Fix ioctls on 32bit/64bit userspace/kernel, for 4.10

Hi,

could you please merge this single-patch pull request, for 4.10 still? There are quite a few patches on top of v4.10-rc7 so this IMHO does not look like look too bad even late in the release cycle. Though it's a fix for an uncommon usecase of 32bit userspace on 64bit kernel, it fixes basically operation of the ioctls. Thanks.

The following changes since commit 57b59ed2e5b91e958843609c7884794e29e6c4cb:

Btrfs: remove ->{get, set}_acl() from btrfs_dir_ro_inode_operations (2017-01-26 15:48:56 -0800)

are available in the git repository at:

git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git fixes-4.10

for you to fetch changes up to 2a362249187a8d0f6d942d6e1d763d150a296f47:

btrfs: fix btrfs_compat_ioctl failures on non-compat ioctls (2017-02-08 17:47:30 +0100)

----------------------------------------------------------------
Jeff Mahoney (1):
btrfs: fix btrfs_compat_ioctl failures on non-compat ioctls

 fs/btrfs/ioctl.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Hi Dave, I'll pull this in and it, thanks.

-chris

It's not uncommon. Pretty much every 32-on-64 combination was broken, and some archs (like mips, both endians) use 32-on-64 on all non-museal hardware.

I've tested that your patch fixes at least:
* x32 on amd64
* armhf on arm64

So big thanks for this fix!

There are other broken ioctls, for example:
/mnt/vol1/b: fiemap error 25: Inappropriate ioctl for device /mnt/vol1/a: fiemap error 25: Inappropriate ioctl for device but the last I checked, fiemap doesn't live in fs/btrfs/

Meow!

Autotools hint: to do a zx-spectrum build on a pdp11 host, type:
  ./configure --host=zx-spectrum --build=pdp11