->count is honest reference count unlike ->in_use.

Link: http://lkml.kernel.org/r/20180313174550.GA4332@avx2Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>