[PATCH 07/13] erofs-utils: lib: add erofs_read_xattrs_from_disk() helper

[Jingbo Xu]

On 8/14/23 2:46 PM, Gao Xiang wrote:
> 
> 
> On 2023/8/14 11:42, Jingbo Xu wrote:
>> Add erofs_read_xattrs_from_disk() helper to read extended attributes
>> from disk.
>>
>> Signed-off-by: Jingbo Xu <jefflexu at linux.alibaba.com>
>> ---
>>   include/erofs/xattr.h |  1 +
>>   lib/xattr.c           | 76 +++++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 77 insertions(+)
>>
>> diff --git a/include/erofs/xattr.h b/include/erofs/xattr.h
>> index dc27cf6..634daf9 100644
>> --- a/include/erofs/xattr.h
>> +++ b/include/erofs/xattr.h
>> @@ -85,6 +85,7 @@ int erofs_xattr_write_name_prefixes(struct
>> erofs_sb_info *sbi, FILE *f);
>>     int erofs_setxattr(struct erofs_inode *inode, char *key,
>>              const void *value, size_t size);
>> +int erofs_read_xattrs_from_disk(struct erofs_inode *inode);
>>     #ifdef __cplusplus
>>   }
>> diff --git a/lib/xattr.c b/lib/xattr.c
>> index 12f580e..8d8f9f0 100644
>> --- a/lib/xattr.c
>> +++ b/lib/xattr.c
>> @@ -493,6 +493,82 @@ int erofs_scan_file_xattrs(struct erofs_inode
>> *inode)
>>       return erofs_droid_xattr_set_caps(inode);
>>   }
>>   +static struct xattr_item *erofs_read_xattr_from_disk(struct
>> erofs_inode *inode,
>> +                             char *key)
>> +{
>> +    ssize_t ret;
>> +    u8 prefix;
>> +    u16 prefixlen;
>> +    unsigned int len[2];
>> +    char *kvbuf;
>> +
>> +    if (!match_prefix(key, &prefix, &prefixlen))
>> +        return ERR_PTR(-ENODATA);
>> +
>> +    ret = erofs_getxattr(inode, key, NULL, 0);
>> +    if (ret < 0)
>> +        return ERR_PTR(-errno);
>> +
>> +    /* allocate key-value buffer */
>> +    len[0] = strlen(key) - prefixlen;
>> +    len[1] = ret;
>> +    kvbuf = malloc(len[0] + len[1]);
>> +    if (!kvbuf)
>> +        return ERR_PTR(-ENOMEM);
>> +    memcpy(kvbuf, key + prefixlen, len[0]);
>> +    if (len[1]) {
>> +        ret = erofs_getxattr(inode, key, kvbuf + len[0], len[1]);
>> +        if (ret < 0) {
>> +            free(kvbuf);
>> +            return ERR_PTR(-errno);
>> +        }
>> +        if (ret != len[1]) {
>> +            erofs_err("size of xattr value got changed just now (%u->
>> %ld)",
>> +                  len[1], (long)ret);
>> +            len[1] = ret;
>> +        }
> 
> Can this actually happen? Maybe just:
>         DBG_BUGON(ret != len[1]);

Make sense.


-- 
Thanks,
Jingbo