Re: [PATCH] fib_trie: rescan if key is lost during dump
From: Stephen Hemminger <[EMAIL PROTECTED]> Date: Thu, 24 Jan 2008 13:51:12 -0800 > Normally during a dump the key of the last dumped entry is used for > continuation, but since lock is dropped it might be lost. In that case > fallback to the old counter based N^2 behaviour. This means the dump will > end up > skipping some routes which matches what FIB_HASH does. > > Signed-off-by: Stephen Hemminger <[EMAIL PROTECTED]> Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] fib_trie: rescan if key is lost during dump
On Fri, Jan 25, 2008 at 08:13:15AM -0800, Stephen Hemminger wrote: ... > 2. RCU is unnecessary here because of use of RTNL. I am going to defer >on this till after #1. That patch is much less important. Thanks! (I've started to suspect another advanced RCU trick already...) Jarek P. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] fib_trie: rescan if key is lost during dump
On Fri, 25 Jan 2008 09:23:00 +0100 Jarek Poplawski <[EMAIL PROTECTED]> wrote: > On 24-01-2008 22:51, Stephen Hemminger wrote: > > Normally during a dump the key of the last dumped entry is used for > > continuation, but since lock is dropped it might be lost. In that case > > fallback to the old counter based N^2 behaviour. This means the dump will > > end up > > skipping some routes which matches what FIB_HASH does. > > > > Signed-off-by: Stephen Hemminger <[EMAIL PROTECTED]> > ... > > @@ -1918,35 +1931,37 @@ static int fn_trie_dump(struct fib_table > > struct leaf *l; > > struct trie *t = (struct trie *) tb->tb_data; > > t_key key = cb->args[2]; > > + int count = cb->args[3]; > > > > rcu_read_lock(); > > Sorry, but I lost the point: is rtnl held or not held here at the moment? > If held, how this rcu_read_lock can help? Maybe some additional comment > in the code? > > Thanks, > Jarek P. There are two different issues, (therefore two different patches). 1. How to handle multipart resume when the key was deleted during the period the lock was dropped. That is what this patch addresses. 2. RCU is unnecessary here because of use of RTNL. I am going to defer on this till after #1. That patch is much less important. -- Stephen Hemminger <[EMAIL PROTECTED]> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] fib_trie: rescan if key is lost during dump
On 24-01-2008 22:51, Stephen Hemminger wrote: > Normally during a dump the key of the last dumped entry is used for > continuation, but since lock is dropped it might be lost. In that case > fallback to the old counter based N^2 behaviour. This means the dump will > end up > skipping some routes which matches what FIB_HASH does. > > Signed-off-by: Stephen Hemminger <[EMAIL PROTECTED]> ... > @@ -1918,35 +1931,37 @@ static int fn_trie_dump(struct fib_table > struct leaf *l; > struct trie *t = (struct trie *) tb->tb_data; > t_key key = cb->args[2]; > + int count = cb->args[3]; > > rcu_read_lock(); Sorry, but I lost the point: is rtnl held or not held here at the moment? If held, how this rcu_read_lock can help? Maybe some additional comment in the code? Thanks, Jarek P. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH] fib_trie: rescan if key is lost during dump
Normally during a dump the key of the last dumped entry is used for
continuation, but since lock is dropped it might be lost. In that case
fallback to the old counter based N^2 behaviour. This means the dump will end
up
skipping some routes which matches what FIB_HASH does.
Signed-off-by: Stephen Hemminger <[EMAIL PROTECTED]>
--- a/include/linux/netlink.h 2008-01-24 13:39:40.0 -0800
+++ b/include/linux/netlink.h 2008-01-24 13:42:05.0 -0800
@@ -219,7 +219,7 @@ struct netlink_callback
int (*dump)(struct sk_buff * skb, struct netlink_callback
*cb);
int (*done)(struct netlink_callback *cb);
int family;
- longargs[5];
+ longargs[6];
};
struct netlink_notify
--- a/net/ipv4/fib_trie.c 2008-01-24 13:39:40.0 -0800
+++ b/net/ipv4/fib_trie.c 2008-01-24 13:44:26.0 -0800
@@ -1743,6 +1743,19 @@ static struct leaf *trie_nextleaf(struct
return leaf_walk_rcu(p, c);
}
+static struct leaf *trie_leafindex(struct trie *t, int index)
+{
+ struct leaf *l = trie_firstleaf(t);
+
+ while (index-- > 0) {
+ l = trie_nextleaf(l);
+ if (!l)
+ break;
+ }
+ return l;
+}
+
+
/*
* Caller must hold RTNL.
*/
@@ -1848,7 +1861,7 @@ static int fn_trie_dump_fa(t_key key, in
struct fib_alias *fa;
__be32 xkey = htonl(key);
- s_i = cb->args[4];
+ s_i = cb->args[5];
i = 0;
/* rcu_read_lock is hold by caller */
@@ -1869,12 +1882,12 @@ static int fn_trie_dump_fa(t_key key, in
plen,
fa->fa_tos,
fa->fa_info, NLM_F_MULTI) < 0) {
- cb->args[4] = i;
+ cb->args[5] = i;
return -1;
}
i++;
}
- cb->args[4] = i;
+ cb->args[5] = i;
return skb->len;
}
@@ -1885,7 +1898,7 @@ static int fn_trie_dump_leaf(struct leaf
struct hlist_node *node;
int i, s_i;
- s_i = cb->args[3];
+ s_i = cb->args[4];
i = 0;
/* rcu_read_lock is hold by caller */
@@ -1896,19 +1909,19 @@ static int fn_trie_dump_leaf(struct leaf
}
if (i > s_i)
- cb->args[4] = 0;
+ cb->args[5] = 0;
if (list_empty(&li->falh))
continue;
if (fn_trie_dump_fa(l->key, li->plen, &li->falh, tb, skb, cb) <
0) {
- cb->args[3] = i;
+ cb->args[4] = i;
return -1;
}
i++;
}
- cb->args[3] = i;
+ cb->args[4] = i;
return skb->len;
}
@@ -1918,35 +1931,37 @@ static int fn_trie_dump(struct fib_table
struct leaf *l;
struct trie *t = (struct trie *) tb->tb_data;
t_key key = cb->args[2];
+ int count = cb->args[3];
rcu_read_lock();
/* Dump starting at last key.
* Note: 0.0.0.0/0 (ie default) is first key.
*/
- if (!key)
+ if (count == 0)
l = trie_firstleaf(t);
else {
+ /* Normally, continue from last key, but if that is missing
+* fallback to using slow rescan
+*/
l = fib_find_node(t, key);
- if (!l) {
- /* The table changed during the dump, rather than
-* giving partial data, just make application retry.
-*/
- rcu_read_unlock();
- return -EBUSY;
- }
+ if (!l)
+ l = trie_leafindex(t, count);
}
while (l) {
cb->args[2] = l->key;
if (fn_trie_dump_leaf(l, tb, skb, cb) < 0) {
+ cb->args[3] = count;
rcu_read_unlock();
return -1;
}
+ ++count;
l = trie_nextleaf(l);
- memset(&cb->args[3], 0,
- sizeof(cb->args) - 3*sizeof(cb->args[0]));
+ memset(&cb->args[4], 0,
+ sizeof(cb->args) - 4*sizeof(cb->args[0]));
}
+ cb->args[3] = count;
rcu_read_unlock();
return skb->len;
--
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