Kernel build with CONFIG_DEBUG_SLAB or CONFIG_SLUB_DEBUG slub_debug=FPZ
gives me kernel BUG at fs/ext4/extents_status.c:142! That's the
BUG_ON(es->start + es->len < es->start) in extent_status_end() called
from ext4_es_insert_extent(). tree->cache_es has been freed and poisoned.
This comes from when ext4_es_try_to_merge_left() merges es into leftward
es1, but ext4_es_insert_extent()'s out then updates cache_es to the freed
extent_status. ext4_es_try_to_merge_right() does not pose a problem.
Change ext4_es_try_to_merge_left() to return whichever extent_status
should be recorded in tree->cache_es. Remove cache_es update from
both of them, leaving that to ext4_es_insert_extent()'s out label.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---
fs/ext4/extents_status.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
--- mmotm/fs/ext4/extents_status.c 2012-09-26 10:15:29.340071552 -0700
+++ linux/fs/ext4/extents_status.c 2012-09-27 11:52:59.284937056 -0700
@@ -244,24 +244,24 @@ static void ext4_es_free_extent(struct e
kmem_cache_free(ext4_es_cachep, es);
}
-static void ext4_es_try_to_merge_left(struct ext4_es_tree *tree,
- struct extent_status *es)
+static struct extent_status *
+ext4_es_try_to_merge_left(struct ext4_es_tree *tree, struct extent_status *es)
{
struct extent_status *es1;
struct rb_node *node;
node = rb_prev(&es->rb_node);
if (!node)
- return;
+ return es;
es1 = rb_entry(node, struct extent_status, rb_node);
if (es->start == extent_status_end(es1) + 1) {
es1->len += es->len;
rb_erase(&es->rb_node, &tree->root);
- if (es == tree->cache_es)
- tree->cache_es = es1;
ext4_es_free_extent(es);
+ es = es1; /* Caller will update tree->cache_es to this */
}
+ return es;
}
static void ext4_es_try_to_merge_right(struct ext4_es_tree *tree,
@@ -278,9 +278,8 @@ static void ext4_es_try_to_merge_right(s
if (es1->start == extent_status_end(es) + 1) {
es->len += es1->len;
rb_erase(node, &tree->root);
- if (es1 == tree->cache_es)
- tree->cache_es = es;
ext4_es_free_extent(es1);
+ /* Caller will update tree->cache_es to es */
}
}
@@ -318,7 +317,7 @@ int ext4_es_insert_extent(struct inode *
es_debug("cached by [%u/%u)\n", es->start, es->len);
es->start = offset;
es->len += len;
- ext4_es_try_to_merge_left(tree, es);
+ es = ext4_es_try_to_merge_left(tree, es);
goto out;
} else if (es && in_range(offset, es->start, es->len)) {
es_debug("cached by [%u/%u)\n", es->start, es->len);
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
