mm, fs: remove remaining PAGE_CACHE_* and page_cache_{get,release} usage

Mostly direct substitution with occasional adjustment or removing
outdated comments.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 93d696d..d247fc0 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3264,13 +3264,11 @@
 			goto done;
 		}
 		/*
-		 * delalloc_end is already one less than the total
-		 * length, so we don't subtract one from
-		 * PAGE_CACHE_SIZE
+		 * delalloc_end is already one less than the total length, so
+		 * we don't subtract one from PAGE_SIZE
 		 */
 		delalloc_to_write += (delalloc_end - delalloc_start +
-				      PAGE_SIZE) >>
-				      PAGE_SHIFT;
+				      PAGE_SIZE) >> PAGE_SHIFT;
 		delalloc_start = delalloc_end + 1;
 	}
 	if (wbc->nr_to_write < delalloc_to_write) {