bcachefs: fix can_write_extent()

Failing to check the return value of bch2_dev_rcu(): we could
(technically) race with device removal.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/data_update.c b/fs/bcachefs/data_update.c
index c39ea51e9e484cb3cd62fc62c03a29a6833fce43..de096ca65b4babf7749c8bbe1436bd7c533f9e0e 100644 (file)
--- a/fs/bcachefs/data_update.c
+++ b/fs/bcachefs/data_update.c
@@ -744,7 +744,9 @@ static int can_write_extent(struct bch_fs *c, struct data_update *m)
        rcu_read_lock();
        unsigned nr_replicas = 0, i;
        for_each_set_bit(i, devs.d, BCH_SB_MEMBERS_MAX) {
-               struct bch_dev *ca = bch2_dev_rcu(c, i);
+               struct bch_dev *ca = bch2_dev_rcu_noerror(c, i);
+               if (!ca)
+                       continue;
 
                struct bch_dev_usage usage;
                bch2_dev_usage_read_fast(ca, &usage);