[PATCH 06/13] rbd: use bio_clone_fast() instead of bio_clone()
From: NeilBrown <hidden>
Date: 2017-05-02 03:46:30
Also in:
lkml
Subsystem:
block layer, rados block device (rbd), the rest · Maintainers:
Jens Axboe, Ilya Dryomov, Linus Torvalds
bio_clone() makes a copy of the bi_io_vec, but rbd never changes that, so there is no need for a copy. bio_clone_fast() can be used instead, which avoids making the copy. This requires that we provide a bio_set. bio_clone() uses fs_bio_set, but it isn't, in general, safe to use the same bio_set at different levels of the stack, as that can lead to deadlocks. As filesystems use fs_bio_set, block devices shouldn't. As rbd never stacks, it is safe to have a single global bio_set for all rbd devices to use. So allocate that when the module is initialised, and use it with bio_clone_fast(). Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: NeilBrown <redacted> --- drivers/block/rbd.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 089ac4179919..52120ed9385f 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c@@ -441,6 +441,8 @@ static DEFINE_SPINLOCK(rbd_client_list_lock); static struct kmem_cache *rbd_img_request_cache; static struct kmem_cache *rbd_obj_request_cache; +static struct bio_set *rbd_bio_clone; + static int rbd_major; static DEFINE_IDA(rbd_dev_id_ida);
@@ -1362,7 +1364,7 @@ static struct bio *bio_clone_range(struct bio *bio_src, { struct bio *bio; - bio = bio_clone(bio_src, gfpmask); + bio = bio_clone_fast(bio_src, gfpmask, rbd_bio_clone); if (!bio) return NULL; /* ENOMEM */
@@ -6342,8 +6344,16 @@ static int rbd_slab_init(void) if (!rbd_obj_request_cache) goto out_err; + rbd_assert(!rbd_bio_clone); + rbd_bio_clone = bioset_create(BIO_POOL_SIZE, 0, 0); + if (!rbd_bio_clone) + goto out_err_clone; + return 0; +out_err_clone: + kmem_cache_destroy(rbd_obj_request_cache); + rbd_obj_request_cache = NULL; out_err: kmem_cache_destroy(rbd_img_request_cache); rbd_img_request_cache = NULL;
@@ -6359,6 +6369,10 @@ static void rbd_slab_exit(void) rbd_assert(rbd_img_request_cache); kmem_cache_destroy(rbd_img_request_cache); rbd_img_request_cache = NULL; + + rbd_assert(rbd_bio_clone); + bioset_free(rbd_bio_clone); + rbd_bio_clone = NULL; } static int __init rbd_init(void)