Re: [PATCH 2/2] btrfs: check generation as replace duplicates devid+uuid

[Wang Shilong <wangsl.fnst@cn.fujitsu.com>]

Hi Anand,

On 06/13/2014 12:26 PM, Anand Jain wrote:
>   
<..snip..>
> @@ -523,6 +523,16 @@ static noinline int device_list_add(const char *path,
>   
>   		if (fs_devices->opened)
>   			return -EBUSY;
> +		else {
> +			/*
> +			 * That is if the FS is _not_ mounted and if you are here, that
> +			 * means there is more than one disk with same uuid and devid.
> +			 * We keep the one with larger generation number or the last-in
> +			 * if generation are equal.
> +			 */
> +			if (found_transid < device->generation)
> +				return -EINVAL;
> +		}
I tried this patch it outputed the following message if it encounter two 
device with the same uuid and device id:

Scanning for Btrfs filesystems
ERROR: device scan failed '/dev/sdc' - Invalid argument

Same comment as your first patch here.
>   
>   		name = rcu_string_strdup(path, GFP_NOFS);
>   		if (!name)
> @@ -535,6 +545,15 @@ static noinline int device_list_add(const char *path,
>   		}
>   	}
>   
> +	/*
> +	 * Unmount does not free the btrfs_device struct but would zero
> +	 * generation along with most of the other members. So just update
> +	 * it back. We need it to pick the disk with largest generation
> +	 * (as above).
> +	 */
> +	if (!fs_devices->opened)
> +		device->generation = found_transid;
> +
>   	if (found_transid > fs_devices->latest_trans) {
>   		fs_devices->latest_devid = devid;
>   		fs_devices->latest_trans = found_transid;