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Thu, 10 Sep 2026 01:11:18 -0700 (PDT) From: Jack Wang To: Song Liu , Yu Kuai , linux-raid@vger.kernel.org, Nilay Shroff , abd.masalkhi@gmail.com Cc: linux-block@vger.kernel.org, Jens Axboe , Christoph Hellwig , Damien Le Moal , Ming Lei , Xiao Ni , Li Nan , Mike Snitzer , Mikulas Patocka , dm-devel@lists.linux.dev, linux-kernel@vger.kernel.org, Jack Wang Subject: [PATCH v2 2/8] md: don't wait for q->limits_lock in check_sb_changes() Date: Thu, 10 Sep 2026 10:11:07 +0200 Message-ID: <20260910081114.1605746-3-jinpu.wang@ionos.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260910081114.1605746-1-jinpu.wang@ionos.com> References: <20260910081114.1605746-1-jinpu.wang@ionos.com> Precedence: bulk X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jack Wang check_sb_changes() activates a spare another node added, reached from md_reload_sb() -> process_metadata_update() with reconfig_mutex held. Stacking the device's limits there waits for q->limits_lock under that mutex, which deadlocks: the lock's holder waits for the queue to drain, and that I/O can be waiting for a superblock update needing reconfig_mutex. The device is already a member, so its limits are stacked. Add it with MDDEV_STACK_SKIP and leave them alone. Assisted-by: LLM Signed-off-by: Jack Wang --- drivers/md/md.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 28fc903ffeea..e60dc2c7eb90 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -10885,7 +10885,14 @@ static void check_sb_changes(struct mddev *mddev, struct md_rdev *rdev) rdev2->saved_raid_disk = -1; else rdev2->saved_raid_disk = role; - ret = remove_and_add_spares(mddev, rdev2, NULL); + /* + * reconfig_mutex is held, so q->limits_lock + * cannot be taken here. The device is + * already a member, its limits are stacked, + * so add it without touching them. + */ + ret = remove_and_add_spares(mddev, rdev2, + MDDEV_STACK_SKIP); pr_info("Activated spare: %pg\n", rdev2->bdev); /* wakeup mddev->thread here, so array could -- 2.43.0