Re: modify chmod

[Jim Meyering]

jeff.liu wrote:

> Jim Meyering 写道:
>> jeff.liu wrote:
>>
>>> A tiny patch, make chmod do not touch the inode if the new file
>>> permission mode is same as it was before.
>>>
>> ...
>>
>>> +static bool
>>> +may_have_nfsacl(const char *file)
>>> +{
>>> +# if HAVE_SYS_VFS_H && HAVE_SYS_STATFS_H && HAVE_STRUCT_STATFS_F_TYPE
>>> + struct statfs buf;
>>> +
>>> + /* If statfs fails, assume we can't use the optimization. */
>>> + if (statfs (file, &buf) < 0)
>>>
>>
>> This function should accept a file descriptor, not a file name,
>> and should call fstatfs, not statfs.
>>
>>
> Thanks for the correction.
> IMHO, to get a fd, then call fstatfs ranther than statfs here, is to
> ensure the same file object proceeding to operated on?

fts provides a file descriptor for every directory it processes,
so you can use an "FTS_ENT const *ent" parameter instead.
When it refers to a directory, use ent->fts_fts->fts_cwd_fd as the
file descriptor.  Otherwise, you will have to call statfs after all.
At first, I was thinking we could avoid statfs most of the time (i.e.,
change device only at a directory), but with bind-mounted regular files,
the device can change at any time during a traversal.