Using fstatfs on a ZFS disk

[Rodney W. Grimes]

> Hi,
> 
> > On 19 Feb 2018, at 15:50, Willem Jan Withagen <wjw at digiware.nl> wrote:
> > 
> > On 19-2-2018 16:00, Bob Bishop wrote:
> >> Hi,
> >>> On 19 Feb 2018, at 14:48, Willem Jan Withagen <wjw at digiware.nl> wrote:
> >>> 
> >>> Hi,
> >>> 
> >>> I'm trying to find the values of the returned f_type for ZFS
> >>> in the fstatfs call when a file is on ZFS....
> >>> 
> >>> But I have not yet found the definitions of the ENUMS that
> >>> would fill that value... Let alone the value for ZFS.
> >> I chased this particular wild goose myself recently. It?s FS_... in  /usr/include/sys/disklabel,h that you want.
> > 
> > Hi Bob,
> > 
> > I grepped on MAGIC and FS, but the combo did not deliver anything useful. So this is already more that I found.
> > I did get:
> > /usr/include/ufs/ffs/fs.h:#define       FS_UFS1_MAGIC   0x011954 /* UFS1 fast filesystem magic number */
> > /usr/include/ufs/ffs/fs.h:#define       FS_UFS2_MAGIC   0x19540119 /* UFS2 fast filesystem magic number */
> > /usr/include/ufs/ffs/fs.h:#define       FS_BAD_MAGIC    0x19960408 /* UFS incomplete newfs magic number */
> 
> Those I believe are magic numbers for UFS superblocks... 
> 
> > So I was looking for something like: FS_ZFS_MAGIC
> 
> ... so you won?t find that.
> 
> > disklabel.h contains:
> > #ifdef  FSTYPENAMES
> > static const char *fstypenames[] = {
> > 
> > And further search:
> > /usr/include/sys/disk/bsd.h:#define     FS_ZFS  27    /* Sun's ZFS */
> > 
> > Running:
> > #include "stdio.h"
> > 
> > #include <sys/param.h>
> > #include <sys/mount.h>
> > 
> > int main() {
> >        struct statfs fstr;
> >        char * str;
> > 
> >        str = "/tmp";
> >        statfs(str, &fstr);
> >        printf("%s, ftype: 0x%x.\n", str, fstr.f_type);
> > }
> > results in:
> > 	/tmp, ftype: 0xde.
> > 
> > Now 0xde != 27, so the question is, where is this 0xde specified.
> > And more important is this f_type constant over all FreeBSD ZFS filesystems?
> 
> You got me. And a quick look at sys/kern/vfs_syscalls.c doesn?t help except to imply that the type is set when the filesystem is mounted. I have no idea where 0xde comes from.

Could that 0xde be the start of 0xdeadcode?

0xde is 222 decimal, that does not ring a bell for me either.


> > --WjW
> > 
> >>>     struct statfs {
> >>>     uint32_t f_version;             /* structure version number */
> >>>     uint32_t f_type;                /* type of filesystem */
> >>>     uint64_t f_flags;               /* copy of mount exported flags */
> >>>     ......
> >>>     }
> >>> 
> >>> Any hints where to look would be welcomed.
> >>> 
> >>> Thanx,
> >>> --WjW
> >> --
> >> Bob Bishop
> >> rb at gid.co.uk
> --
> Bob Bishop       t: +44 (0)118 940 1243
> rb at gid.co.uk     m: +44 (0)783 626 4518

-- 
Rod Grimes                                                 rgrimes at freebsd.org