This is preferred to opencoding an IDA_INIT.

Link: http://lkml.kernel.org/r/20180313132639.17387-2-willy@infradead.orgSigned-off-by: NMatthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>