From 1cc523271ef0b6305c565a143e3d48f6fff826dd Mon Sep 17 00:00:00 2001 From: stephen hemminger Date: Mon, 22 Feb 2010 07:57:17 +0000 Subject: seq_file: add RCU versions of new hlist/list iterators (v3) Many usages of seq_file use RCU protected lists, so non RCU iterators will not work safely. Signed-off-by: Stephen Hemminger Signed-off-by: David S. Miller --- fs/seq_file.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) (limited to 'fs/seq_file.c') diff --git a/fs/seq_file.c b/fs/seq_file.c index f65b16f02da3..5afd554efad3 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -750,3 +750,74 @@ struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head, return node->next; } EXPORT_SYMBOL(seq_hlist_next); + +/** + * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU + * @head: the head of the hlist + * @pos: the start position of the sequence + * + * Called at seq_file->op->start(). + * + * This list-traversal primitive may safely run concurrently with + * the _rcu list-mutation primitives such as hlist_add_head_rcu() + * as long as the traversal is guarded by rcu_read_lock(). + */ +struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head, + loff_t pos) +{ + struct hlist_node *node; + + __hlist_for_each_rcu(node, head) + if (pos-- == 0) + return node; + return NULL; +} +EXPORT_SYMBOL(seq_hlist_start_rcu); + +/** + * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU + * @head: the head of the hlist + * @pos: the start position of the sequence + * + * Called at seq_file->op->start(). Call this function if you want to + * print a header at the top of the output. + * + * This list-traversal primitive may safely run concurrently with + * the _rcu list-mutation primitives such as hlist_add_head_rcu() + * as long as the traversal is guarded by rcu_read_lock(). + */ +struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head, + loff_t pos) +{ + if (!pos) + return SEQ_START_TOKEN; + + return seq_hlist_start_rcu(head, pos - 1); +} +EXPORT_SYMBOL(seq_hlist_start_head_rcu); + +/** + * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU + * @v: the current iterator + * @head: the head of the hlist + * @pos: the current posision + * + * Called at seq_file->op->next(). + * + * This list-traversal primitive may safely run concurrently with + * the _rcu list-mutation primitives such as hlist_add_head_rcu() + * as long as the traversal is guarded by rcu_read_lock(). + */ +struct hlist_node *seq_hlist_next_rcu(void *v, + struct hlist_head *head, + loff_t *ppos) +{ + struct hlist_node *node = v; + + ++*ppos; + if (v == SEQ_START_TOKEN) + return rcu_dereference(head->first); + else + return rcu_dereference(node->next); +} +EXPORT_SYMBOL(seq_hlist_next_rcu); -- cgit v1.2.3-70-g09d2