block: partition: convert percpu ref

Percpu refcount is the perfect match for partition's case,
and the conversion is quite straight.

With the convertion, one pair of atomic inc/dec can be saved
for accounting block I/O, which is run in hot path of block I/O.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/block/genhd.c b/block/genhd.c
index 85df45292dba..0c706f33a599 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1284,7 +1284,11 @@ struct gendisk *alloc_disk_node(int minors, int node_id)
                  * converted to make use of bd_mutex and sequence counters.
                  */
                 seqcount_init(&disk->part0.nr_sects_seq);
-                hd_ref_init(&disk->part0);
+                if (hd_ref_init(&disk->part0)) {
+                        hd_free_part(&disk->part0);
+                        kfree(disk);
+                        return NULL;
+                }
 
                 disk->minors = minors;
                 rand_initialize_disk(disk);