linux-kernel - [PATCH 5.15 531/667] bfq: Avoid false marking of bic as stably merged

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Message-Id: <20220607164950.628242842@linuxfoundation.org>
Date:   Tue,  7 Jun 2022 19:03:16 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "yukuai (C)" <yukuai3@...wei.com>,
        Jan Kara <jack@...e.cz>, Christoph Hellwig <hch@....de>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.15 531/667] bfq: Avoid false marking of bic as stably merged

From: Jan Kara <jack@...e.cz>

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@...r.kernel.org
Tested-by: "yukuai (C)" <yukuai3@...wei.com>
Fixes: 430a67f9d616 ("block, bfq: merge bursts of newly-created queues")
Signed-off-by: Jan Kara <jack@...e.cz>
Reviewed-by: Christoph Hellwig <hch@....de>
Link: https://lore.kernel.org/r/20220401102752.8599-1-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 block/bfq-iosched.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -2773,9 +2773,12 @@ bfq_setup_cooperator(struct bfq_data *bf
 				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;