block: don't check for BIO_MAX_PAGES in blk_bio_segment_split() (58c94cc1) · Commits · 戴 / test

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> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/blk-merge.c

+0 −16

Original line number	Diff line number	Diff line
		@@ -108,24 +108,8 @@ 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.

Admin message