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 8A521606A32E for ; Sat, 31 Oct 2026 09:43:24 +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=4iRGOQy2; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=CxsFcgDy 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:Cc:To:In-Reply-To:References :Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date: 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=GgO1WtfTPr95CMg999FmZUV6ZtgV/+NdH4f6NGhd5j0=; b=4iRGOQy2zh6jwG mYyiz95XGqcdxDNuQObd0BOnsOTiSA5Ky9nQfjH6Mj1zdaivgnZrqSPzKO+/zCaxdLVRdkzCdaKDd 3iF5eKP8Adb1ho3QUzVNV5ziBZWjqjrY2U7jdwnijf+hAb/jE9oRvPFBDfzWxEtu9FJl93W81O3f7 HaDoj7rqSo4ilOrYginIndlka0ZfdJXldYCWicXXz/MIOoMAupCNyNuUvmAkC0NfZsinXd4bNbrCi itjYAoE4tLkSEd8aP1R4Un+/Phfry8M7YCpgvbyTJCRRDefqS7uVwPhacrkyT7ZXXDlTosn1cpPf6 jbq2zKAhKrfR7qvifyyw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xN5cS-0000000D9av-0soo; Sat, 31 Oct 2026 09:43:24 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xN5cQ-0000000D9ag-3TYr for kexec@lists.infradead.org; Sat, 31 Oct 2026 09:43:22 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 442D2600D4; Sat, 31 Oct 2026 09:43:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 160C51F00919; Sat, 31 Oct 2026 09:43:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793439802; bh=GgO1WtfTPr95CMg999FmZUV6ZtgV/+NdH4f6NGhd5j0=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=CxsFcgDyR62puXwpfrdBVjYlxXqi56LRd0wVMMbXZa5WFwuvsy+6B5cy3b5Iwa7MG 8sBreHtjQSLv2LeLQKpzyJ9OA/zafCF1rZfSEe71N8/KoTuH72Iv5RrwCIu6BR776N rit21O2a2/iegjkgJJmtCXLN/B5tjBc0jHK5yfrE3y3//41Tqx3IWR5oe4TS+os+n6 ptEh7dACU7b2BPKFq38dpUCDEsrJ22Xstg+i7L5YBJ9fCPw4qlIKnuDlvaG8jeKsdk BkK2l2ir4IGtFTyrtwd8Hn8khr+C9Zv5YUX+w0Yu3RfTm9WrN67lUNWU9CeYw8a5vf ObyYSDr/u9RcA== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:39:41 +0100 Subject: [PATCH v3 12/47] mm/huge_memory: fix livelock on device private folio X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261031-fixes_core-v3-12-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> In-Reply-To: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: 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 Bacik , Muhammad Usama Anjum , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2310; i=david@kernel.org; h=from:subject:message-id; bh=rOFEKHXFU3ik6VWKIWSfoeHTdwlufJwdJhailtQlKpY=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebk/za/NTTZLZMb9d0VIwTeN1JKe3lyNXr2ZuQ2vQL Sd5S7uOUhYGMQ4GWTFFlqDg+wYvX66rrXbjY4aZw8oEMoSBi1MAJjK1geF/tMmjs8UW6zzCmsKP 8PM9FLOuXFwt+GBBhUqxj81F95jVjAxT18xRsTObx+3OeGvHkv7eWddSHXf02q6afunNbalWsQ+ 8AA== X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A 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=-18.9 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,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 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] Reviewed-by: Zi Yan Reviewed-by: Lance Yang Tested-by: Muhammad Usama Anjum Signed-off-by: David Hildenbrand (Arm) --- mm/filemap.c | 4 ++-- mm/huge_memory.c | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index b04be64a5069f..e85a4114d2ecc 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1395,8 +1395,8 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr, #ifdef CONFIG_MIGRATION /** - * softleaf_entry_wait_on_locked - Wait for a migration entry or - * device_private entry to be removed. + * softleaf_entry_wait_on_locked - Wait for a migration entry to be removed + * or a device-private folio in a device-private entry to get unlocked. * @entry: migration or device_private swap entry. * @ptl: already locked ptl. This function will drop the lock. * diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 283c4bc8b927c..2b31a425c7a32 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1500,7 +1500,7 @@ vm_fault_t do_huge_pmd_device_private(struct vm_fault *vmf) folio_unlock(folio); folio_put(folio); } else { - spin_unlock(ptl); + softleaf_entry_wait_on_locked(entry, ptl); } return ret; -- 2.43.0