From: Tang Junhui <tang.junhui@xxxxxxxxxx>
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 <tang.junhui@xxxxxxxxxx>
---
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
