diff options
| -rw-r--r-- | fs/btrfs/volumes.c | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index deaf1997a3a5..33fa73668534 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -8250,6 +8250,36 @@ int btrfs_run_dev_stats(struct btrfs_trans_handle *trans) struct btrfs_device *device; int stats_cnt; int ret = 0; + bool need_update_dev_stats = false; + + /* + * Do an initial pass using RCU to see if we need to update any dev + * stats item. This is to avoid taking the device_list_mutex which is + * acquired by the fitrim operation and can take a while since it does + * discard operations while holding that mutex. Most of the time, if + * we are on a healthy filesystem, we don't have new stat updates, so + * this avoids blocking on that mutex, which is specially important + * because we are called during the critical section of a transaction + * commit, therefore blocking new transactions from starting while + * discard is running. + * + * Also note that adding/removing devices also requires starting a + * transaction, and since we are called from the critical section of a + * transaction commit, no one can be concurrently adding or removing a + * device. + */ + rcu_read_lock(); + list_for_each_entry_rcu(device, &fs_devices->devices, dev_list) { + if (device->dev_stats_valid && + atomic_read(&device->dev_stats_ccnt) != 0) { + need_update_dev_stats = true; + break; + } + } + rcu_read_unlock(); + + if (!need_update_dev_stats) + return 0; mutex_lock(&fs_devices->device_list_mutex); list_for_each_entry(device, &fs_devices->devices, dev_list) { |