xfs: don't open-code u64_to_user_ptr

Don't open-code what the kernel already provides.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

xfs: add parent pointer ioctls

This patch adds a pair of new file ioctls to retrieve the parent pointer
of a given inode. They both return the same results, but one operates
on the file descriptor passed to ioctl() whereas the other allows the
caller to specify a file handle for which the caller wants results.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

xfs: split out handle management helpers a bit

Split out the functions that generate file/fs handles and map them back
into dentries in preparation for the GETPARENTS ioctl next.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

xfs: move handle ioctl code to xfs_handle.c

Move the handle managemnet code (and the attrmulti code that uses it) to
xfs_handle.c.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>