Merge tag 'for-linus-20180906' of git://git.kernel.dk/linux-block

Pull block fixes from Jens Axboe:
 "Small collection of fixes that should go into this release. This
  contains:

   - Small series that fixes a race between blkcg teardown and writeback
     (Dennis Zhou)

   - Fix disallowing invalid block size settings from the nbd ioctl (me)

   - BFQ fix for a use-after-free on last release of a bfqg (Konstantin
     Khlebnikov)

   - Fix for the "don't warn for flush" fix (Mikulas)"

* tag 'for-linus-20180906' of git://git.kernel.dk/linux-block:
  block: bfq: swap puts in bfqg_and_blkg_put
  block: don't warn when doing fsync on read-only devices
  nbd: don't allow invalid blocksize settings
  blkcg: use tryget logic when associating a blkg with a bio
  blkcg: delay blkg destruction until after writeback has finished
  Revert "blk-throttle: fix race between blkcg_bio_issue_check() and cgroup_rmdir()"

1 files changed, 5 insertions, 0 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index f5981e9d6ae2..8a8bb8796c6c 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -491,6 +491,7 @@ static void cgwb_release_workfn(struct work_struct *work)
 {
 	struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
 						release_work);
+	struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css);
 
 	mutex_lock(&wb->bdi->cgwb_release_mutex);
 	wb_shutdown(wb);
@@ -499,6 +500,9 @@ static void cgwb_release_workfn(struct work_struct *work)
 	css_put(wb->blkcg_css);
 	mutex_unlock(&wb->bdi->cgwb_release_mutex);
 
+	/* triggers blkg destruction if cgwb_refcnt becomes zero */
+	blkcg_cgwb_put(blkcg);
+
 	fprop_local_destroy_percpu(&wb->memcg_completions);
 	percpu_ref_exit(&wb->refcnt);
 	wb_exit(wb);
@@ -597,6 +601,7 @@ static int cgwb_create(struct backing_dev_info *bdi,
 			list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
 			list_add(&wb->memcg_node, memcg_cgwb_list);
 			list_add(&wb->blkcg_node, blkcg_cgwb_list);
+			blkcg_cgwb_get(blkcg);
 			css_get(memcg_css);
 			css_get(blkcg_css);
 		}