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fib_trie: inflate/halve nodes in a more RCU friendly way 

This change pulls the node_set_parent functionality out of put_child_reorg
and instead leaves that to the function to take care of as well.  By doing
this we can fully construct the new cluster of tnodes and all of the
pointers out of it before we start routing pointers into it.

I am suspecting this will likely fix some concurency issues though I don't
have a good test to show as such.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexander Duyck 2014-12-31 10:56:55 -08:00 committed by David S. Miller
parent fc86a93b46
commit 12c081a5c8
1 changed files with 120 additions and 126 deletions
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246
net/ipv4/fib_trie.c
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@ -391,8 +391,6 @@ static void put_child(struct tnode *tn, unsigned long i, struct tnode *n)
else if (!wasfull && isfull) else if (!wasfull && isfull)
tn->full_children++; tn->full_children++;
node_set_parent(n, tn);
rcu_assign_pointer(tn->child[i], n); rcu_assign_pointer(tn->child[i], n);
} }
@ -436,10 +434,8 @@ static void tnode_free(struct tnode *tn)
static int inflate(struct trie *t, struct tnode *oldtnode) static int inflate(struct trie *t, struct tnode *oldtnode)
{ {
unsigned long olen = tnode_child_length(oldtnode); struct tnode *inode, *node0, *node1, *tn, *tp;
struct tnode *tp = node_parent(oldtnode); unsigned long i, j, k;
struct tnode *tn;
unsigned long i;
t_key m; t_key m;
pr_debug("In inflate\n"); pr_debug("In inflate\n");
@ -448,43 +444,13 @@ static int inflate(struct trie *t, struct tnode *oldtnode)
if (!tn) if (!tn)
return -ENOMEM; return -ENOMEM;
/* /* Assemble all of the pointers in our cluster, in this case that
* Preallocate and store tnodes before the actual work so we * represents all of the pointers out of our allocated nodes that
* don't get into an inconsistent state if memory allocation * point to existing tnodes and the links between our allocated
* fails. In case of failure we return the oldnode and inflate * nodes.
* of tnode is ignored.
*/ */
for (i = 0, m = 1u << tn->pos; i < olen; i++) { for (i = tnode_child_length(oldtnode), m = 1u << tn->pos; i;) {
struct tnode *inode = tnode_get_child(oldtnode, i); inode = tnode_get_child(oldtnode, --i);
if (tnode_full(oldtnode, inode) && (inode->bits > 1)) {
struct tnode *left, *right;
left = tnode_new(inode->key & ~m, inode->pos,
inode->bits - 1);
if (!left)
goto nomem;
tnode_free_append(tn, left);
right = tnode_new(inode->key | m, inode->pos,
inode->bits - 1);
if (!right)
goto nomem;
tnode_free_append(tn, right);
put_child(tn, 2*i, left);
put_child(tn, 2*i+1, right);
}
}
/* prepare oldtnode to be freed */
tnode_free_init(oldtnode);
for (i = 0; i < olen; i++) {
struct tnode *inode = tnode_get_child(oldtnode, i);
struct tnode *left, *right;
unsigned long size, j;
/* An empty child */ /* An empty child */
if (inode == NULL) if (inode == NULL)
@ -496,65 +462,99 @@ static int inflate(struct trie *t, struct tnode *oldtnode)
continue; continue;
} }
/* drop the node in the old tnode free list */
tnode_free_append(oldtnode, inode);
/* An internal node with two children */ /* An internal node with two children */
if (inode->bits == 1) { if (inode->bits == 1) {
put_child(tn, 2*i, rtnl_dereference(inode->child[0])); put_child(tn, 2 * i + 1, tnode_get_child(inode, 1));
put_child(tn, 2*i+1, rtnl_dereference(inode->child[1])); put_child(tn, 2 * i, tnode_get_child(inode, 0));
continue; continue;
} }
/* An internal node with more than two children */
/* We will replace this node 'inode' with two new /* We will replace this node 'inode' with two new
* ones, 'left' and 'right', each with half of the * ones, 'node0' and 'node1', each with half of the
* original children. The two new nodes will have * original children. The two new nodes will have
* a position one bit further down the key and this * a position one bit further down the key and this
* means that the "significant" part of their keys * means that the "significant" part of their keys
* (see the discussion near the top of this file) * (see the discussion near the top of this file)
* will differ by one bit, which will be "0" in * will differ by one bit, which will be "0" in
* left's key and "1" in right's key. Since we are * node0's key and "1" in node1's key. Since we are
* moving the key position by one step, the bit that * moving the key position by one step, the bit that
* we are moving away from - the bit at position * we are moving away from - the bit at position
* (inode->pos) - is the one that will differ between * (tn->pos) - is the one that will differ between
* left and right. So... we synthesize that bit in the * node0 and node1. So... we synthesize that bit in the
* two new keys. * two new keys.
* The mask 'm' below will be a single "one" bit at
* the position (inode->pos)
*/ */
node1 = tnode_new(inode->key | m, inode->pos, inode->bits - 1);
if (!node1)
goto nomem;
tnode_free_append(tn, node1);
/* Use the old key, but set the new significant node0 = tnode_new(inode->key & ~m, inode->pos, inode->bits - 1);
* bit to zero. if (!node0)
*/ goto nomem;
tnode_free_append(tn, node0);
left = tnode_get_child(tn, 2*i); /* populate child pointers in new nodes */
put_child(tn, 2*i, NULL); for (k = tnode_child_length(inode), j = k / 2; j;) {
put_child(node1, --j, tnode_get_child(inode, --k));
BUG_ON(!left); put_child(node0, j, tnode_get_child(inode, j));
put_child(node1, --j, tnode_get_child(inode, --k));
right = tnode_get_child(tn, 2*i+1); put_child(node0, j, tnode_get_child(inode, j));
put_child(tn, 2*i+1, NULL);
BUG_ON(!right);
size = tnode_child_length(left);
for (j = 0; j < size; j++) {
put_child(left, j, rtnl_dereference(inode->child[j]));
put_child(right, j, rtnl_dereference(inode->child[j + size]));
} }
put_child(tn, 2 * i, left); /* link new nodes to parent */
put_child(tn, 2 * i + 1, right); NODE_INIT_PARENT(node1, tn);
NODE_INIT_PARENT(node0, tn);
/* resize child nodes */ /* link parent to nodes */
resize(t, left); put_child(tn, 2 * i + 1, node1);
resize(t, right); put_child(tn, 2 * i, node0);
} }
/* setup the parent pointer into and out of this node */
tp = node_parent(oldtnode);
NODE_INIT_PARENT(tn, tp);
put_child_root(tp, t, tn->key, tn); put_child_root(tp, t, tn->key, tn);
/* prepare oldtnode to be freed */
tnode_free_init(oldtnode);
/* update all child nodes parent pointers to route to us */
for (i = tnode_child_length(oldtnode); i;) {
inode = tnode_get_child(oldtnode, --i);
/* A leaf or an internal node with skipped bits */
if (!tnode_full(oldtnode, inode)) {
node_set_parent(inode, tn);
continue;
}
/* drop the node in the old tnode free list */
tnode_free_append(oldtnode, inode);
/* fetch new nodes */
node1 = tnode_get_child(tn, 2 * i + 1);
node0 = tnode_get_child(tn, 2 * i);
/* bits == 1 then node0 and node1 represent inode's children */
if (inode->bits == 1) {
node_set_parent(node1, tn);
node_set_parent(node0, tn);
continue;
}
/* update parent pointers in child node's children */
for (k = tnode_child_length(inode), j = k / 2; j;) {
node_set_parent(tnode_get_child(inode, --k), node1);
node_set_parent(tnode_get_child(inode, --j), node0);
node_set_parent(tnode_get_child(inode, --k), node1);
node_set_parent(tnode_get_child(inode, --j), node0);
}
/* resize child nodes */
resize(t, node1);
resize(t, node0);
}
/* we completed without error, prepare to free old node */ /* we completed without error, prepare to free old node */
tnode_free(oldtnode); tnode_free(oldtnode);
return 0; return 0;
@ -566,10 +566,8 @@ static int inflate(struct trie *t, struct tnode *oldtnode)
static int halve(struct trie *t, struct tnode *oldtnode) static int halve(struct trie *t, struct tnode *oldtnode)
{ {
unsigned long olen = tnode_child_length(oldtnode); struct tnode *tn, *tp, *inode, *node0, *node1;
struct tnode *tp = node_parent(oldtnode); unsigned long i;
struct tnode *tn, *left, *right;
int i;
pr_debug("In halve\n"); pr_debug("In halve\n");
@ -577,68 +575,64 @@ static int halve(struct trie *t, struct tnode *oldtnode)
if (!tn) if (!tn)
return -ENOMEM; return -ENOMEM;
/* /* Assemble all of the pointers in our cluster, in this case that
* Preallocate and store tnodes before the actual work so we * represents all of the pointers out of our allocated nodes that
* don't get into an inconsistent state if memory allocation * point to existing tnodes and the links between our allocated
* fails. In case of failure we return the oldnode and halve * nodes.
* of tnode is ignored.
*/ */
for (i = tnode_child_length(oldtnode); i;) {
node1 = tnode_get_child(oldtnode, --i);
node0 = tnode_get_child(oldtnode, --i);
for (i = 0; i < olen; i += 2) { /* At least one of the children is empty */
left = tnode_get_child(oldtnode, i); if (!node1 || !node0) {
right = tnode_get_child(oldtnode, i+1); put_child(tn, i / 2, node1 ? : node0);
continue;
/* Two nonempty children */
if (left && right) {
struct tnode *newn;
newn = tnode_new(left->key, oldtnode->pos, 1);
if (!newn) {
tnode_free(tn);
return -ENOMEM;
}
tnode_free_append(tn, newn);
put_child(tn, i/2, newn);
} }
/* Two nonempty children */
inode = tnode_new(node0->key, oldtnode->pos, 1);
if (!inode) {
tnode_free(tn);
return -ENOMEM;
}
tnode_free_append(tn, inode);
/* initialize pointers out of node */
put_child(inode, 1, node1);
put_child(inode, 0, node0);
NODE_INIT_PARENT(inode, tn);
/* link parent to node */
put_child(tn, i / 2, inode);
} }
/* setup the parent pointer out of and back into this node */
tp = node_parent(oldtnode);
NODE_INIT_PARENT(tn, tp);
put_child_root(tp, t, tn->key, tn);
/* prepare oldtnode to be freed */ /* prepare oldtnode to be freed */
tnode_free_init(oldtnode); tnode_free_init(oldtnode);
for (i = 0; i < olen; i += 2) { /* update all of the child parent pointers */
struct tnode *newBinNode; for (i = tnode_child_length(tn); i;) {
inode = tnode_get_child(tn, --i);
left = tnode_get_child(oldtnode, i); /* only new tnodes will be considered "full" nodes */
right = tnode_get_child(oldtnode, i+1); if (!tnode_full(tn, inode)) {
node_set_parent(inode, tn);
/* At least one of the children is empty */
if (left == NULL) {
if (right == NULL) /* Both are empty */
continue;
put_child(tn, i/2, right);
continue;
}
if (right == NULL) {
put_child(tn, i/2, left);
continue; continue;
} }
/* Two nonempty children */ /* Two nonempty children */
newBinNode = tnode_get_child(tn, i/2); node_set_parent(tnode_get_child(inode, 1), inode);
put_child(newBinNode, 0, left); node_set_parent(tnode_get_child(inode, 0), inode);
put_child(newBinNode, 1, right);
put_child(tn, i / 2, newBinNode);
/* resize child node */ /* resize child node */
resize(t, newBinNode); resize(t, inode);
} }
put_child_root(tp, t, tn->key, tn);
/* all pointers should be clean so we are done */ /* all pointers should be clean so we are done */
tnode_free(oldtnode); tnode_free(oldtnode);