Re: [PATCH v2 1/5] btrfs: always open the device read-only in btrfs_scan_one_device

[Qu Wenruo <wqu@suse.com>]

在 2025/6/11 19:32, Johannes Thumshirn 写道:
> From: Christoph Hellwig <hch@lst.de>
> 
> btrfs_scan_one_device opens the block device only to read the super
> block.  Instead of passing a blk_mode_t argument to sometimes open
> it for writing, just hard code BLK_OPEN_READ as it will never write
> to the device or hand the block_device out to someone else.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu

> ---
>   fs/btrfs/super.c   | 9 ++++-----
>   fs/btrfs/volumes.c | 4 ++--
>   fs/btrfs/volumes.h | 2 +-
>   3 files changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 2d0d8c6e77b4..b9e08a59da4e 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -364,10 +364,9 @@ static int btrfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
>   		break;
>   	case Opt_device: {
>   		struct btrfs_device *device;
> -		blk_mode_t mode = btrfs_open_mode(fc);
>   
>   		mutex_lock(&uuid_mutex);
> -		device = btrfs_scan_one_device(param->string, mode, false);
> +		device = btrfs_scan_one_device(param->string, false);
>   		mutex_unlock(&uuid_mutex);
>   		if (IS_ERR(device))
>   			return PTR_ERR(device);
> @@ -1855,7 +1854,7 @@ static int btrfs_get_tree_super(struct fs_context *fc)
>   	 * With 'true' passed to btrfs_scan_one_device() (mount time) we expect
>   	 * either a valid device or an error.
>   	 */
> -	device = btrfs_scan_one_device(fc->source, mode, true);
> +	device = btrfs_scan_one_device(fc->source, true);
>   	ASSERT(device != NULL);
>   	if (IS_ERR(device)) {
>   		mutex_unlock(&uuid_mutex);
> @@ -2233,7 +2232,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
>   		 * Scanning outside of mount can return NULL which would turn
>   		 * into 0 error code.
>   		 */
> -		device = btrfs_scan_one_device(vol->name, BLK_OPEN_READ, false);
> +		device = btrfs_scan_one_device(vol->name, false);
>   		ret = PTR_ERR_OR_ZERO(device);
>   		mutex_unlock(&uuid_mutex);
>   		break;
> @@ -2251,7 +2250,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
>   		 * Scanning outside of mount can return NULL which would turn
>   		 * into 0 error code.
>   		 */
> -		device = btrfs_scan_one_device(vol->name, BLK_OPEN_READ, false);
> +		device = btrfs_scan_one_device(vol->name, false);
>   		if (IS_ERR_OR_NULL(device)) {
>   			mutex_unlock(&uuid_mutex);
>   			if (IS_ERR(device))
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 1535a425e8f9..1ebfc69012a2 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1440,7 +1440,7 @@ static bool btrfs_skip_registration(struct btrfs_super_block *disk_super,
>    * the device or return an error. Multi-device and seeding devices are registered
>    * in both cases.
>    */
> -struct btrfs_device *btrfs_scan_one_device(const char *path, blk_mode_t flags,
> +struct btrfs_device *btrfs_scan_one_device(const char *path,
>   					   bool mount_arg_dev)
>   {
>   	struct btrfs_super_block *disk_super;
> @@ -1461,7 +1461,7 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, blk_mode_t flags,
>   	 * values temporarily, as the device paths of the fsid are the only
>   	 * required information for assembling the volume.
>   	 */
> -	bdev_file = bdev_file_open_by_path(path, flags, NULL, NULL);
> +	bdev_file = bdev_file_open_by_path(path, BLK_OPEN_READ, NULL, NULL);
>   	if (IS_ERR(bdev_file))
>   		return ERR_CAST(bdev_file);
>   
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 6d8b1f38e3ee..afa71d315c46 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -719,7 +719,7 @@ struct btrfs_block_group *btrfs_create_chunk(struct btrfs_trans_handle *trans,
>   void btrfs_mapping_tree_free(struct btrfs_fs_info *fs_info);
>   int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
>   		       blk_mode_t flags, void *holder);
> -struct btrfs_device *btrfs_scan_one_device(const char *path, blk_mode_t flags,
> +struct btrfs_device *btrfs_scan_one_device(const char *path,
>   					   bool mount_arg_dev);
>   int btrfs_forget_devices(dev_t devt);
>   void btrfs_close_devices(struct btrfs_fs_devices *fs_devices);