Re: [PATCH v4 2/2] btrfs: get device pointer from btrfs_scan_one_device

[Nikolay Borisov <nborisov@suse.com>]

On 12.07.2018 09:23, Gu Jinxiang wrote:
> Instead of pointer to btrfs_fs_devices as an arg in
> btrfs_scan_one_device, better to make it as a return value.
> 
> And since btrfs_fs_devices can be get by btrfs_device,
> better to return btrfs_device than fs_btrfs_devices.
> 
> Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

> ---
> 
> Changelog:
> v4: as suggested by Anand, change return value of
>     btrfs_scan_one_device from btrfs_fs_devices to btrfs_device.
> v3: as comment by robot, use PTR_ERR_OR_ZERO, and rebase to misc-next.
> v2: as comment by Nikolay, use ERR_CAST instead of cast type manually.
> 
>  fs/btrfs/super.c   | 37 ++++++++++++++++++++++++-------------
>  fs/btrfs/volumes.c | 17 ++++++-----------
>  fs/btrfs/volumes.h |  4 ++--
>  3 files changed, 32 insertions(+), 26 deletions(-)
> 
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 44f58bdb5fa6..e73d547eacff 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -888,7 +888,7 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
>  {
>  	substring_t args[MAX_OPT_ARGS];
>  	char *device_name, *opts, *orig, *p;
> -	struct btrfs_fs_devices *fs_devices = NULL;
> +	struct btrfs_device *device = NULL;
>  	int error = 0;
>  
>  	if (!options)
> @@ -916,11 +916,13 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
>  				error = -ENOMEM;
>  				goto out;
>  			}
> -			error = btrfs_scan_one_device(device_name,
> -					flags, holder, &fs_devices);
> +			device = btrfs_scan_one_device(device_name,
> +					flags, holder);
>  			kfree(device_name);
> -			if (error)
> +			if (IS_ERR(device)) {
> +				error = PTR_ERR(device);
>  				goto out;
> +			}
>  		}
>  	}
>  
> @@ -1516,6 +1518,7 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
>  {
>  	struct block_device *bdev = NULL;
>  	struct super_block *s;
> +	struct btrfs_device *device = NULL;
>  	struct btrfs_fs_devices *fs_devices = NULL;
>  	struct btrfs_fs_info *fs_info = NULL;
>  	struct security_mnt_opts new_sec_opts;
> @@ -1537,9 +1540,13 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
>  			return ERR_PTR(error);
>  	}
>  
> -	error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices);
> -	if (error)
> +	device = btrfs_scan_one_device(device_name, mode, fs_type);
> +	if (IS_ERR(device)) {
> +		error = PTR_ERR(device);
>  		goto error_sec_opts;
> +	}
> +
> +	fs_devices = device->fs_devices;
>  
>  	/*
>  	 * Setup a dummy root and fs_info for test/set super.  This is because
> @@ -2220,7 +2227,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
>  				unsigned long arg)
>  {
>  	struct btrfs_ioctl_vol_args *vol;
> -	struct btrfs_fs_devices *fs_devices;
> +	struct btrfs_device *device = NULL;
>  	int ret = -ENOTTY;
>  
>  	if (!capable(CAP_SYS_ADMIN))
> @@ -2232,15 +2239,19 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
>  
>  	switch (cmd) {
>  	case BTRFS_IOC_SCAN_DEV:
> -		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
> -					    &btrfs_root_fs_type, &fs_devices);
> +		device = btrfs_scan_one_device(vol->name, FMODE_READ,
> +					    &btrfs_root_fs_type);
> +		ret = PTR_ERR_OR_ZERO(device);
>  		break;
>  	case BTRFS_IOC_DEVICES_READY:
> -		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
> -					    &btrfs_root_fs_type, &fs_devices);
> -		if (ret)
> +		device = btrfs_scan_one_device(vol->name, FMODE_READ,
> +					    &btrfs_root_fs_type);
> +		if (IS_ERR(device)) {
> +			ret = PTR_ERR(device);
>  			break;
> -		ret = !(fs_devices->num_devices == fs_devices->total_devices);
> +		}
> +		ret = !(device->fs_devices->num_devices ==
> +				device->fs_devices->total_devices);
>  		break;
>  	case BTRFS_IOC_GET_SUPPORTED_FEATURES:
>  		ret = btrfs_ioctl_get_supported_features((void __user*)arg);
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 52abada5c789..3bc479e8cc22 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1212,14 +1212,13 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
>   * and we are not allowed to call set_blocksize during the scan. The superblock
>   * is read via pagecache
>   */
> -int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
> -			  struct btrfs_fs_devices **fs_devices_ret)
> +struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags,
> +					    void *holder)
>  {
>  	struct btrfs_super_block *disk_super;
> -	struct btrfs_device *device;
> +	struct btrfs_device *ret = NULL;
>  	struct block_device *bdev;
>  	struct page *page;
> -	int ret = 0;
>  	u64 bytenr;
>  
>  	/*
> @@ -1233,19 +1232,15 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
>  
>  	bdev = blkdev_get_by_path(path, flags, holder);
>  	if (IS_ERR(bdev))
> -		return PTR_ERR(bdev);
> +		return ERR_CAST(bdev);
>  
>  	if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super)) {
> -		ret = -EINVAL;
> +		ret = ERR_PTR(-EINVAL);
>  		goto error_bdev_put;
>  	}
>  
>  	mutex_lock(&uuid_mutex);
> -	device = device_list_add(path, disk_super);
> -	if (IS_ERR(device))
> -		ret = PTR_ERR(device);
> -	else
> -		*fs_devices_ret = device->fs_devices;
> +	ret = device_list_add(path, disk_super);
>  	mutex_unlock(&uuid_mutex);
>  
>  	btrfs_release_disk_super(page);
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 9665b84b1026..06d8bb7dd557 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -403,8 +403,8 @@ blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
>  			   int mirror_num, int async_submit);
>  int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
>  		       fmode_t flags, void *holder);
> -int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
> -			  struct btrfs_fs_devices **fs_devices_ret);
> +struct btrfs_device *btrfs_scan_one_device(const char *path,
> +					   fmode_t flags, void *holder);
>  int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
>  void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step);
>  void btrfs_assign_next_active_device(struct btrfs_fs_info *fs_info,
>