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 AF61F4A92D7; Tue, 8 Sep 2026 13:52:06 +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=1788875541; cv=none; b=OT7swWNJxtWN1hKPNCdUOKEMWm3wmrXDwjmi1rQGTP4/Z0jHfBMvsa+xR97Nj5W36Z7xL53Lm/o0+nJ/pH+LafkpN19CaPZeNCKxUM/v6UGgmiUKh9gfjAoDytKdzXinw8DkYzpyE4f7Jsn5H3mTDVbiExOMxdug9BVTZRHxC9A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788875541; c=relaxed/simple; bh=LgpzZwApGv4Mf3DVIQPh9CC2QnA5d+vuXcWDfFntOAg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iUPObOhl8rlYJTmNRY3PAobOEQPY5HJvzSTFE3MDSwLQD6iCL7LCTIlqYYnFXoAyBdJ4fCn/Peysr4cI1gEx3ahZY+y/uUyflaGFaguS0IdBi/BdBEzsvjZq0jcW83vcbwpzXo51k0cAMsJv8H7fdYmkc8MQeiHGytcEOw7bzyE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OMph5lxd; 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="OMph5lxd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4AC801F00A3F; Tue, 8 Sep 2026 13:52:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788875524; bh=AChODC5AHZLUdfC+ioRgIkad6KpONv/acCA4JtBhMak=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=OMph5lxdwJPFP27MCU5ckrGtAumdEQ53z1H3ThxtpdEwMOOIpqKEJUuSpfL+ejXL4 I/+huYYYGxVpn2d5Q1DcUtlw7rlZ2IU0C5KErJIsm2i2qYU/TAjg+Ta0otZloeIdm6 GkPabVyGquEO4w29MHJui6yuNwFjVSfkIYMhy8YNxgZRoVQ9Tf80ks3n45prLoeMbu eEuMVzLrteuNpqsCd1daSvIEHkMg86PHi4ss2sRY5Fp2PGCan1Yo3j1TisitL9KGaf TD/okaz5/bW1iwY2fLJTnykbuw+EtfphToMcCVl1NOEthVd+0ZPUfLsrzcYaZQQoox WoxJLRbo8QQZQ== From: SJ Park To: Andrew Morton Cc: Krishna Iyer , SJ Park , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v3 2/3] mm/damon/ops-common: handle hugetlb folios in folio mkold/young rmap walkers Date: Tue, 8 Sep 2026 06:51:54 -0700 Message-ID: <20260908135156.97481-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260908135156.97481-1-sj@kernel.org> References: <20260908135156.97481-1-sj@kernel.org> Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Krishna Iyer damon_folio_mkold_one() and damon_folio_young_one() assume the folios they walk are mapped by normal PTEs or THP PMDs. When the folio is a hugetlb folio, page_vma_mapped_walk() returns the huge PTE in pvmw.pte with its page table lock held, but the walkers treat it as a normal PTE: they read and age it with PAGE_SIZE-granularity helpers, which is wrong for huge PTEs (up to PUD level), and notify secondary MMUs for only PAGE_SIZE of the mapping. Add hugetlb branches to both walkers. The mkold walker reuses damon_hugetlb_mkold(), which the virtual address space operations set has been using for hugetlb aging: it clears the young bit of the huge PTE via set_huge_pte_at() and calls mmu_notifier_clear_young() spanning the whole huge page size. The young walker gets an equivalent new helper, damon_hugetlb_young(), which reads the huge PTE with huge_ptep_get() and consults the page idle flag and mmu_notifier_test_young() like the existing PTE branch. Locking mirrors what page_vma_mapped_walk() provides: the huge PTE's page table lock is held inside the walk, and for shared hugetlb mappings (the only ones subject to huge PMD sharing), rmap_walk_file() already holds i_mmap_rwsem, satisfying hugetlb_walk()'s locking requirements. This is currently dead code: both rmap walkers are only reachable through damon_get_folio(), which rejects hugetlb folios since they are not on the LRU lists. A following commit will let the physical address space monitoring primitives opt in to hugetlb folios. Link: https://lore.kernel.org/20260902025700.17975-3-kiyer@crusoe.ai Cc: Andrew Morton Assisted-by: Claude:claude-fable-5 Signed-off-by: Krishna Iyer Reviewed-by: SJ Park Signed-off-by: SJ Park --- mm/damon/ops-common.c | 61 +++++++++++++++++++++++++++++++++---------- 1 file changed, 47 insertions(+), 14 deletions(-) diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c index 995cc1f3b9f32..349e1604cc1b1 100644 --- a/mm/damon/ops-common.c +++ b/mm/damon/ops-common.c @@ -205,10 +205,15 @@ static bool damon_folio_mkold_one(struct folio *folio, while (page_vma_mapped_walk(&pvmw)) { addr = pvmw.address; - if (pvmw.pte) - damon_ptep_mkold(pvmw.pte, vma, addr); - else + if (pvmw.pte) { + if (folio_test_hugetlb(folio)) + damon_hugetlb_mkold(pvmw.pte, vma->vm_mm, vma, + addr); + else + damon_ptep_mkold(pvmw.pte, vma, addr); + } else { damon_pmdp_mkold(pvmw.pmd, vma, addr); + } } return true; } @@ -233,27 +238,55 @@ void damon_folio_mkold(struct folio *folio) } +#ifdef CONFIG_HUGETLB_PAGE +static bool damon_hugetlb_young(pte_t *pte, struct vm_area_struct *vma, + unsigned long addr, struct folio *folio) +{ + pte_t entry = huge_ptep_get(vma->vm_mm, addr, pte); + + return (pte_present(entry) && pte_young(entry)) || + !folio_test_idle(folio) || + mmu_notifier_test_young(vma->vm_mm, addr); +} +#else +static bool damon_hugetlb_young(pte_t *pte, struct vm_area_struct *vma, + unsigned long addr, struct folio *folio) +{ + return false; +} +#endif /* CONFIG_HUGETLB_PAGE */ + +static bool damon_pte_young(pte_t *pte, struct vm_area_struct *vma, + unsigned long addr, struct folio *folio) +{ + pte_t entry = ptep_get(pte); + + /* + * PFN swap PTEs, such as device-exclusive ones, that actually map + * pages are "old" from a CPU perspective. The MMU notifier takes care + * of any device aspects. + */ + return (pte_present(entry) && pte_young(entry)) || + !folio_test_idle(folio) || + mmu_notifier_test_young(vma->vm_mm, addr); +} + static bool damon_folio_young_one(struct folio *folio, struct vm_area_struct *vma, unsigned long addr, void *arg) { bool *accessed = arg; DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, addr, 0); - pte_t pte; *accessed = false; while (page_vma_mapped_walk(&pvmw)) { addr = pvmw.address; if (pvmw.pte) { - pte = ptep_get(pvmw.pte); - - /* - * PFN swap PTEs, such as device-exclusive ones, that - * actually map pages are "old" from a CPU perspective. - * The MMU notifier takes care of any device aspects. - */ - *accessed = (pte_present(pte) && pte_young(pte)) || - !folio_test_idle(folio) || - mmu_notifier_test_young(vma->vm_mm, addr); + if (folio_test_hugetlb(folio)) + *accessed = damon_hugetlb_young(pvmw.pte, vma, + addr, folio); + else + *accessed = damon_pte_young(pvmw.pte, vma, + addr, folio); } else { #ifdef CONFIG_TRANSPARENT_HUGEPAGE pmd_t pmd = pmdp_get(pvmw.pmd); -- 2.47.3