clone ioctl return values

[Christoph Hellwig <hch@infradead.org>]

Hi Darrick,

your new generic/157 xfs test brings up an interesting issue:  error
returns forthe various clone failure cases.  It seems like this case
was written fo the XFS case which differs a lot from the error chosen
by btrfs and mostly followed by NFS.  I'd say it might be a better idea
to follow the btrfs example as the btrfs ioctls have been in use for
a while.  The only shortcoming I see in btrfs is that id doesn't
explicitly check for non-directory, non-regular file items as the
source.  I have to admit I'm kinda surprised that it doesn't blow up,
given that NFS instantly did when I removed those checks.

FYI, output from the test on btrfs below:


--- tests/generic/157.out	2015-11-14 07:56:31.000000000 +0000
+++ /root/xfstests/results//generic/157.out.bad	2015-11-16 11:58:52.879078894 +0000
@@ -2,24 +2,24 @@
 Format and mount
 Create the original files
 Try cross-device reflink
-XFS_IOC_CLONE_RANGE: Invalid cross-device link
+reflink: Invalid cross-device link
 Try unaligned reflink
-XFS_IOC_CLONE_RANGE: Invalid argument
+reflink: Invalid argument
 Try overlapping reflink
-XFS_IOC_CLONE_RANGE: Invalid argument
+reflink: Invalid argument
 Try reflink past EOF
-XFS_IOC_CLONE_RANGE: Invalid argument
+reflink: Invalid argument
 Try to reflink a dir
-XFS_IOC_CLONE_RANGE: Is a directory
+reflink: Is a directory
 Try to reflink a device
-XFS_IOC_CLONE_RANGE: Invalid argument
+/mnt/test/test-157/dev1: No such device or address
 Try to reflink to a dir
-/mnt/test-157/dir1: Is a directory
+/mnt/test/test-157/dir1: Is a directory
 Try to reflink to a device
-XFS_IOC_CLONE_RANGE: Operation not supported
+/mnt/test/test-157/dev1: No such device or address
 Try to reflink to a fifo
-XFS_IOC_CLONE_RANGE: Operation not supported
+reflink: Inappropriate ioctl for device
 Try to reflink an append-only file
-XFS_IOC_CLONE_RANGE: Bad file descriptor
+reflink: Invalid argument
 Reflink two files
 Check scratch fs