From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7C6BCE81BBE for ; Mon, 9 Feb 2026 13:07:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A76E06B0005; Mon, 9 Feb 2026 08:07:02 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A247C6B0088; Mon, 9 Feb 2026 08:07:02 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 906476B0089; Mon, 9 Feb 2026 08:07:02 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 7C2566B0005 for ; Mon, 9 Feb 2026 08:07:02 -0500 (EST) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 1E5ED16016F for ; Mon, 9 Feb 2026 13:07:02 +0000 (UTC) X-FDA: 84424943484.29.2F518CB Received: from mail-yx1-f49.google.com (mail-yx1-f49.google.com [74.125.224.49]) by imf16.hostedemail.com (Postfix) with ESMTP id 4F5D118000D for ; Mon, 9 Feb 2026 13:07:00 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=KIvpWnhJ; spf=pass (imf16.hostedemail.com: domain of kartikey406@gmail.com designates 74.125.224.49 as permitted sender) smtp.mailfrom=kartikey406@gmail.com; arc=pass ("google.com:s=arc-20240605:i=1"); dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1770642420; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=HWW2dvpLSF4DVyfBqWuCpyd4sQ2XDuJUQdmIqKmHiRU=; b=x1wjSuhGzOICVUGHfnQ8jv3ZGt2jv3/VXyGh0bZhyK2uhYKN1b4ozOrPqkoi1RxJeEUyuM W6vmJW6lj5YegYdk5RLtDHtFN6WH6XCbLGnvWkXPB2PAxsuoEjEltHfM3NStOzmPVvw7BO 5g7X2lQJyVgekEQtk1O18QMewRJVlVU= ARC-Authentication-Results: i=2; imf16.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=KIvpWnhJ; spf=pass (imf16.hostedemail.com: domain of kartikey406@gmail.com designates 74.125.224.49 as permitted sender) smtp.mailfrom=kartikey406@gmail.com; arc=pass ("google.com:s=arc-20240605:i=1"); dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1770642420; a=rsa-sha256; cv=pass; b=p/y0s8WIxRxOoLL96f5PMm2iVLNsDIEr603aqS3AK0wmfESrh4rnFRjgR6LnGW69VDegS1 5rYeTgj0MeJQYgJ5iXGgADmAOaVlf6XD47G9Q43dlxyCV00qnWU+kZlfIKCLhUWZLLCn+V FEZiQpBaQTELDy5oG0ndPCugN8PX4BU= Received: by mail-yx1-f49.google.com with SMTP id 956f58d0204a3-64ad62a294bso1944000d50.1 for ; Mon, 09 Feb 2026 05:07:00 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1770642419; cv=none; d=google.com; s=arc-20240605; b=lDSz7QvFVmpfSFDT+VenGbjvPq4kdk4ggzVyJkYwRhWpn0+wY5VNs3azT2fzTQM563 6uVwocjlvAaNfzcuyfNHdCuQGmKPnHRuYIoS2i4wzW76mkgp2WUAuNGOSpokWzOSG3hY EGC9oZh6M57w2KJjUdV4vaIhr6XfiAouZsEMFmiHmVbAKiBiVvUFvWibnAqVxks5nYAX GQhbwRwuokzYpMV5wt02IQSs0g4teY8dAI1yutz7w43dKKyt1Y7xhuZp8aWRiCVQKlRl CA/AV+PCY3srUt1bE81wQus2/jih8YMfYhOS3fKuKHd+mYumLQhdTZnbnRyia4QzOlXj RDIw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20240605; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:dkim-signature; bh=HWW2dvpLSF4DVyfBqWuCpyd4sQ2XDuJUQdmIqKmHiRU=; fh=lfiCJPlW3ScS0NPVYe6qv8r76KBXLEJ0jxnL8kmSFKM=; b=cG/T3igcMXSGYdpGmFFU/bLEwiumsrXfGQFqXvo0nb4ruxjL5Rdjq36FNvrBSQ7uQ7 q9Kr1F3ylSMlACpKRbKMJsMeoC1xBZJzF7KSAefODeGmfhPgDUlGJjfpC98ukEPgY6Ih wji54sfvQe3U62NGU8HUn0H4bh1juVO1H0wzwgG3mhVltIE62Jv38qNt1P9VNbl7aFUQ 54MLRVBH0SQ3rIc6n5HxURtH5ksHjf8H9r6C7r79KoaLH2uJCz460XdonFfBr7t+N9aW 8ciokV4iBmsx64IjE7P1xa7ClIvSwcccenZ6dkvkaZ09ReCi8VaxKQxQo6M36U5zIzN8 NPHw==; darn=kvack.org ARC-Authentication-Results: i=1; mx.google.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1770642419; x=1771247219; darn=kvack.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=HWW2dvpLSF4DVyfBqWuCpyd4sQ2XDuJUQdmIqKmHiRU=; b=KIvpWnhJXBgYdEfDpILdtrbiQn9YFLW5g4qVfucQxcvaUTkjhjHqUf7tJChXmysaQw 5mVMp1nBqKyLzZ+G7X9TVKQ5KmRWZ3ev3JinKHYJwdJU0c6q4EV+Sfileybc9EF6Ewci j9qsovvlM/V5NwqYfSgUfHXdTbZywspeuJchpYp5qQVLwNApmL21nYO87xiYidRd2ADo 4JtoS5Fdp7gcdpFld1JKgT6iy4k7I/EbdUOiLjbcatx0+rG4f/QMpuJyvbbBFoT9xHcO A4KPp/HSGyxie9A2UfQEqonDuCMam45+fp74DJIB7QtESucDEzfhpt7NELJDAI0Tarm5 pjrQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1770642419; x=1771247219; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=HWW2dvpLSF4DVyfBqWuCpyd4sQ2XDuJUQdmIqKmHiRU=; b=GJqP8nNk9efmgQ0ju+VuUZkf/IEsqBi2dPYQ/kiHzsua5SFjym4ovmZnbEd4Dz5R5d BO8HRIeAKGpJZCVge7xaNJF/oqjADjelqhabkwhuabmeKY5pq1M7HKUEq+P2Nacn0Zd8 i1lKYqnMDpNYvOf/8k6S5XfEwxIhn8FGoJmT8umczEK5K7+wbLRPVt0Cn0ZMVOH2GOsH egx9zcgFPqSDgYHXw6k5XDD66ZU4ibY0PiDkjS0nnAW67cMWFgGypB0ON3r5QaRKgeCr YtHHLJbJMFA7DHHEu13kcpDgxM1AHd8Mw2JY+H+qv14ghegMlv0o5q270CFgnLxhyWU1 bhHQ== X-Forwarded-Encrypted: i=1; AJvYcCUA9YstmhF7yw/2vlm8PPg51tep3Q/AIDl3cd5LEV0TIm8AjDdFWBqyyI0g78OktZyLw1MVGJ8Utw==@kvack.org X-Gm-Message-State: AOJu0Yw2fr+EPnhN0/v1Z8wSmlwEAa1DNx955Drb9sM0Q2/hd/ytCSjT p1uETTXTs3JXI9RklK3Kro+5BHYxaKQepZLfypSVPxrtzPRcb9JJbAXQDp+lGMfG75LeJnVBAwV w935y+xs1GCCorEP7Xdgzk9MUr5H38OA= X-Gm-Gg: AZuq6aJn0VJrKEFbjFqu1MfN3cMzSlWiCdY4l68YhKY9r+oTIg29vKGc6yFvlWN4CrB /jJkQhpLg67ifnxdcNO+/B9jF3hD4Txrj84lNqSGt1rY1AcG5NRYL4oVTEtBtb8gS/UvXVL/9VN RUsk1qad2oWFALMx9TclsqNfYQSPDEKd8XVm8YM6ULFi4Ls7YOsEn2Zm4zNe8oFdGkOGNYZmHYC byJwC390gq8OxPHkO3tyy85lVkDBs/EteJD31ImO4+/hHyZCWLEKoWxJNf91QxZ3m66lrq2ef65 1XG5iJn3fDqfRiXJO5dms3U1Vh8ks7AnPyMoIQhJAGgmqJyzp/nx6d+1nF3n4E0x5aXWHQU= X-Received: by 2002:a05:690e:4106:b0:64a:db3a:f846 with SMTP id 956f58d0204a3-64adb3af9c3mr4460457d50.85.1770642419041; Mon, 09 Feb 2026 05:06:59 -0800 (PST) MIME-Version: 1.0 References: <20260209033558.22943-1-kartikey406@gmail.com> <0d9cada8-7148-4a5c-a09d-120ef54559d7@kernel.org> In-Reply-To: From: Deepanshu Kartikey Date: Mon, 9 Feb 2026 18:36:47 +0530 X-Gm-Features: AZwV_QjiKYGdWwPkUnVtXKZwmEjXVmwqYV1pe963qiJF8xJEq7WmyxztRDhej7k Message-ID: Subject: Re: [PATCH] mm: thp: Deny THP for guest_memfd and secretmem in file_thp_enabled() To: "David Hildenbrand (Arm)" Cc: akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, ackerleytng@google.com, seanjc@google.com, pbonzini@redhat.com, michael.roth@amd.com, vannapurve@google.com, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, syzbot+33a04338019ac7e43a44@syzkaller.appspotmail.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 4F5D118000D X-Stat-Signature: 1fwms7hu4j66tpm7caou44yj987snh4a X-Rspam-User: X-HE-Tag: 1770642420-117063 X-HE-Meta: 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 Wsl6SDXs luhE87+NIpJgqZ3RIjXET9Sej+j1SIVTTP5Yqh5mQivUJIC+WWjCQSUi8vV/xj0rSbON43USFu0oa8Pw1ngXAbIPhuSbVB/0ddpnkAuzy1FgiY+UAo6vk/W3OW5GOaO5Tffk8bChTNP5oEZ67+rS7kcNdm4LdVmGmIwylhMzWa+URgJZvnS3YcyMYRW91PK1uZUHOBXMebj4HiouKYjv2AA33uiggBrqzSc+Y08H9w2b/UuM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Feb 9, 2026 at 4:12=E2=80=AFPM David Hildenbrand (Arm) wrote: > > > Maybe introduce a AS_NO_READ_ONLY_THP_FOR_FS, which we can just easily > > rip out along with CONFIG_READ_ONLY_THP_FOR_FS later? > > On second thought, why do we pass the > > !inode_is_open_for_write(inode) > > in file_thp_enabled()? > > Isn't that the main problem for these memfd things? > > Maybe a get_write_access() is missing somewhere? > Hi David, Thanks for the suggestion. I looked into the get_write_access() path. Both guest_memfd and secretmem use alloc_file_pseudo() which skips calling get_write_access(), so i_writecount stays 0. That's why file_thp_enabled() sees them as read-only files. We could add get_write_access() after alloc_file_pseudo() in both, but I think that would be a hack rather than a proper fix: - i_writecount has a specific semantic: tracking how many fds have the file open for writing. We'd be bumping it just to influence file_thp_enabled() behavior. - It doesn't express the actual intent. The real issue is that CONFIG_READ_ONLY_THP_FOR_FS was never meant for pseudo-filesystem backed files. I think the AS_NO_READ_ONLY_THP_FOR_FS flag you suggested earlier is the cleaner approach. It is explicit, has no side effects, and is easy to rip out when CONFIG_READ_ONLY_THP_FOR_FS goes away. Here is the diff: diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index ec442af3f886..23f559fc1a4c 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -211,6 +211,7 @@ enum mapping_flags { AS_KERNEL_FILE =3D 10, /* mapping for a fake kernel file that sh= ouldn't account usage to user cgroups */ AS_NO_DATA_INTEGRITY =3D 11, /* no data integrity guarantees */ + AS_NO_READ_ONLY_THP_FOR_FS =3D 12, /* Bits 16-25 are used for FOLIO_ORDER */ AS_FOLIO_ORDER_BITS =3D 5, AS_FOLIO_ORDER_MIN =3D 16, diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 40cf59301c21..4bdda92ce01e 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -94,6 +94,9 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma) inode =3D file_inode(vma->vm_file); + if (test_bit(AS_NO_READ_ONLY_THP_FOR_FS, &inode->i_mapping->flags)) + return false; + return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); } diff --git a/mm/secretmem.c b/mm/secretmem.c index edf111e0a1bb..56d93a74f5fc 100644 --- a/mm/secretmem.c +++ b/mm/secretmem.c @@ -205,7 +205,8 @@ static struct file *secretmem_file_create(unsigned long flags) mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); mapping_set_unevictable(inode->i_mapping); + set_bit(AS_NO_READ_ONLY_THP_FOR_FS, &inode->i_mapping->flags); inode->i_op =3D &secretmem_iops; inode->i_mapping->a_ops =3D &secretmem_aops; diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index fdaea3422c30..b93a324c81bd 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -597,6 +597,7 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags) inode->i_size =3D size; mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); mapping_set_inaccessible(inode->i_mapping); + set_bit(AS_NO_READ_ONLY_THP_FOR_FS, &inode->i_mapping->flags); /* Unmovable mappings are supposed to be marked unevictable as well= . */ WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping)); Please let me know if this looks good and I will send a formal v2. Thanks, Deepanshu