From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AB62128C03B for ; Mon, 21 Jul 2025 09:28:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753090139; cv=none; b=oZYYwFPCWGx/CvPICGIr72hanSwpgQ0TkNrEOL4npvkTgrHrpAIfLtkoatv/01yKEGrP3h3OIuM6zUTnyMaqqR9xSEEmLEB26pH2u7avTEnn/MPBSs2xemOtjq4j6crABbd7MATqPuUDGdC4z8v0HlK2XPQcgu63vvKqNOAI6SQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753090139; c=relaxed/simple; bh=e3MjNw40SX9uSql+9WWt4ZuNq+HJ7mKB5glLjQZhIwA=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=fYu7NlOvNHvAtcR9XHkTOliZtWqy66NT9HAcH58KyOl5LTwKhZQYq0VUKnXHf2jSrSW2niW4V9zMC9L+mAZIlnjfPf00nwKfx0mmOSmJy7++n9/Aw/FvhrW9poxzlpcP9Lo66pEnTXzDUCoNMqVbsJZRCXnm/S28FRQ81L5xCyA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DmrxHLoc; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DmrxHLoc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 50857C4CEF7; Mon, 21 Jul 2025 09:28:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753090139; bh=e3MjNw40SX9uSql+9WWt4ZuNq+HJ7mKB5glLjQZhIwA=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=DmrxHLocad1e5UmD+gC/k3Kg1u3jitMAQ4eHyWaueJxvbaoneX/MGxSs/4n19lbjh o+vlJ6PZ7JsUvLnXodZtV9i/mS7OJ4AWuSbLo7jKJw4sWKjiYttb0h0d8QHB2mkGVW Fy9lZ4Xvty542YzW4cfGsb2mQoZ7XnjwrCdHnLW7cLl/9CdZBd7DEDlOKZ1DDxEF+q j5iDY6psq/YlPU4bQeas8aIcna7BmOCyr16xC93N+1//P99DXAVIjsVIc+k/SW8Boc 7RVYrCtNAigPiZdX3ose8yoj37FzSujhlSofEshnIue7QqPVKkGCe4b/GuG3hr3zaR LQGnnit8zr3nw== Message-ID: Date: Mon, 21 Jul 2025 17:28:56 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: chao@kernel.org, LKML Subject: Re: [PATCH v5 1/2] erofs: add on-disk definition for metadata compression To: Gao Xiang , linux-erofs@lists.ozlabs.org References: <20250716173314.308744-1-hsiangkao@linux.alibaba.com> <20250717070804.1446345-1-hsiangkao@linux.alibaba.com> <20250717070804.1446345-2-hsiangkao@linux.alibaba.com> Content-Language: en-US From: Chao Yu In-Reply-To: <20250717070804.1446345-2-hsiangkao@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/17/25 15:08, Gao Xiang wrote: > Filesystem metadata has a high degree of redundancy, so it should > compress well in the general case. > > Although metadata compression can increase overall I/O latency, many > users care more about minimized image sizes than extreme runtime > performance. Let's implement metadata compression in response to user > requests [1]. > > Actually, it's quite simple to implement metadata compression: since > EROFS already supports per-inode compression, we can simply treat a > special inode (called `the metabox inode`) as a container for compressed > inode metadata. Since EROFS supports multiple algorithms, users can > even specify LZ4 for metadata and LZMA for data. > > To better support incremental builds, the MSB of NIDs indicates where > the inode metadata is located: if bit 63 is set, the inode itself should > be read from `the metabox inode`. > > Optionally, shared xattrs can also be kept in `the metabox inode` if > COMPAT_SHARED_EA_IN_METABOX is set. > > [1] https://issues.redhat.com/browse/RHEL-75783 > Signed-off-by: Gao Xiang Acked-by: Chao Yu Thanks,