Re: [PATCH] btrfs: improve messages when devices rescanned

[Nikolay Borisov <nborisov@suse.com>]

On 3.09.20 г. 10:27 ч., Anand Jain wrote:
> Systems booting without the initramfs seems to scan an unusual kind
> of device path. And at a later time, the device is updated to the
> correct path. We generally print the process name and PID of the process
> scanning the device but we don't capture the same information if the
> device path is rescanned with a different pathname.
> 
> But the current message is too long, so drop the unwanted words and add
> process name and PID.
> 
> While at this also update the duplicate device warning to include the
> process name and PID.
> 
> Reported-by: https://bugzilla.kernel.org/show_bug.cgi?id=89721
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> ---
>  fs/btrfs/volumes.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index dc81646b13c0..c386ad722ae1 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -942,16 +942,18 @@ static noinline struct btrfs_device *device_list_add(const char *path,
>  				bdput(path_bdev);
>  				mutex_unlock(&fs_devices->device_list_mutex);
>  				btrfs_warn_in_rcu(device->fs_info,
> -			"duplicate device fsid:devid for %pU:%llu old:%s new:%s",
> -					disk_super->fsid, devid,
> -					rcu_str_deref(device->name), path);
> +	"duplicate device %s devid %llu generation %llu scanned by %s (%d)",
> +						  path, devid, found_transid,
> +						  current->comm,
> +						  task_pid_nr(current));
>  				return ERR_PTR(-EEXIST);
>  			}
>  			bdput(path_bdev);
>  			btrfs_info_in_rcu(device->fs_info,
> -				"device fsid %pU devid %llu moved old:%s new:%s",
> -				disk_super->fsid, devid,
> -				rcu_str_deref(device->name), path);
> +				"device path %s changed to %s by %s (pid %d)",
> +					  rcu_str_deref(device->name),
> +					  path, current->comm,
> +					  task_pid_nr(current));

This 2nd messages is misleading, it's not the process calling
device_list_add which have changed the path per-se but rather it sees
the changed path. It's not possible to know why it changed in this
context. The idea here is "

"Process %pid saw different dev path %new_dev_path for dev %old_path"

>  		}
>  
>  		name = rcu_string_strdup(path, GFP_NOFS);
>