xfs: Check for delayed allocations before setting extsize

commit 2a492ff6 upstream.

Extsize should only be allowed to be set on files with no data in it.
For this, we check if the files have extents but miss to check if
delayed extents are present. This patch adds that check.

While we are at it, also refactor this check into a helper since
it's used in some other places as well like xfs_inactive() or
xfs_ioctl_setattr_xflags()

**Without the patch (SUCCEEDS)**

$ xfs_io -c 'open -f testfile' -c 'pwrite 0 1024' -c 'extsize 65536'

wrote 1024/1024 bytes at offset 0
1 KiB, 1 ops; 0.0002 sec (4.628 MiB/sec and 4739.3365 ops/sec)

**With the patch (FAILS as expected)**

$ xfs_io -c 'open -f testfile' -c 'pwrite 0 1024' -c 'extsize 65536'

wrote 1024/1024 bytes at offset 0
1 KiB, 1 ops; 0.0002 sec (4.628 MiB/sec and 4739.3365 ops/sec)
xfs_io: FS_IOC_FSSETXATTR testfile: Invalid argument

Fixes: e94af02a ("[XFS] fix old xfs_setattr mis-merge from irix; mostly harmless esp if not using xfs rt")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
Signed-off-by: Catherine Hoang <catherine.hoang@oracle.com>
Acked-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>