[PATCH v5 0/8] block: prepare for multipage bvecs

[PATCH v5 0/8] block: prepare for multipage bvecs

[Ming Lei]

Hi,

Interests[1] have been shown in multipage bvecs, so this patchset
try to prepare for the support and do two things:

1) the 1st 4 patches use bvec iterator to implement iterate_bvec(),
then we can drop the non-standard way for iterating bvec, which
can be thought as a good cleanup for lib/iov_iter.c

2) remove BIO_MAX_SECTORS & BIO_MAX_SIZE, and now there is only
one user for each. Once multipage bvecs is introduced, one bio
may hold lots of sectors, and we should always use sort of BIO_MAX_VECS
which should be introduced in future and is similiar with current
BIO_MAX_PAGES.

The only functional change is iterate_bvec():lib/iov_iter.c

xfstests(-a auto) over loop aio is run for ext4/xfs to verify 
the change and no regression found with this patchset.

Jens, I am confidant this time, so please give it a go if no one
objects. I appreciate someone(AI? or anyone) can give a review on
the patch 4/8 about iterate_bvec() change.

V5:
	- use bvec's iterator to figure new base vec address and
	update 'skip' correctly
	- run xfstests(-a auto) on loop aio/dio for verifying
	the change in iterate_bvec(), and no regression reported
	- use stree-ng to trigger heavy swap over swapfile to verify
	change in iterate_bvec() too, looks everything is fine
V4:
	- make xfstests cover xfs
	- rebase on for-next of block tree
V3:
	- include kenrel.h & bug.h in bvec.h for fix comiling failure on arm
	as reported by 0day ktest
	- build test on arm & arm64

V2:
	- rename bvec_iter.h as bvec.h
	- always include bvec.h into blk_types.h as suggested by Christoph

V1:
	- don't move BIO_MAX_* to bvec_iter.h as pointed out by Christoph
	- run xfstests against v4.6-rc1-next-20160329
	- add Reviewed-by
	- for 1,4 and 5, Reviewd-by not added, Christoph still expressed
	'this looks fine to me.'


Ming Lei (8):
  block: move bvec iterator into include/linux/bvec.h
  block: move two bvec structure into bvec.h
  block: mark 1st parameter of bvec_iter_advance as const
  iov_iter: use bvec iterator to implement iterate_bvec()
  fs: xfs: replace BIO_MAX_SECTORS with BIO_MAX_PAGES
  block: bio: remove BIO_MAX_SECTORS
  block: drbd: avoid to use BIO_MAX_SIZE
  block: bio: remove BIO_MAX_SIZE

 drivers/block/drbd/drbd_int.h |  4 +-
 fs/xfs/xfs_buf.c              |  4 +-
 include/linux/bio.h           | 52 -----------------------
 include/linux/blk_types.h     | 22 +---------
 include/linux/bvec.h          | 96 +++++++++++++++++++++++++++++++++++++++++++
 lib/iov_iter.c                | 45 +++++++-------------
 6 files changed, 115 insertions(+), 108 deletions(-)
 create mode 100644 include/linux/bvec.h

-- 
1.9.1

[PATCH v5 1/8] block: move bvec iterator into include/linux/bvec.h

[Ming Lei]

bvec iterator helpers should be used to implement by
iterate_bvec():lib/iov_iter.c too, and move them into
one header, so that we can keep bvec iterator header
out of CONFIG_BLOCK. Then we can remove the reinventing
of wheel in iterate_bvec().

Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 include/linux/bio.h  | 51 +-----------------------------------
 include/linux/bvec.h | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+), 50 deletions(-)
 create mode 100644 include/linux/bvec.h

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 6b7481f..1c06184 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -31,6 +31,7 @@
 
 /* struct bio, bio_vec and BIO_* flags are defined in blk_types.h */
 #include <linux/blk_types.h>
+#include <linux/bvec.h>
 
 #define BIO_DEBUG
 
@@ -57,29 +58,6 @@
 	(bio)->bi_rw |= ((unsigned long) (prio) << BIO_PRIO_SHIFT);	\
 } while (0)
 
-/*
- * various member access, note that bio_data should of course not be used
- * on highmem page vectors
- */
-#define __bvec_iter_bvec(bvec, iter)	(&(bvec)[(iter).bi_idx])
-
-#define bvec_iter_page(bvec, iter)				\
-	(__bvec_iter_bvec((bvec), (iter))->bv_page)
-
-#define bvec_iter_len(bvec, iter)				\
-	min((iter).bi_size,					\
-	    __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
-
-#define bvec_iter_offset(bvec, iter)				\
-	(__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
-
-#define bvec_iter_bvec(bvec, iter)				\
-((struct bio_vec) {						\
-	.bv_page	= bvec_iter_page((bvec), (iter)),	\
-	.bv_len		= bvec_iter_len((bvec), (iter)),	\
-	.bv_offset	= bvec_iter_offset((bvec), (iter)),	\
-})
-
 #define bio_iter_iovec(bio, iter)				\
 	bvec_iter_bvec((bio)->bi_io_vec, (iter))
 
@@ -193,33 +171,6 @@ static inline void *bio_data(struct bio *bio)
 #define bio_for_each_segment_all(bvl, bio, i)				\
 	for (i = 0, bvl = (bio)->bi_io_vec; i < (bio)->bi_vcnt; i++, bvl++)
 
-static inline void bvec_iter_advance(struct bio_vec *bv, struct bvec_iter *iter,
-				     unsigned bytes)
-{
-	WARN_ONCE(bytes > iter->bi_size,
-		  "Attempted to advance past end of bvec iter\n");
-
-	while (bytes) {
-		unsigned len = min(bytes, bvec_iter_len(bv, *iter));
-
-		bytes -= len;
-		iter->bi_size -= len;
-		iter->bi_bvec_done += len;
-
-		if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
-			iter->bi_bvec_done = 0;
-			iter->bi_idx++;
-		}
-	}
-}
-
-#define for_each_bvec(bvl, bio_vec, iter, start)			\
-	for (iter = (start);						\
-	     (iter).bi_size &&						\
-		((bvl = bvec_iter_bvec((bio_vec), (iter))), 1);	\
-	     bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
-
-
 static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
 				    unsigned bytes)
 {
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
new file mode 100644
index 0000000..29c459d
--- /dev/null
+++ b/include/linux/bvec.h
@@ -0,0 +1,74 @@
+/*
+ * bvec iterator
+ *
+ * Copyright (C) 2001 Ming Lei <ming.lei@canonical.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public Licens
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
+ */
+#ifndef __LINUX_BVEC_ITER_H
+#define __LINUX_BVEC_ITER_H
+
+#include <linux/blk_types.h>
+
+/*
+ * various member access, note that bio_data should of course not be used
+ * on highmem page vectors
+ */
+#define __bvec_iter_bvec(bvec, iter)	(&(bvec)[(iter).bi_idx])
+
+#define bvec_iter_page(bvec, iter)				\
+	(__bvec_iter_bvec((bvec), (iter))->bv_page)
+
+#define bvec_iter_len(bvec, iter)				\
+	min((iter).bi_size,					\
+	    __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
+
+#define bvec_iter_offset(bvec, iter)				\
+	(__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
+
+#define bvec_iter_bvec(bvec, iter)				\
+((struct bio_vec) {						\
+	.bv_page	= bvec_iter_page((bvec), (iter)),	\
+	.bv_len		= bvec_iter_len((bvec), (iter)),	\
+	.bv_offset	= bvec_iter_offset((bvec), (iter)),	\
+})
+
+static inline void bvec_iter_advance(struct bio_vec *bv, struct bvec_iter *iter,
+				     unsigned bytes)
+{
+	WARN_ONCE(bytes > iter->bi_size,
+		  "Attempted to advance past end of bvec iter\n");
+
+	while (bytes) {
+		unsigned len = min(bytes, bvec_iter_len(bv, *iter));
+
+		bytes -= len;
+		iter->bi_size -= len;
+		iter->bi_bvec_done += len;
+
+		if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
+			iter->bi_bvec_done = 0;
+			iter->bi_idx++;
+		}
+	}
+}
+
+#define for_each_bvec(bvl, bio_vec, iter, start)			\
+	for (iter = (start);						\
+	     (iter).bi_size &&						\
+		((bvl = bvec_iter_bvec((bio_vec), (iter))), 1);	\
+	     bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
+
+#endif /* __LINUX_BVEC_ITER_H */
-- 
1.9.1

[PATCH v5 2/8] block: move two bvec structure into bvec.h

[Ming Lei]

This patch moves 'struct bio_vec' and 'struct bvec_iter'
into 'include/linux/bvec.h', then always include this header
into 'include/linux/blk_types.h'.

With this change, both 'struct bvec_iter' and bvec iterator
helpers don't depend on CONFIG_BLOCK any more, then we can
use bvec iterator to implement iterate_bvec(): lib/iov_iter.c.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 include/linux/bio.h       |  1 -
 include/linux/blk_types.h | 22 +---------------------
 include/linux/bvec.h      | 23 ++++++++++++++++++++++-
 3 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 1c06184..96835a0 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -31,7 +31,6 @@
 
 /* struct bio, bio_vec and BIO_* flags are defined in blk_types.h */
 #include <linux/blk_types.h>
-#include <linux/bvec.h>
 
 #define BIO_DEBUG
 
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 86a38ea..a8d8e1f 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -6,6 +6,7 @@
 #define __LINUX_BLK_TYPES_H
 
 #include <linux/types.h>
+#include <linux/bvec.h>
 
 struct bio_set;
 struct bio;
@@ -17,28 +18,7 @@ struct cgroup_subsys_state;
 typedef void (bio_end_io_t) (struct bio *);
 typedef void (bio_destructor_t) (struct bio *);
 
-/*
- * was unsigned short, but we might as well be ready for > 64kB I/O pages
- */
-struct bio_vec {
-	struct page	*bv_page;
-	unsigned int	bv_len;
-	unsigned int	bv_offset;
-};
-
 #ifdef CONFIG_BLOCK
-
-struct bvec_iter {
-	sector_t		bi_sector;	/* device address in 512 byte
-						   sectors */
-	unsigned int		bi_size;	/* residual I/O count */
-
-	unsigned int		bi_idx;		/* current index into bvl_vec */
-
-	unsigned int            bi_bvec_done;	/* number of bytes completed in
-						   current bvec */
-};
-
 /*
  * main unit of I/O for the block layer and lower layers (ie drivers and
  * stacking drivers)
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 29c459d..096efd2 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -20,7 +20,28 @@
 #ifndef __LINUX_BVEC_ITER_H
 #define __LINUX_BVEC_ITER_H
 
-#include <linux/blk_types.h>
+#include <linux/kernel.h>
+#include <linux/bug.h>
+
+/*
+ * was unsigned short, but we might as well be ready for > 64kB I/O pages
+ */
+struct bio_vec {
+	struct page	*bv_page;
+	unsigned int	bv_len;
+	unsigned int	bv_offset;
+};
+
+struct bvec_iter {
+	sector_t		bi_sector;	/* device address in 512 byte
+						   sectors */
+	unsigned int		bi_size;	/* residual I/O count */
+
+	unsigned int		bi_idx;		/* current index into bvl_vec */
+
+	unsigned int            bi_bvec_done;	/* number of bytes completed in
+						   current bvec */
+};
 
 /*
  * various member access, note that bio_data should of course not be used
-- 
1.9.1

[PATCH v5 3/8] block: mark 1st parameter of bvec_iter_advance as const

[Ming Lei]

bvec_iter_advance() only writes the parameter of iterator,
so the base address of bvec can be marked as const safely.

Without the change, we can see compiling warning in the
following patch for implementing iterate_bvec(): lib/iov_iter.c
with bvec iterator.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 include/linux/bvec.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 096efd2..701b64a 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -66,7 +66,8 @@ struct bvec_iter {
 	.bv_offset	= bvec_iter_offset((bvec), (iter)),	\
 })
 
-static inline void bvec_iter_advance(struct bio_vec *bv, struct bvec_iter *iter,
+static inline void bvec_iter_advance(const struct bio_vec *bv,
+				     struct bvec_iter *iter,
 				     unsigned bytes)
 {
 	WARN_ONCE(bytes > iter->bi_size,
-- 
1.9.1

[PATCH v5 4/8] iov_iter: use bvec iterator to implement iterate_bvec()

[Ming Lei]

bvec has one native/mature iterator for long time, so not
necessary to use the reinvented wheel for iterating bvecs
in lib/iov_iter.c.

Two ITER_BVEC test cases are run:
	- xfstest(-g auto) on loop dio/aio, no regression found
	- swap file works well under extreme stress(stress-ng --all 64 -t
	  800 -v), and lots of OOMs are triggerd, and the whole
	system still survives

Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 lib/iov_iter.c | 45 +++++++++++++++------------------------------
 1 file changed, 15 insertions(+), 30 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 5fecddc..8e30ea5 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -56,37 +56,24 @@
 	n = wanted;					\
 }
 
-#define iterate_bvec(i, n, __v, __p, skip, STEP) {	\
-	size_t wanted = n;				\
-	__p = i->bvec;					\
-	__v.bv_len = min_t(size_t, n, __p->bv_len - skip);	\
-	if (likely(__v.bv_len)) {			\
-		__v.bv_page = __p->bv_page;		\
-		__v.bv_offset = __p->bv_offset + skip; 	\
-		(void)(STEP);				\
-		skip += __v.bv_len;			\
-		n -= __v.bv_len;			\
-	}						\
-	while (unlikely(n)) {				\
-		__p++;					\
-		__v.bv_len = min_t(size_t, n, __p->bv_len);	\
-		if (unlikely(!__v.bv_len))		\
+#define iterate_bvec(i, n, __v, __bi, skip, STEP) {	\
+	struct bvec_iter __start;			\
+	__start.bi_size = n;				\
+	__start.bi_bvec_done = skip;			\
+	__start.bi_idx = 0;				\
+	for_each_bvec(__v, i->bvec, __bi, __start) {	\
+		if (!__v.bv_len)			\
 			continue;			\
-		__v.bv_page = __p->bv_page;		\
-		__v.bv_offset = __p->bv_offset;		\
 		(void)(STEP);				\
-		skip = __v.bv_len;			\
-		n -= __v.bv_len;			\
 	}						\
-	n = wanted;					\
 }
 
 #define iterate_all_kinds(i, n, v, I, B, K) {			\
 	size_t skip = i->iov_offset;				\
 	if (unlikely(i->type & ITER_BVEC)) {			\
-		const struct bio_vec *bvec;			\
 		struct bio_vec v;				\
-		iterate_bvec(i, n, v, bvec, skip, (B))		\
+		struct bvec_iter __bi;				\
+		iterate_bvec(i, n, v, __bi, skip, (B))		\
 	} else if (unlikely(i->type & ITER_KVEC)) {		\
 		const struct kvec *kvec;			\
 		struct kvec v;					\
@@ -101,15 +88,13 @@
 #define iterate_and_advance(i, n, v, I, B, K) {			\
 	size_t skip = i->iov_offset;				\
 	if (unlikely(i->type & ITER_BVEC)) {			\
-		const struct bio_vec *bvec;			\
+		const struct bio_vec *bvec = i->bvec;		\
 		struct bio_vec v;				\
-		iterate_bvec(i, n, v, bvec, skip, (B))		\
-		if (skip == bvec->bv_len) {			\
-			bvec++;					\
-			skip = 0;				\
-		}						\
-		i->nr_segs -= bvec - i->bvec;			\
-		i->bvec = bvec;					\
+		struct bvec_iter __bi;				\
+		iterate_bvec(i, n, v, __bi, skip, (B))		\
+		i->bvec = __bvec_iter_bvec(i->bvec, __bi);	\
+		i->nr_segs -= i->bvec - bvec;			\
+		skip = __bi.bi_bvec_done;			\
 	} else if (unlikely(i->type & ITER_KVEC)) {		\
 		const struct kvec *kvec;			\
 		struct kvec v;					\
-- 
1.9.1

[PATCH v5 5/8] fs: xfs: replace BIO_MAX_SECTORS with BIO_MAX_PAGES

[Ming Lei]

BIO_MAX_PAGES is used as maximum count of bvecs, so
replace BIO_MAX_SECTORS with BIO_MAX_PAGES since
BIO_MAX_SECTORS is to be removed.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 fs/xfs/xfs_buf.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 9a2191b..b9ecb2d 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1161,9 +1161,7 @@ xfs_buf_ioapply_map(
 
 next_chunk:
 	atomic_inc(&bp->b_io_remaining);
-	nr_pages = BIO_MAX_SECTORS >> (PAGE_SHIFT - BBSHIFT);
-	if (nr_pages > total_nr_pages)
-		nr_pages = total_nr_pages;
+	nr_pages = min(total_nr_pages, BIO_MAX_PAGES);
 
 	bio = bio_alloc(GFP_NOIO, nr_pages);
 	bio->bi_bdev = bp->b_target->bt_bdev;
-- 
1.9.1

[PATCH v5 6/8] block: bio: remove BIO_MAX_SECTORS

[Ming Lei]

No one need this macro, so remove it. The motivation is
for supporting multipage bvecs, in which we only know
what the max count of bvecs is supported in the bio,
instead of max size or max sectors.

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

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 96835a0..d9beea7 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -42,7 +42,6 @@
 
 #define BIO_MAX_PAGES		256
 #define BIO_MAX_SIZE		(BIO_MAX_PAGES << PAGE_SHIFT)
-#define BIO_MAX_SECTORS		(BIO_MAX_SIZE >> 9)
 
 /*
  * upper 16 bits of bi_rw define the io priority of this bio
-- 
1.9.1

[PATCH v5 7/8] block: drbd: avoid to use BIO_MAX_SIZE

[Ming Lei]

drbd is the only user of BIO_MAX_SIZE, so use BIO_MAX_PAGES
instead.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 drivers/block/drbd/drbd_int.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 7a1cf7e..e6e4b08 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -1327,14 +1327,14 @@ struct bm_extent {
 #endif
 #endif
 
-/* BIO_MAX_SIZE is 256 * PAGE_SIZE,
+/* Estimate max bio size as 256 * PAGE_SIZE,
  * so for typical PAGE_SIZE of 4k, that is (1<<20) Byte.
  * Since we may live in a mixed-platform cluster,
  * we limit us to a platform agnostic constant here for now.
  * A followup commit may allow even bigger BIO sizes,
  * once we thought that through. */
 #define DRBD_MAX_BIO_SIZE (1U << 20)
-#if DRBD_MAX_BIO_SIZE > BIO_MAX_SIZE
+#if DRBD_MAX_BIO_SIZE > (BIO_MAX_PAGES << PAGE_SHIFT)
 #error Architecture not supported: DRBD_MAX_BIO_SIZE > BIO_MAX_SIZE
 #endif
 #define DRBD_MAX_BIO_SIZE_SAFE (1U << 12)       /* Works always = 4k */
-- 
1.9.1

[PATCH v5 8/8] block: bio: remove BIO_MAX_SIZE

[Ming Lei]

No one need this macro now, so remove it. The motivation is
for supporting multipage bvecs, in which we only know
what the max count of bvecs is supported in the bio,
instead of max bio size.

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

diff --git a/include/linux/bio.h b/include/linux/bio.h
index d9beea7..c8553fe 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -41,7 +41,6 @@
 #endif
 
 #define BIO_MAX_PAGES		256
-#define BIO_MAX_SIZE		(BIO_MAX_PAGES << PAGE_SHIFT)
 
 /*
  * upper 16 bits of bi_rw define the io priority of this bio
-- 
1.9.1

Re: [PATCH v5 1/8] block: move bvec iterator into include/linux/bvec.h

[Christoph Hellwig]

Looks fine,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v5 2/8] block: move two bvec structure into bvec.h

[Christoph Hellwig]

Looks fine,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v5 4/8] iov_iter: use bvec iterator to implement iterate_bvec()

[Christoph Hellwig]

Looks fine,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v5 5/8] fs: xfs: replace BIO_MAX_SECTORS with BIO_MAX_PAGES

[Christoph Hellwig]

On Mon, Apr 18, 2016 at 05:29:54AM +0800, Ming Lei wrote:
> BIO_MAX_PAGES is used as maximum count of bvecs, so
> replace BIO_MAX_SECTORS with BIO_MAX_PAGES since
> BIO_MAX_SECTORS is to be removed.
> 
> Signed-off-by: Ming Lei <ming.lei@canonical.com>

Looks fine,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v5 0/8] block: prepare for multipage bvecs

[Ming Lei]

On Mon, Apr 18, 2016 at 5:29 AM, Ming Lei <ming.lei@canonical.com> wrote:
> Hi,
>
> Interests[1] have been shown in multipage bvecs, so this patchset
> try to prepare for the support and do two things:
>
> 1) the 1st 4 patches use bvec iterator to implement iterate_bvec(),
> then we can drop the non-standard way for iterating bvec, which
> can be thought as a good cleanup for lib/iov_iter.c
>
> 2) remove BIO_MAX_SECTORS & BIO_MAX_SIZE, and now there is only
> one user for each. Once multipage bvecs is introduced, one bio
> may hold lots of sectors, and we should always use sort of BIO_MAX_VECS
> which should be introduced in future and is similiar with current
> BIO_MAX_PAGES.
>
> The only functional change is iterate_bvec():lib/iov_iter.c
>
> xfstests(-a auto) over loop aio is run for ext4/xfs to verify
> the change and no regression found with this patchset.
>
> Jens, I am confidant this time, so please give it a go if no one
> objects. I appreciate someone(AI? or anyone) can give a review on
> the patch 4/8 about iterate_bvec() change.
>
> V5:
>         - use bvec's iterator to figure new base vec address and
>         update 'skip' correctly
>         - run xfstests(-a auto) on loop aio/dio for verifying
>         the change in iterate_bvec(), and no regression reported
>         - use stree-ng to trigger heavy swap over swapfile to verify
>         change in iterate_bvec() too, looks everything is fine

Hi Jens,

Any possibility to make v5 into v4.7 so that we can move on about
multipage bvecs?

BTW, even though not considering mp bvecs, this patchset is still a
good cleanup.

thanks,
Ming

> V4:
>         - make xfstests cover xfs
>         - rebase on for-next of block tree
> V3:
>         - include kenrel.h & bug.h in bvec.h for fix comiling failure on arm
>         as reported by 0day ktest
>         - build test on arm & arm64
>
> V2:
>         - rename bvec_iter.h as bvec.h
>         - always include bvec.h into blk_types.h as suggested by Christoph
>
> V1:
>         - don't move BIO_MAX_* to bvec_iter.h as pointed out by Christoph
>         - run xfstests against v4.6-rc1-next-20160329
>         - add Reviewed-by
>         - for 1,4 and 5, Reviewd-by not added, Christoph still expressed
>         'this looks fine to me.'
>
>
> Ming Lei (8):
>   block: move bvec iterator into include/linux/bvec.h
>   block: move two bvec structure into bvec.h
>   block: mark 1st parameter of bvec_iter_advance as const
>   iov_iter: use bvec iterator to implement iterate_bvec()
>   fs: xfs: replace BIO_MAX_SECTORS with BIO_MAX_PAGES
>   block: bio: remove BIO_MAX_SECTORS
>   block: drbd: avoid to use BIO_MAX_SIZE
>   block: bio: remove BIO_MAX_SIZE
>
>  drivers/block/drbd/drbd_int.h |  4 +-
>  fs/xfs/xfs_buf.c              |  4 +-
>  include/linux/bio.h           | 52 -----------------------
>  include/linux/blk_types.h     | 22 +---------
>  include/linux/bvec.h          | 96 +++++++++++++++++++++++++++++++++++++++++++
>  lib/iov_iter.c                | 45 +++++++-------------
>  6 files changed, 115 insertions(+), 108 deletions(-)
>  create mode 100644 include/linux/bvec.h
>
> --
> 1.9.1
>

Re: [PATCH v5 0/8] block: prepare for multipage bvecs

[Christoph Hellwig]

On Tue, May 03, 2016 at 09:03:58AM +0800, Ming Lei wrote:
> Any possibility to make v5 into v4.7 so that we can move on about
> multipage bvecs?
> 
> BTW, even though not considering mp bvecs, this patchset is still a
> good cleanup.

Agreed.  I'm fine with the series and it looks harmless enough for
4.7.