1 files changed, 26 insertions, 7 deletions

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 7a67ef5b67b6..04b3a808fca9 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -114,6 +114,14 @@ static void bucket_table_free(const struct bucket_table *tbl)
 	kvfree(tbl);
 }
 
+static void bucket_table_free_atomic(const struct bucket_table *tbl)
+{
+	if (tbl->nest)
+		nested_bucket_table_free(tbl);
+
+	kvfree_atomic(tbl);
+}
+
 static void bucket_table_free_rcu(struct rcu_head *head)
 {
 	bucket_table_free(container_of(head, struct bucket_table, rcu));
@@ -496,7 +504,7 @@ static int rhashtable_insert_rehash(struct rhashtable *ht,
 
 	err = rhashtable_rehash_attach(ht, tbl, new_tbl);
 	if (err) {
-		bucket_table_free(new_tbl);
+		bucket_table_free_atomic(new_tbl);
 		if (err == -EEXIST)
 			err = 0;
 	} else
@@ -1166,6 +1174,11 @@ static void rhashtable_free_one(struct rhashtable *ht, struct rhash_head *obj,
  * This function will eventually sleep to wait for an async resize
  * to complete. The caller is responsible that no further write operations
  * occurs in parallel.
+ *
+ * After cancel_work_sync() has returned, the deferred rehash worker is
+ * quiesced and, per the contract above, no other concurrent access to the
+ * rhashtable is possible. The tables are therefore owned exclusively by
+ * this function and can be walked without ht->mutex held.
  */
 void rhashtable_free_and_destroy(struct rhashtable *ht,
 				 void (*free_fn)(void *ptr, void *arg),
@@ -1177,8 +1190,15 @@ void rhashtable_free_and_destroy(struct rhashtable *ht,
 	irq_work_sync(&ht->run_irq_work);
 	cancel_work_sync(&ht->run_work);
 
-	mutex_lock(&ht->mutex);
-	tbl = rht_dereference(ht->tbl, ht);
+	/*
+	 * Do NOT take ht->mutex here. The rehash worker establishes
+	 * ht->mutex -> fs_reclaim via GFP_KERNEL bucket allocation under
+	 * the mutex; callers on the reclaim path (e.g. simple_xattr_ht_free()
+	 * from evict() under the dcache shrinker for shmem/kernfs/pidfs
+	 * inodes) would otherwise close a circular dependency
+	 * fs_reclaim -> ht->mutex.
+	 */
+	tbl = rcu_dereference_raw(ht->tbl);
 restart:
 	if (free_fn) {
 		for (i = 0; i < tbl->size; i++) {
@@ -1187,22 +1207,21 @@ restart:
 			cond_resched();
 			for (pos = rht_ptr_exclusive(rht_bucket(tbl, i)),
 			     next = !rht_is_a_nulls(pos) ?
-					rht_dereference(pos->next, ht) : NULL;
+					rcu_dereference_raw(pos->next) : NULL;
 			     !rht_is_a_nulls(pos);
 			     pos = next,
 			     next = !rht_is_a_nulls(pos) ?
-					rht_dereference(pos->next, ht) : NULL)
+					rcu_dereference_raw(pos->next) : NULL)
 				rhashtable_free_one(ht, pos, free_fn, arg);
 		}
 	}
 
-	next_tbl = rht_dereference(tbl->future_tbl, ht);
+	next_tbl = rcu_dereference_raw(tbl->future_tbl);
 	bucket_table_free(tbl);
 	if (next_tbl) {
 		tbl = next_tbl;
 		goto restart;
 	}
-	mutex_unlock(&ht->mutex);
 }
 EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);