From adc6a3ab192eb40fb9d8b093c87d9aa785af4513 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Fri, 12 Apr 2019 11:52:08 +1000 Subject: rhashtable: move dereference inside rht_ptr() Rather than dereferencing a pointer to a bucket and then passing the result to rht_ptr(), we now pass in the pointer and do the dereference in rht_ptr(). This requires that we pass in the tbl and hash as well to support RCU checks, and means that the various rht_for_each functions can expect a pointer that can be dereferenced without further care. There are two places where we dereference a bucket pointer where there is no testable protection - in each case we know that we much have exclusive access without having taken a lock. The previous code used rht_dereference() to pretend that holding the mutex provided protects, but holding the mutex never provides protection for accessing buckets. So instead introduce rht_ptr_exclusive() that can be used when there is known to be exclusive access without holding any locks. Signed-off-by: NeilBrown Signed-off-by: David S. Miller --- lib/rhashtable.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'lib/rhashtable.c') diff --git a/lib/rhashtable.c b/lib/rhashtable.c index e387ceb00e86..237368ea98c5 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -231,7 +231,8 @@ static int rhashtable_rehash_one(struct rhashtable *ht, err = -ENOENT; - rht_for_each_from(entry, rht_ptr(*bkt), old_tbl, old_hash) { + rht_for_each_from(entry, rht_ptr(bkt, old_tbl, old_hash), + old_tbl, old_hash) { err = 0; next = rht_dereference_bucket(entry->next, old_tbl, old_hash); @@ -248,8 +249,7 @@ static int rhashtable_rehash_one(struct rhashtable *ht, rht_lock_nested(new_tbl, &new_tbl->buckets[new_hash], SINGLE_DEPTH_NESTING); - head = rht_ptr(rht_dereference_bucket(new_tbl->buckets[new_hash], - new_tbl, new_hash)); + head = rht_ptr(new_tbl->buckets + new_hash, new_tbl, new_hash); RCU_INIT_POINTER(entry->next, head); @@ -491,7 +491,7 @@ static void *rhashtable_lookup_one(struct rhashtable *ht, int elasticity; elasticity = RHT_ELASTICITY; - rht_for_each_from(head, rht_ptr(*bkt), tbl, hash) { + rht_for_each_from(head, rht_ptr(bkt, tbl, hash), tbl, hash) { struct rhlist_head *list; struct rhlist_head *plist; @@ -557,7 +557,7 @@ static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht, if (unlikely(rht_grow_above_100(ht, tbl))) return ERR_PTR(-EAGAIN); - head = rht_ptr(rht_dereference_bucket(*bkt, tbl, hash)); + head = rht_ptr(bkt, tbl, hash); RCU_INIT_POINTER(obj->next, head); if (ht->rhlist) { @@ -1139,7 +1139,7 @@ restart: struct rhash_head *pos, *next; cond_resched(); - for (pos = rht_ptr(rht_dereference(*rht_bucket(tbl, i), ht)), + for (pos = rht_ptr_exclusive(rht_bucket(tbl, i)), next = !rht_is_a_nulls(pos) ? rht_dereference(pos->next, ht) : NULL; !rht_is_a_nulls(pos); -- cgit