lib: radix-tree: update callback for changing leaf nodes

Support handing __radix_tree_replace() a callback that gets invoked for
all leaf nodes that change or get freed as a result of the slot
replacement, to assist users tracking nodes with node->private_list.

This prepares for putting page cache shadow entries into the radix tree
root again and drastically simplifying the shadow tracking.

Link: http://lkml.kernel.org/r/20161117193134.GD23430@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <mawilcox@linuxonhyperv.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 3149dde..abd7403 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -311,7 +311,8 @@ static int shmem_radix_tree_replace(struct address_space *mapping,
 		return -ENOENT;
 	if (item != expected)
 		return -ENOENT;
-	__radix_tree_replace(&mapping->page_tree, node, pslot, replacement);
+	__radix_tree_replace(&mapping->page_tree, node, pslot,
+			     replacement, NULL, NULL);
 	return 0;
 }