[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 01/27] block: bio: introduce 3 helpers for cleanup

[Ming Lei]

Some drivers access bio->bi_vcnt and bio->bi_io_vec directly.
Firstly it isn't a good practice. Secondly it may cause trouble
for 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.

So this patches introduces 3 helpers for cleaning up this kind
of usage.

bio_pages() can be convertd to support multipage bvecs easily.

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 easy to audit access
of .bi_io_vec and .bi_vcnt and check if this kind of use is good
for supporting multipage bvecs.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 include/linux/bio.h | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 6b7481f..2229006d 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -310,6 +310,27 @@ static inline void bio_clear_flag(struct bio *bio, unsigned int bit)
 	bio->bi_flags &= ~(1U << bit);
 }
 
+static inline struct bio_vec *bio_get_base_vec(struct bio *bio)
+{
+	return __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
+}
+
+/* This helper should be used for setting bvec table on a new bio */
+static inline void bio_set_vec_table(struct bio *bio, struct bio_vec *table,
+			      unsigned max_vecs)
+{
+	bio->bi_io_vec = table;
+	bio->bi_max_vecs = max_vecs;
+}
+
+/* For singlepage bvecs, one segment includes one page */
+static inline unsigned bio_pages(struct bio *bio)
+{
+	if (!bio_flagged(bio, BIO_CLONED))
+		return bio->bi_vcnt;
+	return bio_segments(bio);
+}
+
 static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv)
 {
 	*bv = bio_iovec(bio);
-- 
1.9.1

[PATCH v1 02/27] block: drbd: use bio_get_base_vec() to retrieve the 1st bvec

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/block/drbd/drbd_bitmap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
index 92d6fc0..ccbd1e0 100644
--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -938,7 +938,9 @@ static void drbd_bm_endio(struct bio *bio)
 	struct drbd_bm_aio_ctx *ctx = bio->bi_private;
 	struct drbd_device *device = ctx->device;
 	struct drbd_bitmap *b = device->bitmap;
-	unsigned int idx = bm_page_to_idx(bio->bi_io_vec[0].bv_page);
+	/* single bvec bio */
+	const struct bio_vec *bvec = bio_get_base_vec(bio);
+	unsigned int idx = bm_page_to_idx(bvec->bv_page);
 
 	if ((ctx->flags & BM_AIO_COPY_PAGES) == 0 &&
 	    !bm_test_page_unchanged(b->bm_pages[idx]))
-- 
1.9.1

[PATCH v1 03/27] block: drbd: remove impossible failure handling

[Ming Lei]

For a non-cloned bio, bio_add_page() only returns failure when
the io vec table is full, but in that case, bio->bi_vcnt can't
be zero at all.

So remove the impossible failure handling.

Acked-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/block/drbd/drbd_receiver.c | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 050aaa1..1b0ed15 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1465,20 +1465,8 @@ next_bio:
 
 	page_chain_for_each(page) {
 		unsigned len = min_t(unsigned, data_size, PAGE_SIZE);
-		if (!bio_add_page(bio, page, len, 0)) {
-			/* A single page must always be possible!
-			 * But in case it fails anyways,
-			 * we deal with it, and complain (below). */
-			if (bio->bi_vcnt == 0) {
-				drbd_err(device,
-					"bio_add_page failed for len=%u, "
-					"bi_vcnt=0 (bi_sector=%llu)\n",
-					len, (uint64_t)bio->bi_iter.bi_sector);
-				err = -ENOSPC;
-				goto fail;
-			}
+		if (!bio_add_page(bio, page, len, 0))
 			goto next_bio;
-		}
 		data_size -= len;
 		sector += len >> 9;
 		--nr_pages;
-- 
1.9.1

[PATCH v1 04/27] block: loop: use bio_get_base_vec() to retrive bvec table

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/block/loop.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 7e5e27a..e2e9dcd 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -477,7 +477,7 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
 		     loff_t pos, bool rw)
 {
 	struct iov_iter iter;
-	struct bio_vec *bvec;
+	const struct bio_vec *bvec;
 	struct bio *bio = cmd->rq->bio;
 	struct file *file = lo->lo_backing_file;
 	int ret;
@@ -485,7 +485,8 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
 	/* nomerge for loop request queue */
 	WARN_ON(cmd->rq->bio != cmd->rq->biotail);
 
-	bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
+	/* passed to iterate_bvec() */
+	bvec = bio_get_base_vec(bio);
 	iov_iter_bvec(&iter, ITER_BVEC | rw, bvec,
 		      bio_segments(bio), blk_rq_bytes(cmd->rq));
 
-- 
1.9.1

[PATCH v1 05/27] block: pktcdvd: use bio_get_base_vec() to retrive bvec table

[Ming Lei]

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

diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index d06c62e..8f37435 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -1298,7 +1298,8 @@ try_next_bio:
 static void pkt_start_write(struct pktcdvd_device *pd, struct packet_data *pkt)
 {
 	int f;
-	struct bio_vec *bvec = pkt->w_bio->bi_io_vec;
+	/* need to fix this usage after multipage bvecs */
+	struct bio_vec *bvec = bio_get_base_vec(pkt->w_bio);
 
 	bio_reset(pkt->w_bio);
 	pkt->w_bio->bi_iter.bi_sector = pkt->sector;
-- 
1.9.1

[PATCH v1 06/27] block: floppy: use bio_set_vec_table()

[Ming Lei]

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

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 84708a5..b5b0e68 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -3811,7 +3811,7 @@ static int __floppy_read_block_0(struct block_device *bdev, int drive)
 	cbdata.drive = drive;
 
 	bio_init(&bio);
-	bio.bi_io_vec = &bio_vec;
+	bio_set_vec_table(&bio, &bio_vec, 1);
 	bio_vec.bv_page = page;
 	bio_vec.bv_len = size;
 	bio_vec.bv_offset = 0;
-- 
1.9.1

[PATCH v1 07/27] block: floppy: use bio_add_page()

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/block/floppy.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index b5b0e68..a093de0 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -3812,17 +3812,14 @@ static int __floppy_read_block_0(struct block_device *bdev, int drive)
 
 	bio_init(&bio);
 	bio_set_vec_table(&bio, &bio_vec, 1);
-	bio_vec.bv_page = page;
-	bio_vec.bv_len = size;
-	bio_vec.bv_offset = 0;
-	bio.bi_vcnt = 1;
-	bio.bi_iter.bi_size = size;
 	bio.bi_bdev = bdev;
 	bio.bi_iter.bi_sector = 0;
 	bio.bi_flags |= (1 << BIO_QUIET);
 	bio.bi_private = &cbdata;
 	bio.bi_end_io = floppy_rb0_cb;
 
+	bio_add_page(&bio, page, size, 0);
+
 	submit_bio(READ, &bio);
 	process_fd_request();
 
-- 
1.9.1

[PATCH v1 08/27] staging: lustre: avoid to use bio->bi_vcnt directly

[Ming Lei]

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/staging/lustre/lustre/llite/lloop.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/lustre/lustre/llite/lloop.c b/drivers/staging/lustre/lustre/llite/lloop.c
index f169c0d..c7bdc2f 100644
--- a/drivers/staging/lustre/lustre/llite/lloop.c
+++ b/drivers/staging/lustre/lustre/llite/lloop.c
@@ -302,19 +302,20 @@ static unsigned int loop_get_bio(struct lloop_device *lo, struct bio **req)
 	}
 
 	/* TODO: need to split the bio, too bad. */
-	LASSERT(first->bi_vcnt <= LLOOP_MAX_SEGMENTS);
+	LASSERT(bio_pages(first) <= LLOOP_MAX_SEGMENTS);
 
 	rw = first->bi_rw;
 	bio = &lo->lo_bio;
 	while (*bio && (*bio)->bi_rw == rw) {
+		unsigned curr_cnt = bio_pages(*bio);
 		CDEBUG(D_INFO, "bio sector %llu size %u count %u vcnt%u\n",
 		       (unsigned long long)(*bio)->bi_iter.bi_sector,
 		       (*bio)->bi_iter.bi_size,
-		       page_count, (*bio)->bi_vcnt);
-		if (page_count + (*bio)->bi_vcnt > LLOOP_MAX_SEGMENTS)
+		       page_count, curr_cnt);
+		if (page_count + curr_cnt > LLOOP_MAX_SEGMENTS)
 			break;
 
-		page_count += (*bio)->bi_vcnt;
+		page_count += curr_cnt;
 		count++;
 		bio = &(*bio)->bi_next;
 	}
-- 
1.9.1

[PATCH v1 09/27] target: avoid to access .bi_vcnt directly

[Ming Lei]

When the bio is full, bio_add_pc_page() will return zero,
so use this way to handle full bio.

Also replace access to .bi_vcnt for pr_debug() with bio_segments().

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/target/target_core_pscsi.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index de18790..66320e8 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -945,13 +945,9 @@ pscsi_map_sg(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
 
 			rc = bio_add_pc_page(pdv->pdv_sd->request_queue,
 					bio, page, bytes, off);
-			if (rc != bytes)
-				goto fail;
-
 			pr_debug("PSCSI: bio->bi_vcnt: %d nr_vecs: %d\n",
-				bio->bi_vcnt, nr_vecs);
-
-			if (bio->bi_vcnt > nr_vecs) {
+				bio_segments(bio), nr_vecs);
+			if (rc != bytes) {
 				pr_debug("PSCSI: Reached bio->bi_vcnt max:"
 					" %d i: %d bio: %p, allocating another"
 					" bio\n", bio->bi_vcnt, i, bio);
-- 
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

[PATCH v1 21/27] fs: logfs: use bio_set_vec_table()

[Ming Lei]

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

diff --git a/fs/logfs/dev_bdev.c b/fs/logfs/dev_bdev.c
index cc26f8f..9f15b53 100644
--- a/fs/logfs/dev_bdev.c
+++ b/fs/logfs/dev_bdev.c
@@ -20,8 +20,7 @@ static int sync_request(struct page *page, struct block_device *bdev, int rw)
 	struct bio_vec bio_vec;
 
 	bio_init(&bio);
-	bio.bi_max_vecs = 1;
-	bio.bi_io_vec = &bio_vec;
+	bio_set_vec_table(&bio, &bio_vec, 1);
 	bio_vec.bv_page = page;
 	bio_vec.bv_len = PAGE_SIZE;
 	bio_vec.bv_offset = 0;
-- 
1.9.1

[PATCH v1 22/27] fs: logfs: convert to bio_add_page() in sync_request()

[Ming Lei]

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 fs/logfs/dev_bdev.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/fs/logfs/dev_bdev.c b/fs/logfs/dev_bdev.c
index 9f15b53..9623812 100644
--- a/fs/logfs/dev_bdev.c
+++ b/fs/logfs/dev_bdev.c
@@ -21,13 +21,10 @@ static int sync_request(struct page *page, struct block_device *bdev, int rw)
 
 	bio_init(&bio);
 	bio_set_vec_table(&bio, &bio_vec, 1);
-	bio_vec.bv_page = page;
-	bio_vec.bv_len = PAGE_SIZE;
-	bio_vec.bv_offset = 0;
-	bio.bi_vcnt = 1;
 	bio.bi_bdev = bdev;
 	bio.bi_iter.bi_sector = page->index * (PAGE_SIZE >> 9);
-	bio.bi_iter.bi_size = PAGE_SIZE;
+
+	bio_add_page(&bio, page, PAGE_SIZE, 0);
 
 	return submit_bio_wait(rw, &bio);
 }
-- 
1.9.1

[PATCH v1 23/27] fs: logfs: use bio_add_page() in __bdev_writeseg()

[Ming Lei]

Also this patch simplify the code a bit.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 fs/logfs/dev_bdev.c | 51 +++++++++++++++++++++------------------------------
 1 file changed, 21 insertions(+), 30 deletions(-)

diff --git a/fs/logfs/dev_bdev.c b/fs/logfs/dev_bdev.c
index 9623812..e2c38f9 100644
--- a/fs/logfs/dev_bdev.c
+++ b/fs/logfs/dev_bdev.c
@@ -72,54 +72,45 @@ static int __bdev_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
 {
 	struct logfs_super *super = logfs_super(sb);
 	struct address_space *mapping = super->s_mapping_inode->i_mapping;
-	struct bio *bio;
+	struct bio *bio = NULL;
 	struct page *page;
 	unsigned int max_pages;
-	int i;
+	int i, ret;
 
 	max_pages = min_t(size_t, nr_pages, BIO_MAX_PAGES);
 
-	bio = bio_alloc(GFP_NOFS, max_pages);
-	BUG_ON(!bio);
-
 	for (i = 0; i < nr_pages; i++) {
-		if (i >= max_pages) {
-			/* Block layer cannot split bios :( */
-			bio->bi_vcnt = i;
-			bio->bi_iter.bi_size = i * PAGE_SIZE;
+		if (!bio) {
+			bio = bio_alloc(GFP_NOFS, max_pages);
+			BUG_ON(!bio);
 			bio->bi_bdev = super->s_bdev;
 			bio->bi_iter.bi_sector = ofs >> 9;
 			bio->bi_private = sb;
 			bio->bi_end_io = writeseg_end_io;
-			atomic_inc(&super->s_pending_writes);
-			submit_bio(WRITE, bio);
-
-			ofs += i * PAGE_SIZE;
-			index += i;
-			nr_pages -= i;
-			i = 0;
-
-			bio = bio_alloc(GFP_NOFS, max_pages);
-			BUG_ON(!bio);
 		}
+
 		page = find_lock_page(mapping, index + i);
 		BUG_ON(!page);
-		bio->bi_io_vec[i].bv_page = page;
-		bio->bi_io_vec[i].bv_len = PAGE_SIZE;
-		bio->bi_io_vec[i].bv_offset = 0;
+
+		ret = bio_add_page(bio, page, PAGE_SIZE, 0);
 
 		BUG_ON(PageWriteback(page));
 		set_page_writeback(page);
 		unlock_page(page);
+		if (!ret) {
+			/* Block layer cannot split bios :( */
+			ofs += bio->bi_iter.bi_size;
+			atomic_inc(&super->s_pending_writes);
+			submit_bio(WRITE, bio);
+
+			bio = NULL;
+		}
+	}
+
+	if (bio) {
+		atomic_inc(&super->s_pending_writes);
+		submit_bio(WRITE, bio);
 	}
-	bio->bi_vcnt = nr_pages;
-	bio->bi_iter.bi_size = nr_pages * PAGE_SIZE;
-	bio->bi_bdev = super->s_bdev;
-	bio->bi_iter.bi_sector = ofs >> 9;
-	bio->bi_private = sb;
-	bio->bi_end_io = writeseg_end_io;
-	atomic_inc(&super->s_pending_writes);
-	submit_bio(WRITE, bio);
 	return 0;
 }
 
-- 
1.9.1

[PATCH v1 24/27] fs: logfs: use bio_add_page() in do_erase()

[Ming Lei]

Also code gets simplified a bit.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 fs/logfs/dev_bdev.c | 45 ++++++++++++++++++---------------------------
 1 file changed, 18 insertions(+), 27 deletions(-)

diff --git a/fs/logfs/dev_bdev.c b/fs/logfs/dev_bdev.c
index e2c38f9..a3a446c 100644
--- a/fs/logfs/dev_bdev.c
+++ b/fs/logfs/dev_bdev.c
@@ -154,47 +154,38 @@ static int do_erase(struct super_block *sb, u64 ofs, pgoff_t index,
 		size_t nr_pages)
 {
 	struct logfs_super *super = logfs_super(sb);
-	struct bio *bio;
+	struct bio *bio = NULL;
 	unsigned int max_pages;
-	int i;
+	int i, ret;
 
 	max_pages = min_t(size_t, nr_pages, BIO_MAX_PAGES);
 
-	bio = bio_alloc(GFP_NOFS, max_pages);
-	BUG_ON(!bio);
-
 	for (i = 0; i < nr_pages; i++) {
-		if (i >= max_pages) {
-			/* Block layer cannot split bios :( */
-			bio->bi_vcnt = i;
-			bio->bi_iter.bi_size = i * PAGE_SIZE;
+		if (!bio) {
+			bio = bio_alloc(GFP_NOFS, max_pages);
+			BUG_ON(!bio);
+
 			bio->bi_bdev = super->s_bdev;
 			bio->bi_iter.bi_sector = ofs >> 9;
 			bio->bi_private = sb;
 			bio->bi_end_io = erase_end_io;
+		}
+
+		ret = bio_add_page(bio, super->s_erase_page, PAGE_SIZE, 0);
+		if (!ret) {
+			/* Block layer cannot split bios :( */
+			ofs += bio->bi_iter.bi_size;
 			atomic_inc(&super->s_pending_writes);
 			submit_bio(WRITE, bio);
 
-			ofs += i * PAGE_SIZE;
-			index += i;
-			nr_pages -= i;
-			i = 0;
-
-			bio = bio_alloc(GFP_NOFS, max_pages);
-			BUG_ON(!bio);
+			bio = NULL;
 		}
-		bio->bi_io_vec[i].bv_page = super->s_erase_page;
-		bio->bi_io_vec[i].bv_len = PAGE_SIZE;
-		bio->bi_io_vec[i].bv_offset = 0;
 	}
-	bio->bi_vcnt = nr_pages;
-	bio->bi_iter.bi_size = nr_pages * PAGE_SIZE;
-	bio->bi_bdev = super->s_bdev;
-	bio->bi_iter.bi_sector = ofs >> 9;
-	bio->bi_private = sb;
-	bio->bi_end_io = erase_end_io;
-	atomic_inc(&super->s_pending_writes);
-	submit_bio(WRITE, bio);
+
+	if (bio) {
+		atomic_inc(&super->s_pending_writes);
+		submit_bio(WRITE, bio);
+	}
 	return 0;
 }
 
-- 
1.9.1

[PATCH v1 25/27] fs: logfs: remove unnecesary check

[Ming Lei]

The check on bio->bi_vcnt doesn't make sense in erase_end_io().

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 fs/logfs/dev_bdev.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/logfs/dev_bdev.c b/fs/logfs/dev_bdev.c
index a3a446c..29a3fe3 100644
--- a/fs/logfs/dev_bdev.c
+++ b/fs/logfs/dev_bdev.c
@@ -144,7 +144,6 @@ static void erase_end_io(struct bio *bio)
 	struct logfs_super *super = logfs_super(sb); 
 
 	BUG_ON(bio->bi_error); /* FIXME: Retry io or write elsewhere */ 
-	BUG_ON(bio->bi_vcnt == 0); 
 	bio_put(bio); 
 	if (atomic_dec_and_test(&super->s_pending_writes))
 		wake_up(&wq); 
-- 
1.9.1

[PATCH v1 26/27] kernel/power/swap.c: use bio_get_base_vec()

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 kernel/power/swap.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/power/swap.c b/kernel/power/swap.c
index 12cd989..cedf752 100644
--- a/kernel/power/swap.c
+++ b/kernel/power/swap.c
@@ -230,7 +230,15 @@ static void hib_init_batch(struct hib_bio_batch *hb)
 static void hib_end_io(struct bio *bio)
 {
 	struct hib_bio_batch *hb = bio->bi_private;
-	struct page *page = bio->bi_io_vec[0].bv_page;
+
+	/*
+	 * Single bvec bio.
+	 *
+	 * 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 page *page = bvec->bv_page;
 
 	if (bio->bi_error) {
 		printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
-- 
1.9.1

[PATCH v1 27/27] mm: page_io.c: use bio_get_base_vec()

[Ming Lei]

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 mm/page_io.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index cd92e3d..1ced9d3 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -43,7 +43,14 @@ static struct bio *get_swap_bio(gfp_t gfp_flags,
 
 void end_swap_bio_write(struct bio *bio)
 {
-	struct page *page = bio->bi_io_vec[0].bv_page;
+	/*
+	 * Single bvec bio.
+	 *
+	 * 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 page *page = bvec->bv_page;
 
 	if (bio->bi_error) {
 		SetPageError(page);
@@ -116,7 +123,14 @@ static void swap_slot_free_notify(struct page *page)
 
 static void end_swap_bio_read(struct bio *bio)
 {
-	struct page *page = bio->bi_io_vec[0].bv_page;
+	/*
+	 * Single bvec bio.
+	 *
+	 * 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 page *page = bvec->bv_page;
 
 	if (bio->bi_error) {
 		SetPageError(page);
-- 
1.9.1