Commit 384209cd authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: create a bio_try_merge_pc_page helper 



Passsthrough bio handling should be the same as normal bio handling,
except that we need to take hardware limitations into account.  Thus
use the common try_merge implementation after checking the hardware
limits.  This changes behavior in that we now also check segment
and dma boundary settings for same page merges, which is a little
more work but has no effect as those need to be larger than the
page size.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 320ea869

block/bio.c

+10 −24
Original line number Diff line number Diff line
@@ -646,25 +646,20 @@ static inline bool page_is_mergeable(const struct bio_vec *bv, 
	return true;

}



/*

 * Check if the @page can be added to the current segment(@bv), and make

 * sure to call it only if page_is_mergeable(@bv, @page) is true

 */

static bool can_add_page_to_seg(struct request_queue *q,

		struct bio_vec *bv, struct page *page, unsigned len,

		unsigned offset)

static bool bio_try_merge_pc_page(struct request_queue *q, struct bio *bio,

		struct page *page, unsigned len, unsigned offset,

		bool *same_page)

{

	struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];

	unsigned long mask = queue_segment_boundary(q);

	phys_addr_t addr1 = page_to_phys(bv->bv_page) + bv->bv_offset;

	phys_addr_t addr2 = page_to_phys(page) + offset + len - 1;



	if ((addr1 | mask) != (addr2 | mask))

		return false;



	if (bv->bv_len + len > queue_max_segment_size(q))

		return false;



	return true;

	return __bio_try_merge_page(bio, page, len, offset, same_page);

}



/**
@@ -700,26 +695,18 @@ static int __bio_add_pc_page(struct request_queue *q, struct bio *bio, 
		return 0;



	if (bio->bi_vcnt > 0) {

		bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];



		if (page == bvec->bv_page &&

		    offset == bvec->bv_offset + bvec->bv_len) {

			if (put_same_page)

		if (bio_try_merge_pc_page(q, bio, page, len, offset,

				&same_page)) {

			if (put_same_page && same_page)

				put_page(page);

			bvec->bv_len += len;

			goto done;

		}



		if (page_is_mergeable(bvec, page, len, offset, &same_page) &&

		    can_add_page_to_seg(q, bvec, page, len, offset)) {

			bvec->bv_len += len;

			goto done;

			return len;

		}



		/*

		 * If the queue doesn't support SG gaps and adding this segment

		 * would create a gap, disallow it.

		 */

		bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];

		if (bvec_gap_to_prev(q, bvec, offset))

			return 0;

	}
@@ -735,7 +722,6 @@ static int __bio_add_pc_page(struct request_queue *q, struct bio *bio, 
	bvec->bv_len = len;

	bvec->bv_offset = offset;

	bio->bi_vcnt++;

 done:

	bio->bi_iter.bi_size += len;

	return len;

}

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