From: Tejun Heo tj@kernel.org
[ Upstream commit 813e693023ba10da9e75067780f8378465bf27cc ]
When a gendisk is successfully initialized but add_disk() fails such as when a loop device has invalid number of minor device numbers specified, blkcg_init_disk() is called during init and then blkcg_exit_disk() during error handling. Unfortunately, iolatency gets initialized in the former but doesn't get cleaned up in the latter.
This is because, in non-error cases, the cleanup is performed by del_gendisk() calling rq_qos_exit(), the assumption being that rq_qos policies, iolatency being one of them, can only be activated once the disk is fully registered and visible. That assumption is true for wbt and iocost, but not so for iolatency as it gets initialized before add_disk() is called.
It is desirable to lazy-init rq_qos policies because they are optional features and add to hot path overhead once initialized - each IO has to walk all the registered rq_qos policies. So, we want to switch iolatency to lazy init too. However, that's a bigger change. As a fix for the immediate problem, let's just add an extra call to rq_qos_exit() in blkcg_exit_disk(). This is safe because duplicate calls to rq_qos_exit() become noop's.
Signed-off-by: Tejun Heo tj@kernel.org Reported-by: darklight2357@icloud.com Cc: Josef Bacik josef@toxicpanda.com Cc: Linus Torvalds torvalds@linux-foundation.org Fixes: d70675121546 ("block: introduce blk-iolatency io controller") Cc: stable@vger.kernel.org # v4.19+ Reviewed-by: Christoph Hellwig hch@lst.de Link: https://lore.kernel.org/r/Y5TQ5gm3O4HXrXR3@slm.duckdns.org Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/blk-cgroup.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index cd682fe46d2f..ee517fb06aa6 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -33,6 +33,7 @@ #include "blk-cgroup.h" #include "blk-ioprio.h" #include "blk-throttle.h" +#include "blk-rq-qos.h"
/* * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation. @@ -1299,6 +1300,7 @@ int blkcg_init_disk(struct gendisk *disk) void blkcg_exit_disk(struct gendisk *disk) { blkg_destroy_all(disk); + rq_qos_exit(disk->queue); blk_throtl_exit(disk); }