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authorDennis Zhou <dennis@kernel.org>2018-12-12 02:03:08 +0300
committerJens Axboe <axboe@kernel.dk>2018-12-13 03:43:33 +0300
commit0273ac349f08f4ff9ef88aaaf9c9f2aa6e87d2be (patch)
tree66eca0900055858fa5e9d34bf8ae3b867a945ee7 /block/blk-cgroup.c
parent544fbd16a461a318cd80537d1331c0df5c6cf930 (diff)
downloadlinux-0273ac349f08f4ff9ef88aaaf9c9f2aa6e87d2be.tar.xz
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>
Diffstat (limited to 'block/blk-cgroup.c')
-rw-r--r--block/blk-cgroup.c6
1 files changed, 6 insertions, 0 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;