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bcache: Fix a race when freeing btree nodes 

This isn't a bulletproof fix; btree_node_free() -> bch_bucket_free() puts the
bucket on the unused freelist, where it can be reused right away without any
ordering requirements. It would be better to wait on at least a journal write to
go down before reusing the bucket. bch_btree_set_root() does this, and inserting
into non leaf nodes is completely synchronous so we should be ok, but future
patches are just going to get rid of the unused freelist - it was needed in the
past for various reasons but shouldn't be anymore.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
This commit is contained in:
Kent Overstreet 2014-03-17 18:22:34 -07:00
parent 4fe6a81670
commit 05335cff9f
1 changed files with 20 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

53
drivers/md/bcache/btree.c
View File

@ -1006,8 +1006,6 @@ static void btree_node_prefetch(struct cache_set *c, struct bkey *k, int level)
static void btree_node_free(struct btree *b)
{
unsigned i;
trace_bcache_btree_node_free(b);
BUG_ON(b == b->c->root);
@ -1019,14 +1017,6 @@ static void btree_node_free(struct btree *b)
cancel_delayed_work(&b->work);
mutex_lock(&b->c->bucket_lock);
for (i = 0; i < KEY_PTRS(&b->key); i++) {
BUG_ON(atomic_read(&PTR_BUCKET(b->c, &b->key, i)->pin));
bch_inc_gen(PTR_CACHE(b->c, &b->key, i),
PTR_BUCKET(b->c, &b->key, i));
}
bch_bucket_free(b->c, &b->key);
mca_bucket_free(b);
mutex_unlock(&b->c->bucket_lock);
@ -1086,16 +1076,19 @@ static void make_btree_freeing_key(struct btree *b, struct bkey *k)
{
unsigned i;
mutex_lock(&b->c->bucket_lock);
atomic_inc(&b->c->prio_blocked);
bkey_copy(k, &b->key);
bkey_copy_key(k, &ZERO_KEY);
for (i = 0; i < KEY_PTRS(k); i++) {
uint8_t g = PTR_BUCKET(b->c, k, i)->gen + 1;
for (i = 0; i < KEY_PTRS(k); i++)
SET_PTR_GEN(k, i,
bch_inc_gen(PTR_CACHE(b->c, &b->key, i),
PTR_BUCKET(b->c, &b->key, i)));
SET_PTR_GEN(k, i, g);
}
atomic_inc(&b->c->prio_blocked);
mutex_unlock(&b->c->bucket_lock);
}
static int btree_check_reserve(struct btree *b, struct btree_op *op)
@ -1342,6 +1335,13 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
bch_keylist_add(keylist, &new_nodes[i]->key);
}
closure_sync(&cl);
/* We emptied out this node */
BUG_ON(btree_bset_first(new_nodes[0])->keys);
btree_node_free(new_nodes[0]);
rw_unlock(true, new_nodes[0]);
for (i = 0; i < nodes; i++) {
if (__bch_keylist_realloc(keylist, bkey_u64s(&r[i].b->key)))
goto out_nocoalesce;
@ -1350,12 +1350,8 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
bch_keylist_push(keylist);
}
/* We emptied out this node */
BUG_ON(btree_bset_first(new_nodes[0])->keys);
btree_node_free(new_nodes[0]);
rw_unlock(true, new_nodes[0]);
closure_sync(&cl);
bch_btree_insert_node(b, op, keylist, NULL, NULL);
BUG_ON(!bch_keylist_empty(keylist));
for (i = 0; i < nodes; i++) {
btree_node_free(r[i].b);
@ -1364,9 +1360,6 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
r[i].b = new_nodes[i];
}
bch_btree_insert_node(b, op, keylist, NULL, NULL);
BUG_ON(!bch_keylist_empty(keylist));
memmove(r, r + 1, sizeof(r[0]) * (nodes - 1));
r[nodes - 1].b = ERR_PTR(-EINTR);
@ -1456,12 +1449,11 @@ static int btree_gc_recurse(struct btree *b, struct btree_op *op,
keys.top);
bch_keylist_push(&keys);
btree_node_free(last->b);
bch_btree_insert_node(b, op, &keys,
NULL, NULL);
BUG_ON(!bch_keylist_empty(&keys));
btree_node_free(last->b);
rw_unlock(true, last->b);
last->b = n;
@ -1924,26 +1916,21 @@ static int btree_split(struct btree *b, struct btree_op *op,
closure_sync(&cl);
bch_btree_set_root(n3);
rw_unlock(true, n3);
btree_node_free(b);
} else if (!b->parent) {
/* Root filled up but didn't need to be split */
closure_sync(&cl);
bch_btree_set_root(n1);
btree_node_free(b);
} else {
/* Split a non root node */
closure_sync(&cl);
make_btree_freeing_key(b, parent_keys.top);
bch_keylist_push(&parent_keys);
btree_node_free(b);
bch_btree_insert_node(b->parent, op, &parent_keys, NULL, NULL);
BUG_ON(!bch_keylist_empty(&parent_keys));
}
btree_node_free(b);
rw_unlock(true, n1);
bch_time_stats_update(&b->c->btree_split_time, start_time);