rbd: use bio_clone_fast() instead of bio_clone() (f856dc36) · Commits · 戴 / test

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 <neilb@suse.com> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

drivers/block/rbd.c

+15 −1

Original line number	Diff line number	Diff line
		@@ -442,6 +442,8 @@ 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);

		@@ -1363,7 +1365,7 @@ 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 */

		@@ -6416,8 +6418,16 @@ 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;
		@@ -6433,6 +6443,10 @@ 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)

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