From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 662C3606A31A for ; Wed, 28 Oct 2026 15:04:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=JiXALqCr; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=DOaintvD DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc: To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Unsubscribe-Post: List-Owner; bh=77xhCh2ORMf6NIfM90rhR5yS555x+O+M+p2I+XHyw1I=; b=JiXALqCr5lf6tp 2uFKUxbiXvu1GI0MztLP8MbA055WJyTKvSI425M+gUrLxSqEhsXK+FaymYzhY8nIi4l+zugqnn2EG RBAXiFwa/yXj9LEZFfPw8blMwaF4c3ZeEqBVlN4IsJDrML0xhmL1qddHb7c96NtUgycsvDgOq/1k1 gBMu4cd1HVjPjvIdhaC/ttpccxcZkKEoqkrkaEaKYqZt+8Q03bFWEbGr1leWQ8kOI6pAWFOFsogW8 sADpJXmnhXXwAID5CcXri5bjBWEdw93gev5IGtJcxvvOmAxZrf+0RwH7xCzH//PqryOrT0qEaiJPz 3PDS9l4Lb/czdQLkDvmQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xM5CR-00000007IPG-28LQ; Wed, 28 Oct 2026 15:04:23 +0000 Received: from out-16.mta1.migadu.com ([95.215.58.16] helo=mta1.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xM5CO-00000007IMC-3GQJ for kexec@lists.infradead.org; Wed, 28 Oct 2026 15:04:22 +0000 X-Envelope-To: kexec@lists.infradead.org DKIM-Signature: a=rsa-sha256; bh=77xhCh2ORMf6NIfM90rhR5yS555x+O+M+p2I+XHyw1I=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793199857; v=1; x=1793804657; b=DOaintvDCkIU/aM4mbDkTUbB7KXdOwz/1W14lJYmnPjR1UglE6lkfhl7iisk2fyDHg/P6GP3 5jciE740/d15e8va8jnQE3dPdseWY1LxdNQxUpMbCZtLmWnGJY0gb3M1wALTIAly7eJpWAaE9h7 sOj/QiLSS8wumYpDbu7phDXs= X-Envelope-To: kexec@lists.infradead.org Received: by smtp.migadu.com with ESMTPS id d7967b914a90b8c6; 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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261028_080421_027906_DC3BD594 X-CRM114-Status: UNSURE ( 7.39 ) X-CRM114-Notice: Please train this message. X-Spam-Score: -2.8 (--) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" X-Spam-Status: No, score=-13.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 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