fs: don't open code lru_to_page()

Multiple filesystems open code lru_to_page().  Rectify this by moving
the macro from mm_inline (which is specific to lru stuff) to the more
generic mm.h header and start using the macro where appropriate.

No functional changes.

Link: http://lkml.kernel.org/r/20181129104810.23361-1-nborisov@suse.com
Link: https://lkml.kernel.org/r/20181129075301.29087-1-nborisov@suse.com
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Pankaj gupta <pagupta@redhat.com>
Acked-by: "Yan, Zheng" <zyan@redhat.com>		[ceph]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 5e40516..e3e3a75 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -33,6 +33,7 @@
 #include <linux/mount.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
+#include <linux/mm.h>
 #include <asm/div64.h>
 #include "cifsfs.h"
 #include "cifspdu.h"
@@ -3964,7 +3965,7 @@ readpages_get_pages(struct address_space *mapping, struct list_head *page_list,
 
 	INIT_LIST_HEAD(tmplist);
 
-	page = list_entry(page_list->prev, struct page, lru);
+	page = lru_to_page(page_list);
 
 	/*
 	 * Lock the page and put it in the cache. Since no one else