block: add bioset_create_nobvec()

Users of bio_clone_fast() do not want bios with their own bvecs.
Allocating a bvec mempool as part of the bioset intended for such users
is a waste of memory.

bioset_create_nobvec() creates a bioset that doesn't have the bvec
mempool.

Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/bio.c b/block/bio.c
index 3e6331d25d90c6aa507acd43bb90f2001c9e6641..3e6e1986a5b2c0c217532b816dc911cd544e3e11 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -428,6 +428,9 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
                front_pad = 0;
                inline_vecs = nr_iovecs;
        } else {
+               /* should not use nobvec bioset for nr_iovecs > 0 */
+               if (WARN_ON_ONCE(!bs->bvec_pool && nr_iovecs > 0))
+                       return NULL;
                /*
                 * generic_make_request() converts recursion to iteration; this
                 * means if we're running beneath it, any bios we allocate and
@@ -1900,20 +1903,9 @@ void bioset_free(struct bio_set *bs)
 }
 EXPORT_SYMBOL(bioset_free);
 
-/**
- * bioset_create  - Create a bio_set
- * @pool_size: Number of bio and bio_vecs to cache in the mempool
- * @front_pad: Number of bytes to allocate in front of the returned bio
- *
- * Description:
- *    Set up a bio_set to be used with @bio_alloc_bioset. Allows the caller
- *    to ask for a number of bytes to be allocated in front of the bio.
- *    Front pad allocation is useful for embedding the bio inside
- *    another structure, to avoid allocating extra data to go with the bio.
- *    Note that the bio must be embedded at the END of that structure always,
- *    or things will break badly.
- */
-struct bio_set *bioset_create(unsigned int pool_size, unsigned int front_pad)
+static struct bio_set *__bioset_create(unsigned int pool_size,
+                                      unsigned int front_pad,
+                                      bool create_bvec_pool)
 {
        unsigned int back_pad = BIO_INLINE_VECS * sizeof(struct bio_vec);
        struct bio_set *bs;
@@ -1938,9 +1930,11 @@ struct bio_set *bioset_create(unsigned int pool_size, unsigned int front_pad)
        if (!bs->bio_pool)
                goto bad;
 
-       bs->bvec_pool = biovec_create_pool(pool_size);
-       if (!bs->bvec_pool)
-               goto bad;
+       if (create_bvec_pool) {
+               bs->bvec_pool = biovec_create_pool(pool_size);
+               if (!bs->bvec_pool)
+                       goto bad;
+       }
 
        bs->rescue_workqueue = alloc_workqueue("bioset", WQ_MEM_RECLAIM, 0);
        if (!bs->rescue_workqueue)
@@ -1951,8 +1945,41 @@ bad:
        bioset_free(bs);
        return NULL;
 }
+
+/**
+ * bioset_create  - Create a bio_set
+ * @pool_size: Number of bio and bio_vecs to cache in the mempool
+ * @front_pad: Number of bytes to allocate in front of the returned bio
+ *
+ * Description:
+ *    Set up a bio_set to be used with @bio_alloc_bioset. Allows the caller
+ *    to ask for a number of bytes to be allocated in front of the bio.
+ *    Front pad allocation is useful for embedding the bio inside
+ *    another structure, to avoid allocating extra data to go with the bio.
+ *    Note that the bio must be embedded at the END of that structure always,
+ *    or things will break badly.
+ */
+struct bio_set *bioset_create(unsigned int pool_size, unsigned int front_pad)
+{
+       return __bioset_create(pool_size, front_pad, true);
+}
 EXPORT_SYMBOL(bioset_create);
 
+/**
+ * bioset_create_nobvec  - Create a bio_set without bio_vec mempool
+ * @pool_size: Number of bio to cache in the mempool
+ * @front_pad: Number of bytes to allocate in front of the returned bio
+ *
+ * Description:
+ *    Same functionality as bioset_create() except that mempool is not
+ *    created for bio_vecs. Saving some memory for bio_clone_fast() users.
+ */
+struct bio_set *bioset_create_nobvec(unsigned int pool_size, unsigned int front_pad)
+{
+       return __bioset_create(pool_size, front_pad, false);
+}
+EXPORT_SYMBOL(bioset_create_nobvec);
+
 #ifdef CONFIG_BLK_CGROUP
 /**
  * bio_associate_current - associate a bio with %current

diff --git a/include/linux/bio.h b/include/linux/bio.h
index ce6b75964b7129206e81f578727437fb3b2f7968..7347f486ceca4ff9e64989c5ae5d6578524c0d8f 100644 (file)
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -378,6 +378,7 @@ static inline struct bio *bio_next_split(struct bio *bio, int sectors,
 }
 
 extern struct bio_set *bioset_create(unsigned int, unsigned int);
+extern struct bio_set *bioset_create_nobvec(unsigned int, unsigned int);
 extern void bioset_free(struct bio_set *);
 extern mempool_t *biovec_create_pool(int pool_entries);