rhashtable: Fix walker list corruption

The commit a81a2a2e2fe2b926cf0df7fa5478b8fd1a8be867 ("rhashtable:
Fix sleeping inside RCU critical section in walk_stop") introduced
a new spinlock for the walker list.  However, it did not convert
all existing users of the list over to the new spin lock.  Some
continued to use the old mutext for this purpose.  This obviously
led to corruption of the list.

The fix is to use the spin lock everywhere where we touch the list.

This also allows us to do rcu_rad_lock before we take the lock in
rhashtable_walk_start.  With the old mutex this would've deadlocked
but it's safe with the new spin lock.

Fixes: a81a2a2e2fe2 ("rhashtable: Fix sleeping inside RCU...")
Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index a98e71db7dd21d9fc76d9a87460059e0d6d5beb8..eb9240c458fad6a0c4a55b5e211ada4e6aace6b0 100644 (file)
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -518,10 +518,10 @@ int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter)
        if (!iter->walker)
                return -ENOMEM;
 
-       mutex_lock(&ht->mutex);
+       spin_lock(&ht->lock);
        iter->walker->tbl = rht_dereference(ht->tbl, ht);
        list_add(&iter->walker->list, &iter->walker->tbl->walkers);
-       mutex_unlock(&ht->mutex);
+       spin_unlock(&ht->lock);
 
        return 0;
 }
@@ -535,10 +535,10 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_init);
  */
 void rhashtable_walk_exit(struct rhashtable_iter *iter)
 {
-       mutex_lock(&iter->ht->mutex);
+       spin_lock(&iter->ht->lock);
        if (iter->walker->tbl)
                list_del(&iter->walker->list);
-       mutex_unlock(&iter->ht->mutex);
+       spin_unlock(&iter->ht->lock);
        kfree(iter->walker);
 }
 EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
@@ -562,14 +562,12 @@ int rhashtable_walk_start(struct rhashtable_iter *iter)
 {
        struct rhashtable *ht = iter->ht;
 
-       mutex_lock(&ht->mutex);
+       rcu_read_lock();
 
+       spin_lock(&ht->lock);
        if (iter->walker->tbl)
                list_del(&iter->walker->list);
-
-       rcu_read_lock();
-
-       mutex_unlock(&ht->mutex);
+       spin_unlock(&ht->lock);
 
        if (!iter->walker->tbl) {
                iter->walker->tbl = rht_dereference_rcu(ht->tbl, ht);