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Mon, 12 May 2025 09:29:55 +0000 (GMT) From: Nilay Shroff To: linux-block@vger.kernel.org Cc: ming.lei@redhat.com, hch@lst.de, axboe@kernel.dk, gjoyce@ibm.com Subject: [PATCH] block: unfreeze queue if realloc tag set fails during nr_hw_queues update Date: Mon, 12 May 2025 14:43:38 +0530 Message-ID: <20250512092952.135887-1-nilay@linux.ibm.com> X-Mailer: git-send-email 2.49.0 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=OOUn3TaB c=1 sm=1 tr=0 ts=6821bf99 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=dt9VzEwgFbYA:10 a=VnNF1IyMAAAA:8 a=7ZNjnjnpTjzHF3BlZ_YA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: 7PyGhDj-kNRUWNT5yUIJm5_xGuCfbckC X-Proofpoint-GUID: 7PyGhDj-kNRUWNT5yUIJm5_xGuCfbckC X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTEyMDA5NSBTYWx0ZWRfX4kuW/7CYsBEO wpBse7bx/NSpyxokv5OOQVE8gRTZyRiqW4mZ6ntIr/QRiiQg71SGNMicKwIU9AGHfohG9cdZM1p m4eXW/u5x4bCJHnATsCnJKfHjizkmbGc8wk8nQan/2UiPdohWcKfwIzScR/5T2/PLqWQaCoPv2j 3RqWH1OWCEWN9FvGqO95ZZsXTQzidjb6KvVfJucI03xUSgX+8D2nOkAbe1yhsAg9Qa4TRCCTv2X uDFLdMX3gzz+KXmSchJ01c7ohe/ulVCOTx5Y8WhMOospi4W5zCAjT2Vq/jU2td6sd24AgrItZ+5 /nMKSDohzLrri+sIw4cO61KvkmC1HMAEEmRRr13GiD1jAFoobhFPK+gxDzJuMpxXOg0tKo8IdkZ Bc/Wk8nwUIm/RBrkq8XxLKGt8Ind2VHcJ+JgvXyxzKknupIfUTOsdtxFT/kzLn2v7nMNLobR X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-12_03,2025-05-09_01,2025-02-21_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 phishscore=0 suspectscore=0 spamscore=0 lowpriorityscore=0 impostorscore=0 clxscore=1015 bulkscore=0 malwarescore=0 adultscore=0 mlxscore=0 mlxlogscore=999 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2504070000 definitions=main-2505120095 In __blk_mq_update_nr_hw_queues(), the current sequence involves: 1. unregistering sysfs/debugfs attributes 2. freeze the queue 3. reallocating the tag set 4. updating the queue map 5. reallocating hardware contexts 6. updating the elevator (which unfreeze the queue again) 7. re-register sysfs/debugfs attributes If tag set reallocation fails at step 3, the function skips steps 4–6 and proceeds directly to step 7, re-registering the sysfs/debugfs attributes without unfreezing the queue first. This is incorrect and can lead to a system hang or lockdep splat, as the queue remains frozen and is never properly unfrozen. This patch addresses the issue by explicitly unfreezing the queue before re-registering the sysfs/debugfs attributes in the event of a tag set reallocation failure. Fixes: 9dc7a882ce96 ("block: move hctx debugfs/sysfs registering out of freezing queue") Signed-off-by: Nilay Shroff --- block/blk-mq.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 4f79a9808fd1..cbc9a9f97a31 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -5002,8 +5002,11 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, list_for_each_entry(q, &set->tag_list, tag_set_list) blk_mq_freeze_queue_nomemsave(q); - if (blk_mq_realloc_tag_set_tags(set, nr_hw_queues) < 0) + if (blk_mq_realloc_tag_set_tags(set, nr_hw_queues) < 0) { + list_for_each_entry(q, &set->tag_list, tag_set_list) + blk_mq_unfreeze_queue_nomemrestore(q); goto reregister; + } fallback: blk_mq_update_queue_map(set); -- 2.49.0