Btrfs: using rcu lock in the reader side of devices list
fs_devices->devices is only updated on remove and add device paths, so we can
use rcu to protect it in the reader side
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index ce773fb..0de71fe 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -281,8 +281,9 @@
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
- mutex_lock(&fs_info->fs_devices->device_list_mutex);
- list_for_each_entry(device, &fs_info->fs_devices->devices, dev_list) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(device, &fs_info->fs_devices->devices,
+ dev_list) {
if (!device->bdev)
continue;
q = bdev_get_queue(device->bdev);
@@ -292,7 +293,7 @@
minlen);
}
}
- mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+ rcu_read_unlock();
if (!num_devices)
return -EOPNOTSUPP;