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[80.230.48.7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48e6d895781sm104480065e9.0.2026.05.11.02.01.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 May 2026 02:01:54 -0700 (PDT) Date: Mon, 11 May 2026 05:01:49 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: "David Hildenbrand (Arm)" , Jason Wang , Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= , Muchun Song , Oscar Salvador , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Hugh Dickins , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , virtualization@lists.linux.dev, linux-mm@kvack.org, Andrea Arcangeli Subject: [PATCH resend v6 02/30] mm: mempolicy: fix interleave index for unaligned VMA start Message-ID: <41bd50fdaae943e1a79215ea4000322e74a823be.1778489843.git.mst@redhat.com> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent The NUMA interleave index formula (addr - vm_start) >> shift gives wrong results when vm_start is not aligned to the folio size: the subtraction before the shift allows low bits to affect the result via borrows. Use (addr >> shift) - (vm_start >> shift) instead, which independently aligns both values before computing the difference. No functional change for current callers: the fix only affects NUMA interleave and weighted-interleave policies. Current large-order callers either pre-align the address (vma_alloc_anon_folio_pmd) or do not use NUMA interleave (drm_pagemap). All other callers use order 0 where the old and new formulas are equivalent. However subsequent patches in this series add large-order callers that pass unaligned fault addresses, making this fix necessary. Signed-off-by: Michael S. Tsirkin --- mm/mempolicy.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 6832cc68120f..39e556e3d263 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2049,7 +2049,8 @@ struct mempolicy *get_vma_policy(struct vm_area_struct *vma, if (pol->mode == MPOL_INTERLEAVE || pol->mode == MPOL_WEIGHTED_INTERLEAVE) { *ilx += vma->vm_pgoff >> order; - *ilx += (addr - vma->vm_start) >> (PAGE_SHIFT + order); + *ilx += (addr >> (PAGE_SHIFT + order)) - + (vma->vm_start >> (PAGE_SHIFT + order)); } return pol; } -- MST