On Wed, Mar 29, 2017 at 05:23:28PM -0700, Darrick J. Wong wrote:
> On Thu, Mar 30, 2017 at 12:57:08AM +0100, David Howells wrote:
> > Should XFS_IOC_FSGEOMETRY work on fds that are opened O_PATH on an XFS
> > filesystem? Or should xfs_io not call that ioctl on O_PATH fds?
>
> Given that read/write don't work under O_PATH, I wouldn't expect ioctls
> to work either.
>
> I tried to write a two line program to call FSGEOMETRY to see what
> actually happens but got so bogged down in trying to figure out what
> magic incantation of C headers one needs to pull in the appropriate
> structure typedefs for an ioctl I wasn't even trying to call that I gave
> up.
>
> Seriously, what the f*ck do you have to #include just to be able to use
> O_PATH?
>From open(2):
"The O_DIRECT, O_NOATIME, O_PATH, and O_TMPFILE flags are
Linux-specific. One must define _GNU_SOURCE to obtain their definitions."
Also, ioctl() with an O_PATH file descriptor always fails with EBADF because
sys_ioctl() uses fdget() rather than fdget_raw(). The filesystem isn't involved
at all. This is intentional, I believe.
- Eric
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