kill bio_clone_kmalloc and bio_clone_bioset

kill bio_clone_kmalloc and bio_clone_bioset

[Christoph Hellwig]

Hi all,

this series removes all but one users of the traditional deep bio clone,
and then moves bio_clone_bioset to its only caller so that we get rid
of the deep bio cloning in the block layer API.

[PATCH 1/5] bcache: don't clone bio in bch_data_verify

[Christoph Hellwig]

We immediately overwrite the biovec array, so instead just allocate
a new bio and copy over the disk, setor and size.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Coly Li <colyli@suse.de>
---
 drivers/md/bcache/debug.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c
index d030ce3025a6..04d146711950 100644
--- a/drivers/md/bcache/debug.c
+++ b/drivers/md/bcache/debug.c
@@ -110,11 +110,15 @@ void bch_data_verify(struct cached_dev *dc, struct bio *bio)
 	struct bio_vec bv, cbv;
 	struct bvec_iter iter, citer = { 0 };
 
-	check = bio_clone_kmalloc(bio, GFP_NOIO);
+	check = bio_kmalloc(GFP_NOIO, bio_segments(bio));
 	if (!check)
 		return;
+	check->bi_disk = bio->bi_disk;
 	check->bi_opf = REQ_OP_READ;
+	check->bi_iter.bi_sector = bio->bi_iter.bi_sector;
+	check->bi_iter.bi_size = bio->bi_iter.bi_size;
 
+	bch_bio_map(check, NULL);
 	if (bch_bio_alloc_pages(check, GFP_NOIO))
 		goto out_put;
 
-- 
2.18.0

[PATCH 2/5] exofs: use bio_clone_fast in _write_mirror

[Christoph Hellwig]

The mirroring code never changes the bio data or biovecs.  This means
we can reuse the biovec allocation easily instead of duplicating it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by Boaz Harrosh <ooo@electrozaur.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
 fs/exofs/ore.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/exofs/ore.c b/fs/exofs/ore.c
index 1b8b44637e70..5331a15a61f1 100644
--- a/fs/exofs/ore.c
+++ b/fs/exofs/ore.c
@@ -873,8 +873,8 @@ static int _write_mirror(struct ore_io_state *ios, int cur_comp)
 			struct bio *bio;
 
 			if (per_dev != master_dev) {
-				bio = bio_clone_kmalloc(master_dev->bio,
-							GFP_KERNEL);
+				bio = bio_clone_fast(master_dev->bio,
+						     GFP_KERNEL, NULL);
 				if (unlikely(!bio)) {
 					ORE_DBGMSG(
 					      "Failed to allocate BIO size=%u\n",
-- 
2.18.0

[PATCH 3/5] block: remove bio_clone_kmalloc

[Christoph Hellwig]

Unused now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
 include/linux/bio.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index ab221c517f4e..b861baa59454 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -443,12 +443,6 @@ static inline struct bio *bio_kmalloc(gfp_t gfp_mask, unsigned int nr_iovecs)
 	return bio_alloc_bioset(gfp_mask, nr_iovecs, NULL);
 }
 
-static inline struct bio *bio_clone_kmalloc(struct bio *bio, gfp_t gfp_mask)
-{
-	return bio_clone_bioset(bio, gfp_mask, NULL);
-
-}
-
 extern blk_qc_t submit_bio(struct bio *);
 
 extern void bio_endio(struct bio *);
-- 
2.18.0

[PATCH 4/5] md: remove a bogus comment

[Christoph Hellwig]

The function name mentioned doesn't exist, and the code next to it
doesn't match the description either.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/md/md.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index f6e58dbca0d4..cb4eb5faa519 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -204,10 +204,6 @@ static int start_readonly;
  */
 static bool create_on_open = true;
 
-/* bio_clone_mddev
- * like bio_clone_bioset, but with a local bio set
- */
-
 struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
 			    struct mddev *mddev)
 {
-- 
2.18.0

[PATCH 5/5] block: unexport bio_clone_bioset

[Christoph Hellwig]

Now only used by the bounce code, so move it there and mark the function
static.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
 block/bio.c         | 77 ---------------------------------------------
 block/bounce.c      | 69 +++++++++++++++++++++++++++++++++++++++-
 include/linux/bio.h |  1 -
 3 files changed, 68 insertions(+), 79 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 8ecc95615941..d1313d73009d 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -646,83 +646,6 @@ struct bio *bio_clone_fast(struct bio *bio, gfp_t gfp_mask, struct bio_set *bs)
 }
 EXPORT_SYMBOL(bio_clone_fast);
 
-/**
- * 	bio_clone_bioset - clone a bio
- * 	@bio_src: bio to clone
- *	@gfp_mask: allocation priority
- *	@bs: bio_set to allocate from
- *
- *	Clone bio. Caller will own the returned bio, but not the actual data it
- *	points to. Reference count of returned bio will be one.
- */
-struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
-			     struct bio_set *bs)
-{
-	struct bvec_iter iter;
-	struct bio_vec bv;
-	struct bio *bio;
-
-	/*
-	 * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
-	 * bio_src->bi_io_vec to bio->bi_io_vec.
-	 *
-	 * We can't do that anymore, because:
-	 *
-	 *  - The point of cloning the biovec is to produce a bio with a biovec
-	 *    the caller can modify: bi_idx and bi_bvec_done should be 0.
-	 *
-	 *  - The original bio could've had more than BIO_MAX_PAGES biovecs; if
-	 *    we tried to clone the whole thing bio_alloc_bioset() would fail.
-	 *    But the clone should succeed as long as the number of biovecs we
-	 *    actually need to allocate is fewer than BIO_MAX_PAGES.
-	 *
-	 *  - Lastly, bi_vcnt should not be looked at or relied upon by code
-	 *    that does not own the bio - reason being drivers don't use it for
-	 *    iterating over the biovec anymore, so expecting it to be kept up
-	 *    to date (i.e. for clones that share the parent biovec) is just
-	 *    asking for trouble and would force extra work on
-	 *    __bio_clone_fast() anyways.
-	 */
-
-	bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
-	if (!bio)
-		return NULL;
-	bio->bi_disk		= bio_src->bi_disk;
-	bio->bi_opf		= bio_src->bi_opf;
-	bio->bi_write_hint	= bio_src->bi_write_hint;
-	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
-	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;
-
-	switch (bio_op(bio)) {
-	case REQ_OP_DISCARD:
-	case REQ_OP_SECURE_ERASE:
-	case REQ_OP_WRITE_ZEROES:
-		break;
-	case REQ_OP_WRITE_SAME:
-		bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
-		break;
-	default:
-		bio_for_each_segment(bv, bio_src, iter)
-			bio->bi_io_vec[bio->bi_vcnt++] = bv;
-		break;
-	}
-
-	if (bio_integrity(bio_src)) {
-		int ret;
-
-		ret = bio_integrity_clone(bio, bio_src, gfp_mask);
-		if (ret < 0) {
-			bio_put(bio);
-			return NULL;
-		}
-	}
-
-	bio_clone_blkcg_association(bio, bio_src);
-
-	return bio;
-}
-EXPORT_SYMBOL(bio_clone_bioset);
-
 /**
  *	bio_add_pc_page	-	attempt to add page to bio
  *	@q: the target queue
diff --git a/block/bounce.c b/block/bounce.c
index fd31347b7836..bc63b3a2d18c 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -195,6 +195,73 @@ static void bounce_end_io_read_isa(struct bio *bio)
 	__bounce_end_io_read(bio, &isa_page_pool);
 }
 
+static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
+		struct bio_set *bs)
+{
+	struct bvec_iter iter;
+	struct bio_vec bv;
+	struct bio *bio;
+
+	/*
+	 * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
+	 * bio_src->bi_io_vec to bio->bi_io_vec.
+	 *
+	 * We can't do that anymore, because:
+	 *
+	 *  - The point of cloning the biovec is to produce a bio with a biovec
+	 *    the caller can modify: bi_idx and bi_bvec_done should be 0.
+	 *
+	 *  - The original bio could've had more than BIO_MAX_PAGES biovecs; if
+	 *    we tried to clone the whole thing bio_alloc_bioset() would fail.
+	 *    But the clone should succeed as long as the number of biovecs we
+	 *    actually need to allocate is fewer than BIO_MAX_PAGES.
+	 *
+	 *  - Lastly, bi_vcnt should not be looked at or relied upon by code
+	 *    that does not own the bio - reason being drivers don't use it for
+	 *    iterating over the biovec anymore, so expecting it to be kept up
+	 *    to date (i.e. for clones that share the parent biovec) is just
+	 *    asking for trouble and would force extra work on
+	 *    __bio_clone_fast() anyways.
+	 */
+
+	bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
+	if (!bio)
+		return NULL;
+	bio->bi_disk		= bio_src->bi_disk;
+	bio->bi_opf		= bio_src->bi_opf;
+	bio->bi_write_hint	= bio_src->bi_write_hint;
+	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
+	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;
+
+	switch (bio_op(bio)) {
+	case REQ_OP_DISCARD:
+	case REQ_OP_SECURE_ERASE:
+	case REQ_OP_WRITE_ZEROES:
+		break;
+	case REQ_OP_WRITE_SAME:
+		bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
+		break;
+	default:
+		bio_for_each_segment(bv, bio_src, iter)
+			bio->bi_io_vec[bio->bi_vcnt++] = bv;
+		break;
+	}
+
+	if (bio_integrity(bio_src)) {
+		int ret;
+
+		ret = bio_integrity_clone(bio, bio_src, gfp_mask);
+		if (ret < 0) {
+			bio_put(bio);
+			return NULL;
+		}
+	}
+
+	bio_clone_blkcg_association(bio, bio_src);
+
+	return bio;
+}
+
 static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 			       mempool_t *pool)
 {
@@ -222,7 +289,7 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 		generic_make_request(*bio_orig);
 		*bio_orig = bio;
 	}
-	bio = bio_clone_bioset(*bio_orig, GFP_NOIO, passthrough ? NULL :
+	bio = bounce_clone_bio(*bio_orig, GFP_NOIO, passthrough ? NULL :
 			&bounce_bio_set);
 
 	bio_for_each_segment_all(to, bio, i) {
diff --git a/include/linux/bio.h b/include/linux/bio.h
index b861baa59454..51371740d2a8 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -429,7 +429,6 @@ extern void bio_put(struct bio *);
 
 extern void __bio_clone_fast(struct bio *, struct bio *);
 extern struct bio *bio_clone_fast(struct bio *, gfp_t, struct bio_set *);
-extern struct bio *bio_clone_bioset(struct bio *, gfp_t, struct bio_set *bs);
 
 extern struct bio_set fs_bio_set;
 
-- 
2.18.0

Re: kill bio_clone_kmalloc and bio_clone_bioset

[Jens Axboe]

On 7/24/18 12:52 AM, Christoph Hellwig wrote:
> Hi all,
> 
> this series removes all but one users of the traditional deep bio clone,
> and then moves bio_clone_bioset to its only caller so that we get rid
> of the deep bio cloning in the block layer API.

Applied for 4.19.

-- 
Jens Axboe