Re: [MINI-OS PATCH v2 1/2] 9pfs: add fstat file operation hook

[Jan Beulich <jbeulich@xxxxxxxx>]

On 23.03.2025 15:57, Jürgen Groß wrote:
> On 23.03.25 01:01, Samuel Thibault wrote:
>> Juergen Gross, le ven. 21 mars 2025 10:31:44 +0100, a ecrit:
>>> Add a file operations fstat hook to the 9pfs frontend.
>>>
>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>>> Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>
>>> ---
>>> V2:
>>> - or file access mode into st_mode (Jason Andryuk)
>>> ---
>>>   9pfront.c | 29 +++++++++++++++++++++++++++++
>>>   1 file changed, 29 insertions(+)
>>>
>>> diff --git a/9pfront.c b/9pfront.c
>>> index 1741d600..7257a07e 100644
>>> --- a/9pfront.c
>>> +++ b/9pfront.c
>>> @@ -85,6 +85,8 @@ struct file_9pfs {
>>>   
>>>   #define P9_QID_SIZE    13
>>>   
>>> +#define QID_TYPE_DIR   0x80     /* Applies to qid[0]. */
>>> +
>>>   struct p9_header {
>>>       uint32_t size;
>>>       uint8_t cmd;
>>> @@ -950,6 +952,32 @@ static int write_9pfs(struct file *file, const void 
>>> *buf, size_t nbytes)
>>>       return ret;
>>>   }
>>>   
>>> +static int fstat_9pfs(struct file *file, struct stat *buf)
>>> +{
>>> +    struct file_9pfs *f9pfs = file->filedata;
>>> +    struct p9_stat stat;
>>> +    int ret;
>>> +
>>> +    ret = p9_stat(f9pfs->dev, f9pfs->fid, &stat);
>>> +    if ( ret )
>>> +    {
>>> +        errno = EIO;
>>> +        return -1;
>>> +    }
>>> +
>>> +    buf->st_mode = (stat.qid[0] == QID_TYPE_DIR) ? S_IFDIR : S_IFREG;
>>> +    buf->st_mode |= stat.mode & 0777;
>>> +    buf->st_atime = stat.atime;
>>> +    buf->st_mtime = stat.mtime;
>>
>> Should we perhaps also fill st_ctime? Leaving it at 0 could surprise
>> other software layers.
> 
> I can set it to the same value as st_mtime.

Maybe the smaller of atime and mtime?

Jan

> I don't think there is a way
> to get the "real" ctime value via the 9p protocol.
> 
> 
> Juergen