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 384BCC4320A for ; Fri, 20 Aug 2021 18:12:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 167D26115A for ; Fri, 20 Aug 2021 18:12:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235644AbhHTSMi (ORCPT ); Fri, 20 Aug 2021 14:12:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:44966 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231757AbhHTSMh (ORCPT ); Fri, 20 Aug 2021 14:12:37 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4CCD0608FE; Fri, 20 Aug 2021 18:11:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1629483119; bh=Ug/nWYFe3aKoUQ5ituPguHYC0Y4myQql1SYX/rV6X0I=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Iw/pdnyA1ONdK54eU3zepv0FOEWjZfqHh/RkIXhlPBxtuC4OmDr9Kk2O1pfyJ4C9M 3h6MZ9qQYAKU97s+TaFb/HaVE95J5ceCxEz7ZqHZhuSHC7CoQauuvQxrufQMZ34JSd jYcc9/nS1IX0yUszV5lG4L8UPYx2BXAgGucNqeQ00P6YdkNfKs9eJOYpoKMW2ARgoN m2ClveBPVxKXayI/GIMjgKYm/m4hn4rxgWaiMDX726PO1vZJunLmoEGljqXGzTbWaq fEqJHXaAA1sCy7qpwRTnSPNiUGQ7y5CXZiWIyMWUmW9AQv7IVRz2iRLKoAXZQAWJZS nKbPOK5SQHcMA== Date: Fri, 20 Aug 2021 11:11:57 -0700 From: Eric Biggers To: Chao Yu Cc: Jaegeuk Kim , Theodore Ts'o , linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] f2fs: remove broken support for allocating DIO writes Message-ID: References: <20210728015154.171507-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Aug 20, 2021 at 05:35:21PM +0800, Chao Yu wrote: > > > > > > > > > > Hmm, I'm still trying to deal with this as a corner case where the writes > > > > > haven't completed due to an error. How about keeping the preallocated block > > > > > offsets and releasing them if we get an error? Do we need to handle EIO right? > > > > > > > > What about the case that CP + SPO following DIO preallocation? User will > > > > encounter uninitialized block after recovery. > > > > > > I think buffered writes as a workaround can expose the last unwritten block as > > > well, if SPO happens right after block allocation. We may need to compromise > > > at certain level? > > > > > > > Freeing preallocated blocks on error would be better than nothing, although note > > that the preallocated blocks may have filled an arbitrary sequence of holes -- > > so simply truncating past EOF would *not* be sufficient. > > > > But really filesystems need to be designed to never expose uninitialized data, > > even if I/O errors or a sudden power failure occurs. It is unfortunate that > > f2fs apparently wasn't designed with that goal in mind. > > > > In any case, I don't think we can proceed with any other f2fs direct I/O > > improvements until this data leakage bug can be solved one way or another. If > > my patch to remove support for allocating writes isn't acceptable and the > > desired solution is going to require some more invasive f2fs surgery, are you or > > Chao going to work on it? I'm not sure there's much I can do here. > > I may have time to take look into the implementation as I proposed above, maybe > just enabling this in FSYNC_MODE_STRICT mode if user concerns unwritten data? > thoughts? > What does this have to do with fsync? - Eric