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| author |   Dennis Zhou <dennis@kernel.org> | 2018-12-11 18:03:08 -0500 |
|---|---|---|
| committer |   Jens Axboe <axboe@kernel.dk> | 2018-12-12 17:43:33 -0700 |
| commit | 0273ac349f08f4ff9ef88aaaf9c9f2aa6e87d2be (patch) | |
| tree | 66eca0900055858fa5e9d34bf8ae3b867a945ee7 | |
| parent | block: deactivate blk_stat timer in wbt_disable_default() (diff) | |
| download | linux-dev-0273ac349f08f4ff9ef88aaaf9c9f2aa6e87d2be.tar.xz linux-dev-0273ac349f08f4ff9ef88aaaf9c9f2aa6e87d2be.zip | |
blkcg: handle dying request_queue when associating a blkg
Between v3 [1] and v4 [2] of the blkg association series, the
association point moved from generic_make_request_checks(), which is
called after the request enters the queue, to bio_set_dev(), which is when
the bio is formed before submit_bio(). When the request_queue goes away,
the blkgs supporting the request_queue are destroyed and then the
q->root_blkg is set to %NULL.
This patch adds a %NULL check to blkg_tryget_closest() to prevent the
NPE caused by the above. It also adds a guard to see if the
request_queue is dying when creating a blkg to prevent creating a blkg
for a dead request_queue.
[1] https://lore.kernel.org/lkml/20180911184137.35897-1-dennisszhou@gmail.com/
[2] https://lore.kernel.org/lkml/20181126211946.77067-1-dennis@kernel.org/
Fixes: 5cdf2e3fea5e ("blkcg: associate blkg when associating a device")
Reported-and-tested-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | block/blk-cgroup.c | 6 | ||||
| -rw-r--r-- | include/linux/blk-cgroup.h | 2 |
2 files changed, 7 insertions, 1 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 6bd0619a7d6e..c30661ddc873 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -202,6 +202,12 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, WARN_ON_ONCE(!rcu_read_lock_held()); lockdep_assert_held(&q->queue_lock); + /* request_queue is dying, do not create/recreate a blkg */ + if (blk_queue_dying(q)) { + ret = -ENODEV; + goto err_free_blkg; + } + /* blkg holds a reference to blkcg */ if (!css_tryget_online(&blkcg->css)) { ret = -ENODEV; diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h index bf13ecb0fe4f..f025fd1e22e6 100644 --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -511,7 +511,7 @@ static inline bool blkg_tryget(struct blkcg_gq *blkg) */ static inline struct blkcg_gq *blkg_tryget_closest(struct blkcg_gq *blkg) { - while (!percpu_ref_tryget(&blkg->refcnt)) + while (blkg && !percpu_ref_tryget(&blkg->refcnt)) blkg = blkg->parent; return blkg; |