lkml.org 
[lkml]   [2012]   [Jun]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [bisected commit 0fc9d10] NFS-server corruption with 3.4
Proper fix in attachment.

Konstantin Khlebnikov wrote:
> OGAWA Hirofumi wrote:
>> Konstantin Khlebnikov<khlebnikov@openvz.org> 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...
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/

radix-tree: fix contiguous iterator

From: Konstantin Khlebnikov <khlebnikov@openvz.org>

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@openvz.org>
Reported-and-bisected-by: Hans de Bruin <jmdebruin@xmsnet.nl>
Reported-and-bisected-by: Ondrej Zary <linux@rainbow-software.org>
Reported-and-bisected-by: Toralf Förster <toralf.foerster@gmx.de>
---
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)
\
 
 \ /
  Last update: 2012-06-05 18:41    [W:0.058 / U:0.160 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site