[PATCH 07/13 V2] drbd: use bio_clone_fast() instead of bio_clone()

NeilBrown
2017-05-02T23:20:20Z

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drbd does not modify the bi_io_vec of the cloned bio,
so there is no need to clone that part. So bio_clone_fast()
is the better choice.
For bio_clone_fast() we need to specify a bio_set.
We could use fs_bio_set, which bio_clone() uses, or
drbd_md_io_bio_set, which drbd uses for metadata, but it is
generally best to avoid sharing bio_sets unless you can
be certain that there are no interdependencies.

So create a new bio_set, drbd_io_bio_set, and use bio_clone_fast().

Also remove a "XXX cannot fail ???" comment because it definitely
cannot fail - bio_clone_fast() doesn't fail if the GFP flags allow for
sleeping.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: NeilBrown <neilb@suse.com>
---

This patch needed to be refreshed after long lines were
wrapped in an earlier patch.
Also added the BIOSET_NEED_RESCUER flag for new bioset as
it is not trivially obvious that this isn't needed.

NeilBrown

drivers/block/drbd/drbd_int.h | 3 +++
drivers/block/drbd/drbd_main.c | 9 +++++++++
drivers/block/drbd/drbd_req.h | 2 +-
3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index d5da45bb03a6..f91982515a6b 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -1441,6 +1441,9 @@ extern struct bio_set *drbd_md_io_bio_set;
/* to allocate from that set */
extern struct bio *bio_alloc_drbd(gfp_t gfp_mask);

+/* And a bio_set for cloning */
+extern struct bio_set *drbd_io_bio_set;
+
extern struct mutex resources_mutex;

extern int conn_lowest_minor(struct drbd_connection *connection);
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index bdf51b6977cf..90680034ef57 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -128,6 +128,7 @@ mempool_t *drbd_request_mempool;
mempool_t *drbd_ee_mempool;
mempool_t *drbd_md_io_page_pool;
struct bio_set *drbd_md_io_bio_set;
+struct bio_set *drbd_io_bio_set;

/* I do not use a standard mempool, because:
1) I want to hand out the pre-allocated objects first.
@@ -2098,6 +2099,8 @@ static void drbd_destroy_mempools(void)

/* D_ASSERT(device, atomic_read(&drbd_pp_vacant)==0); */

+ if (drbd_io_bio_set)
+ bioset_free(drbd_io_bio_set);
if (drbd_md_io_bio_set)
bioset_free(drbd_md_io_bio_set);
if (drbd_md_io_page_pool)
@@ -2115,6 +2118,7 @@ static void drbd_destroy_mempools(void)
if (drbd_al_ext_cache)
kmem_cache_destroy(drbd_al_ext_cache);

+ drbd_io_bio_set = NULL;
drbd_md_io_bio_set = NULL;
drbd_md_io_page_pool = NULL;
drbd_ee_mempool = NULL;
@@ -2142,6 +2146,7 @@ static int drbd_create_mempools(void)
drbd_pp_pool = NULL;
drbd_md_io_page_pool = NULL;
drbd_md_io_bio_set = NULL;
+ drbd_io_bio_set = NULL;

/* caches */
drbd_request_cache = kmem_cache_create(
@@ -2165,6 +2170,10 @@ static int drbd_create_mempools(void)
goto Enomem;

/* mempools */
+ drbd_io_bio_set = bioset_create(BIO_POOL_SIZE, 0, BIOSET_NEED_RESCUER);
+ if (drbd_io_bio_set == NULL)
+ goto Enomem;
+
drbd_md_io_bio_set = bioset_create(DRBD_MIN_POOL_PAGES, 0,
BIOSET_NEED_BVECS |
BIOSET_NEED_RESCUER);
diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
index eb49e7f2da91..9e1866ab238f 100644
--- a/drivers/block/drbd/drbd_req.h
+++ b/drivers/block/drbd/drbd_req.h
@@ -263,7 +263,7 @@ enum drbd_req_state_bits {
static inline void drbd_req_make_private_bio(struct drbd_request *req, struct bio *bio_src)
{
struct bio *bio;
- bio = bio_clone(bio_src, GFP_NOIO); /* XXX cannot fail?? */
+ bio = bio_clone_fast(bio_src, GFP_NOIO, drbd_io_bio_set);

req->private_bio = bio;

--
2.12.2

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