrown
2017-05-02T03:42:26Z

blk_bio_segment_split() makes sure bios have no more than
BIO_MAX_PAGES entries in the bi_io_vec.
This was done because bio_clone_bioset() (when given a
mempool bioset) could not handle larger io_vecs.

No driver uses bio_clone_bioset() any more, they all
use bio_clone_fast() if anything, and bio_clone_fast()
doesn't clone the bi_io_vec.

The main user of of bio_clone_bioset() at this level
is bounce.c, and bouncing now happens before blk_bio_segment_split(),
so that is not of concern.

So remove the big helpful comment and the code.

Signed-off-by: NeilBrown <neilb@suse.com>
---
block/blk-merge.c | 16 ----------------
1 file changed, 16 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index e7862e9dcc39..cea544ec5d96 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -108,25 +108,9 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
bool do_split = true;
struct bio *new = NULL;
const unsigned max_sectors = get_max_io_size(q, bio);
- unsigned bvecs = 0;

bio_for_each_segment(bv, bio, iter) {
/*
- * With arbitrary bio size, the incoming bio may be very
- * big. We have to split the bio into small bios so that
- * each holds at most BIO_MAX_PAGES bvecs because
- * bio_clone_bioset() can fail to allocate big bvecs.
- *
- * Those drivers which will need to use bio_clone_bioset()
- * should tell us in some way. For now, impose the
- * BIO_MAX_PAGES limit on all queues.
- *
- * TODO: handle users of bio_clone_bioset() differently.
- */
- if (bvecs++ >= BIO_MAX_PAGES)
- goto split;
-
- /*
* If the queue doesn't support SG gaps and adding this
* offset would create a gap, disallow it.
*/