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 664D810F284C for ; Fri, 27 Mar 2026 16:14:59 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A6D956B0095; Fri, 27 Mar 2026 12:14:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A44DC6B0096; Fri, 27 Mar 2026 12:14:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 982846B0098; Fri, 27 Mar 2026 12:14:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 867976B0095 for ; Fri, 27 Mar 2026 12:14:58 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 2D1F116090E for ; Fri, 27 Mar 2026 16:14:58 +0000 (UTC) X-FDA: 84592341876.30.10884D7 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf19.hostedemail.com (Postfix) with ESMTP id 6850C1A0008 for ; Fri, 27 Mar 2026 16:14:56 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ZYqHZHqo; spf=pass (imf19.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1774628096; 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=d12OfPYOY1zhSu6WUZypvyObYOsxUhXXyZg3eNDRHd0=; b=chIw5nHaXIsP1zeMvJRZNxvB2xTmEDv52VcqeBebDcADlYnW1LYgQhhWoV3mmdaDtm1WqD JbR5sqKkAUxmYBwk7rrZ1h1j5YiCTluWvoq4pgANk9aJd2bz2sDSqMbL7qNdMErJM8MvSi 7/68jZbbaUf2Yu/dSV4fWdpc0AC7iLU= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ZYqHZHqo; spf=pass (imf19.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1774628096; a=rsa-sha256; cv=none; b=eUBaq333pjxX90zvaPKsvMsHqf8B0IxIamOTYKKF/a+X06kAcHe/eTOTRnDYRIEAfqfMCj Eg6bxU8HAGQ46rQbIhEl303TcgwNH+UY8chET4JTgUiGFAgq6uvBSv6fin0LboOICSPbOZ prEAYPN8tu/RFB2aVrsl6fPP8NzC1M8= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 7E90F42A12; Fri, 27 Mar 2026 16:14:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A2C0FC2BCB0; Fri, 27 Mar 2026 16:14:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774628095; bh=zXNUom4JcbcJe5P17bW0VcYg3BF2y3vbuxuAyWXA2Yk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZYqHZHqoR6y2KHbwdL3I4ZDGCUvKQVvkCNilvo9VFfK+sdEwwTjvdXUng8CkB7/R0 y2A0V03w7X6WjHqqd/kgfuhGJBSA3J/q3PjhoVwq2zkB98Ka8b6A5oXju/bsSPygDJ PKUxVg2T7fMjcYFKT6FpqBH5sNByY0nEl3Z5ay7vWhaILcHJEXiefoudbSUOHxvR3A T0ovJe0NHcSU3WmsVuhpWMI9QpGMOnSw7wFCAKv87aJ4oQX4wzMlN60Bslfs6nVHHC DqLMrUA6eTo1ei9iwueDiBgHjCJE9VKB30Fz4xqvTB8jm0kztjIvo6g8oQxdV5olSM t6qw8eZhk8WPg== Date: Fri, 27 Mar 2026 16:14:47 +0000 From: "Lorenzo Stoakes (Oracle)" To: Zi Yan Cc: "Matthew Wilcox (Oracle)" , Song Liu , Chris Mason , David Sterba , Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , David Hildenbrand , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v1 05/10] mm/huge_memory: remove READ_ONLY_THP_FOR_FS from file_thp_enabled() Message-ID: References: <20260327014255.2058916-1-ziy@nvidia.com> <20260327014255.2058916-6-ziy@nvidia.com> <5ac47338-1954-43ce-9984-56d70f7c392f@lucifer.local> <075A4C69-B386-4557-BDAA-4038EB36370D@nvidia.com> <14af57ba-09bc-40ff-812a-b41dfb78a03c@lucifer.local> <59A91369-9BCB-4545-AEF8-083B52998CC3@nvidia.com> <10b04dc8-e155-4a31-84b6-17b302e65c7c@lucifer.local> <52CACB9A-A782-4D11-8B6F-66DA8D345C78@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <52CACB9A-A782-4D11-8B6F-66DA8D345C78@nvidia.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6850C1A0008 X-Stat-Signature: 1agn18kmsn7drz97nwyqpwyh5rwysj1r X-Rspam-User: X-HE-Tag: 1774628096-118869 X-HE-Meta: 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 wwgYcnl/ jpendH48jviHT2fRp4h6BdAfZnBgWjh17g9ENcPH7wB5VXF5OttstgRw7qtmq2bkMtR64/VBhR5ASkZoPZjzGsSH6EjcxQwWdeSBSgD2+oPKFqcM3Aibq2ebn0wkGMdajuUrLUqEEssLEV2q4rJq92l/VkEPO4Nk1+iLIdDbRX9mEPye+3fRyvz7hLyGxV0m7r+wPfbDy5fTNUM/0TOnx+fLl7rYsoreSH+pUTDsuw6aBEQ7Ax27HHTHpPr/VdALsNHwmcs1rQXBPCLR/M1PtE1Lshdh9WOlI0jtZ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Mar 27, 2026 at 12:12:04PM -0400, Zi Yan wrote: > On 27 Mar 2026, at 12:08, Lorenzo Stoakes (Oracle) wrote: > > So actually: > > > > | PF | MADV_COLLAPSE | khugepaged | > > |-----------|---------------|------------| > > large folio fs | ✓ | x | x | > > READ_ONLY_THP_FOR_FS | x | ✓ | ✓ | > > both! | ✓ | ✓ | ✓ | > > > > (Where it's impllied it's a read-only mapping obviously for the later two > > cases.) > > > > Now without READ_ONLY_THP_FOR_FS you're going to: > > > > | PF | MADV_COLLAPSE | khugepaged | > > |-----------|---------------|------------| > > large folio fs | ✓ | x | x | > > large folio + r/o | ✓ | ✓ | ✓ | > > > > And intentionally leaving behind the 'not large folio fs, r/o' case because > > those file systems need to implement large folio support. > > > > I guess we'll regress those users but we don't care? > > Yes. This also motivates FSes without large folio support to add large folio > support instead of relying on READ_ONLY_THP_FOR_FS hack. Ack that's something I can back :) > > > > > I do think all this needs to be spelled out in the commit message though as it's > > subtle. > > > > Turns out this PitA config option is going to kick and scream a bit first before > > it goes... > > Sure. I will shameless steal your tables. Thank you for the contribution. ;) > Haha good I love to spread ASCII art :) Cheers, Lorenzo