Re: [PATCH] btrfs: Fix suspicious RCU usage warning in device_list_add

[Anand Jain]

On 11/14/2018 03:24 PM, Lu Fengqi wrote:

=============================
WARNING: suspicious RCU usage
4.20.0-rc2+ #23 Tainted: G           O
-----------------------------
fs/btrfs/volumes.c:886 suspicious rcu_dereference_check() usage!

Use btrfs_info_in_rcu instead of pr_info for the required lock/unlock of
RCU string.

Fixes: 1f265fc6f58b ("btrfs: harden agaist duplicate fsid on scanned devices")
Signed-off-by: Lu Fengqi <lufq.f...@cn.fujitsu.com>

 Thanks Lu. I missed it.
 Reviewed-by: Anand Jain <anand.j...@oracle.com>

---
  fs/btrfs/volumes.c | 8 ++++----
  1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 2186300bab91..6039ae5c549e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -873,15 +873,15 @@ static noinline struct btrfs_device 
*device_list_add(const char *path,
                        if (device->bdev != path_bdev) {
                                bdput(path_bdev);
                                mutex_unlock(&fs_devices->device_list_mutex);
-                               pr_warn(
-               "BTRFS: duplicate device fsid:devid for %pU:%llu old:%s 
new:%s\n",
+                               btrfs_warn_in_rcu(device->fs_info,
+                       "duplicate device fsid:devid for %pU:%llu old:%s 
new:%s\n",
                                        disk_super->fsid, devid,
                                        rcu_str_deref(device->name), path);
                                return ERR_PTR(-EEXIST);
                        }
                        bdput(path_bdev);
-                       pr_info(
-                       "BTRFS: device fsid %pU devid %llu moved old:%s 
new:%s\n",
+                       btrfs_info_in_rcu(device->fs_info,
+                       "device fsid %pU devid %llu moved old:%s new:%s\n",
                                disk_super->fsid, devid,
                                rcu_str_deref(device->name), path);
                }