Two of the USB Gadgets were poking around in the internals of struct ida in order to determine if it is empty. Add the appropriate abstraction. Link: http://lkml.kernel.org/r/1480369871-5271-63-git-send-email-mawilcox@linuxonhyperv.com Signed-off-by: Matthew Wilcox <willy@linux.intel.com> Acked-by: Konstantin Khlebnikov <koct9i@gmail.com> Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Felipe Balbi <balbi@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Michal Nazarewicz <mina86@mina86.com> Cc: Matthew Wilcox <mawilcox@microsoft.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>