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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 14676C4363A for ; Mon, 5 Oct 2020 16:20:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DFCD4206DD for ; Mon, 5 Oct 2020 16:20:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728984AbgJEQU4 (ORCPT ); Mon, 5 Oct 2020 12:20:56 -0400 Received: from mx2.suse.de ([195.135.220.15]:41670 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726638AbgJEQUz (ORCPT ); Mon, 5 Oct 2020 12:20:55 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id E14F0AD2C; Mon, 5 Oct 2020 16:20:53 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id B30DC1E12F3; Mon, 5 Oct 2020 18:20:53 +0200 (CEST) Date: Mon, 5 Oct 2020 18:20:53 +0200 From: Jan Kara To: Josh Triplett Cc: Linus Torvalds , Theodore Ts'o , Andreas Dilger , Jan Kara , Linux Kernel Mailing List , linux-ext4@vger.kernel.org Subject: Re: ext4 regression in v5.9-rc2 from e7bfb5c9bb3d on ro fs with overlapped bitmaps Message-ID: <20201005162053.GG4225@quack2.suse.cz> References: <20201005081454.GA493107@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201005081454.GA493107@localhost> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 05-10-20 01:14:54, Josh Triplett wrote: > Ran into an ext4 regression when testing upgrades to 5.9-rc kernels: > > Commit e7bfb5c9bb3d ("ext4: handle add_system_zone() failure in > ext4_setup_system_zone()") breaks mounting of read-only ext4 filesystems > with intentionally overlapping bitmap blocks. > > On an always-read-only filesystem explicitly marked with > EXT4_FEATURE_RO_COMPAT_SHARED_BLOCKS, prior to that commit, it's safe to > point all the block and inode bitmaps to a single block of all 1s, > because a read-only filesystem will never allocate or free any blocks or > inodes. > > However, after that commit, the block validity check rejects such > filesystems with -EUCLEAN and "failed to initialize system zone (-117)". > This causes systems that previously worked correctly to fail when > upgrading to v5.9-rc2 or later. > > This was obviously a bugfix, and I'm not suggesting that it should be > reverted; it looks like this effectively worked by accident before, > because the block_validity check wasn't fully functional. However, this > does break real systems, and I'd like to get some kind of regression fix > in before 5.9 final if possible. I think it would suffice to make > block_validity default to false if and only if > EXT4_FEATURE_RO_COMPAT_SHARED_BLOCKS is set. > > Does that seem like a reasonable fix? > > Here's a quick sketch of a patch, which I've tested and confirmed to > work: > > ----- 8< ----- > Subject: [PATCH] Fix ext4 regression in v5.9-rc2 on ro fs with overlapped bitmaps > > Commit e7bfb5c9bb3d ("ext4: handle add_system_zone() failure in > ext4_setup_system_zone()") breaks mounting of read-only ext4 filesystems > with intentionally overlapping bitmap blocks. > > On an always-read-only filesystem explicitly marked with > EXT4_FEATURE_RO_COMPAT_SHARED_BLOCKS, prior to that commit, it's safe to > point all the block and inode bitmaps to a single block of all 1s, > because a read-only filesystem will never allocate or free any blocks or > inodes. > > However, after that commit, the block validity check rejects such > filesystems with -EUCLEAN and "failed to initialize system zone (-117)". > This causes systems that previously worked correctly to fail when > upgrading to v5.9-rc2 or later. > > Fix this by defaulting block_validity to off when > EXT4_FEATURE_RO_COMPAT_SHARED_BLOCKS is set. > > Signed-off-by: Josh Triplett > Fixes: e7bfb5c9bb3d ("ext4: handle add_system_zone() failure in ext4_setup_system_zone()") The patch looks fine to me. Thanks for fixing this and for educating me about the feature :) You can add: Reviewed-by: Jan Kara Honza > --- > fs/ext4/ext4.h | 2 ++ > fs/ext4/super.c | 3 ++- > 2 files changed, 4 insertions(+), 1 deletion(-) > > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h > index 523e00d7b392..7874028fa864 100644 > --- a/fs/ext4/ext4.h > +++ b/fs/ext4/ext4.h > @@ -1834,6 +1834,7 @@ static inline bool ext4_verity_in_progress(struct inode *inode) > #define EXT4_FEATURE_RO_COMPAT_METADATA_CSUM 0x0400 > #define EXT4_FEATURE_RO_COMPAT_READONLY 0x1000 > #define EXT4_FEATURE_RO_COMPAT_PROJECT 0x2000 > +#define EXT4_FEATURE_RO_COMPAT_SHARED_BLOCKS 0x4000 > #define EXT4_FEATURE_RO_COMPAT_VERITY 0x8000 > > #define EXT4_FEATURE_INCOMPAT_COMPRESSION 0x0001 > @@ -1930,6 +1931,7 @@ EXT4_FEATURE_RO_COMPAT_FUNCS(bigalloc, BIGALLOC) > EXT4_FEATURE_RO_COMPAT_FUNCS(metadata_csum, METADATA_CSUM) > EXT4_FEATURE_RO_COMPAT_FUNCS(readonly, READONLY) > EXT4_FEATURE_RO_COMPAT_FUNCS(project, PROJECT) > +EXT4_FEATURE_RO_COMPAT_FUNCS(shared_blocks, SHARED_BLOCKS) > EXT4_FEATURE_RO_COMPAT_FUNCS(verity, VERITY) > > EXT4_FEATURE_INCOMPAT_FUNCS(compression, COMPRESSION) > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index ea425b49b345..f57a7e966e44 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -3954,7 +3954,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) > else > set_opt(sb, ERRORS_RO); > /* block_validity enabled by default; disable with noblock_validity */ > - set_opt(sb, BLOCK_VALIDITY); > + if (!ext4_has_feature_shared_blocks(sb)) > + set_opt(sb, BLOCK_VALIDITY); > if (def_mount_opts & EXT4_DEFM_DISCARD) > set_opt(sb, DISCARD); > > -- Jan Kara SUSE Labs, CR