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[FIB]: Fix rcu_dereference() abuses in fib_trie.c

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node_parent() and tnode_get_child() currently use rcu_dereference().

These functions are called from both
- readers only paths (where rcu_dereference() is needed), and
- writer path (where rcu_dereference() is not needed)

To make explicit where rcu_dereference() is really needed, I
introduced new node_parent_rcu() and tnode_get_child_rcu() functions
which use rcu_dereference(), while node_parent() and tnode_get_child()
dont use it.

Then I changed calling sites where rcu_dereference() was really needed
to call the _rcu() variants.

This should have no impact but for alpha architecture, and may help
future sparse checks.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2008-01-18 03:31:36 -08:00 committed by David S. Miller
parent 95b7d924a5
commit b59cfbf77d
1 changed files with 22 additions and 13 deletions
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35
net/ipv4/fib_trie.c
View file

@ -165,9 +165,13 @@ static struct kmem_cache *fn_alias_kmem __read_mostly;
static inline struct tnode *node_parent(struct node *node) static inline struct tnode *node_parent(struct node *node)
{ {
struct tnode *ret; return (struct tnode *)(node->parent & ~NODE_TYPE_MASK);
}
static inline struct tnode *node_parent_rcu(struct node *node)
{
struct tnode *ret = node_parent(node);
ret = (struct tnode *)(node->parent & ~NODE_TYPE_MASK);
return rcu_dereference(ret); return rcu_dereference(ret);
} }
@ -177,13 +181,18 @@ static inline void node_set_parent(struct node *node, struct tnode *ptr)
(unsigned long)ptr | NODE_TYPE(node)); (unsigned long)ptr | NODE_TYPE(node));
} }
/* rcu_read_lock needs to be hold by caller from readside */ static inline struct node *tnode_get_child(struct tnode *tn, unsigned int i)
static inline struct node *tnode_get_child(struct tnode *tn, int i)
{ {
BUG_ON(i >= 1 << tn->bits); BUG_ON(i >= 1U << tn->bits);
return rcu_dereference(tn->child[i]); return tn->child[i];
}
static inline struct node *tnode_get_child_rcu(struct tnode *tn, unsigned int i)
{
struct node *ret = tnode_get_child(tn, i);
return rcu_dereference(ret);
} }
static inline int tnode_child_length(const struct tnode *tn) static inline int tnode_child_length(const struct tnode *tn)
@ -938,7 +947,7 @@ fib_find_node(struct trie *t, u32 key)
if (tkey_sub_equals(tn->key, pos, tn->pos-pos, key)) { if (tkey_sub_equals(tn->key, pos, tn->pos-pos, key)) {
pos = tn->pos + tn->bits; pos = tn->pos + tn->bits;
n = tnode_get_child(tn, tkey_extract_bits(key, tn->pos, tn->bits)); n = tnode_get_child_rcu(tn, tkey_extract_bits(key, tn->pos, tn->bits));
} else } else
break; break;
} }
@ -1688,7 +1697,7 @@ static struct leaf *nextleaf(struct trie *t, struct leaf *thisleaf)
p = (struct tnode*) trie; /* Start */ p = (struct tnode*) trie; /* Start */
} else } else
p = node_parent(c); p = node_parent_rcu(c);
while (p) { while (p) {
int pos, last; int pos, last;
@ -1725,7 +1734,7 @@ static struct leaf *nextleaf(struct trie *t, struct leaf *thisleaf)
up: up:
/* No more children go up one step */ /* No more children go up one step */
c = (struct node *) p; c = (struct node *) p;
p = node_parent(c); p = node_parent_rcu(c);
} }
return NULL; /* Ready. Root of trie */ return NULL; /* Ready. Root of trie */
} }
@ -1987,7 +1996,7 @@ static struct node *fib_trie_get_next(struct fib_trie_iter *iter)
iter->tnode, iter->index, iter->depth); iter->tnode, iter->index, iter->depth);
rescan: rescan:
while (cindex < (1<<tn->bits)) { while (cindex < (1<<tn->bits)) {
struct node *n = tnode_get_child(tn, cindex); struct node *n = tnode_get_child_rcu(tn, cindex);
if (n) { if (n) {
if (IS_LEAF(n)) { if (IS_LEAF(n)) {
@ -2006,7 +2015,7 @@ rescan:
} }
/* Current node exhausted, pop back up */ /* Current node exhausted, pop back up */
p = node_parent((struct node *)tn); p = node_parent_rcu((struct node *)tn);
if (p) { if (p) {
cindex = tkey_extract_bits(tn->key, p->pos, p->bits)+1; cindex = tkey_extract_bits(tn->key, p->pos, p->bits)+1;
tn = p; tn = p;
@ -2315,7 +2324,7 @@ static int fib_trie_seq_show(struct seq_file *seq, void *v)
if (v == SEQ_START_TOKEN) if (v == SEQ_START_TOKEN)
return 0; return 0;
if (!node_parent(n)) { if (!node_parent_rcu(n)) {
if (iter->trie == iter->trie_local) if (iter->trie == iter->trie_local)
seq_puts(seq, "<local>:\n"); seq_puts(seq, "<local>:\n");
else else