Re: [PATCH 7/7] btrfs: add helper function check device delete able

[David Sterba <dsterba@suse.cz>]

On Mon, Jul 16, 2018 at 10:58:12PM +0800, Anand Jain wrote:
> Move the section of the code which performs the check if the device is
> indelible, move that into a helper function.
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> ---
> v1->v2: Rename function to btrfs_get_device_for_delete(), thanks
> Nikolay.
> 
>  fs/btrfs/volumes.c | 49 ++++++++++++++++++++++++++++++-------------------
>  1 file changed, 30 insertions(+), 19 deletions(-)
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 1c0b56374992..0cefc24b028c 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1859,6 +1859,33 @@ static inline u64 btrfs_num_devices(struct btrfs_fs_info *fs_info)
>  	return num_devices;
>  }
>  
> +static struct btrfs_device *btrfs_get_device_for_delete(
> +				struct btrfs_fs_info *fs_info,
> +				const char *device_path, u64 devid)
> +{
> +	int ret;
> +	struct btrfs_device *device;
> +
> +	ret = btrfs_check_raid_min_devices(fs_info,
> +					   btrfs_num_devices(fs_info) - 1);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	ret = btrfs_find_device_by_devspec(fs_info, devid, device_path,
> +					   &device);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	if (test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state))
> +		return ERR_PTR(BTRFS_ERROR_DEV_TGT_REPLACE);

This is wrong, the BTRFS_ERROR valueas are >= 1, but the IS_ERR, ERR_PTR
work for errno values -4095..0 .

Thouth ERR_PTR would cast the integer into pointer, the callers of
btrfs_get_device_for_delete will not detect the error and continue.

> +
> +	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
> +	    fs_info->fs_devices->rw_devices == 1)
> +		return ERR_PTR(BTRFS_ERROR_DEV_ONLY_WRITABLE);
> +
> +	return device;
> +}
> +
>  int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path,
>  		u64 devid)
>  {
> @@ -1872,25 +1899,9 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path,
>  
>  	mutex_lock(&uuid_mutex);
>  
> -	num_devices = btrfs_num_devices(fs_info);
> -
> -	ret = btrfs_check_raid_min_devices(fs_info, num_devices - 1);
> -	if (ret)
> -		goto out;
> -
> -	ret = btrfs_find_device_by_devspec(fs_info, devid, device_path,
> -					   &device);
> -	if (ret)
> -		goto out;
> -
> -	if (test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state)) {
> -		ret = BTRFS_ERROR_DEV_TGT_REPLACE;
> -		goto out;
> -	}
> -
> -	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
> -	    fs_info->fs_devices->rw_devices == 1) {
> -		ret = BTRFS_ERROR_DEV_ONLY_WRITABLE;
> +	device = btrfs_get_device_for_delete(fs_info, device_path, devid);
> +	if (IS_ERR(device)) {

BTRFS_ERROR_DEV_ONLY_WRITABLE won't work here.

> +		ret = PTR_ERR(device);
>  		goto out;
>  	}
>  
> -- 
> 2.7.0
> 
> --
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