bfq: Avoid false marking of bic as stably merged

BugLink: https://bugs.launchpad.net/bugs/1981864
commit 70456e5210f40ffdb8f6d905acfdcec5bd5fad9e upstream.

bfq_setup_cooperator() can mark bic as stably merged even though it
decides to not merge its bfqqs (when bfq_setup_merge() returns NULL).
Make sure to mark bic as stably merged only if we are really going to
merge bfqqs.

CC: stable@vger.kernel.org
Tested-by: "yukuai (C)" <yukuai3@huawei.com>
Fixes: 430a67f9d616 ("block, bfq: merge bursts of newly-created queues")
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220401102752.8599-1-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 343ca559ab8a205c9b82cff580f54d4c67e2b941..95420e1784c1638d2d5f4c2f4e0c84584afac8c8 100644 (file)
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -2773,9 +2773,12 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
                                struct bfq_queue *new_bfqq =
                                        bfq_setup_merge(bfqq, stable_merge_bfqq);
 
-                               bic->stably_merged = true;
-                               if (new_bfqq && new_bfqq->bic)
-                                       new_bfqq->bic->stably_merged = true;
+                               if (new_bfqq) {
+                                       bic->stably_merged = true;
+                                       if (new_bfqq->bic)
+                                               new_bfqq->bic->stably_merged =
+                                                                       true;
+                               }
                                return new_bfqq;
                        } else
                                return NULL;