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charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: DM8PR04MB8037.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 6a3aa461-9745-4421-a102-08da54f631de X-MS-Exchange-CrossTenant-originalarrivaltime: 23 Jun 2022 08:56:00.1552 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: nm9+lLM+3VdNaBjPeBCQE+zHgqnSUUfs855fvj+rG9e0payCDuYdYaxY3zATHwjsiCxXiidq0G+EWjErhRu4DoyppCNFgzWo2tD7MLbDq/E= X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN6PR04MB3966 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Jun 21, 2022 / 10:07, Jens Axboe wrote: > If rq_qos_throttle() ends up blocking, then we will have invalidated and > flushed our current plug. Since blk_mq_get_cached_request() hasn't > popped the cached request off the plug list just yet, we end holding a > pointer to a request that is no longer valid. This insta-crashes with > rq->mq_hctx being NULL in the validity checks just after. >=20 > Pop the request off the cached list before doing rq_qos_throttle() to > avoid using a potentially stale request. >=20 > Fixes: 0a5aa8d161d1 ("block: fix blk_mq_attempt_bio_merge and rq_qos_thro= ttle protection") > Reported-by: Dylan Yudaken > Signed-off-by: Jens Axboe Thank you for the fix and sorry for the trouble. The patch passed my test s= et: Tested-by: Shin'ichiro Kawasaki BTW, may I know the workload or script which triggers the failure? I'm interested in if we can add a blktests test case to exercises qos throttle and prevent similar bugs in the future. --=20 Shin'ichiro Kawasaki=