It gets it indirectly from blkdev.h when CONFIG_BLOCK is enabled, but it
needs it unconditionally for the definition of mapping_cap_writeback_dirty.
Noticed and bisected down to
4af3c9cc4fad54c3627e9afebf905aafde5690ed
("Drop some headers from mm.h") by Avuton Olrich.
Cc: Avuton Olrich <avuton@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
#include <linux/uio.h>
#include <linux/hash.h>
#include <linux/writeback.h>
+#include <linux/backing-dev.h>
#include <linux/pagevec.h>
#include <linux/blkdev.h>
#include <linux/security.h>