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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 1164DC433E0 for ; Tue, 22 Dec 2020 15:19:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D79CD22B2B for ; Tue, 22 Dec 2020 15:19:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727872AbgLVPTZ (ORCPT ); Tue, 22 Dec 2020 10:19:25 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:42791 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727792AbgLVPTY (ORCPT ); Tue, 22 Dec 2020 10:19:24 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608650277; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=9tTFkFhqQiFvkcjFjc4tkOpbQPJev2vnoHc/ozrwHws=; b=Uxe4+pUvEpPH4bN6Ey47ytxc2em1+y0AT2HgNmcsN25eilKXQxQwH4daFAgTjt7m6nYSlo J2liz7zV0yJnMKCv63f/D1sqLbp+LmH+PrZAVKPXX/XKZbJUzMf4hRBq7noiPxHTCvOHOq rwqe1cSA3kh6kKFPwSLKmpK3pZhPql0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-267-Xve2CONNOLCdr03yvpH2uQ-1; Tue, 22 Dec 2020 10:17:55 -0500 X-MC-Unique: Xve2CONNOLCdr03yvpH2uQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 85EB1107ACE4; Tue, 22 Dec 2020 15:17:53 +0000 (UTC) Received: from horse.redhat.com (ovpn-114-207.rdu2.redhat.com [10.10.114.207]) by smtp.corp.redhat.com (Postfix) with ESMTP id 10F9C1971C; Tue, 22 Dec 2020 15:17:53 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 934A0220BCF; Tue, 22 Dec 2020 10:17:52 -0500 (EST) Date: Tue, 22 Dec 2020 10:17:52 -0500 From: Vivek Goyal To: NeilBrown Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-unionfs@vger.kernel.org, jlayton@kernel.org, amir73il@gmail.com, sargun@sargun.me, miklos@szeredi.hu, willy@infradead.org, jack@suse.cz, neilb@suse.com, viro@zeniv.linux.org.uk, hch@lst.de Subject: Re: [PATCH 1/3] vfs: Do not ignore return code from s_op->sync_fs Message-ID: <20201222151752.GA3248@redhat.com> References: <20201221195055.35295-1-vgoyal@redhat.com> <20201221195055.35295-2-vgoyal@redhat.com> <878s9qmy68.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <878s9qmy68.fsf@notabene.neil.brown.name> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 22, 2020 at 12:23:11PM +1100, NeilBrown wrote: [...] > > diff --git a/fs/sync.c b/fs/sync.c > > index 1373a610dc78..b5fb83a734cd 100644 > > --- a/fs/sync.c > > +++ b/fs/sync.c > > @@ -30,14 +30,18 @@ > > */ > > static int __sync_filesystem(struct super_block *sb, int wait) > > { > > + int ret, ret2; > > + > > if (wait) > > sync_inodes_sb(sb); > > else > > writeback_inodes_sb(sb, WB_REASON_SYNC); > > > > if (sb->s_op->sync_fs) > > - sb->s_op->sync_fs(sb, wait); > > - return __sync_blockdev(sb->s_bdev, wait); > > + ret = sb->s_op->sync_fs(sb, wait); > > + ret2 = __sync_blockdev(sb->s_bdev, wait); > > + > > + return ret ? ret : ret2; > > I'm surprised that the compiler didn't complain that 'ret' might be used > uninitialized. Indeed. That "ret" can be used uninitialized. Here is the fixed patch. Subject: vfs: Do not ignore return code from s_op->sync_fs Current implementation of __sync_filesystem() ignores the return code from ->sync_fs(). I am not sure why that's the case. Ignoring ->sync_fs() return code is problematic for overlayfs where it can return error if sync_filesystem() on upper super block failed. That error will simply be lost and sycnfs(overlay_fd), will get success (despite the fact it failed). Al Viro noticed that there are other filesystems which can sometimes return error in ->sync_fs() and these errors will be ignored too. fs/btrfs/super.c:2412: .sync_fs = btrfs_sync_fs, fs/exfat/super.c:204: .sync_fs = exfat_sync_fs, fs/ext4/super.c:1674: .sync_fs = ext4_sync_fs, fs/f2fs/super.c:2480: .sync_fs = f2fs_sync_fs, fs/gfs2/super.c:1600: .sync_fs = gfs2_sync_fs, fs/hfsplus/super.c:368: .sync_fs = hfsplus_sync_fs, fs/nilfs2/super.c:689: .sync_fs = nilfs_sync_fs, fs/ocfs2/super.c:139: .sync_fs = ocfs2_sync_fs, fs/overlayfs/super.c:399: .sync_fs = ovl_sync_fs, fs/ubifs/super.c:2052: .sync_fs = ubifs_sync_fs, Hence, this patch tries to fix it and capture error returned by ->sync_fs() and return to caller. I am specifically interested in syncfs() path and return error to user. I am assuming that we want to continue to call __sync_blockdev() despite the fact that there have been errors reported from ->sync_fs(). So this patch continues to call __sync_blockdev() even if ->sync_fs() returns an error. Al noticed that there are few other callsites where ->sync_fs() error code is being ignored. sync_fs_one_sb(): For this it seems desirable to ignore the return code. dquot_disable(): Jan Kara mentioned that ignoring return code here is fine because we don't want to fail dquot_disable() just beacuse caches might be incoherent. dquot_quota_sync(): Jan thinks that it might make some sense to capture return code here. But I am leaving it untouched for now. When somebody needs it, they can easily fix it. Signed-off-by: Vivek Goyal --- fs/sync.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) Index: redhat-linux/fs/sync.c =================================================================== --- redhat-linux.orig/fs/sync.c 2020-12-22 09:56:04.543483440 -0500 +++ redhat-linux/fs/sync.c 2020-12-22 10:01:28.560483440 -0500 @@ -30,14 +30,18 @@ */ static int __sync_filesystem(struct super_block *sb, int wait) { + int ret = 0, ret2; + if (wait) sync_inodes_sb(sb); else writeback_inodes_sb(sb, WB_REASON_SYNC); if (sb->s_op->sync_fs) - sb->s_op->sync_fs(sb, wait); - return __sync_blockdev(sb->s_bdev, wait); + ret = sb->s_op->sync_fs(sb, wait); + ret2 = __sync_blockdev(sb->s_bdev, wait); + + return ret ? ret : ret2; } /*