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 BA775CD8C85 for ; Thu, 13 Nov 2025 15:30:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F3B138E0006; Thu, 13 Nov 2025 10:30:37 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id EEB848E0002; Thu, 13 Nov 2025 10:30:37 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E01728E0006; Thu, 13 Nov 2025 10:30:37 -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 CA8BF8E0002 for ; Thu, 13 Nov 2025 10:30:37 -0500 (EST) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 6FD431A09E8 for ; Thu, 13 Nov 2025 15:30:37 +0000 (UTC) X-FDA: 84105970914.21.5A7E7F7 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf27.hostedemail.com (Postfix) with ESMTP id 9D3AE40017 for ; Thu, 13 Nov 2025 15:30:35 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=kpEFMGxf; spf=pass (imf27.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@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=1763047835; 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=1iJOtTMVD3vDu1xrrqghzFercbuhhPz6QU4Ku2BIczw=; b=AkKku7al0hTrN3I1z1/t2PradygilWRnRfkzEQBZrQWebtnOv7Fm5zmJF0ezDCbGVsUPYo K5TOv92uy+MrmiNP8mRIpHe8/r3tGNolEUhez+lOiPnLqQY4689/g3F5pppQkaJQaezF8P /Av7oTxGy1lNHYsdpzOQa3THCOsbYCs= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=kpEFMGxf; spf=pass (imf27.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763047835; a=rsa-sha256; cv=none; b=fOIdWBUHxanG9PSHBAEXmp0NPjIQZQ3/n6Q9dGR0iznvPFJQGiuAyexRCY1FgxEYW/UK9X L5U8vCBwYlQHOjVRFkefHI9H8uoo5U3/pzOHau1rKcz1YOAbLYq0u/3USk6yDRnpeB1kqz rKCTaZaliKTrw5Gp6ojGKdxlO4XOz1w= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id A729544122; Thu, 13 Nov 2025 15:30:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B1AAC4CEF7; Thu, 13 Nov 2025 15:30:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763047834; bh=tGGALCCjS204ssR6DDHUnCXjhFK8nMBYVU+owIpKMMg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=kpEFMGxf0CQGJGG9BMrBulPuHLSsbaZmz2F10q+U5lQNVex6ThzpOGw7+DyIt2PnK JV0/5CVAlX2KfTg0ks5PYMUa+Oi5pyphqsK2EErkq7wlNXdUGarSi4HWS75zN5v+Qk G++EoGJzrq+W5oj0gLFTPGyJl7KOSGp9Es1OUOubdrYn6UDDO2ETHBHpwGs1MUe+Jz U8C+XjZX88rViP4mw8W8o3CedxRXAd6OP4hzOp370+Z18EJ7ZxaQk9jfZhrU9mNPmK OUuZT3OTj//qPL0mMpoarjHmHdDHd+blv1yaY7uZfsNvXE+QcomCJPrRBh6t1+NqdA Gy4FgH8ONHsZw== Message-ID: <0c9f5b83-10db-460f-bdee-897396b49838@kernel.org> Date: Thu, 13 Nov 2025 16:30:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm/khugepaged: do synchronous writeback for MADV_COLLAPSE To: "Garg, Shivank" , Matthew Wilcox Cc: Lorenzo Stoakes , Andrew Morton , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Zach O'Keefe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Branden Moore References: <20251110113254.77822-1-shivankg@amd.com> <39c8a4ed-53b5-48e3-baea-f67cc1e8be4f@amd.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 9D3AE40017 X-Stat-Signature: hjh87ngq1ef6araik8sma7z9ddtrpeo8 X-Rspam-User: X-HE-Tag: 1763047835-141951 X-HE-Meta: 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 CBfxnLvb cwMYciLUNbZkZhjwcrWukW6T3+4E2BqdQZ6pyT9SZosvpjuuPhQV0kyfjsqIoHUfKM8ayCMMl/3c57N8vQKM7BEov8m1k3Q3cvfX+Hgi91vGvm/4+vuiosTxX+Jug1qr5mVt6QiXp+Dyv16SYBGL1ApWFLVbfIksuXGz9RV7dSA2yaiz9KARVoAXgqhUUkxA/4hx8O9a0aDyTbiBMhu6UyQCTfbD7NVy7zkd45u8k8FMbsexwMliLmc1cp/K7kbWS7qMvssxy2c0GTH0b4QwdVoR8YSwR966QgxbsoH9Wy4pUDPyyTR49sSCZAA== 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 11.11.25 06:58, Garg, Shivank wrote: > > > On 11/10/2025 7:58 PM, Matthew Wilcox wrote: >> On Mon, Nov 10, 2025 at 07:50:17PM +0530, Garg, Shivank wrote: >>> The issue is copying those binary to a freshly mounted filesystem. >>> The page cache folios remain dirty until background writeback completes. >>> >>> Reproduces 100% for me: fresh XFS/EXT4 mount -> copy binary -> execute -> MADV_COLLAPSE fails. >> >> Yes, but this is an uncommon thing to do. Really, it's the kind of >> thing you do when you're testing something (like, whether ext4 supports >> large folios, and whether that yields a performance improvement). >> It's more reasonable to change userspace than the kernel to solve this >> problem you're having. > > Fair point. > > You're right that this is primarily a testing scenario, though it may also > potentially affect JIT compilers writing executables (also uncommon) but more > research is needed. > > For userspace workarounds, calling fsync() before MADV_COLLAPSE works. Right. But do we want document that any caller of MADV_COLLAPSE should issue an fsync() if MADV_COLLAPSE fails to try again? IMHO this just reveals a problem that might also be triggered in a container that just got downloaded or after upgrading a package, no? -- Cheers David