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Sat, 5 Apr 2025 14:00:22 +0000 (GMT) Message-ID: Date: Sat, 5 Apr 2025 19:30:21 +0530 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] block: don't grab elevator lock during queue initialization To: Ming Lei Cc: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig , syzbot+4c7e0f9b94ad65811efb@syzkaller.appspotmail.com References: <20250403105402.1334206-1-ming.lei@redhat.com> <9933c2e6-1cbd-464c-a519-b7fa722a8e4d@linux.ibm.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: loQ2BvfruCmaAj3DmLwTANgTJnkkA06L X-Proofpoint-GUID: loQ2BvfruCmaAj3DmLwTANgTJnkkA06L X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1095,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-04-05_06,2025-04-03_03,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 adultscore=0 impostorscore=0 mlxlogscore=642 malwarescore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 priorityscore=1501 clxscore=1015 mlxscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502280000 definitions=main-2504050087 >> I don't know why we think your earlier fix which cut dependency between >> ->elevator_lock and ->freeze_lock doesn't work. But anyways, my view >> is that we've got into these lock chains from two different code paths: > > As I explained, blk_mq_enter_no_io() is same with freeze queue, just the > lock in __bio_queue_enter() isn't modeled. If it is done, every lockdep > warning will be re-triggered too. > Oh I see, because I tested your earlier patches without lock modeled I didn't encounter any lockdep warning. >> >> path1: elevator_lock >> -> fs_reclaim (GFP_KERNEL) >> -> freeze_lock >> >> path2: freeze_lock(memalloc_noio) >> -> elevator_lock >> -> fs_reclaim (this becomes NOP in this case due to memalloc_noio) > > No, there isn't fs_reclaim in path2, and memalloc_noio() will avoid it. > Yes correct and so I mentioned above NOP for fs_reclaim in path2. Thanks, --Nilay