From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EDAFA175A93; Sun, 2 Aug 2026 16:26:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785688004; cv=none; b=VwOhAUEknjxJEZQwMAQncTAKy4cKrxjyIjcAzY00ralVG2yw4kjhQIlodxe9fA56oaTGgPVdP2X+gvQsWX3JN1rpm/2uVZz2m+uU/cpm07McS6yk41/iKnMyuexIJp4dgirupCgY8I3Npziw1dW5KdlNNPFuQXAlbLQEm+RmRPw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785688004; c=relaxed/simple; bh=6Z73CbNxQYTOYNM3TzN9z5SgCwrzw1We6fTUP5ae8l4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=toUcb8sk02dqgMS9Hmbs7uccKzZd7Q+wRuPYYGNdnY6Wht9IkwV5GoTaKI6rps+PwnTO6iRz9voSic0Qkhevce69oQamX3p0QWY3jf8bAIPr7kMlBu8IJdjcAImMA/BQXmpqFSprNMrmT7+q2UpOs6PhH+LaqV7D373D+eqJNcM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UHv5cTEZ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UHv5cTEZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 57BCE1F00A3E; Sun, 2 Aug 2026 16:26:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785688002; bh=SLM/iGuOERBTFxu8mql/4ATf4p59p9Me6R2GTZoj17M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=UHv5cTEZKzhRB7KsY5VAqfOxGEnCzIj6KjzB0a08BwYuiVUZm5dUk3A9CQ6IYXwd7 zKYys125rvcGQqMNhi9zD0aoOaZULn3BZAzEYWybMJEHkYC01ydwu7vj/IeEoLuRKG mTyRuK7EF0pbeTrTAcyX2qbHeMrRsnXkp9FpzACFFHklhZr/RrisibHGmEAd/0KyN9 r4v6hmC4t+5ccvvw8aBeGaUR0mHF4A9TsCnPrlzyjSybliWNZa8oeC2V+00ipZ4oII C2MWXntanRysslwPs0u5qSFKfLPZBF6jJzOrg/ZdZvt2RBUUD1gADaAiqBEL6W7Kyu 0P/vWXnFhoBsQ== From: SJ Park To: Cc: SJ Park , stable@vger.kernel.org, Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v1.1 6/9] mm/damon/vaddr: respect folio end for DAMOS_MIGRATE_{HOT,COLD} Date: Sun, 2 Aug 2026 09:26:27 -0700 Message-ID: <20260802162631.90304-7-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260802162631.90304-1-sj@kernel.org> References: <20260802162631.90304-1-sj@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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