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 X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C5AB0C4338F for ; Sun, 25 Jul 2021 17:57:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9DA6F604DC for ; Sun, 25 Jul 2021 17:57:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229709AbhGYRQr (ORCPT ); Sun, 25 Jul 2021 13:16:47 -0400 Received: from mail.kernel.org ([198.145.29.99]:49804 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229545AbhGYRQr (ORCPT ); Sun, 25 Jul 2021 13:16:47 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2FCE06052B; Sun, 25 Jul 2021 17:57:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627235837; bh=e/IOT6aLgM/vFCn/0MMYqLC9/0uViRF4ZtqRX35F+sU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=VYXgZljB7L/v8+LISB1zPqkBLZ+KVdE58D8YU92HaY2sNgpnh191qmRSdAcIcf9xr fCG0bnZeif5q/Jol0JhZANiZXv7veDY0bCgaMITJuU8wbJgy6VhOxtby/83Epde6/d wdzpa9GDDhL1A7IJPK1SEHrkPQDdVfoT9Rq/5nh7mDh0+fKqypOZXaDwahKTqZGHi4 aUAcH1jNsgAPZyYQB4UF8D1a97/UnXwAwIL/S+5yZ70lRmAua9TnpX0UL/epsVNYpL yicORP/grKkfV2Z+yysiNyZAnie7wJouR/8OgVFCPne6LxmVjow/UGhZF6dQMhn6o0 6q7tk9egQI7Xw== Date: Sun, 25 Jul 2021 10:57:15 -0700 From: Eric Biggers To: Chao Yu Cc: linux-f2fs-devel@lists.sourceforge.net, Jaegeuk Kim , linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, Satya Tangirala , Changheun Lee , Matthew Bobrowski Subject: Re: [PATCH 3/9] f2fs: rework write preallocations Message-ID: References: <20210716143919.44373-1-ebiggers@kernel.org> <20210716143919.44373-4-ebiggers@kernel.org> <14782036-f6a5-878a-d21f-e7dd7008a285@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <14782036-f6a5-878a-d21f-e7dd7008a285@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Sun, Jul 25, 2021 at 06:50:51PM +0800, Chao Yu wrote: > On 2021/7/16 22:39, Eric Biggers wrote: > > From: Eric Biggers > > > > f2fs_write_begin() assumes that all blocks were preallocated by > > default unless FI_NO_PREALLOC is explicitly set. This invites data > > corruption, as there are cases in which not all blocks are preallocated. > > Commit 47501f87c61a ("f2fs: preallocate DIO blocks when forcing > > buffered_io") fixed one case, but there are others remaining. > > Could you please explain which cases we missed to handle previously? > then I can check those related logic before and after the rework. Any case where a buffered write happens while not all blocks were preallocated but FI_NO_PREALLOC wasn't set. For example when ENOSPC was hit in the middle of the preallocations for a direct write that will fall back to a buffered write, e.g. due to f2fs_force_buffered_io() or page cache invalidation failure. > > > - /* > > - * If force_buffere_io() is true, we have to allocate > > - * blocks all the time, since f2fs_direct_IO will fall > > - * back to buffered IO. > > - */ > > - if (!f2fs_force_buffered_io(inode, iocb, from) && > > - f2fs_lfs_mode(F2FS_I_SB(inode))) > > - goto write; > > We should keep this OPU DIO logic, otherwise, in lfs mode, write dio > will always allocate two block addresses for each 4k append IO. > > I jsut test based on codes of last f2fs dev-test branch. Yes, I had misread that due to the weird goto and misleading comment and translated it into: /* If it will be an in-place direct write, don't bother. */ if (dio && !f2fs_lfs_mode(sbi)) return 0; It should be: if (dio && f2fs_lfs_mode(sbi)) return 0; Do you have a proper explanation for why preallocations shouldn't be done in this case? Note that preallocations are still done for buffered writes, which may be out-of-place as well; how are those different? - Eric