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b=BkOGbXHtNIV35nOD5BO38v1EVSPQbb31jM9e4LeI3O8uWXuBhWBo26gj2J8OGjLyA bfkqbYKmd4jKEKq4DT5PjTxpucmJ3jX62oeonMNLCn2iuBLx7v/zkOn4cFcNx8bnXP N3eM8+zvmHvTrM+Jr9oBoI+blmqUHzNMiDt2+/Nufo4giN+U0slj6n1VyeaakH/Ocx R9pMr52UT7DuImtFuJq78RdTnmyazUlmpGAUH5tnRlIGl80T863jBTjmNoVhCay7sl 0bZNFQAD/fVDF3jQWDuVk5+X+n5bZp8Qvh5IyVv1ANMJZT+kW4VU6Vao7kENYxmTOZ f++qIJtRLtwMA== From: SJ Park To: Andrew Morton Cc: SJ Park , stable@vger.kernel.org, damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 5/8] mm/damon/vaddr: respect folio end for DAMOS_MIGRATE_{HOT,COLD} Date: Tue, 1 Sep 2026 06:18:46 -0700 Message-ID: <20260901131850.98037-6-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260901131850.98037-1-sj@kernel.org> References: <20260901131850.98037-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 485674000B X-Stat-Signature: u4pja543r6c7trf3qi5hurb7rqrwry1r X-HE-Tag: 1788268741-950669 X-HE-Meta: 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 KR1c9xMQ F3hpq04696bcI4IFCYQ5XWWuu7igZ9iWfD/R3owYEMX9C/hS+xIeA5vNY5bA9FYdkQfQOWx/NjvTjj2NoqmrK3mIDHTYkA4SOtMo8AYwOJhTASX28gpGVqcYiYuV+prwqgQBmeBqpYbZUieeiW/4Vgi6M1h8iyG9MesmjYflM+Z2lKPZO9pX+lx4q+fnG6NPWRByaTZ53EOv8OUQ/HL61tsPkPAbVyp+I74ac5g7N0CzdmeQ4t3dluTg44r8s4KMqq6ivY4QatesBRXCOvEQ81lbJfsGJGV5tiZ141sbOCniR9z7jRRCPCW4owA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: For applying DAMOS_MIGRATE_{HOT,COLD} actions to a region, DAMON virtual address space operation set (vaddr) calls walk_page_range[_vma]() for the region. The pmd walk entry function, namely damon_va_migrate_pmd_entry(), collects folios of addresses of the region in the pmd. It starts from the walking address and advances the address by the size of the folio of the address until it goes out of the pmd or the region. Let's suppose it is for the first pmd of the region, and the region start address is in the middle of a large folio. Also, the next folios are small. Then, some of the next folios could be skipped. Fix the issue by advancing the address to exactly the start address of the next folio. The user impact is that DAMOS action is applied to less than expected amount of memory. Given the best effort nature of DAMON, it is no big problem, but it is clearly a bug that is better to be fixed. The issue was discovered [1] by Sashiko. [1] https://lore.kernel.org/20260514015053.149396-1-sj@kernel.org Fixes: 09efc56a3b1c ("mm/damon/vaddr: consistently use only pmd_entry for damos_migrate") Cc: # 6.19.x Signed-off-by: SJ Park --- mm/damon/vaddr.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c index 4b0b5edf67952..c8c32b2ae0402 100644 --- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -669,6 +669,8 @@ static int damos_va_migrate_pmd_entry(pmd_t *pmd, unsigned long addr, return 0; for (; addr < next; pte += nr, addr += nr * PAGE_SIZE) { + unsigned long page_idx; + nr = 1; ptent = ptep_get(pte); @@ -681,7 +683,8 @@ static int damos_va_migrate_pmd_entry(pmd_t *pmd, unsigned long addr, continue; damos_va_migrate_dests_add(folio, walk->vma, addr, dests, migration_lists); - nr = folio_nr_pages(folio); + page_idx = folio_page_idx(folio, pte_page(ptent)); + nr = folio_nr_pages(folio) - page_idx; } pte_unmap_unlock(start_pte, ptl); return 0; -- 2.47.3