dax: remove DAX code from page_cache_tree_insert()

Now that we no longer insert struct page pointers in DAX radix trees we
can remove the special casing for DAX in page_cache_tree_insert().

This also allows us to make dax_wake_mapping_entry_waiter() local to
fs/dax.c, removing it from dax.h.

Link: http://lkml.kernel.org/r/20170724170616.25810-5-ross.zwisler@linux.intel.com
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/filemap.c

@@ -130,17 +130,8 @@ static int page_cache_tree_insert(struct address_space *mapping,
 			return -EEXIST;
 
 		mapping->nrexceptional--;
-		if (!dax_mapping(mapping)) {
-			if (shadowp)
-				*shadowp = p;
-		} else {
-			/* DAX can replace empty locked entry with a hole */
-			WARN_ON_ONCE(p !=
-				dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
-			/* Wakeup waiters for exceptional entry lock */
-			dax_wake_mapping_entry_waiter(mapping, page->index, p,
-						      true);
-		}
+		if (shadowp)
+			*shadowp = p;
 	}
 	__radix_tree_replace(&mapping->page_tree, node, slot, page,
 			     workingset_update_node, mapping);