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

[Jürgen Groß <jgross@xxxxxxxx>]

On 24.03.25 11:30, Samuel Thibault wrote:
> Jan Beulich, le lun. 24 mars 2025 11:21:48 +0100, a ecrit:
> > 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?
> That'd be better, yes.
According to the references I could find ctime is changed whenever
either file contents OR file status (uid, gid, permissions) are
modified. So using the same value as mtime seems appropriate.


Juergen

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