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Commit c66a14d0 authored by Kent Overstreet's avatar Kent Overstreet Committed by Jens Axboe
Browse files

block: simplify bio_add_page() 



Since generic_make_request() can now handle arbitrary size bios, all we
have to do is make sure the bvec array doesn't overflow.
__bio_add_page() doesn't need to call ->merge_bvec_fn(), where
we can get rid of unnecessary code paths.

Removing the call to ->merge_bvec_fn() is also fine, as no driver that
implements support for BLOCK_PC commands even has a ->merge_bvec_fn()
method.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarKent Overstreet <kent.overstreet@gmail.com>
[dpark: rebase and resolve merge conflicts, change a couple of comments,
 make bio_add_page() warn once upon a cloned bio.]
Signed-off-by: default avatarDongsu Park <dpark@posteo.net>
Signed-off-by: default avatarMing Lin <ming.l@ssi.samsung.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 54efd50b

block/bio.c

+55 −80
Original line number Diff line number Diff line
@@ -716,9 +716,23 @@ int bio_get_nr_vecs(struct block_device *bdev) 
}

EXPORT_SYMBOL(bio_get_nr_vecs);



static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page

			  *page, unsigned int len, unsigned int offset,

			  unsigned int max_sectors)

/**

 *	bio_add_pc_page	-	attempt to add page to bio

 *	@q: the target queue

 *	@bio: destination bio

 *	@page: page to add

 *	@len: vec entry length

 *	@offset: vec entry offset

 *

 *	Attempt to add a page to the bio_vec maplist. This can fail for a

 *	number of reasons, such as the bio being full or target block device

 *	limitations. The target block device must allow bio's up to PAGE_SIZE,

 *	so it is always possible to add a single page to an empty bio.

 *

 *	This should only be used by REQ_PC bios.

 */

int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page

		    *page, unsigned int len, unsigned int offset)

{

	int retried_segments = 0;

	struct bio_vec *bvec;
@@ -729,7 +743,7 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page 
	if (unlikely(bio_flagged(bio, BIO_CLONED)))

		return 0;



	if (((bio->bi_iter.bi_size + len) >> 9) > max_sectors)

	if (((bio->bi_iter.bi_size + len) >> 9) > queue_max_hw_sectors(q))

		return 0;



	/*
@@ -742,28 +756,7 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page 


		if (page == prev->bv_page &&

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

			unsigned int prev_bv_len = prev->bv_len;

			prev->bv_len += len;



			if (q->merge_bvec_fn) {

				struct bvec_merge_data bvm = {

					/* prev_bvec is already charged in

					   bi_size, discharge it in order to

					   simulate merging updated prev_bvec

					   as new bvec. */

					.bi_bdev = bio->bi_bdev,

					.bi_sector = bio->bi_iter.bi_sector,

					.bi_size = bio->bi_iter.bi_size -

						prev_bv_len,

					.bi_rw = bio->bi_rw,

				};



				if (q->merge_bvec_fn(q, &bvm, prev) < prev->bv_len) {

					prev->bv_len -= len;

					return 0;

				}

			}



			bio->bi_iter.bi_size += len;

			goto done;

		}
@@ -806,27 +799,6 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page 
		blk_recount_segments(q, bio);

	}



	/*

	 * if queue has other restrictions (eg varying max sector size

	 * depending on offset), it can specify a merge_bvec_fn in the

	 * queue to get further control

	 */

	if (q->merge_bvec_fn) {

		struct bvec_merge_data bvm = {

			.bi_bdev = bio->bi_bdev,

			.bi_sector = bio->bi_iter.bi_sector,

			.bi_size = bio->bi_iter.bi_size - len,

			.bi_rw = bio->bi_rw,

		};



		/*

		 * merge_bvec_fn() returns number of bytes it can accept

		 * at this offset

		 */

		if (q->merge_bvec_fn(q, &bvm, bvec) < bvec->bv_len)

			goto failed;

	}



	/* If we may be able to merge these biovecs, force a recount */

	if (bio->bi_vcnt > 1 && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec)))

		bio_clear_flag(bio, BIO_SEG_VALID);
@@ -843,53 +815,56 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page 
	blk_recount_segments(q, bio);

	return 0;

}

EXPORT_SYMBOL(bio_add_pc_page);



/**

 *	bio_add_pc_page	-	attempt to add page to bio

 *	@q: the target queue

 *	bio_add_page	-	attempt to add page to bio

 *	@bio: destination bio

 *	@page: page to add

 *	@len: vec entry length

 *	@offset: vec entry offset

 *

 *	Attempt to add a page to the bio_vec maplist. This can fail for a

 *	number of reasons, such as the bio being full or target block device

 *	limitations. The target block device must allow bio's up to PAGE_SIZE,

 *	so it is always possible to add a single page to an empty bio.

 *

 *	This should only be used by REQ_PC bios.

 *	Attempt to add a page to the bio_vec maplist. This will only fail

 *	if either bio->bi_vcnt == bio->bi_max_vecs or it's a cloned bio.

 */

int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page *page,

int bio_add_page(struct bio *bio, struct page *page,

		 unsigned int len, unsigned int offset)

{

	return __bio_add_page(q, bio, page, len, offset,

			      queue_max_hw_sectors(q));

}

EXPORT_SYMBOL(bio_add_pc_page);

	struct bio_vec *bv;



/**

 *	bio_add_page	-	attempt to add page to bio

 *	@bio: destination bio

 *	@page: page to add

 *	@len: vec entry length

 *	@offset: vec entry offset

 *

 *	Attempt to add a page to the bio_vec maplist. This can fail for a

 *	number of reasons, such as the bio being full or target block device

 *	limitations. The target block device must allow bio's up to PAGE_SIZE,

 *	so it is always possible to add a single page to an empty bio.

	/*

	 * cloned bio must not modify vec list

	 */

int bio_add_page(struct bio *bio, struct page *page, unsigned int len,

		 unsigned int offset)

{

	struct request_queue *q = bdev_get_queue(bio->bi_bdev);

	unsigned int max_sectors;

	if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))

		return 0;



	max_sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);

	if ((max_sectors < (len >> 9)) && !bio->bi_iter.bi_size)

		max_sectors = len >> 9;

	/*

	 * For filesystems with a blocksize smaller than the pagesize

	 * we will often be called with the same page as last time and

	 * a consecutive offset.  Optimize this special case.

	 */

	if (bio->bi_vcnt > 0) {

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



	return __bio_add_page(q, bio, page, len, offset, max_sectors);

		if (page == bv->bv_page &&

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

			bv->bv_len += len;

			goto done;

		}

	}



	if (bio->bi_vcnt >= bio->bi_max_vecs)

		return 0;



	bv		= &bio->bi_io_vec[bio->bi_vcnt];

	bv->bv_page	= page;

	bv->bv_len	= len;

	bv->bv_offset	= offset;



	bio->bi_vcnt++;

done:

	bio->bi_iter.bi_size += len;

	return len;

}

EXPORT_SYMBOL(bio_add_page);