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[131.94.134.89]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-5bf6f5e0f38sm14365479e0c.2.2026.07.16.00.34.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Jul 2026 00:34:53 -0700 (PDT) From: Chao Shi To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , Weidong Zhu Subject: [PATCH 6.6.y] block: skip sync_blockdev() on surprise removal in bdev_mark_dead() Date: Thu, 16 Jul 2026 03:34:52 -0400 Message-ID: <20260716073452.3246468-1-coshi036@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <2026071548-remember-handling-8672@gregkh> References: <2026071548-remember-handling-8672@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit commit 49f06cff50a4ccf3b7a1a662ceb892b3b21a527a upstream. bdev_mark_dead()'s @surprise == true means the device is already gone. The filesystem callback fs_bdev_mark_dead() honours this and skips sync_filesystem(), but the bare block device path (no ->mark_dead op) lost its !surprise guard when the holder ->mark_dead callback was wired up (see Fixes), and now calls sync_blockdev() unconditionally, which can hang forever waiting on writeback that can no longer complete. syzkaller hit this via nvme_reset_work()'s "I/O queues lost" path: nvme_mark_namespaces_dead() -> blk_mark_disk_dead() -> bdev_mark_dead(bdev, true) -> sync_blockdev() blocks in folio_wait_writeback(), wedging the reset worker and every task waiting on it. Skip the sync on surprise removal, matching fs_bdev_mark_dead(); invalidate_bdev() still runs. Orderly removal (surprise == false) is unchanged. Found by FuzzNvme. Fixes: d8530de5a6e8 ("block: call into the file system for bdev_mark_dead") Acked-by: Sungwoo Kim Acked-by: Dave Tian Acked-by: Weidong Zhu Signed-off-by: Chao Shi Reviewed-by: Christoph Hellwig Link: https://patch.msgid.link/20260522220025.1770388-1-coshi036@gmail.com Signed-off-by: Jens Axboe [ adjusted for 6.6.y: bdev_mark_dead() there still unlocks bd_holder_lock after the if/else and the else arm is a bare sync_blockdev(), so the !surprise guard is added as "else if (!surprise)" instead of inside the mainline else block. ] Signed-off-by: Chao Shi --- block/bdev.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/block/bdev.c b/block/bdev.c index f3b13aa1b7d4..2bbe0408dac2 100644 --- a/block/bdev.c +++ b/block/bdev.c @@ -961,7 +961,12 @@ void bdev_mark_dead(struct block_device *bdev, bool surprise) mutex_lock(&bdev->bd_holder_lock); if (bdev->bd_holder_ops && bdev->bd_holder_ops->mark_dead) bdev->bd_holder_ops->mark_dead(bdev, surprise); - else + /* + * On surprise removal the device is already gone; syncing is + * futile and can hang forever waiting on I/O that will never + * complete. Match fs_bdev_mark_dead(), which also skips it. + */ + else if (!surprise) sync_blockdev(bdev); mutex_unlock(&bdev->bd_holder_lock); -- 2.43.0