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Mon, 02 Nov 2026 11:44:49 +0000 X-Mizu-Trace-ID: 6ed161f8dd0a3c59 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, stable@vger.kernel.org, usama.anjum@arm.com Subject: Re: [PATCH v3 30/47] mm/mremap: use pudp_huge_get_and_clear() when moving huge PUDs Date: Mon, 2 Nov 2026 19:44:42 +0800 Message-ID: <20261102114442.65682-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261031-fixes_core-v3-30-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-30-d6437171ecc3@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: B9E1E40004 X-Stat-Signature: aycsrrp6h73o7f1rx68gk91qyocsw1fp X-Rspamd-Server: rspam06 X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,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: 1793619891-372287 X-HE-Meta: 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 SC5ewRt4 uZtWuxzRSgSUInXVGItwvJ1ifb7LJ5dwp0EfndpoRY6uxCKafu6K3JgjB4f3xY7D5uJdTGgO2c28e/kTA3Tg1z0eTyuX34+ZWKNbhQUZI5dkeCkKm0mf5tiCGQ7PhWHKFfGfuDL+a1R8GmkBOIhNbJcixCtN4lfkVc3cMLhqUPEtKVH/DUaDAmbHbrj+QMsgXT4ISk9SRUxf1Vq90wemC2dnMgZ8+7BhWbEDnQGLlD+PbqID4DGFjcQ0yu7tGdk2vWjBv5TRpVyFzH6ZDYIBfdzY6YgfjAU4ZeW1YbdxRja3bQPSdgKYUXLpAa6cxOWiMbE4lmvrsRf2etFdRbiHEgLtC+nM9MDWljDKmtpyyt3cGbrWPIc+WuHqXTUjrV942RKXKgqe75V9d4zCDYUR5kuq7BeiKxmHPSb/N5JouTLYJUPAVryi8Tnc6mA== 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 Sat, Oct 31, 2026 at 10:39:59AM +0100, David Hildenbrand (Arm) wrote: >move_huge_pud() reads the old PUD and clears it in separate operations. >Hardware accessed or dirty updates between those operations can be lost >when the saved entry is installed at the new address. Yep. HW can still update the A/D bits while the PUD lock is held :) >The raw pud_clear() also bypasses page_table_check_pud_clear(), while >set_pud_at() accounts for the destination mapping. This leaves the >checker counts unbalanced for mappings tracked by page table checking. > >To fix it, simply use pudp_huge_get_and_clear(). > >Fixes: 7d846db7d0e2 ("mm/mremap: convert huge PUD move to separate helper") >Cc: stable@vger.kernel.org >Reviewed-by: Lorenzo Stoakes (ARM) >Reviewed-by: Pedro Falcato >Reviewed-by: Dev Jain >Tested-by: Muhammad Usama Anjum >Signed-off-by: David Hildenbrand (Arm) >--- > mm/mremap.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > >diff --git a/mm/mremap.c b/mm/mremap.c >index 0d06d7f37f19a..16e736c72d9cb 100644 >--- a/mm/mremap.c >+++ b/mm/mremap.c >@@ -509,8 +509,7 @@ static bool move_huge_pud(struct pagetable_move_control *pmc, > spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); > > /* Clear the pud */ >- pud = *old_pud; >- pud_clear(old_pud); >+ pud = pudp_huge_get_and_clear(mm, pmc->old_addr, old_pud); Reviewed-by: Lance Yang > > VM_BUG_ON(!pud_none(*new_pud)); > > >-- >2.43.0 > >