Proper fix in attachment.
Konstantin Khlebnikov wrote:
OGAWA Hirofumi wrote:
Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx> writes:
Hmm, very interesting!
Please try this patch, it must fix the problem and print some numbers to debug.
I think the bug is in radix_tree_for_each_contig().
radix_tree_next_slot() returns NULL if the slot was NULL (i.e. there is
hole). But, slot == NULL is not meaning to stop iterate here. Actually,
if slot is NULL, it gets next chunk.
Bang.
Yeah, you are right, I already found this too.
Currently I think how to fix this more accurately...
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radix-tree: fix contiguous iterator
From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
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 <khlebnikov@xxxxxxxxxx>
Reported-and-bisected-by: Hans de Bruin <jmdebruin@xxxxxxxxx>
Reported-and-bisected-by: Ondrej Zary <linux@xxxxxxxxxxxxxxxxxxxx>
Reported-and-bisected-by: Toralf Förster <toralf.foerster@xxxxxx>
---
include/linux/radix-tree.h | 5 ++++-
lib/radix-tree.c | 3 +++
2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 0d04cd6..ffc444c 100644
--- 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
index 86516f5..3ac50dc 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -673,6 +673,9 @@ 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)
