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bh=fgRhZQDSEmJFZyIgGkSRYKnhjZ4Z1l5m8LV8w/ZXnHw=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793619890; v=1; x=1794224690; b=Zb1GeGbojxXveT3cZxDPn//4R8A7h+RMO72HLl435m67FVvM9SHf44yaVVp55n3SAPWWoirq Hz8XE56QJlzs5IpeJmF7MvIRESwEWtyXzDq/oA5mLYy34SDIJOr+HdZ4EG3OGTtz9aHGD3cJfWY yqj/TBZodxsUUHX+M5Y8plAE= X-Envelope-To: linux-fsdevel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 6ed161f8dd0a3c59; 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-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 > >