From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f180.google.com (mail-dy1-f180.google.com [74.125.82.180]) (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 5A7DD4279EE for ; Wed, 1 Jul 2026 11:47:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782906454; cv=none; b=XEycOR78asAHGHuS0ZN4pgEaxA64v5AONbb5yoKR3Q7ueISHsFIX+ZZpazmE+O1r8KZNAjXn/Vv5mbA0AmmhSCGa+PvpAv25LTM/szoQsGU0jP99SCOmjDnomkuwAjYaX/axk7WKqretJbg9hZ/ptja2ufnQU02UFhTLfZNuxc4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782906454; c=relaxed/simple; bh=pk1b3RFCvS1kz5GHfFQRutp3IArlWwmoY4XWmITZX2A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Qto2vv8VDPeUuEkYwvmZzC7zBwXD2t8w6LcTiArmdzy1AIwSwkuQpns3pI7DDmzwuSCv3dDu0k2tRnSKNXIhuyd6eS91KO3+ntK7jGoEgGK+y91lCY8CuvAudDY7XSk+WffBQ0bP98CaTdW4oQK84MOcZVx4khRX1NKxhpS5o28= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=ldpGfKK0; arc=none smtp.client-ip=74.125.82.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ldpGfKK0" Received: by mail-dy1-f180.google.com with SMTP id 5a478bee46e88-30cac93dfd7so1322326eec.1 for ; Wed, 01 Jul 2026 04:47:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1782906452; x=1783511252; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=prz2mwcezODKOS8in2sKwxdy9E9jg7GzDEkRG5HC3ao=; b=ldpGfKK0467sYV2GXdS6/CIVSLWKvbGj5tc+OFwwVZ1wxFP+rXRgYiXk3p2zIEm3a4 3DFbO1Nhqum1jfLKTqtN3u7yDlbDSFx6wCw1lXAtYZmIfHjr5UaWHn6csedZxNwXpsWt QTSKUI00IxSDM77uU5g0FVqzVPeFwrxVP6MIyUo0TDbWtuniFwfxef7KbKyfKk+xvDEV z4LhK8m7h13v3sepjdMKWv12vd7qAYEc64f0iYurMkco79hZsLK37cOL0dZnQMZkvfya OPrPceRvaRWLa0Q9stt2/mbw51hyYIOn4quVbXMT0lV7LMHDyMivf6VQViTP9C67LpRw tyrg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782906452; x=1783511252; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=prz2mwcezODKOS8in2sKwxdy9E9jg7GzDEkRG5HC3ao=; b=kC4VP51ui3SlV7PmomsusInBslo8gW9MS9VEC9UJPKlD5909XsyXJA7AAwyteNpvyD qX40tQwn7ywC/x7vg1iwGUL/Bg5lrU+siGoy6XC8B7/31VmACo0Tqqyq3LNX3LNEHmtZ /o88vmX7FU6MgLeHNoMPSNUCqNv/0Bfbtu9jDLZmxebJv30RET3g6l1y4BSJj9Iym5id i1uBCRWBYDpRObc13tMO+hFnQQbZVCvypr4t3tpdOhLKm5Ow+52jlTnDNjQw2J5Wauwk +kSIijJUr3/RgulzDkwSfu0qAjCCiF/bx+2BJ9s5sJKeQi0jnA2axF0QC/bEnlwLHN3q cAfw== X-Gm-Message-State: AOJu0YyQKHfHRNxsV36IIbHpFzXWVNOhbdcmfyGLZ4X654MBRStrwCyo 9zTxH8blHcWwUhbzTqQfrinFIN0a4Mfzlb7iIIzuprWGU23Tbi6M1FnJ X-Gm-Gg: AfdE7ckVSCpBIlnDlmHuFn5xUCQUUdvHwCKFt//VSL3DKCNz4ZgG3JRY2rhq+UBS0G0 c4feyxDv+LilJaroRZ6hdftAUYfr/bdIXMpXMj8Ig9cPWlgp+izi7ZGJGp4kCSmw5hXv0LKDw6p fGbTljUV1XJBQw9dorelQ+GKkAvbGc0mAqQ7UuRy/hoqiWYk5hiokVCeZzgeFie6asd2l8SfDnu 4YFU9Qd86Janvk5v4W3lH7DixA+aTt9wy37XJ/YApmbCd+rpm/h/6MAa3g5xNdhYubs2ZeONi7I uiY7NPeRs+gmtTdpRJ+JBsEdbFZWiAJmHG0bxm4tQLQOxIm+9Ui1Y5wnYFXFSU6NoEXmrV1h8TM wByTAW7aTJQMRFsDygdAj3kPKbIr5zimRvnHdhOIkE0O+KNokKH+xUFBvEGHmRxGQeIsFQroQgB /uQw== X-Received: by 2002:a05:7301:1f0d:b0:304:cd0d:9ea5 with SMTP id 5a478bee46e88-30efe710e66mr1921630eec.7.1782906452417; Wed, 01 Jul 2026 04:47:32 -0700 (PDT) Received: from localhost.localdomain ([2607:f130:0:11a::31]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-30ee327cea7sm22518169eec.31.2026.07.01.04.47.28 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 01 Jul 2026 04:47:32 -0700 (PDT) From: wang lian To: damon@lists.linux.dev, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, sj@kernel.org, gutierrez.asier@huawei-partners.com, daichaobing@sangfor.com.cn, lianux.wang@processmission.com, Wang Lian , Kunwu Chan Subject: [PATCH v2 2/5] mm/khugepaged: add damon_collapse_folio_range() for external callers Date: Wed, 1 Jul 2026 19:47:13 +0800 Message-ID: <20260701114716.56503-3-lianux.mm@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260701114716.56503-1-lianux.mm@gmail.com> References: <20260701114716.56503-1-lianux.mm@gmail.com> 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: Wang Lian Export a thin wrapper around collapse_huge_page() that allows external subsystems such as DAMON to trigger THP collapse on a target address range. Currently restricted to PMD order (HPAGE_PMD_ORDER), since collapse_huge_page() does not yet support arbitrary mTHP orders. The restriction can be relaxed when khugepaged gains mTHP support. The caller must hold a reference to @mm. Do not hold mmap lock: collapse_huge_page() acquires mmap_read_lock for validation, releases it, then acquires mmap_write_lock for the actual collapse. Holding an outer mmap_read_lock would cause a self-deadlock when the same thread attempts the inner mmap_write_lock. Co-developed-by: Kunwu Chan Signed-off-by: Kunwu Chan Signed-off-by: Wang Lian Signed-off-by: Wang Lian --- include/linux/khugepaged.h | 3 +++ mm/khugepaged.c | 39 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 42 insertions(+) diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h index d7a9053ff4fe..6fb8a6857790 100644 --- a/include/linux/khugepaged.h +++ b/include/linux/khugepaged.h @@ -20,6 +20,9 @@ extern bool current_is_khugepaged(void); void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, bool install_pmd); +int damon_collapse_folio_range(struct mm_struct *mm, unsigned long start_addr, + unsigned int target_order); + static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm) { if (mm_flags_test(MMF_VM_HUGEPAGE, oldmm)) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 617bca76db49..0387841ba2e7 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -3272,3 +3272,42 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, return thps == ((hend - hstart) >> HPAGE_PMD_SHIFT) ? 0 : madvise_collapse_errno(last_fail); } + +/** + * damon_collapse_folio_range() - Collapse base pages in range into a THP + * @mm: mm_struct of the target process + * @start_addr: start address (must be order-aligned) + * @target_order: page order of the collapse result (currently only + * HPAGE_PMD_ORDER is supported) + * + * Thin wrapper around collapse_huge_page() for external callers such as + * DAMON. The caller must hold a reference to @mm. Do not hold mmap + * lock: collapse_huge_page() acquires mmap_read_lock for validation, + * releases it, then acquires mmap_write_lock for the collapse. Holding + * an outer mmap_read_lock would self-deadlock. + * + * Return: 0 on success, -EINVAL on bad arguments, negative error from + * madvise_collapse_errno() otherwise. + */ +int damon_collapse_folio_range(struct mm_struct *mm, unsigned long start_addr, + unsigned int target_order) +{ + struct collapse_control cc = { + .is_khugepaged = false, + }; + enum scan_result result; + + if (target_order != HPAGE_PMD_ORDER) { + pr_warn_once("%s: only PMD order (%u) is supported, got %u\n", + __func__, HPAGE_PMD_ORDER, target_order); + return -EINVAL; + } + if (start_addr & ((PAGE_SIZE << target_order) - 1)) + return -EINVAL; + + result = collapse_huge_page(mm, start_addr, 1, 0, &cc, target_order); + if (result == SCAN_SUCCEED) + return 0; + return madvise_collapse_errno(result); +} +EXPORT_SYMBOL_GPL(damon_collapse_folio_range); -- 2.50.1 (Apple Git-155)