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Mon, 26 Oct 2026 10:40:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793011247; bh=EP4HK2sAGEG6Sk9+NnIgjZnlbU/DTAHtGnb+M3I0RHo=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=ojG/I6nARC+3zNB6Jjc/jmbjIcDZSvlgu9MpO8czPyyVpMlw/KnmvJ8TE4BnjY+Hn 6XknwjXP+TIpYh9goWlaatrny8u2RobcbspIIXWMIsnDIT/IvbMf3Wac8s64gRZQe5 NjJf0VkaT+DmzoH4zyorAxT3yQhgjYLstjrkN3YSJnhmki9x0WjG+01iaWzq/46qh3 LNTc/mDsxGmuWcpa/EdoTY/Nb0IsG9zv+lH3qT+ZRuHUGl0QzdUOAvylwYxbLlhplD 9H3Qqs5njDSCGn4tWYZGhos4V/WNA/SXY8C+yR4xUnjqNSX/B+uzbgkwgAAZIImtqn kHyKsZ2islK3A== Date: Mon, 26 Oct 2026 11:40:37 +0100 From: Gao Xiang To: Zhan Xusheng Cc: xiang@kernel.org, chao@kernel.org, zbestahu@gmail.com, jefflexu@163.com, dhavale@google.com, hongbohbli@tencent.com, guochunhai@vivo.com, giuseppe@scrivano.org, linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org, zhanxusheng@xiaomi.com Subject: Re: [PATCH v2] erofs: don't reuse a superblock for a mount that passes device= Message-ID: Mail-Followup-To: Zhan Xusheng , xiang@kernel.org, chao@kernel.org, zbestahu@gmail.com, jefflexu@163.com, dhavale@google.com, hongbohbli@tencent.com, guochunhai@vivo.com, giuseppe@scrivano.org, linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org, zhanxusheng@xiaomi.com References: <20261026092217.2129604-1-zhanxusheng1024@gmail.com> X-Mailing-List: linux-erofs@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Subscribe: , , Precedence: list X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20261026092217.2129604-1-zhanxusheng1024@gmail.com> X-Spam-Status: No, score=-11.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Mon, Oct 26, 2026 at 05:22:17PM +0800, Zhan Xusheng wrote: > From: Zhan Xusheng > > superblock_share together with device= is rejected in > erofs_fc_fill_super(): > > if (test_opt(&sbi->opt, SUPERBLOCK_SHARE) && > sbi->devs->extra_devices) > return -EINVAL; > > but extra_devices is kept in sbi->devs, not in sbi->opt, and > erofs_sb_share_test_super() compares only the backing inode, the > fsoffset and sbi->opt. So once the image is mounted with > superblock_share, a second mount with superblock_share,device= matches > that superblock and get_tree_super() reuses it without calling > fill_super() at all. > > The same command line therefore either fails with -EINVAL or succeeds > with device= quietly dropped, depending on whether a compatible mount > already exists. > > Refuse to match a context that brought device= options, so that it gets > a superblock of its own and fill_super() decides as it does today. > > Only the incoming context can be tested: a shared superblock may have > extra_devices set itself, because erofs_scan_devices() fills the device > table from the image when no device= was given. > > Fixes: cd4108319bb3 ("erofs: reuse superblock for file-backed mounts") > Signed-off-by: Zhan Xusheng Reviewed-by: Gao Xiang Also I will update the subject as "erofs: fix disallowing superblock_share if device= is set". Thanks, Gao Xiang