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 A0D742F8EA3 for ; Fri, 4 Sep 2026 15:13:07 +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=1788534788; cv=none; b=oGveeI7OXQ2BVl5zMcAqQK1GMBAgBArcicQy785TMMuLVfE32UiBfVoCA+GNdTa53c1w/LQQ4f/UiALum/dwyRqyLF7BYYmmeIurTw8O4rfpr3ogM6Pmr04GgShQACc6ymt1W3EwIrgDLg0+Jt4dUwpoiVInJblM2AS6Tz7H524= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788534788; c=relaxed/simple; bh=1c+ecH8uuNYp3IKgpKgpW07tV0l3TB+x9EGP2nGu9ZI=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=prRM045N/ocmFG4b++Zg/59jx4vZEatxfnv+RVbjk59tBywH4iQjQ8aI8S7BhwElYZLv6mMEr0Q1/Cd3Br2yKx2ZegRv7tDkeCxn+g9Usrlk77uH2Hu37znjtfC2RpU5uEpqGpvZBllYPQwFlP70hyEShowAoTKz+1Be+mf1AVE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gS8SMNln; 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="gS8SMNln" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2D08D1F00A3D; Fri, 4 Sep 2026 15:13:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788534787; bh=YTDhqWyU63qquth7ntQA9BiabBhfNeU/n3wjNRNaWCc=; h=From:Date:Subject:To:Cc; b=gS8SMNlnyBJwyDzDX8NtqkSCNTK4xkoeKOCPQuDtlyVCFYf6rYD8kz0s4kFo2o5zq I2xZLrCjbJ7ZadErkGTUjIg5VsYNd2M6a0O39W2bSyNi3JxB5emRqrRFuAuXRgH21l 19Vownn4M/4cBuAP2Tr6DTPDkSuzWY8dZu6SvQ0PWgCl5/ywYVpjpAhWqZtI2Hxhdq qU85lOSH5pcrobw2QGe8H5pQbWvHl98R8m/ir/O3Dr8I41ZmVHzqA73GkDgj+OiaEx fOLsK7UNkVp7nS6hsFPDjP4qhTQcNvzpBqWERrepvcCadG1LYlVv+DOcGk5ujpNzQ0 CScblm/h/YzUQ== From: "Lorenzo Stoakes (ARM)" Date: Fri, 04 Sep 2026 16:12:53 +0100 Subject: [PATCH] mm/madvise: swap in CoW'd MAP_PRIVATE-file mappings on MADV_WILLNEED Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260904-madv-will-need-map-private-v1-1-6b83cc99fcff@kernel.org> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/x3MwQqEIBQF0F+Jt54HplQ0vxKzkLzVg3JEw4Lo3 5OWZ3MuSoiCRN/qoogsSf6+oP5UNC7Wz2BxxaSVblWvDG/WZT5kXdkDrjBwiJLtDq51AwM9dWr sqAQhYpLzzYfffT9GuzzMbAAAAA== X-Change-ID: 20260903-madv-will-need-map-private-125e3e2f70c7 To: Andrew Morton , "Liam R. Howlett" , David Hildenbrand , Vlastimil Babka , Jann Horn Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mike Kaplinskiy , zhaozhengzhuo , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=1694; i=ljs@kernel.org; h=from:subject:message-id; bh=1c+ecH8uuNYp3IKgpKgpW07tV0l3TB+x9EGP2nGu9ZI=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLJm3f+3guFgy/vda766BCzVTUw7GKH9uXvt8upur6Cyi 5dCsln6O0pZGMS4GGTFFFmefxHfHyQSNq/zgr8bzBxWJpAhDFycAjARn02MDE+sf7/kKp7qcblV b4Xbju8bDJuZpTdbvmC5VdXh927RWyZGhgWzjs6/7Dd1qll3pdA3Ab7mlb/VBI5/lZzJ/XzL8i/ yO/gA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Currently MADV_WILLNEED treats file-backed and pure anonymous mappings entirely separately - using POSIX_FADV_WILLNEED (equivalent of a readahead) for the former and a tree walk and swap in to swap cache for the latter. MAP_PRIVATE-file backed mappings straddle the two and currently get treated as if they were purely file-backed, meaning any swapped out private pages remain swapped out. Resolve the issue by explicitly checking for CoW'd MAP_PRIVATE-file backed mappings and performing both walks in this case. Since the logic checks for vma->anon_vma this means un-CoW'd MAP_PRIVATE-file backed mappings retain only the single file walk. Reported-by: Mike Kaplinskiy Closes: https://lore.kernel.org/all/CABeknB_S2XJSHFgnHdgnN0rjzHhH4oQJs_APq9fvxHztQ_pgiA@mail.gmail.com/ Signed-off-by: Lorenzo Stoakes (ARM) --- mm/madvise.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 73c2901b9adb..d0510dd49dde 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -297,10 +297,12 @@ static long madvise_willneed(struct madvise_behavior *madv_behavior) loff_t offset; #ifdef CONFIG_SWAP - if (!file) { + if (!file || (vma_is_cow_mapping(vma) && vma->anon_vma)) { walk_page_range_vma(vma, start, end, &swapin_walk_ops, vma); lru_add_drain(); /* Push any new pages onto the LRU now */ - return 0; + + if (!file) + return 0; } if (shmem_mapping(file->f_mapping)) { --- base-commit: e3b5239afe1b8f0194db7436b17c33e94c1988c4 change-id: 20260903-madv-will-need-map-private-125e3e2f70c7 Best regards, -- Lorenzo Stoakes (ARM)