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Sun, 15 Feb 2026 13:34:53 +0000 (GMT) Message-ID: Date: Sun, 15 Feb 2026 19:04:51 +0530 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] blk-mq: use NOIO context to prevent deadlock during debugfs creation To: Yu Kuai , axboe@kernel.dk, ming.lei@redhat.com, hch@lst.de Cc: yi.zhang@redhat.com, shinichiro.kawasaki@wdc.com, kbusch@kernel.org, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org References: <20260214054350.2322436-1-yukuai@fnnas.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: <20260214054350.2322436-1-yukuai@fnnas.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=E+/AZKdl c=1 sm=1 tr=0 ts=6991cb87 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=HzLeVaNsDn8A:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22 a=GgsMoib0sEa3-_RKJdDe:22 a=VwQbUJbxAAAA:8 a=pGLkceISAAAA:8 a=20KFwNOVAAAA:8 a=JF9118EUAAAA:8 a=tJLSzyRPAAAA:8 a=VnNF1IyMAAAA:8 a=IYyPFNahz8ouDM3NFjgA:9 a=QEXdDO2ut3YA:10 a=xVlTc564ipvMDusKsbsT:22 a=H0xsmVfZzgdqH4_HIfU3:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjE1MDEwOCBTYWx0ZWRfX7sP2HGckZMqt DemqwAQ27FNN0xM2/BeMZxYRJuDj6ugENnAsalyMkL/3tC/qrRNJSKaxoRD3oE6f5ApI1JZ69xw sdPojGmMw4773YWXE8xtgOn5/Kudud9uMBEHq7COiHxhNClBGqJlhB/bFcvW/6r/CxHk1bTHuwK CMr1Hz9mylgmVgeqYHiO0IydUk72hKrBS0/S7cYaQe/EWWgx2eS3T8TYwRpQcQ/5XFOOa7DmoER 5YRGooThRKohhX0lD2Mw3Y+u22DRt/Qeo1S/CUhcbYHN7N3zVIVLTwsXnJ8OyDtwTHaGpvFCvpv +QBlTo7Y2akn7mSBppP9y17XjMmN+RQ2UzyuWO3JjPuLKqlY15huwkGLFA0DyIdHXgBL2UGgalm vCGnk0wCFket3X1dStsnBvV1iVlV4ulDf0g663RbKlv8AGiMfnz//vw6FX6KusiTy+O5S0khvtv 4tVN24ezxsX2eOEFiBQ== X-Proofpoint-ORIG-GUID: MPP4kn1W_IYiNqbji8zmbKoKXO3BGuGB X-Proofpoint-GUID: MPP4kn1W_IYiNqbji8zmbKoKXO3BGuGB X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-15_04,2026-02-13_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 malwarescore=0 phishscore=0 bulkscore=0 suspectscore=0 spamscore=0 clxscore=1015 impostorscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602150108 On 2/14/26 11:13 AM, Yu Kuai wrote: > Creating debugfs entries can trigger fs reclaim, which can enter back > into the block layer request_queue. This can cause deadlock if the > queue is frozen. > > Previously, a WARN_ON_ONCE check was used in debugfs_create_files() > to detect this condition, but it was racy since the queue can be frozen > from another context at any time. > > Introduce blk_debugfs_lock()/blk_debugfs_unlock() helpers that combine > the debugfs_mutex with memalloc_noio_save()/restore() to prevent fs > reclaim from triggering block I/O. Also add blk_debugfs_lock_nomemsave() > and blk_debugfs_unlock_nomemrestore() variants for callers that don't > need NOIO protection (e.g., debugfs removal or read-only operations). > > Replace all raw debugfs_mutex lock/unlock pairs with these helpers, > using the _nomemsave/_nomemrestore variants where appropriate. > > Reported-by: Yi Zhang > Closes: https://lore.kernel.org/all/CAHj4cs9gNKEYAPagD9JADfO5UH+OiCr4P7OO2wjpfOYeM-RV=A@mail.gmail.com/ > Reported-by: Shinichiro Kawasaki > Closes: https://lore.kernel.org/all/aYWQR7CtYdk3K39g@shinmob/ > Suggested-by: Christoph Hellwig > Signed-off-by: Yu Kuai Looks good to me: Reviewed-by: Nilay Shroff