Re: [PATCH v2] btrfs: cleanup finding rotating device

[David Sterba <dsterba@suse.cz>]

On Thu, Jan 13, 2022 at 03:48:54PM +0800, Anand Jain wrote:
> The pointer to struct request_queue is used only to get device type
> rotating or the non-rotating. So use it directly.
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> ---
> v2: Eliminate the if statement.
> 
>  fs/btrfs/volumes.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 70b085dff500..34d08c4f7b6c 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -601,7 +601,6 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
>  			struct btrfs_device *device, fmode_t flags,
>  			void *holder)
>  {
> -	struct request_queue *q;
>  	struct block_device *bdev;
>  	struct btrfs_super_block *disk_super;
>  	u64 devid;
> @@ -643,9 +642,7 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
>  			set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
>  	}
>  
> -	q = bdev_get_queue(bdev);
> -	if (!blk_queue_nonrot(q))
> -		fs_devices->rotating = true;
> +	fs_devices->rotating = !blk_queue_nonrot(bdev_get_queue(bdev));

This is an equivalent change, in the new code fs_devices->rotating will
be always set according to the last device, while in the old code, any
rotational device will set it to true and never back.

>  
>  	device->bdev = bdev;
>  	clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
> @@ -2590,7 +2587,6 @@ static int btrfs_finish_sprout(struct btrfs_trans_handle *trans)
>  int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path)
>  {
>  	struct btrfs_root *root = fs_info->dev_root;
> -	struct request_queue *q;
>  	struct btrfs_trans_handle *trans;
>  	struct btrfs_device *device;
>  	struct block_device *bdev;
> @@ -2666,7 +2662,6 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
>  		goto error_free_zone;
>  	}
>  
> -	q = bdev_get_queue(bdev);
>  	set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
>  	device->generation = trans->transid;
>  	device->io_width = fs_info->sectorsize;
> @@ -2714,8 +2709,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
>  
>  	atomic64_add(device->total_bytes, &fs_info->free_chunk_space);
>  
> -	if (!blk_queue_nonrot(q))
> -		fs_devices->rotating = true;
> +	fs_devices->rotating = !blk_queue_nonrot(bdev_get_queue(bdev));

Same here.

>  
>  	orig_super_total_bytes = btrfs_super_total_bytes(fs_info->super_copy);
>  	btrfs_set_super_total_bytes(fs_info->super_copy,
> -- 
> 2.33.1