radix-tree: fix contiguous iterator

This patch fixes bug in macro radix_tree_for_each_contig(). If radix_tree_next_slot() sees NULL in next slot it returns NULL, but following radix_tree_next_chunk() switches iterating into next chunk. As result iterating becomes non-contiguous and breaks vfs "splice" and all its users. Signed-off-by: Konstantin Khlebnikov <[email protected]> Reported-and-bisected-by: Hans de Bruin <[email protected]> Reported-and-bisected-by: Ondrej Zary <[email protected]> Reported-bisected-and-tested-by: Toralf Förster <[email protected]> Link: https://lkml.org/lkml/2012/6/5/64 Cc: stable <[email protected]> # 3.4.x Signed-off-by: Linus Torvalds <[email protected]>
mna · Jun 5, 2012 · fffaee3 · fffaee3
1 parent f9ba717
commit fffaee3
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Showing 2 changed files with 7 additions and 1 deletion.
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
@@ -368,8 +368,11 @@ radix_tree_next_slot(void **slot, struct radix_tree_iter *iter, unsigned flags)
 			iter->index++;
 			if (likely(*slot))
 				return slot;
-			if (flags & RADIX_TREE_ITER_CONTIG)
+			if (flags & RADIX_TREE_ITER_CONTIG) {
+				/* forbid switching to the next chunk */
+				iter->next_index = 0;
 				break;
+			}
 		}
 	}
 	return NULL;

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
@@ -686,6 +686,9 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
 	 * during iterating; it can be zero only at the beginning.
 	 * And we cannot overflow iter->next_index in a single step,
 	 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
+	 *
+	 * This condition also used by radix_tree_next_slot() to stop
+	 * contiguous iterating, and forbid swithing to the next chunk.
 	 */
 	index = iter->next_index;
 	if (!index && iter->index)