1 files changed, 46 insertions, 5 deletions

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 2b2b79974b61..9427b5766134 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -668,8 +668,9 @@ EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
  * For a completely stable walk you should construct your own data
  * structure outside the hash table.
  *
- * This function may sleep so you must not call it from interrupt
- * context or with spin locks held.
+ * This function may be called from any process context, including
+ * non-preemptable context, but cannot be called from softirq or
+ * hardirq context.
  *
  * You must call rhashtable_walk_exit after this function returns.
  */
@@ -726,6 +727,7 @@ int rhashtable_walk_start_check(struct rhashtable_iter *iter)
         __acquires(RCU)
 {
         struct rhashtable *ht = iter->ht;
+        bool rhlist = ht->rhlist;
 
         rcu_read_lock();
 
@@ -734,11 +736,52 @@ int rhashtable_walk_start_check(struct rhashtable_iter *iter)
                 list_del(&iter->walker.list);
         spin_unlock(&ht->lock);
 
-        if (!iter->walker.tbl && !iter->end_of_table) {
+        if (iter->end_of_table)
+                return 0;
+        if (!iter->walker.tbl) {
                 iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht);
+                iter->slot = 0;
+                iter->skip = 0;
                 return -EAGAIN;
         }
 
+        if (iter->p && !rhlist) {
+                /*
+                 * We need to validate that 'p' is still in the table, and
+                 * if so, update 'skip'
+                 */
+                struct rhash_head *p;
+                int skip = 0;
+                rht_for_each_rcu(p, iter->walker.tbl, iter->slot) {
+                        skip++;
+                        if (p == iter->p) {
+                                iter->skip = skip;
+                                goto found;
+                        }
+                }
+                iter->p = NULL;
+        } else if (iter->p && rhlist) {
+                /* Need to validate that 'list' is still in the table, and
+                 * if so, update 'skip' and 'p'.
+                 */
+                struct rhash_head *p;
+                struct rhlist_head *list;
+                int skip = 0;
+                rht_for_each_rcu(p, iter->walker.tbl, iter->slot) {
+                        for (list = container_of(p, struct rhlist_head, rhead);
+                             list;
+                             list = rcu_dereference(list->next)) {
+                                skip++;
+                                if (list == iter->list) {
+                                        iter->p = p;
+                                        skip = skip;
+                                        goto found;
+                                }
+                        }
+                }
+                iter->p = NULL;
+        }
+found:
         return 0;
 }
 EXPORT_SYMBOL_GPL(rhashtable_walk_start_check);
@@ -914,8 +957,6 @@ void rhashtable_walk_stop(struct rhashtable_iter *iter)
                 iter->walker.tbl = NULL;
         spin_unlock(&ht->lock);
 
-        iter->p = NULL;
-
 out:
         rcu_read_unlock();
 }