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Wed, 28 Oct 2026 15:04:16 +0000 X-Mizu-Trace-ID: d7967b914a90b8c6 X-Migadu-Flow: FLOW_OUT From: Lance Yang To: david@kernel.org Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, ljs@kernel.org, kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, baoquan.he@linux.dev, baolin.wang@linux.alibaba.com, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, kees@kernel.org, peterz@infradead.org, jannh@google.com, pfalcato@suse.de, hughd@google.com, pasha.tatashin@soleen.com, pratyush@kernel.org, willy@infradead.org, jack@suse.cz, ziy@nvidia.com, lance.yang@linux.dev, riel@surriel.com, harry@kernel.org, apopple@nvidia.com, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, usama.arif@linux.dev, kas@kernel.org, matthew.brost@intel.com, jhubbard@nvidia.com, peterx@redhat.com, will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, osalvador@suse.de, minchan@kernel.org, muchun.song@linux.dev, xu.xin@linux.dev, chengming.zhou@linux.dev, chrisl@kernel.org, shikemeng@huaweicloud.com, nphamcs@gmail.com, youngjun.park@lge.com, gourry@gourry.net, joshua.hahnjy@gmail.com, rakie.kim@sk.com, ying.huang@linux.alibaba.com, jgg@ziepe.ca, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, josef@toxicpanda.com Subject: Re: [PATCH 12/46] mm/huge_memory: fix livelock on device private folio Date: Wed, 28 Oct 2026 23:04:10 +0800 Message-ID: <20261028150410.47065-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261027-fixes_core-v1-12-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-12-6f74bec9a5bb@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 22DC5120012 X-Stat-Signature: nxkq9h3f6f4oy3rnxbdktjqegi9h4j3b X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793199858-170614 X-HE-Meta: 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 asXcx6wH 1AKlp6nkHeKdF3XcO8z+ysTmfMt9Wh3kXgBCLru4epqtMoNrwVQrT+eWkQ0XgK8qRlmaJGBdEZkfAc7l421dwtEUygQRhPg2raTCT1oWPj/EO5f4k95ZOI2C3KBRDdpkqW4nEJM7UmRu3zcSdMOZrhznBnviKReefBbr7YYP1eE4NHlohj9+PoeoaTMBYO3Yfn9NOkbrPM7ryGu/m2Eql6m2wuy9bmXefWxNYMtXebShRhJKeiWc0NTUN7TFpT2TZ0bV2zR5baoRGffmijDo6n7u6CD07cFTj7ff7kLCSwpb3kiigcBMucbJCG1EEIUBI/5wA+7uC/Hc7ckhmm2pnHEA6oMjLR1jScKIJxDcxJ9n7Wn0Jzxmm2l/DB79Wy/i9ELCpw/ITaQGAWg3ArEgDz7f4gKA6mkTkoDBmlP89zJQ/ab0Ftas/DU+iEg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Tue, Oct 27, 2026 at 12:17:32AM +0100, David Hildenbrand (Arm) wrote: >From: Josef Bacik > >If do_huge_pmd_device_private() cannot lock the folio, it simply returns >to try again on the next fault. > >Just like we did in commit b570f37a2ce4 ("mm: Fix a hmm_range_fault() >livelock / starvation problem"), let's wait for the softleaf entry, >which will drop the PTL and wait until the folio was unlocked. This is >precisely what we do in do_swap_page() with device-private folios. This >avoids possibly livelocking. > >Update softleaf_entry_wait_on_locked() documentation to clarify that >device-private entries wait until the folio is unlocked. > >There seems to be no compelling reason to backport this to stable >kernels unless we actually see problems there. > >Fix generated by an LLM and sent by Josef Bacik in private. > >Fixes: 4964099163d0 ("mm/memory/fault: add THP fault handling for zone device private pages") >Signed-off-by: Josef Bacik >[ david: simplify patch description, fixup softleaf_entry_wait_on_locked description] >Signed-off-by: David Hildenbrand (Arm) >--- Nice work! Reviewed-by: Lance Yang