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Groups > linux.kernel > #1668538

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

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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.

Reviewed-by: Christoph Hellwig <hch@lst.de>
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.
 		 */

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[PATCH 00/13] block: assorted cleanup for bio splitting and cloning. NeilBrown <neilb@suse.com> - 2017-06-18 06:40 +0200
  [PATCH 06/13] rbd: use bio_clone_fast() instead of bio_clone() NeilBrown <neilb@suse.com> - 2017-06-18 06:50 +0200
  [PATCH 10/13] xen-blkfront: remove bio splitting. NeilBrown <neilb@suse.com> - 2017-06-18 06:50 +0200
  [PATCH 12/13] block: remove bio_clone() and all references. NeilBrown <neilb@suse.com> - 2017-06-18 06:50 +0200
  [PATCH 11/13] bcache: use kmalloc to allocate bio in  bch_data_verify() NeilBrown <neilb@suse.com> - 2017-06-18 06:50 +0200
  [PATCH 09/13] lightnvm/pblk-read: use bio_clone_fast() NeilBrown <neilb@suse.com> - 2017-06-18 06:50 +0200
  [PATCH 13/13] block: don't check for BIO_MAX_PAGES in  blk_bio_segment_split() NeilBrown <neilb@suse.com> - 2017-06-18 06:50 +0200
  [PATCH 04/13] blk: use non-rescuing bioset for q->bio_split. NeilBrown <neilb@suse.com> - 2017-06-18 06:50 +0200
  [PATCH 07/13] drbd: use bio_clone_fast() instead of bio_clone() NeilBrown <neilb@suse.com> - 2017-06-18 06:50 +0200
  [PATCH 03/13] blk: make the bioset rescue_workqueue optional. NeilBrown <neilb@suse.com> - 2017-06-18 06:50 +0200
  [PATCH 05/13] block: Improvements to bounce-buffer handling NeilBrown <neilb@suse.com> - 2017-06-18 06:50 +0200
  [PATCH 08/13] pktcdvd: use bio_clone_fast() instead of bio_clone() NeilBrown <neilb@suse.com> - 2017-06-18 06:50 +0200
  Re: [PATCH 00/13] block: assorted cleanup for bio splitting and  cloning. Jens Axboe <axboe@kernel.dk> - 2017-06-18 20:50 +0200
    Re: [PATCH 00/13] block: assorted cleanup for bio splitting and cloning. NeilBrown <neilb@suse.com> - 2017-06-18 23:40 +0200

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