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]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9F12C05027 for ; Wed, 15 Feb 2023 01:33:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E62EA6B0072; Tue, 14 Feb 2023 20:33:30 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E13BB6B0073; Tue, 14 Feb 2023 20:33:30 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CD9DF6B0074; Tue, 14 Feb 2023 20:33:30 -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 B9BEC6B0072 for ; Tue, 14 Feb 2023 20:33:30 -0500 (EST) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 88AF3141070 for ; Wed, 15 Feb 2023 01:33:30 +0000 (UTC) X-FDA: 80467803780.13.B644ACC Received: from mail-lf1-f45.google.com (mail-lf1-f45.google.com [209.85.167.45]) by imf05.hostedemail.com (Postfix) with ESMTP id A2913100011 for ; Wed, 15 Feb 2023 01:33:28 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b="Xd/LxmxL"; spf=pass (imf05.hostedemail.com: domain of stevensd@chromium.org designates 209.85.167.45 as permitted sender) smtp.mailfrom=stevensd@chromium.org; dmarc=pass (policy=none) header.from=chromium.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1676424808; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=+w3LbzPvMWbBgPnILe+wwnZS5ZiKny6OZv0ppYywUgw=; b=yiENF5eBYPwRMA36/3aV21CTWmdUPR97c4VIo0vGF+YZwyFS/H0h0UpIDuKvxjLqQfhHjW 9UIcX6QByC8noE1h99M5sZBtXOeLPFR1LCn2ZgIRL8uHXxKPNe4Psny4L6bIp3ANnQasZl fYjJYwMB4lWCOYzUrI66F52fVk8G+Rc= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b="Xd/LxmxL"; spf=pass (imf05.hostedemail.com: domain of stevensd@chromium.org designates 209.85.167.45 as permitted sender) smtp.mailfrom=stevensd@chromium.org; dmarc=pass (policy=none) header.from=chromium.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1676424808; a=rsa-sha256; cv=none; b=RXzy1/T6d9ur6LtnMwG4tSneP+LQUuaN2bIiS2iSOnxb2Q2MNbESfLq2NZbFjxD786fIIx +dDEeK25wrYM1Kh6LsAKH8YIl6zOZlqFNxocwNkuVJ0Reo2sEiZPCTJh2ArQ/K09TnyH/Z j0dniTWGtcLhnLJYN1vYefuChLVJg9s= Received: by mail-lf1-f45.google.com with SMTP id bp15so25771731lfb.13 for ; Tue, 14 Feb 2023 17:33:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=+w3LbzPvMWbBgPnILe+wwnZS5ZiKny6OZv0ppYywUgw=; b=Xd/LxmxL18xkn4GKKw+kk7nmN9AhtdRkFtuyCLu5gaPLEeY4wMTyXXr6/OJTD5jDUW j4yLBrPdNX1ZSPZxQfJ3d9d5ue5mXWNb5pzwRS+1tzEu+Ue9qu7VqJW4s8Yheq4vMVnG K8Qu6JmM1GXlNcprcCCPy0t2SGKaLfdDfp/Sk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=+w3LbzPvMWbBgPnILe+wwnZS5ZiKny6OZv0ppYywUgw=; b=qB5yYsL7qd1ol20pjgXYVQhziygqrWRHPahyMvrUp55yUYK9dix9SuhxEnO2St52oG G+XmTJab8pm37fE508k3KiUh5gp46etafWL15h7r/7dZdnAJ3LtkidYjSFhjbT2/DCqn ZGhjlBVeuIHjPp/5cB4CyvAuKlf0fcDGU3zUnb7bXCZehknjBrie82gbR/A1biOtUKl3 QsqP72iDnDguudnRrB71HruPuVrqiJ/ispDhFuOEmUdQCA5CYYeYTHfqDCl3ZlImJBQn 5FMOAK0/pBslD1okaHbwWMB9z38IlKLCIi7a+w3Se8/9LUyXm7lq+xKMB8uvvr5plVEO fvqw== X-Gm-Message-State: AO0yUKUifa6YjzriY4/0CfVqFTRuWAsLa5QwObfBsd7sYEhOMUgvji/x 0TCigPIHUgxQmlGH1ri/Z3/Fd439D/SNuD+SGtqTLg== X-Google-Smtp-Source: AK7set8TzUas9M+ScnKwXa648gIhE0hdrmRXlNPvZPSxcsb71Aal/1Q2wrlPhyHfQxfYupVzc3m1smfnLm4FF/3jdyk= X-Received: by 2002:ac2:5296:0:b0:4db:266c:433b with SMTP id q22-20020ac25296000000b004db266c433bmr32291lfm.1.1676424806799; Tue, 14 Feb 2023 17:33:26 -0800 (PST) MIME-Version: 1.0 References: <20230214075710.2401855-1-stevensd@google.com> In-Reply-To: From: David Stevens Date: Wed, 15 Feb 2023 10:33:15 +0900 Message-ID: Subject: Re: [PATCH 1/2] mm/khugepaged: set THP as uptodate earlier for shmem To: Matthew Wilcox Cc: linux-mm@kvack.org, Peter Xu , Andrew Morton , "Kirill A . Shutemov" , Yang Shi , David Hildenbrand , Hugh Dickins , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: A2913100011 X-Stat-Signature: twddcugfddi974mpiwyeexyartjxu4x7 X-Rspam-User: X-HE-Tag: 1676424808-33620 X-HE-Meta: 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 FHUNbPra w1yKJrKpGw9/7WWEZ0GosQ4oTxeF6yJ1lTOq37zgxluFMKbb2M/M/QMC0Gj2rQJ1HoNVOpUWCijw8NhKvEUTdZ+FQcP76ms9R9FMurrwOUHM+xHknT1JA3aOTZ/oIlzMIRKEViffqa28ZBegZ6ju9UsZv7IjNS69/ngw3rHnIBtXuA00reuCYbuaQm9EhQam5lna0667JLksMtYW+shHqT+zmy30rFiwRm79Znu24ldmrCXUbd5mhOVJlL29C+G50F3aZkmhw4b5Cln/2TuhaAed98w4zK1dTs1dy6XBPvUNIloE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Feb 15, 2023 at 12:44 AM Matthew Wilcox wrote: > > On Tue, Feb 14, 2023 at 04:57:09PM +0900, David Stevens wrote: > > /* > > - * At this point the hpage is locked and not up-to-date. > > - * It's safe to insert it into the page cache, because nobody would > > - * be able to map it or use it in another way until we unlock it. > > + * Mark hpage as up-to-date before inserting it into the page cache to > > + * prevent it from being mistaken for an fallocated but unwritten page. > > + * Inserting the unfinished hpage into the page cache is safe because > > + * it is locked, so nobody can map it or use it in another way until we > > + * unlock it. > > No, that's not true. The data has to be there before we mark it > uptodate. See filemap_get_pages() for example, used as part of > read(). We don't lock the page unless we need to bring it uptodate > ourselves. I've been focusing on the shmem case for collapse_file and forgot to think about the !is_shmem case. As far as I could tell, shmem doesn't use filemap_get_pages() and everything else in filemap.c/shmem.c that checks folio_test_uptodate also locks the folio. But yeah, this would break the !is_shmem case and is kind of sketchy anyway. I'll put together a better patch. -David