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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11F96C77B61 for ; Mon, 10 Apr 2023 05:27:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229570AbjDJFYY (ORCPT ); Mon, 10 Apr 2023 01:24:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55828 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229485AbjDJFYW (ORCPT ); Mon, 10 Apr 2023 01:24:22 -0400 Received: from out30-98.freemail.mail.aliyun.com (out30-98.freemail.mail.aliyun.com [115.124.30.98]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3593A30C8 for ; Sun, 9 Apr 2023 22:24:20 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R191e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045176;MF=hsiangkao@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0VffRxgD_1681104256; Received: from 30.97.49.25(mailfrom:hsiangkao@linux.alibaba.com fp:SMTPD_---0VffRxgD_1681104256) by smtp.aliyun-inc.com; Mon, 10 Apr 2023 13:24:17 +0800 Message-ID: Date: Mon, 10 Apr 2023 13:24:15 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH 4/7] erofs: introduce on-disk format for long xattr name prefixes To: Jingbo Xu , xiang@kernel.org, chao@kernel.org, huyue2@coolpad.com, linux-erofs@lists.ozlabs.org Cc: linux-kernel@vger.kernel.org References: <20230407141710.113882-1-jefflexu@linux.alibaba.com> <20230407141710.113882-5-jefflexu@linux.alibaba.com> From: Gao Xiang In-Reply-To: <20230407141710.113882-5-jefflexu@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/4/7 22:17, Jingbo Xu wrote: > Besides the predefined xattr name prefixes, introduces long xattr name > prefixes, which work similarly as the predefined name prefixes, except > that they are user specified. > > It is especially useful for use cases together with overlayfs like > Composefs model, which introduces diverse xattr values with only a few > common xattr names (trusted.overlay.redirect, trusted.overlay.digest, > and maybe more in the future). That makes the existing predefined > prefixes ineffective in both image size and runtime performance. > > When a user specified long xattr name prefix is used, only the trailing > part of the xattr name apart from the long xattr name prefix will be > stored in erofs_xattr_entry.e_name. e_name is empty if the xattr name > matches exactly as the long xattr name prefix. All long xattr prefixes > are stored in the packed or meta inode, which depends if fragments > feature is enabled or not. > > For each long xattr name prefix, the on-disk format is kept as the same > as the unique metadata format: ALIGN({__le16 len, data}, 4), where len > represents the total size of struct erofs_xattr_long_prefix, followed > by data of struct erofs_xattr_long_prefix itself. > > Each erofs_xattr_long_prefix keeps predefined prefixes (base_index) > and the remaining prefix string without the trailing '\0'. > > Two fields are introduced to the on-disk superblock, where > xattr_prefix_count represents the total number of the long xattr name > prefixes recorded, and xattr_prefix_start represents the start offset of > recorded name prefixes in the packed/meta inode divided by 4. > > When referring to a long xattr name prefix, the highest bit (bit 7) of > erofs_xattr_entry.e_name_index is set, while the lower bits (bit 0-6) > as a whole represents the index of the referred long name prefix among > all long xattr name prefixes. > > Signed-off-by: Jingbo Xu Reviewed-by: Gao Xiang Thanks, Gao Xiang > --- > fs/erofs/erofs_fs.h | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) > > diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h > index 44876a97cabd..ea62f83dac40 100644 > --- a/fs/erofs/erofs_fs.h > +++ b/fs/erofs/erofs_fs.h > @@ -76,7 +76,8 @@ struct erofs_super_block { > __le16 extra_devices; /* # of devices besides the primary device */ > __le16 devt_slotoff; /* startoff = devt_slotoff * devt_slotsize */ > __u8 dirblkbits; /* directory block size in bit shift */ > - __u8 reserved[5]; > + __u8 xattr_prefix_count; /* # of long xattr name prefixes */ > + __le32 xattr_prefix_start; /* start of long xattr prefixes */ > __le64 packed_nid; /* nid of the special packed inode */ > __u8 reserved2[24]; > }; > @@ -229,6 +230,13 @@ struct erofs_xattr_ibody_header { > #define EROFS_XATTR_INDEX_LUSTRE 5 > #define EROFS_XATTR_INDEX_SECURITY 6 > > +/* > + * bit 7 of e_name_index is set when it refers to a long xattr name prefix, > + * while the remained lower bits represent the index of the prefix. > + */ > +#define EROFS_XATTR_LONG_PREFIX 0x80 > +#define EROFS_XATTR_LONG_PREFIX_MASK 0x7f > + > /* xattr entry (for both inline & shared xattrs) */ > struct erofs_xattr_entry { > __u8 e_name_len; /* length of name */ > @@ -238,6 +246,12 @@ struct erofs_xattr_entry { > char e_name[]; /* attribute name */ > }; > > +/* long xattr name prefix */ > +struct erofs_xattr_long_prefix { > + __u8 base_index; /* short xattr name prefix index */ > + char infix[]; /* infix apart from short prefix */ > +}; > + > static inline unsigned int erofs_xattr_ibody_size(__le16 i_xattr_icount) > { > if (!i_xattr_icount)