[PATCH v1 00/27] block: cleanup direct access to .bi_vcnt & .bi_io_vec

[PATCH v1 00/27] block: cleanup direct access to .bi_vcnt & .bi_io_vec

[Ming Lei]

Hi Guys,

It is always not a good practice to access bio->bi_vcnt and
bio->bi_io_vec from drivers directly. Also this kind of direct
access will cause trouble when converting to multipage bvecs
because currently drivers may suppose one bvec always include
one page, and use the two fields to figure out how to handle
pages.

Even the actual meaning of the two fields arn't change from
block subsystem's view, but it may change from driver or fs's
view, so this patchset takes a conservative approach to cleanup
direct access to the two fields for avoiding regressions.

The 1st patch introduces the following 3 bio helpers which can be
used inside drivers for avoiding direct access to .bi_vcnt and .bi_io_vec.

        bio_pages()
        bio_get_base_vec()
        bio_set_vec_table()

bio_pages() can be easy to convert to multipage bvecs.

For bio_get_base_vec() and bio_set_vec_table(), they are often used
during initializing a new bio or in case of single bvec bio. With the
two new helpers, it becomes quite easy to audit access to .bi_io_vec
and .bi_vcnt.

Most of the other patches use the 3 helpers to clean up most of direct
access to .bi_vcnt and .bi_io_vec from drivers, except for MD and btrfs,
which two subsystems will be handled with different way in future.

For btrfs, its direct access to .bi_vcnt & .bi_io_vec need to be cleanuped
and audited that there isn't issue once converting to multipage bvecs.

For raid(md), given its usage is quite complicated, we can just
not enable multipage bvecs for raid queue until all its usage
are cleaned up and audited. So it won't be a blocker for multipage
bvecs.

Also bio_add_page() is used in floppy, dm-crypt and fs/logfs to
avoiding direct access to .bi_vcnt & .bi_io_vec.

The patchset can be found in the following tree:

https://github.com/ming1/linux/tree/v4.6-rc-block-next-mpbvecs-cleanup.v1

V1:
	- add Reviewed-by
	- remove bio_is_full() helper because target can find it
	via the return value of bio_add_pc_page() (9/27)
	- add comment on another two uses of bio_get_base_vec() (16/27)
	- rebased on latest for-next branch of block tree

Ming Lei (27):
  block: bio: introduce 3 helpers for cleanup
  block: drbd: use bio_get_base_vec() to retrieve the 1st bvec
  block: drbd: remove impossible failure handling
  block: loop: use bio_get_base_vec() to retrive bvec table
  block: pktcdvd: use bio_get_base_vec() to retrive bvec table
  block: floppy: use bio_set_vec_table()
  block: floppy: use bio_add_page()
  staging: lustre: avoid to use bio->bi_vcnt directly
  target: avoid to access .bi_vcnt directly
  bcache: debug: avoid to access .bi_io_vec directly
  bcache: io.c: use bio_set_vec_table
  bcache: journal.c: use bio_set_vec_table()
  bcache: movinggc: use bio_set_vec_table()
  bcache: writeback: use bio_set_vec_table()
  bcache: super: use bio_set_vec_table()
  bcache: super: use bio_get_base_vec
  dm: crypt: use bio_add_page()
  dm: dm-io.c: use bio_get_base_vec()
  dm: dm.c: replace 'bio->bi_vcnt == 1' with !bio_multiple_segments
  dm: dm-bufio.c: use bio_set_vec_table()
  fs: logfs: use bio_set_vec_table()
  fs: logfs: convert to bio_add_page() in sync_request()
  fs: logfs: use bio_add_page() in __bdev_writeseg()
  fs: logfs: use bio_add_page() in do_erase()
  fs: logfs: remove unnecesary check
  kernel/power/swap.c: use bio_get_base_vec()
  mm: page_io.c: use bio_get_base_vec()

 drivers/block/drbd/drbd_bitmap.c            |   4 +-
 drivers/block/drbd/drbd_receiver.c          |  14 +---
 drivers/block/floppy.c                      |   9 +--
 drivers/block/loop.c                        |   5 +-
 drivers/block/pktcdvd.c                     |   3 +-
 drivers/md/bcache/debug.c                   |  11 ++-
 drivers/md/bcache/io.c                      |   3 +-
 drivers/md/bcache/journal.c                 |   3 +-
 drivers/md/bcache/movinggc.c                |   6 +-
 drivers/md/bcache/super.c                   |  33 ++++++---
 drivers/md/bcache/writeback.c               |   4 +-
 drivers/md/dm-bufio.c                       |   3 +-
 drivers/md/dm-crypt.c                       |   8 +--
 drivers/md/dm-io.c                          |   7 +-
 drivers/md/dm.c                             |   3 +-
 drivers/staging/lustre/lustre/llite/lloop.c |   9 +--
 drivers/target/target_core_pscsi.c          |   8 +--
 fs/logfs/dev_bdev.c                         | 107 +++++++++++-----------------
 include/linux/bio.h                         |  21 ++++++
 kernel/power/swap.c                         |  10 ++-
 mm/page_io.c                                |  18 ++++-
 21 files changed, 155 insertions(+), 134 deletions(-)

Thanks,
Ming
-- 
1.9.1

[PATCH v1 10/27] bcache: debug: avoid to access .bi_io_vec directly

[Ming Lei]

Instead we use standard iterator way to do that.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/bcache/debug.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c
index 8b1f1d5..d1ad49d 100644
--- a/drivers/md/bcache/debug.c
+++ b/drivers/md/bcache/debug.c
@@ -106,8 +106,8 @@ void bch_data_verify(struct cached_dev *dc, struct bio *bio)
 {
 	char name[BDEVNAME_SIZE];
 	struct bio *check;
-	struct bio_vec bv, *bv2;
-	struct bvec_iter iter;
+	struct bio_vec bv, cbv, *bv2;
+	struct bvec_iter iter, citer = { 0 };
 	int i;
 
 	check = bio_clone(bio, GFP_NOIO);
@@ -119,9 +119,13 @@ void bch_data_verify(struct cached_dev *dc, struct bio *bio)
 
 	submit_bio_wait(READ_SYNC, check);
 
+	citer.bi_size = UINT_MAX;
 	bio_for_each_segment(bv, bio, iter) {
 		void *p1 = kmap_atomic(bv.bv_page);
-		void *p2 = page_address(check->bi_io_vec[iter.bi_idx].bv_page);
+		void *p2;
+
+		cbv = bio_iter_iovec(check, citer);
+		p2 = page_address(cbv.bv_page);
 
 		cache_set_err_on(memcmp(p1 + bv.bv_offset,
 					p2 + bv.bv_offset,
@@ -132,6 +136,7 @@ void bch_data_verify(struct cached_dev *dc, struct bio *bio)
 				 (uint64_t) bio->bi_iter.bi_sector);
 
 		kunmap_atomic(p1);
+		bio_advance_iter(check, &citer, bv.bv_len);
 	}
 
 	bio_for_each_segment_all(bv2, check, i)
-- 
1.9.1

[PATCH v1 11/27] bcache: io.c: use bio_set_vec_table

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/bcache/io.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/md/bcache/io.c b/drivers/md/bcache/io.c
index 86a0bb8..1c48462 100644
--- a/drivers/md/bcache/io.c
+++ b/drivers/md/bcache/io.c
@@ -26,8 +26,7 @@ struct bio *bch_bbio_alloc(struct cache_set *c)
 
 	bio_init(bio);
 	bio->bi_flags		|= BIO_POOL_NONE << BIO_POOL_OFFSET;
-	bio->bi_max_vecs	 = bucket_pages(c);
-	bio->bi_io_vec		 = bio->bi_inline_vecs;
+	bio_set_vec_table(bio, bio->bi_inline_vecs, bucket_pages(c));
 
 	return bio;
 }
-- 
1.9.1

[PATCH v1 12/27] bcache: journal.c: use bio_set_vec_table()

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/bcache/journal.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index 29eba72..bf8924f 100644
--- a/drivers/md/bcache/journal.c
+++ b/drivers/md/bcache/journal.c
@@ -453,8 +453,7 @@ static void do_journal_discard(struct cache *ca)
 						ca->sb.d[ja->discard_idx]);
 		bio->bi_bdev		= ca->bdev;
 		bio->bi_rw		= REQ_WRITE|REQ_DISCARD;
-		bio->bi_max_vecs	= 1;
-		bio->bi_io_vec		= bio->bi_inline_vecs;
+		bio_set_vec_table(bio, bio->bi_inline_vecs, 1);
 		bio->bi_iter.bi_size	= bucket_bytes(ca);
 		bio->bi_end_io		= journal_discard_endio;
 
-- 
1.9.1

[PATCH v1 13/27] bcache: movinggc: use bio_set_vec_table()

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/bcache/movinggc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/md/bcache/movinggc.c b/drivers/md/bcache/movinggc.c
index b929fc9..dbe5af2 100644
--- a/drivers/md/bcache/movinggc.c
+++ b/drivers/md/bcache/movinggc.c
@@ -85,10 +85,10 @@ static void moving_init(struct moving_io *io)
 	bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
 
 	bio->bi_iter.bi_size	= KEY_SIZE(&io->w->key) << 9;
-	bio->bi_max_vecs	= DIV_ROUND_UP(KEY_SIZE(&io->w->key),
-					       PAGE_SECTORS);
 	bio->bi_private		= &io->cl;
-	bio->bi_io_vec		= bio->bi_inline_vecs;
+	bio_set_vec_table(bio, bio->bi_inline_vecs,
+			  DIV_ROUND_UP(KEY_SIZE(&io->w->key),
+			  PAGE_SECTORS));
 	bch_bio_map(bio, NULL);
 }
 
-- 
1.9.1

[PATCH v1 14/27] bcache: writeback: use bio_set_vec_table()

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/bcache/writeback.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index b9346cd..49a8f8a 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -112,9 +112,9 @@ static void dirty_init(struct keybuf_key *w)
 		bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
 
 	bio->bi_iter.bi_size	= KEY_SIZE(&w->key) << 9;
-	bio->bi_max_vecs	= DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS);
 	bio->bi_private		= w;
-	bio->bi_io_vec		= bio->bi_inline_vecs;
+	bio_set_vec_table(bio, bio->bi_inline_vecs,
+			  DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS));
 	bch_bio_map(bio, NULL);
 }
 
-- 
1.9.1

[PATCH v1 15/27] bcache: super: use bio_set_vec_table()

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/bcache/super.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index f5dbb4e..3fa1ecf 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1151,8 +1151,7 @@ static void register_bdev(struct cache_sb *sb, struct page *sb_page,
 	dc->bdev->bd_holder = dc;
 
 	bio_init(&dc->sb_bio);
-	dc->sb_bio.bi_max_vecs	= 1;
-	dc->sb_bio.bi_io_vec	= dc->sb_bio.bi_inline_vecs;
+	bio_set_vec_table(&dc->sb_bio, dc->sb_bio.bi_inline_vecs, 1);
 	dc->sb_bio.bi_io_vec[0].bv_page = sb_page;
 	get_page(sb_page);
 
@@ -1812,8 +1811,8 @@ static int cache_alloc(struct cache_sb *sb, struct cache *ca)
 	kobject_init(&ca->kobj, &bch_cache_ktype);
 
 	bio_init(&ca->journal.bio);
-	ca->journal.bio.bi_max_vecs = 8;
-	ca->journal.bio.bi_io_vec = ca->journal.bio.bi_inline_vecs;
+	bio_set_vec_table(&ca->journal.bio,
+			  ca->journal.bio.bi_inline_vecs, 8);
 
 	free = roundup_pow_of_two(ca->sb.nbuckets) >> 10;
 
@@ -1850,8 +1849,7 @@ static int register_cache(struct cache_sb *sb, struct page *sb_page,
 	ca->bdev->bd_holder = ca;
 
 	bio_init(&ca->sb_bio);
-	ca->sb_bio.bi_max_vecs	= 1;
-	ca->sb_bio.bi_io_vec	= ca->sb_bio.bi_inline_vecs;
+	bio_set_vec_table(&ca->sb_bio, ca->sb_bio.bi_inline_vecs, 1);
 	ca->sb_bio.bi_io_vec[0].bv_page = sb_page;
 	get_page(sb_page);
 
-- 
1.9.1

[PATCH v1 16/27] bcache: super: use bio_get_base_vec

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/bcache/super.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 3fa1ecf..d7fda32 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -208,7 +208,12 @@ static void write_bdev_super_endio(struct bio *bio)
 
 static void __write_super(struct cache_sb *sb, struct bio *bio)
 {
-	struct cache_sb *out = page_address(bio->bi_io_vec[0].bv_page);
+	/*
+	 * For accessing page pointed to by the 1st bvec, it
+	 * works too after multipage bvecs.
+	 */
+	struct bio_vec *bvec = bio_get_base_vec(bio);
+	struct cache_sb *out = page_address(bvec->bv_page);
 	unsigned i;
 
 	bio->bi_iter.bi_sector	= SB_SECTOR;
@@ -1145,6 +1150,7 @@ static void register_bdev(struct cache_sb *sb, struct page *sb_page,
 	char name[BDEVNAME_SIZE];
 	const char *err = "cannot allocate memory";
 	struct cache_set *c;
+	struct bio_vec *bvec;
 
 	memcpy(&dc->sb, sb, sizeof(struct cache_sb));
 	dc->bdev = bdev;
@@ -1152,7 +1158,9 @@ static void register_bdev(struct cache_sb *sb, struct page *sb_page,
 
 	bio_init(&dc->sb_bio);
 	bio_set_vec_table(&dc->sb_bio, dc->sb_bio.bi_inline_vecs, 1);
-	dc->sb_bio.bi_io_vec[0].bv_page = sb_page;
+	/* single bvec, still works after multipage bvecs */
+	bvec = bio_get_base_vec(&dc->sb_bio);
+	bvec->bv_page = sb_page;
 	get_page(sb_page);
 
 	if (cached_dev_init(dc, sb->block_size << 9))
@@ -1776,6 +1784,11 @@ void bch_cache_release(struct kobject *kobj)
 {
 	struct cache *ca = container_of(kobj, struct cache, kobj);
 	unsigned i;
+	/*
+	 * For accessing page pointed to by the 1st bvec, it
+	 * works too after multipage bvecs.
+	 */
+	struct bio_vec *bvec = bio_get_base_vec(&ca->sb_bio);
 
 	if (ca->set) {
 		BUG_ON(ca->set->cache[ca->sb.nr_this_dev] != ca);
@@ -1793,7 +1806,7 @@ void bch_cache_release(struct kobject *kobj)
 		free_fifo(&ca->free[i]);
 
 	if (ca->sb_bio.bi_inline_vecs[0].bv_page)
-		put_page(ca->sb_bio.bi_io_vec[0].bv_page);
+		put_page(bvec->bv_page);
 
 	if (!IS_ERR_OR_NULL(ca->bdev))
 		blkdev_put(ca->bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
@@ -1843,6 +1856,7 @@ static int register_cache(struct cache_sb *sb, struct page *sb_page,
 	char name[BDEVNAME_SIZE];
 	const char *err = NULL;
 	int ret = 0;
+	struct bio_vec *bvec;
 
 	memcpy(&ca->sb, sb, sizeof(struct cache_sb));
 	ca->bdev = bdev;
@@ -1850,7 +1864,8 @@ static int register_cache(struct cache_sb *sb, struct page *sb_page,
 
 	bio_init(&ca->sb_bio);
 	bio_set_vec_table(&ca->sb_bio, ca->sb_bio.bi_inline_vecs, 1);
-	ca->sb_bio.bi_io_vec[0].bv_page = sb_page;
+	bvec = bio_get_base_vec(&ca->sb_bio);
+	bvec->bv_page = sb_page;
 	get_page(sb_page);
 
 	if (blk_queue_discard(bdev_get_queue(ca->bdev)))
-- 
1.9.1

[PATCH v1 17/27] dm: crypt: use bio_add_page()

[Ming Lei]

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/dm-crypt.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 4f3cb35..a2805c1 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -995,7 +995,6 @@ static struct bio *crypt_alloc_buffer(struct dm_crypt_io *io, unsigned size)
 	gfp_t gfp_mask = GFP_NOWAIT | __GFP_HIGHMEM;
 	unsigned i, len, remaining_size;
 	struct page *page;
-	struct bio_vec *bvec;
 
 retry:
 	if (unlikely(gfp_mask & __GFP_DIRECT_RECLAIM))
@@ -1020,12 +1019,7 @@ retry:
 
 		len = (remaining_size > PAGE_SIZE) ? PAGE_SIZE : remaining_size;
 
-		bvec = &clone->bi_io_vec[clone->bi_vcnt++];
-		bvec->bv_page = page;
-		bvec->bv_len = len;
-		bvec->bv_offset = 0;
-
-		clone->bi_iter.bi_size += len;
+		bio_add_page(clone, page, len, 0);
 
 		remaining_size -= len;
 	}
-- 
1.9.1

[PATCH v1 18/27] dm: dm-io.c: use bio_get_base_vec()

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/dm-io.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index 06d426e..6b0e466 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -221,7 +221,12 @@ static void bio_dp_init(struct dpages *dp, struct bio *bio)
 {
 	dp->get_page = bio_get_page;
 	dp->next_page = bio_next_page;
-	dp->context_ptr = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
+
+	/*
+	 * need to fix both bio_get_page() and bio_next_page()
+	 * before multipage bvecs
+	 */
+	dp->context_ptr = bio_get_base_vec(bio);
 	dp->context_u = bio->bi_iter.bi_bvec_done;
 }
 
-- 
1.9.1

[PATCH v1 19/27] dm: dm.c: replace 'bio->bi_vcnt == 1' with !bio_multiple_segments

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/dm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index be49057..4c34f88 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2172,7 +2172,8 @@ static void dm_request_fn(struct request_queue *q)
 			pos = blk_rq_pos(rq);
 
 		if ((dm_request_peeked_before_merge_deadline(md) &&
-		     md_in_flight(md) && rq->bio && rq->bio->bi_vcnt == 1 &&
+		     md_in_flight(md) && rq->bio &&
+		     !bio_multiple_segments(rq->bio) &&
 		     md->last_rq_pos == pos && md->last_rq_rw == rq_data_dir(rq)) ||
 		    (ti->type->busy && ti->type->busy(ti))) {
 			blk_delay_queue(q, HZ / 100);
-- 
1.9.1

[PATCH v1 20/27] dm: dm-bufio.c: use bio_set_vec_table()

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/dm-bufio.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index cd77216..0e48ad7 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -624,8 +624,7 @@ static void use_inline_bio(struct dm_buffer *b, int rw, sector_t block,
 	int len;
 
 	bio_init(&b->bio);
-	b->bio.bi_io_vec = b->bio_vec;
-	b->bio.bi_max_vecs = DM_BUFIO_INLINE_VECS;
+	bio_set_vec_table(&b->bio, b->bio_vec, DM_BUFIO_INLINE_VECS);
 	b->bio.bi_iter.bi_sector = block << b->c->sectors_per_block_bits;
 	b->bio.bi_bdev = b->c->bdev;
 	b->bio.bi_end_io = inline_endio;
-- 
1.9.1