[PATCH v2 0/8] block: prepare for multipage bvecs

[PATCH v2 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.

xfstests(-a auto) have been run and no regression found by this
patchset against linus v4.6-rc1-next-20160329.

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.'

 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          | 93 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/iov_iter.c                | 30 +++++++------------
 6 files changed, 107 insertions(+), 98 deletions(-)

Thanks,
Ming

[PATCH v2 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.

xfstests(-a auto) have been run and no regression found by this
patchset against linus v4.6-rc1-next-20160329.

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.'

 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          | 93 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/iov_iter.c                | 30 +++++++------------
 6 files changed, 107 insertions(+), 98 deletions(-)

Thanks,
Ming

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http://oss.sgi.com/mailman/listinfo/xfs

[PATCH v2 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 88bc64f..78cf737 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 v2 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 88bc64f..78cf737 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

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http://oss.sgi.com/mailman/listinfo/xfs

[PATCH v2 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      | 20 +++++++++++++++++++-
 3 files changed, 20 insertions(+), 23 deletions(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 78cf737..7f998ac 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..e111124 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -20,7 +20,25 @@
 #ifndef __LINUX_BVEC_ITER_H
 #define __LINUX_BVEC_ITER_H
 
-#include <linux/blk_types.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 v2 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      | 20 +++++++++++++++++++-
 3 files changed, 20 insertions(+), 23 deletions(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 78cf737..7f998ac 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..e111124 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -20,7 +20,25 @@
 #ifndef __LINUX_BVEC_ITER_H
 #define __LINUX_BVEC_ITER_H
 
-#include <linux/blk_types.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

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[PATCH v2 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 e111124..0c6fa42 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -63,7 +63,8 @@ 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 v2 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 e111124..0c6fa42 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -63,7 +63,8 @@ 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

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[PATCH v2 4/8] iov_iter: use bvec iterator to implement iterate_bvec()

[Ming Lei]

bvec has provided one iterator already, so not necessary
to reinvent a new wheel for this job.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 lib/iov_iter.c | 30 ++++++++++--------------------
 1 file changed, 10 insertions(+), 20 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 5fecddc..c8691ac 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -57,35 +57,25 @@
 }
 
 #define iterate_bvec(i, n, __v, __p, skip, STEP) {	\
-	size_t wanted = n;				\
+	struct bvec_iter __bi, __start;			\
+	__start.bi_size = n;				\
+	__start.bi_bvec_done = skip;			\
+	__start.bi_idx = 0;				\
 	__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; 	\
+	for_each_bvec(__v, __p, __bi, __start) {	\
 		(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))		\
-			continue;			\
-		__v.bv_page = __p->bv_page;		\
-		__v.bv_offset = __p->bv_offset;		\
-		(void)(STEP);				\
+	if (!__bi.bi_idx)				\
+		skip += __v.bv_len;			\
+	else						\
 		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;				\
+		struct bio_vec v = { 0 };			\
 		iterate_bvec(i, n, v, bvec, skip, (B))		\
 	} else if (unlikely(i->type & ITER_KVEC)) {		\
 		const struct kvec *kvec;			\
@@ -102,7 +92,7 @@
 	size_t skip = i->iov_offset;				\
 	if (unlikely(i->type & ITER_BVEC)) {			\
 		const struct bio_vec *bvec;			\
-		struct bio_vec v;				\
+		struct bio_vec v = { 0 };			\
 		iterate_bvec(i, n, v, bvec, skip, (B))		\
 		if (skip == bvec->bv_len) {			\
 			bvec++;					\
-- 
1.9.1

[PATCH v2 4/8] iov_iter: use bvec iterator to implement iterate_bvec()

[Ming Lei]

bvec has provided one iterator already, so not necessary
to reinvent a new wheel for this job.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 lib/iov_iter.c | 30 ++++++++++--------------------
 1 file changed, 10 insertions(+), 20 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 5fecddc..c8691ac 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -57,35 +57,25 @@
 }
 
 #define iterate_bvec(i, n, __v, __p, skip, STEP) {	\
-	size_t wanted = n;				\
+	struct bvec_iter __bi, __start;			\
+	__start.bi_size = n;				\
+	__start.bi_bvec_done = skip;			\
+	__start.bi_idx = 0;				\
 	__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; 	\
+	for_each_bvec(__v, __p, __bi, __start) {	\
 		(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))		\
-			continue;			\
-		__v.bv_page = __p->bv_page;		\
-		__v.bv_offset = __p->bv_offset;		\
-		(void)(STEP);				\
+	if (!__bi.bi_idx)				\
+		skip += __v.bv_len;			\
+	else						\
 		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;				\
+		struct bio_vec v = { 0 };			\
 		iterate_bvec(i, n, v, bvec, skip, (B))		\
 	} else if (unlikely(i->type & ITER_KVEC)) {		\
 		const struct kvec *kvec;			\
@@ -102,7 +92,7 @@
 	size_t skip = i->iov_offset;				\
 	if (unlikely(i->type & ITER_BVEC)) {			\
 		const struct bio_vec *bvec;			\
-		struct bio_vec v;				\
+		struct bio_vec v = { 0 };			\
 		iterate_bvec(i, n, v, bvec, skip, (B))		\
 		if (skip == bvec->bv_len) {			\
 			bvec++;					\
-- 
1.9.1

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[PATCH v2 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 v2 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

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[PATCH v2 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 7f998ac..f7e1c27 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_CACHE_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 v2 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 7f998ac..f7e1c27 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_CACHE_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

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Re: [PATCH v2 2/8] block: move two bvec structure into bvec.h

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 2651 bytes --]

Hi Ming,

[auto build test ERROR on block/for-next]
[also build test ERROR on v4.6-rc2 next-20160401]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Ming-Lei/block-prepare-for-multipage-bvecs/20160404-003648
base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-next
config: arm-at91_dt_defconfig (attached as .config)
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=arm 

All errors (new ones prefixed by >>):

   In file included from include/linux/blk_types.h:9:0,
                    from arch/arm/include/asm/io.h:28,
                    from drivers/input/joydev.c:15:
   include/linux/bvec.h: In function 'bvec_iter_advance':
>> include/linux/bvec.h:69:2: error: implicit declaration of function 'WARN_ONCE' [-Werror=implicit-function-declaration]
     WARN_ONCE(bytes > iter->bi_size,
     ^
>> include/linux/bvec.h:73:3: error: implicit declaration of function 'min' [-Werror=implicit-function-declaration]
      unsigned len = min(bytes, bvec_iter_len(bv, *iter));
      ^
   cc1: some warnings being treated as errors

vim +/WARN_ONCE +69 include/linux/bvec.h

0d61ba15 Ming Lei 2016-04-04  63  	.bv_offset	= bvec_iter_offset((bvec), (iter)),	\
0d61ba15 Ming Lei 2016-04-04  64  })
0d61ba15 Ming Lei 2016-04-04  65  
0d61ba15 Ming Lei 2016-04-04  66  static inline void bvec_iter_advance(struct bio_vec *bv, struct bvec_iter *iter,
0d61ba15 Ming Lei 2016-04-04  67  				     unsigned bytes)
0d61ba15 Ming Lei 2016-04-04  68  {
0d61ba15 Ming Lei 2016-04-04 @69  	WARN_ONCE(bytes > iter->bi_size,
0d61ba15 Ming Lei 2016-04-04  70  		  "Attempted to advance past end of bvec iter\n");
0d61ba15 Ming Lei 2016-04-04  71  
0d61ba15 Ming Lei 2016-04-04  72  	while (bytes) {
0d61ba15 Ming Lei 2016-04-04 @73  		unsigned len = min(bytes, bvec_iter_len(bv, *iter));
0d61ba15 Ming Lei 2016-04-04  74  
0d61ba15 Ming Lei 2016-04-04  75  		bytes -= len;
0d61ba15 Ming Lei 2016-04-04  76  		iter->bi_size -= len;

:::::: The code at line 69 was first introduced by commit
:::::: 0d61ba15b7eb4a7478dae53947aaaf898a1bbf30 block: move bvec iterator into include/linux/bvec.h

:::::: TO: Ming Lei <ming.lei@canonical.com>
:::::: CC: 0day robot <fengguang.wu@intel.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/octet-stream, Size: 21005 bytes --]

Re: [PATCH v2 2/8] block: move two bvec structure into bvec.h

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 2651 bytes --]

Hi Ming,

[auto build test ERROR on block/for-next]
[also build test ERROR on v4.6-rc2 next-20160401]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Ming-Lei/block-prepare-for-multipage-bvecs/20160404-003648
base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-next
config: arm-at91_dt_defconfig (attached as .config)
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=arm 

All errors (new ones prefixed by >>):

   In file included from include/linux/blk_types.h:9:0,
                    from arch/arm/include/asm/io.h:28,
                    from drivers/input/joydev.c:15:
   include/linux/bvec.h: In function 'bvec_iter_advance':
>> include/linux/bvec.h:69:2: error: implicit declaration of function 'WARN_ONCE' [-Werror=implicit-function-declaration]
     WARN_ONCE(bytes > iter->bi_size,
     ^
>> include/linux/bvec.h:73:3: error: implicit declaration of function 'min' [-Werror=implicit-function-declaration]
      unsigned len = min(bytes, bvec_iter_len(bv, *iter));
      ^
   cc1: some warnings being treated as errors

vim +/WARN_ONCE +69 include/linux/bvec.h

0d61ba15 Ming Lei 2016-04-04  63  	.bv_offset	= bvec_iter_offset((bvec), (iter)),	\
0d61ba15 Ming Lei 2016-04-04  64  })
0d61ba15 Ming Lei 2016-04-04  65  
0d61ba15 Ming Lei 2016-04-04  66  static inline void bvec_iter_advance(struct bio_vec *bv, struct bvec_iter *iter,
0d61ba15 Ming Lei 2016-04-04  67  				     unsigned bytes)
0d61ba15 Ming Lei 2016-04-04  68  {
0d61ba15 Ming Lei 2016-04-04 @69  	WARN_ONCE(bytes > iter->bi_size,
0d61ba15 Ming Lei 2016-04-04  70  		  "Attempted to advance past end of bvec iter\n");
0d61ba15 Ming Lei 2016-04-04  71  
0d61ba15 Ming Lei 2016-04-04  72  	while (bytes) {
0d61ba15 Ming Lei 2016-04-04 @73  		unsigned len = min(bytes, bvec_iter_len(bv, *iter));
0d61ba15 Ming Lei 2016-04-04  74  
0d61ba15 Ming Lei 2016-04-04  75  		bytes -= len;
0d61ba15 Ming Lei 2016-04-04  76  		iter->bi_size -= len;

:::::: The code at line 69 was first introduced by commit
:::::: 0d61ba15b7eb4a7478dae53947aaaf898a1bbf30 block: move bvec iterator into include/linux/bvec.h

:::::: TO: Ming Lei <ming.lei@canonical.com>
:::::: CC: 0day robot <fengguang.wu@intel.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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[-- Attachment #3: Type: text/plain, Size: 121 bytes --]

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