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authorMatthew Wilcox <willy@linux.intel.com>2016-02-02 16:57:52 -0800
committerSasha Levin <sasha.levin@oracle.com>2016-02-15 15:42:38 -0500
commit164d23c2c000041a707ed50321dde5c8a367787a (patch)
treee7e2cc9ed7de41e9e538e47e31749190b00b10b9 /lib
parent2f7eff9c342c13c923805b7c38ef946bf731e3f7 (diff)
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radix-tree: fix race in gang lookup
[ Upstream commit 46437f9a554fbe3e110580ca08ab703b59f2f95a ] If the indirect_ptr bit is set on a slot, that indicates we need to redo the lookup. Introduce a new function radix_tree_iter_retry() which forces the loop to retry the lookup by setting 'slot' to NULL and turning the iterator back to point at the problematic entry. This is a pretty rare problem to hit at the moment; the lookup has to race with a grow of the radix tree from a height of 0. The consequences of hitting this race are that gang lookup could return a pointer to a radix_tree_node instead of a pointer to whatever the user had inserted in the tree. Fixes: cebbd29e1c2f ("radix-tree: rewrite gang lookup using iterator") Signed-off-by: Matthew Wilcox <willy@linux.intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Ohad Ben-Cohen <ohad@wizery.com> Cc: Konstantin Khlebnikov <khlebnikov@openvz.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Diffstat (limited to 'lib')
-rw-r--r--lib/radix-tree.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 3d2aa27b845b..8399002aa0f0 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -1014,9 +1014,13 @@ radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
return 0;
radix_tree_for_each_slot(slot, root, &iter, first_index) {
- results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot));
+ results[ret] = rcu_dereference_raw(*slot);
if (!results[ret])
continue;
+ if (radix_tree_is_indirect_ptr(results[ret])) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
if (++ret == max_items)
break;
}
@@ -1093,9 +1097,13 @@ radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
return 0;
radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
- results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot));
+ results[ret] = rcu_dereference_raw(*slot);
if (!results[ret])
continue;
+ if (radix_tree_is_indirect_ptr(results[ret])) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
if (++ret == max_items)
break;
}