statvfs and cdrom problem

[Christian Costa]

Hi,

I'm trying to make GetFreeDiskSpace working with CDROM because a game 
needs it.
However, I'm experiencing problem with statvfs...
Indeed, statvfs always returns f_frsize = 0 and f_blocks = 0.
If I cd to /mnt/cdrom or edit a file in it, this does not help however 
if I run a grep or launch Konqueror in that directory,
statvfs magically works.
I suspect supermount is responsible because statvfs needs the cdrom to 
be "physically" mounted.

Is it a know issue? (I am on a Mandrake 9.1 base)
Or the only solution is to keep a fd opened during the statvfs call so 
the drive stays mounted...

Thanks in advance,
Christian

PS: I used the attached code for testing

#include <sys/types.h>
#include <sys/statvfs.h>
#include <sys/statfs.h>

int main()
{
  struct statvfs info;
  struct statfs inf;

if (statfs("/mnt/cdrom", &inf) < 0)
  {
    printf("cannot do statfs\n");
    return 0;
  }
  printf("size = %ld - %ld\n", inf.f_bsize, inf.f_blocks);

if (statvfs("/mnt/cdrom", &info ) < 0)
  {
    printf("cannot do statvfs\n");
    return 0;
  }
  printf("size = %ld - %ld - %ld\n", info.f_bsize, info.f_frsize, info.f_blocks);
  return 1;
}

[Alexandre Julliard]

Christian Costa  writes:
> I'm trying to make GetFreeDiskSpace working with CDROM because a game
> needs it.
> However, I'm experiencing problem with statvfs...
> Indeed, statvfs always returns f_frsize = 0 and f_blocks = 0.
> If I cd to /mnt/cdrom or edit a file in it, this does not help however
> if I run a grep or launch Konqueror in that directory,
> statvfs magically works.
> I suspect supermount is responsible because statvfs needs the cdrom to
> be "physically" mounted.

The plan is to reimplement GetFreeDiskSpace on top of
NtQueryVolumeInformationFile, which should fix the issue since it will
require opening a handle to the directory. The equivalent in your test
program would be to open /mnt/cdrom and do a fstatvfs on the resulting
file descriptor. Could you verify if this does the right thing for
you?

[Christian Costa]

Alexandre Julliard wrote:
> Christian Costa  writes:
> > I'm trying to make GetFreeDiskSpace working with CDROM because a game
> > needs it.
> > However, I'm experiencing problem with statvfs...
> > Indeed, statvfs always returns f_frsize = 0 and f_blocks = 0.
> > If I cd to /mnt/cdrom or edit a file in it, this does not help however
> > if I run a grep or launch Konqueror in that directory,
> > statvfs magically works.
> > I suspect supermount is responsible because statvfs needs the cdrom to
> > be "physically" mounted.
>
> The plan is to reimplement GetFreeDiskSpace on top of
> NtQueryVolumeInformationFile, which should fix the issue since it will
> require opening a handle to the directory. The equivalent in your test
> program would be to open /mnt/cdrom and do a fstatvfs on the resulting
> file descriptor. Could you verify if this does the right thing for
> you?

Yes, this works fine. Thanks. :-)
When do you plan to rewrite GetFreeDiskSpace?

Bye,
Christian

[Alexandre Julliard]

Christian Costa  writes:
> Yes, this works fine. Thanks. :-)
> When do you plan to rewrite GetFreeDiskSpace?

In a few days I guess. There are still some missing features in
NtCreateFile that need to be done first.