From: Tang Junhui <[email protected]> In btree_flush_write(), two places need to take a locker to avoid races:
Firstly, we need take rcu read locker to protect the bucket_hash traverse, since hlist_for_each_entry_rcu() must be called under the protection of rcu read locker. Secondly, we need take b->write_lock locker to protect journal of the btree node, otherwise, the btree node may have been written, and the journal have been assign to NULL. Signed-off-by: Tang Junhui <[email protected]> --- drivers/md/bcache/journal.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c index 02a98dd..505f9f3 100644 --- a/drivers/md/bcache/journal.c +++ b/drivers/md/bcache/journal.c @@ -375,7 +375,9 @@ static void btree_flush_write(struct cache_set *c) retry: best = NULL; - for_each_cached_btree(b, c, i) + rcu_read_lock(); + for_each_cached_btree(b, c, i) { + mutex_lock(&b->write_lock); if (btree_current_write(b)->journal) { if (!best) best = b; @@ -385,6 +387,9 @@ static void btree_flush_write(struct cache_set *c) best = b; } } + mutex_unlock(&b->write_lock); + } + rcu_read_unlock(); b = best; if (b) { -- 1.8.3.1
