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[PATCH v2 0/5] md: use bio_clone_fast()

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  [PATCH v2 0/5] md: use bio_clone_fast() Ming Lei <tom.leiming@gmail.com> - 2017-02-14 16:30 +0100
    [PATCH v2 5/5] md: fast clone bio in bio_clone_mddev() Ming Lei <tom.leiming@gmail.com> - 2017-02-14 16:40 +0100
      Re: [PATCH v2 5/5] md: fast clone bio in bio_clone_mddev() Christoph Hellwig <hch@infradead.org> - 2017-02-14 17:10 +0100
        Re: [PATCH v2 5/5] md: fast clone bio in bio_clone_mddev() Shaohua Li <shli@kernel.org> - 2017-02-15 20:30 +0100
          Re: [PATCH v2 5/5] md: fast clone bio in bio_clone_mddev() Shaohua Li <shli@kernel.org> - 2017-02-16 01:00 +0100
    [PATCH v2 4/5] md: remove unnecessary check on mddev Ming Lei <tom.leiming@gmail.com> - 2017-02-14 16:40 +0100
    [PATCH v2 1/5] block: introduce bio_clone_bioset_partial() Ming Lei <tom.leiming@gmail.com> - 2017-02-14 16:40 +0100
    Re: [PATCH v2 0/5] md: use bio_clone_fast() Shaohua Li <shli@kernel.org> - 2017-02-15 20:30 +0100

#1580599 — [PATCH v2 0/5] md: use bio_clone_fast()

Hi,

This patches replaces bio_clone() with bio_fast_clone() in
bio_clone_mddev() because:

1) bio_clone_mddev() is used in raid normal I/O and isn't in
resync I/O path, and all the direct access to bvec table in
raid happens on resync I/O only except for write behind of raid1.
Write behind is treated specially, so the replacement is safe.

2) for write behind, bio_clone() is kept, but this patchset
introduces bio_clone_bioset_partial() to just clone one specific 
bvecs range instead of whole table. Then write behind is improved
too.

V2:
	1) move 3rd patch into 2nd one
	2) kill  bio_clone_mddev() and use  bio_clone_fast() directly
	3) define local variable 'offset' as sector_t in raid1_write_request()

V1:
	1) don't introduce bio_clone_slow_mddev_partial()
	2) return failure if mddev->bio_set can't be created
	3) remove check in bio_clone_mddev() as suggested by
	Christoph Hellwig.
	4) rename bio_clone_mddev() as bio_clone_fast_mddev()

Ming Lei (5):
  block: introduce bio_clone_bioset_partial()
  md: fail if mddev->bio_set can't be created
  md/raid1: use bio_clone_bioset_partial() in case of write behind
  md: remove unnecessary check on mddev
  md: fast clone bio in bio_clone_mddev()

 block/bio.c         | 61 +++++++++++++++++++++++++++++++++++++++++------------
 drivers/md/faulty.c |  2 +-
 drivers/md/md.c     | 15 ++++---------
 drivers/md/md.h     |  2 --
 drivers/md/raid1.c  | 28 +++++++++++++++++-------
 drivers/md/raid10.c | 11 +++++-----
 drivers/md/raid5.c  |  4 ++--
 include/linux/bio.h | 11 ++++++++--
 8 files changed, 89 insertions(+), 45 deletions(-)

-- 
2.7.4

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#1580606 — [PATCH v2 5/5] md: fast clone bio in bio_clone_mddev()

Firstly bio_clone_mddev() is used in raid normal I/O and isn't
in resync I/O path.

Secondly all the direct access to bvec table in raid happens on
resync I/O except for write behind of raid1, in which we still
use bio_clone() for allocating new bvec table.

So this patch replaces bio_clone() with bio_clone_fast()
in bio_clone_mddev().

Also kill bio_clone_mddev() and call bio_clone_fast() directly, as
suggested by Christoph Hellwig.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/faulty.c |  2 +-
 drivers/md/md.c     |  7 -------
 drivers/md/md.h     |  2 --
 drivers/md/raid1.c  | 10 ++++++----
 drivers/md/raid10.c | 11 +++++------
 drivers/md/raid5.c  |  4 ++--
 6 files changed, 14 insertions(+), 22 deletions(-)

diff --git a/drivers/md/faulty.c b/drivers/md/faulty.c
index 685aa2d77e25..b0536cfd8e17 100644
--- a/drivers/md/faulty.c
+++ b/drivers/md/faulty.c
@@ -214,7 +214,7 @@ static void faulty_make_request(struct mddev *mddev, struct bio *bio)
 		}
 	}
 	if (failit) {
-		struct bio *b = bio_clone_mddev(bio, GFP_NOIO, mddev);
+		struct bio *b = bio_clone_fast(bio, GFP_NOIO, mddev->bio_set);
 
 		b->bi_bdev = conf->rdev->bdev;
 		b->bi_private = bio;
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 6cd96fde2a67..985374f20e2e 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -190,13 +190,6 @@ struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
 }
 EXPORT_SYMBOL_GPL(bio_alloc_mddev);
 
-struct bio *bio_clone_mddev(struct bio *bio, gfp_t gfp_mask,
-			    struct mddev *mddev)
-{
-	return bio_clone_bioset(bio, gfp_mask, mddev->bio_set);
-}
-EXPORT_SYMBOL_GPL(bio_clone_mddev);
-
 /*
  * We have a system wide 'event count' that is incremented
  * on any 'interesting' event, and readers of /proc/mdstat
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 2a514036a83d..a86ad62079de 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -673,8 +673,6 @@ extern void md_rdev_clear(struct md_rdev *rdev);
 
 extern void mddev_suspend(struct mddev *mddev);
 extern void mddev_resume(struct mddev *mddev);
-extern struct bio *bio_clone_mddev(struct bio *bio, gfp_t gfp_mask,
-				   struct mddev *mddev);
 extern struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
 				   struct mddev *mddev);
 
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index b7548e0a9eca..85f309836fd7 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1108,7 +1108,7 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
 	r1_bio->read_disk = rdisk;
 	r1_bio->start_next_window = 0;
 
-	read_bio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+	read_bio = bio_clone_fast(bio, GFP_NOIO, mddev->bio_set);
 	bio_trim(read_bio, r1_bio->sector - bio->bi_iter.bi_sector,
 		 max_sectors);
 
@@ -1372,7 +1372,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 		}
 
 		if (!mbio) {
-			mbio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+			mbio = bio_clone_fast(bio, GFP_NOIO, mddev->bio_set);
 			bio_trim(mbio, offset, max_sectors);
 		}
 
@@ -2283,7 +2283,8 @@ static int narrow_write_error(struct r1bio *r1_bio, int i)
 
 			wbio->bi_vcnt = vcnt;
 		} else {
-			wbio = bio_clone_mddev(r1_bio->master_bio, GFP_NOIO, mddev);
+			wbio = bio_clone_fast(r1_bio->master_bio, GFP_NOIO,
+					      mddev->bio_set);
 		}
 
 		bio_set_op_attrs(wbio, REQ_OP_WRITE, 0);
@@ -2421,7 +2422,8 @@ static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)
 		const unsigned long do_sync
 			= r1_bio->master_bio->bi_opf & REQ_SYNC;
 		r1_bio->read_disk = disk;
-		bio = bio_clone_mddev(r1_bio->master_bio, GFP_NOIO, mddev);
+		bio = bio_clone_fast(r1_bio->master_bio, GFP_NOIO,
+				     mddev->bio_set);
 		bio_trim(bio, r1_bio->sector - bio->bi_iter.bi_sector,
 			 max_sectors);
 		r1_bio->bios[r1_bio->read_disk] = bio;
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 6bc5c2a85160..063c43d83b72 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1132,7 +1132,7 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
 	}
 	slot = r10_bio->read_slot;
 
-	read_bio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+	read_bio = bio_clone_fast(bio, GFP_NOIO, mddev->bio_set);
 	bio_trim(read_bio, r10_bio->sector - bio->bi_iter.bi_sector,
 		 max_sectors);
 
@@ -1406,7 +1406,7 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 		int d = r10_bio->devs[i].devnum;
 		if (r10_bio->devs[i].bio) {
 			struct md_rdev *rdev = conf->mirrors[d].rdev;
-			mbio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+			mbio = bio_clone_fast(bio, GFP_NOIO, mddev->bio_set);
 			bio_trim(mbio, r10_bio->sector - bio->bi_iter.bi_sector,
 				 max_sectors);
 			r10_bio->devs[i].bio = mbio;
@@ -1457,7 +1457,7 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 				smp_mb();
 				rdev = conf->mirrors[d].rdev;
 			}
-			mbio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+			mbio = bio_clone_fast(bio, GFP_NOIO, mddev->bio_set);
 			bio_trim(mbio, r10_bio->sector - bio->bi_iter.bi_sector,
 				 max_sectors);
 			r10_bio->devs[i].repl_bio = mbio;
@@ -2565,7 +2565,7 @@ static int narrow_write_error(struct r10bio *r10_bio, int i)
 		if (sectors > sect_to_write)
 			sectors = sect_to_write;
 		/* Write at 'sector' for 'sectors' */
-		wbio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+		wbio = bio_clone_fast(bio, GFP_NOIO, mddev->bio_set);
 		bio_trim(wbio, sector - bio->bi_iter.bi_sector, sectors);
 		wsector = r10_bio->devs[i].addr + (sector - r10_bio->sector);
 		wbio->bi_iter.bi_sector = wsector +
@@ -2641,8 +2641,7 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
 			   mdname(mddev),
 			   bdevname(rdev->bdev, b),
 			   (unsigned long long)r10_bio->sector);
-	bio = bio_clone_mddev(r10_bio->master_bio,
-			      GFP_NOIO, mddev);
+	bio = bio_clone_fast(r10_bio->master_bio, GFP_NOIO, mddev->bio_set);
 	bio_trim(bio, r10_bio->sector - bio->bi_iter.bi_sector, max_sectors);
 	r10_bio->devs[slot].bio = bio;
 	r10_bio->devs[slot].rdev = rdev;
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index a1b41184e850..c16d09614cf6 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5056,9 +5056,9 @@ static int raid5_read_one_chunk(struct mddev *mddev, struct bio *raid_bio)
 		return 0;
 	}
 	/*
-	 * use bio_clone_mddev to make a copy of the bio
+	 * use bio_clone_fast to make a copy of the bio
 	 */
-	align_bi = bio_clone_mddev(raid_bio, GFP_NOIO, mddev);
+	align_bi = bio_clone_fast(raid_bio, GFP_NOIO, mddev->bio_set);
 	if (!align_bi)
 		return 0;
 	/*
-- 
2.7.4

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#1580625 — Re: [PATCH v2 5/5] md: fast clone bio in bio_clone_mddev()

On Tue, Feb 14, 2017 at 11:29:03PM +0800, Ming Lei wrote:
> Firstly bio_clone_mddev() is used in raid normal I/O and isn't
> in resync I/O path.
> 
> Secondly all the direct access to bvec table in raid happens on
> resync I/O except for write behind of raid1, in which we still
> use bio_clone() for allocating new bvec table.
> 
> So this patch replaces bio_clone() with bio_clone_fast()
> in bio_clone_mddev().
> 
> Also kill bio_clone_mddev() and call bio_clone_fast() directly, as
> suggested by Christoph Hellwig.
> 
> Signed-off-by: Ming Lei <tom.leiming@gmail.com>

Looks fine,

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

Btw, can you also tack on another patch to kill bio_alloc_mddev
to be consistent?

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#1581594 — Re: [PATCH v2 5/5] md: fast clone bio in bio_clone_mddev()

On Tue, Feb 14, 2017 at 08:01:09AM -0800, Christoph Hellwig wrote:
> On Tue, Feb 14, 2017 at 11:29:03PM +0800, Ming Lei wrote:
> > Firstly bio_clone_mddev() is used in raid normal I/O and isn't
> > in resync I/O path.
> > 
> > Secondly all the direct access to bvec table in raid happens on
> > resync I/O except for write behind of raid1, in which we still
> > use bio_clone() for allocating new bvec table.
> > 
> > So this patch replaces bio_clone() with bio_clone_fast()
> > in bio_clone_mddev().
> > 
> > Also kill bio_clone_mddev() and call bio_clone_fast() directly, as
> > suggested by Christoph Hellwig.
> > 
> > Signed-off-by: Ming Lei <tom.leiming@gmail.com>
> 
> Looks fine,
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> Btw, can you also tack on another patch to kill bio_alloc_mddev
> to be consistent?

I'll take care of this

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#1582056 — Re: [PATCH v2 5/5] md: fast clone bio in bio_clone_mddev()

On Wed, Feb 15, 2017 at 11:20:25AM -0800, Shaohua Li wrote:
> On Tue, Feb 14, 2017 at 08:01:09AM -0800, Christoph Hellwig wrote:
> > On Tue, Feb 14, 2017 at 11:29:03PM +0800, Ming Lei wrote:
> > > Firstly bio_clone_mddev() is used in raid normal I/O and isn't
> > > in resync I/O path.
> > > 
> > > Secondly all the direct access to bvec table in raid happens on
> > > resync I/O except for write behind of raid1, in which we still
> > > use bio_clone() for allocating new bvec table.
> > > 
> > > So this patch replaces bio_clone() with bio_clone_fast()
> > > in bio_clone_mddev().
> > > 
> > > Also kill bio_clone_mddev() and call bio_clone_fast() directly, as
> > > suggested by Christoph Hellwig.
> > > 
> > > Signed-off-by: Ming Lei <tom.leiming@gmail.com>
> > 
> > Looks fine,
> > 
> > Reviewed-by: Christoph Hellwig <hch@lst.de>
> > 
> > Btw, can you also tack on another patch to kill bio_alloc_mddev
> > to be consistent?
> 
> I'll take care of this

Hmm, bio_alloc_mddev is a little different, it could be called without the
bio_set. We can only guarantee the bio_set is valid for bio for md personality
not for metadata. Fully fixing the bio_set issue will need rework mddev struct
allocation, don't think it's worthy doing. So below is one removing the export
of the wrap.

From eaf70c32e5cca68110a0cf7a0311ef0ac97f4d42 Mon Sep 17 00:00:00 2001
Message-Id: <eaf70c32e5cca68110a0cf7a0311ef0ac97f4d42.1487200103.git.shli@fb.com>
From: Shaohua Li <shli@fb.com>
Date: Wed, 15 Feb 2017 11:41:21 -0800
Subject: [PATCH] md: don't export bio_alloc_mddev

When mddev is running, it has a valid bio_set, so the bio_alloc_mddev
wrap is unncessary. The problem is we run some IO (eg, load superblock)
before mddev is fully initialized. At that time bio_set isn't
initialized. Moving bio_set creation to md_alloc doesn't help either,
because dm-raid doesn't use it.

Signed-off-by: Shaohua Li <shli@fb.com>
---
 drivers/md/md.c     | 12 ++++++------
 drivers/md/md.h     |  2 --
 drivers/md/raid1.c  |  2 +-
 drivers/md/raid10.c |  2 +-
 4 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 55e7e7a..bef1863 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -171,11 +171,12 @@ static const struct block_device_operations md_fops;
 
 static int start_readonly;
 
-/* bio_clone_mddev
- * like bio_clone, but with a local bio set
+/*
+ * This is only required for meta data related bio, where bio_set might not be
+ * initialized yet. dm-raid doesn't use md_alloc, so we can't alloc bio_set
+ * there.
  */
-
-struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
+static struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
 			    struct mddev *mddev)
 {
 	struct bio *b;
@@ -188,7 +189,6 @@ struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
 		return NULL;
 	return b;
 }
-EXPORT_SYMBOL_GPL(bio_alloc_mddev);
 
 /*
  * We have a system wide 'event count' that is incremented
@@ -393,7 +393,7 @@ static void submit_flushes(struct work_struct *ws)
 			atomic_inc(&rdev->nr_pending);
 			atomic_inc(&rdev->nr_pending);
 			rcu_read_unlock();
-			bi = bio_alloc_mddev(GFP_NOIO, 0, mddev);
+			bi = bio_alloc_bioset(GFP_NOIO, 0, mddev->bio_set);
 			bi->bi_end_io = md_end_flush;
 			bi->bi_private = rdev;
 			bi->bi_bdev = rdev->bdev;
diff --git a/drivers/md/md.h b/drivers/md/md.h
index b8859cb..44fe227 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -673,8 +673,6 @@ extern void md_rdev_clear(struct md_rdev *rdev);
 
 extern void mddev_suspend(struct mddev *mddev);
 extern void mddev_resume(struct mddev *mddev);
-extern struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
-				   struct mddev *mddev);
 
 extern void md_unplug(struct blk_plug_cb *cb, bool from_schedule);
 extern void md_reload_sb(struct mddev *mddev, int raid_disk);
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index ad5c948..2180a9a 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -2281,7 +2281,7 @@ static int narrow_write_error(struct r1bio *r1_bio, int i)
 				vcnt--;
 			}
 
-			wbio = bio_alloc_mddev(GFP_NOIO, vcnt, mddev);
+			wbio = bio_alloc_bioset(GFP_NOIO, vcnt, mddev->bio_set);
 			memcpy(wbio->bi_io_vec, vec, vcnt * sizeof(struct bio_vec));
 
 			wbio->bi_vcnt = vcnt;
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index ade7d69..a1f8e98 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -4473,7 +4473,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
 		return sectors_done;
 	}
 
-	read_bio = bio_alloc_mddev(GFP_KERNEL, RESYNC_PAGES, mddev);
+	read_bio = bio_alloc_bioset(GFP_KERNEL, RESYNC_PAGES, mddev->bio_set);
 
 	read_bio->bi_bdev = rdev->bdev;
 	read_bio->bi_iter.bi_sector = (r10_bio->devs[r10_bio->read_slot].addr
-- 
2.9.3

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#1580609 — [PATCH v2 4/5] md: remove unnecessary check on mddev

mddev is never NULL and neither is ->bio_set, so
remove the check.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/md.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index b5e2adf3493b..6cd96fde2a67 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -193,9 +193,6 @@ EXPORT_SYMBOL_GPL(bio_alloc_mddev);
 struct bio *bio_clone_mddev(struct bio *bio, gfp_t gfp_mask,
 			    struct mddev *mddev)
 {
-	if (!mddev || !mddev->bio_set)
-		return bio_clone(bio, gfp_mask);
-
 	return bio_clone_bioset(bio, gfp_mask, mddev->bio_set);
 }
 EXPORT_SYMBOL_GPL(bio_clone_mddev);
-- 
2.7.4

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#1580615 — [PATCH v2 1/5] block: introduce bio_clone_bioset_partial()

md still need bio clone(not the fast version) for behind write,
and it is more efficient to use bio_clone_bioset_partial().

The idea is simple and just copy the bvecs range specified from
parameters.

Reviewed-by: Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 block/bio.c         | 61 +++++++++++++++++++++++++++++++++++++++++------------
 include/linux/bio.h | 11 ++++++++--
 2 files changed, 57 insertions(+), 15 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 4b564d0c3e29..5eec5e08417f 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -625,21 +625,20 @@ struct bio *bio_clone_fast(struct bio *bio, gfp_t gfp_mask, struct bio_set *bs)
 }
 EXPORT_SYMBOL(bio_clone_fast);
 
-/**
- * 	bio_clone_bioset - clone a bio
- * 	@bio_src: bio to clone
- *	@gfp_mask: allocation priority
- *	@bs: bio_set to allocate from
- *
- *	Clone bio. Caller will own the returned bio, but not the actual data it
- *	points to. Reference count of returned bio will be one.
- */
-struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
-			     struct bio_set *bs)
+static struct bio *__bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
+				      struct bio_set *bs, int offset,
+				      int size)
 {
 	struct bvec_iter iter;
 	struct bio_vec bv;
 	struct bio *bio;
+	struct bvec_iter iter_src = bio_src->bi_iter;
+
+	/* for supporting partial clone */
+	if (offset || size != bio_src->bi_iter.bi_size) {
+		bio_advance_iter(bio_src, &iter_src, offset);
+		iter_src.bi_size = size;
+	}
 
 	/*
 	 * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
@@ -663,7 +662,8 @@ struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
 	 *    __bio_clone_fast() anyways.
 	 */
 
-	bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
+	bio = bio_alloc_bioset(gfp_mask, __bio_segments(bio_src,
+			       &iter_src), bs);
 	if (!bio)
 		return NULL;
 	bio->bi_bdev		= bio_src->bi_bdev;
@@ -680,7 +680,7 @@ struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
 		bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
 		break;
 	default:
-		bio_for_each_segment(bv, bio_src, iter)
+		__bio_for_each_segment(bv, bio_src, iter, iter_src)
 			bio->bi_io_vec[bio->bi_vcnt++] = bv;
 		break;
 	}
@@ -699,9 +699,44 @@ struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
 
 	return bio;
 }
+
+/**
+ * 	bio_clone_bioset - clone a bio
+ * 	@bio_src: bio to clone
+ *	@gfp_mask: allocation priority
+ *	@bs: bio_set to allocate from
+ *
+ *	Clone bio. Caller will own the returned bio, but not the actual data it
+ *	points to. Reference count of returned bio will be one.
+ */
+struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
+			     struct bio_set *bs)
+{
+	return __bio_clone_bioset(bio_src, gfp_mask, bs, 0,
+				  bio_src->bi_iter.bi_size);
+}
 EXPORT_SYMBOL(bio_clone_bioset);
 
 /**
+ * 	bio_clone_bioset_partial - clone a partial bio
+ * 	@bio_src: bio to clone
+ *	@gfp_mask: allocation priority
+ *	@bs: bio_set to allocate from
+ *	@offset: cloned starting from the offset
+ *	@size: size for the cloned bio
+ *
+ *	Clone bio. Caller will own the returned bio, but not the actual data it
+ *	points to. Reference count of returned bio will be one.
+ */
+struct bio *bio_clone_bioset_partial(struct bio *bio_src, gfp_t gfp_mask,
+				     struct bio_set *bs, int offset,
+				     int size)
+{
+	return __bio_clone_bioset(bio_src, gfp_mask, bs, offset, size);
+}
+EXPORT_SYMBOL(bio_clone_bioset_partial);
+
+/**
  *	bio_add_pc_page	-	attempt to add page to bio
  *	@q: the target queue
  *	@bio: destination bio
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 7cf8a6c70a3f..8e521194f6fc 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -183,7 +183,7 @@ static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
 
 #define bio_iter_last(bvec, iter) ((iter).bi_size == (bvec).bv_len)
 
-static inline unsigned bio_segments(struct bio *bio)
+static inline unsigned __bio_segments(struct bio *bio, struct bvec_iter *bvec)
 {
 	unsigned segs = 0;
 	struct bio_vec bv;
@@ -205,12 +205,17 @@ static inline unsigned bio_segments(struct bio *bio)
 		break;
 	}
 
-	bio_for_each_segment(bv, bio, iter)
+	__bio_for_each_segment(bv, bio, iter, *bvec)
 		segs++;
 
 	return segs;
 }
 
+static inline unsigned bio_segments(struct bio *bio)
+{
+	return __bio_segments(bio, &bio->bi_iter);
+}
+
 /*
  * get a reference to a bio, so it won't disappear. the intended use is
  * something like:
@@ -384,6 +389,8 @@ extern void bio_put(struct bio *);
 extern void __bio_clone_fast(struct bio *, struct bio *);
 extern struct bio *bio_clone_fast(struct bio *, gfp_t, struct bio_set *);
 extern struct bio *bio_clone_bioset(struct bio *, gfp_t, struct bio_set *bs);
+extern struct bio *bio_clone_bioset_partial(struct bio *, gfp_t,
+					    struct bio_set *, int, int);
 
 extern struct bio_set *fs_bio_set;
 
-- 
2.7.4

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#1581592

On Tue, Feb 14, 2017 at 11:28:58PM +0800, Ming Lei wrote:
> Hi,
> 
> This patches replaces bio_clone() with bio_fast_clone() in
> bio_clone_mddev() because:
> 
> 1) bio_clone_mddev() is used in raid normal I/O and isn't in
> resync I/O path, and all the direct access to bvec table in
> raid happens on resync I/O only except for write behind of raid1.
> Write behind is treated specially, so the replacement is safe.
> 
> 2) for write behind, bio_clone() is kept, but this patchset
> introduces bio_clone_bioset_partial() to just clone one specific 
> bvecs range instead of whole table. Then write behind is improved
> too.
> 
> V2:
> 	1) move 3rd patch into 2nd one
> 	2) kill  bio_clone_mddev() and use  bio_clone_fast() directly
> 	3) define local variable 'offset' as sector_t in raid1_write_request()
> 
> V1:
> 	1) don't introduce bio_clone_slow_mddev_partial()
> 	2) return failure if mddev->bio_set can't be created
> 	3) remove check in bio_clone_mddev() as suggested by
> 	Christoph Hellwig.
> 	4) rename bio_clone_mddev() as bio_clone_fast_mddev()

Applied, thanks!
 
> Ming Lei (5):
>   block: introduce bio_clone_bioset_partial()
>   md: fail if mddev->bio_set can't be created
>   md/raid1: use bio_clone_bioset_partial() in case of write behind
>   md: remove unnecessary check on mddev
>   md: fast clone bio in bio_clone_mddev()
> 
>  block/bio.c         | 61 +++++++++++++++++++++++++++++++++++++++++------------
>  drivers/md/faulty.c |  2 +-
>  drivers/md/md.c     | 15 ++++---------
>  drivers/md/md.h     |  2 --
>  drivers/md/raid1.c  | 28 +++++++++++++++++-------
>  drivers/md/raid10.c | 11 +++++-----
>  drivers/md/raid5.c  |  4 ++--
>  include/linux/bio.h | 11 ++++++++--
>  8 files changed, 89 insertions(+), 45 deletions(-)
> 
> -- 
> 2.7.4
> 

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