From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f52.google.com (mail-wr1-f52.google.com [209.85.221.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AD194223DD1 for ; Wed, 1 Oct 2025 03:25:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759289107; cv=none; b=UZnIH4dY9zRAzT2401Q65Py9BT8HC4YYaZEUPdkzJaMdS9LMr7PyjS20J6S/UB0G5alckahpyJxPdOl4/q8GusOe4Y3Sou/XbkNLWQ98DXKVJeVp9cIcgPQUn37u5x/dYWuqsAWPFp27a1AmY0CR2rSpFmFBcHNXtlrmMj+ddtY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759289107; c=relaxed/simple; bh=Dr/B6xtTWOMKj5bnaH/RzsqdzfSt5NRhxJfFscrnlcg=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=qDEBIaQwAUfffuQ65OLlJoxNfbpHpTMP7gnSNM7+xYk49mMGAZgeJ5lC1xyx/6VQ6mNvlUKYBTm1rUsPeLqYyHIhpQZe/L1LJtYekiZ6i5/1aYoSmbN2AZAkGifDUNt9+Lu/sUd9cbGjerUL3m3iyUeCw8O/x98VTCqT2zkBbLU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.221.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-wr1-f52.google.com with SMTP id ffacd0b85a97d-3ee12a63af1so4357777f8f.1 for ; Tue, 30 Sep 2025 20:25:04 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1759289103; x=1759893903; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=FA57N8DSQvEdDyyKBkxAad4tUYCW8q9ybdMKiaOoC/o=; b=tQoO+OWPiApj67bgGH0tMTW8yxALwwR1CLna1kWVPFXKpCXSW4dprX/3GJRi33qfk0 fLCMsbRYfMMo0KqjFBHb2M2WxkVQk6r0zncxoZcrLhtC6Ml7TCh5+VK4R/r9BlKxo1Sz GGHmx++G92405eluHZABu8hIQSvChR3XMSTaNRzJ1qEDHTWVmVvqMO9zhgEpCaUY4nqF 4GI411kZthDmuZ4t5rINnZiy5aa+pvYYflP5f3ZQZXg2iVYxhX75jUVJnEWjv/5HGtKH xUKkCmDjb3a2FleepJHaPoRPME4byzNrqhNZpkPBYTW6cu+ZPV6Jx5BMvTX52gMn1j/h ohKQ== X-Forwarded-Encrypted: i=1; AJvYcCU7cJlBclCAlJRUzTmgIDrvr/JpZr2Qsshhk1m2ALKOe7nno8Dwjwdin0Zb5VWnwPlqdCWbVseRW5O9F28=@vger.kernel.org X-Gm-Message-State: AOJu0YzWBNdbWHTqG5xuhw7gAeqkxHA91IXlOxeMTZ94QdzGbmqu1nA8 8wyNkwnATjKvAfBAEQHR8Bp5GO/+ZbKZv/8fniK38NN47Gv7p7XqkMUJ X-Gm-Gg: ASbGncsa8oF9tPslMRNfsPwc8KEy8fyWiSCevTPOq4C1LP9BfFFLiNIoyrjpXm8DOWn SBqsGJNW9A81eRWfm/r82lTuubLlf3aZUaYHMk5t1HyLZHid07QjkqCEJIeB0Qp68ewbJnmJLrI ORiPMUGAHPy771x61DPZfGCXUzaP1UoGyi9XUDeYNoFQTI3m0kBMe/OEjumn2csoRavexNRoKwp vZC/Mk2zIsjc217uJldKvZ380vD4bkKzwlqSZ6MLRXlitJEki7qZFu5wzUqTNRfrEH7SVQ3SaG6 xyXm0jAgPSxJRYmo3v9iBjThbv5PQLTKn0EaGLYwgk2CCNeZxHRE4LKHu361ZCjRJTTH38EacLb fKWwMiwNBt3xgjoGBmX6unS61sJXLm3O6afsDH9Q= X-Google-Smtp-Source: AGHT+IFBchqrZzaojHRR/WFRnhqsxmy4IwBajiOP3XpKUmxGFc7GSlwImuIjkfg4UuEYFnWVH5+X+w== X-Received: by 2002:a05:6000:2388:b0:3e7:4697:297a with SMTP id ffacd0b85a97d-425577f5552mr1219739f8f.24.1759289102832; Tue, 30 Sep 2025 20:25:02 -0700 (PDT) Received: from localhost.localdomain ([2a09:0:1:2::301b]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-40fb72fb017sm24993352f8f.3.2025.09.30.20.24.56 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 30 Sep 2025 20:25:02 -0700 (PDT) From: Lance Yang To: akpm@linux-foundation.org Cc: david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, dev.jain@arm.com, hughd@google.com, ioworker0@gmail.com, kirill@shutemov.name, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mpenttil@redhat.com, npache@redhat.com, ryan.roberts@arm.com, ziy@nvidia.com, richard.weiyang@gmail.com, Lance Yang Subject: [PATCH mm-new v2 1/1] mm/khugepaged: abort collapse scan on non-swap entries Date: Wed, 1 Oct 2025 11:22:51 +0800 Message-ID: <20251001032251.85888-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Lance Yang Currently, special non-swap entries (like migration, hwpoison, or PTE markers) are not caught early in hpage_collapse_scan_pmd(), leading to failures deep in the swap-in logic. hpage_collapse_scan_pmd() `- collapse_huge_page() `- __collapse_huge_page_swapin() -> fails! As David suggested[1], this patch skips any such non-swap entries early. If any one is found, the scan is aborted immediately with the SCAN_PTE_NON_PRESENT result, as Lorenzo suggested[2], avoiding wasted work. [1] https://lore.kernel.org/linux-mm/7840f68e-7580-42cb-a7c8-1ba64fd6df69@redhat.com [2] https://lore.kernel.org/linux-mm/7df49fe7-c6b7-426a-8680-dcd55219c8bd@lucifer.local Suggested-by: David Hildenbrand Suggested-by: Lorenzo Stoakes Signed-off-by: Lance Yang --- v1 -> v2: - Skip all non-present entries except swap entries (per David) thanks! - https://lore.kernel.org/linux-mm/20250924100207.28332-1-lance.yang@linux.dev/ mm/khugepaged.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 7ab2d1a42df3..d0957648db19 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1284,7 +1284,23 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, for (addr = start_addr, _pte = pte; _pte < pte + HPAGE_PMD_NR; _pte++, addr += PAGE_SIZE) { pte_t pteval = ptep_get(_pte); - if (is_swap_pte(pteval)) { + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { + ++none_or_zero; + if (!userfaultfd_armed(vma) && + (!cc->is_khugepaged || + none_or_zero <= khugepaged_max_ptes_none)) { + continue; + } else { + result = SCAN_EXCEED_NONE_PTE; + count_vm_event(THP_SCAN_EXCEED_NONE_PTE); + goto out_unmap; + } + } else if (!pte_present(pteval)) { + if (non_swap_entry(pte_to_swp_entry(pteval))) { + result = SCAN_PTE_NON_PRESENT; + goto out_unmap; + } + ++unmapped; if (!cc->is_khugepaged || unmapped <= khugepaged_max_ptes_swap) { @@ -1293,7 +1309,7 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, * enabled swap entries. Please see * comment below for pte_uffd_wp(). */ - if (pte_swp_uffd_wp_any(pteval)) { + if (pte_swp_uffd_wp(pteval)) { result = SCAN_PTE_UFFD_WP; goto out_unmap; } @@ -1304,18 +1320,6 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, goto out_unmap; } } - if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { - ++none_or_zero; - if (!userfaultfd_armed(vma) && - (!cc->is_khugepaged || - none_or_zero <= khugepaged_max_ptes_none)) { - continue; - } else { - result = SCAN_EXCEED_NONE_PTE; - count_vm_event(THP_SCAN_EXCEED_NONE_PTE); - goto out_unmap; - } - } if (pte_uffd_wp(pteval)) { /* * Don't collapse the page if any of the small -- 2.49.0