Re: [PATCH] btrfs: add stripes filter

[David Sterba <dsterba@suse.cz>]

Hi,

thanks for the patch. The stripe filter is really helpful. There are
some minor comments below but otherwise the patch looks good.

On Mon, Sep 28, 2015 at 10:32:41PM +0000, Gabríel Arthúr Pétursson wrote:
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -849,7 +849,11 @@ struct btrfs_disk_balance_args {
>  	/* BTRFS_BALANCE_ARGS_LIMIT value */
>  	__le64 limit;
>  
> -	__le64 unused[7];
> +	/* btrfs stripes filter */
> +	__le64 sstart;
> +	__le64 send;

Please be more descriptive, eg. min_stripes/max_stripes. The u64 type
seems too much, I think we can fit the stripe count into a 32bit number.
I made a mistake with u64 type for the 'limit' filter but I think that
we can somehow extend it to be two u32 with the min/max meaning as well.
Either way, this is independent of your patch.

> +
> +	__le64 unused[5];
>  } __attribute__ ((__packed__));
>  
>  /*
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -3236,6 +3248,12 @@ static int should_balance_chunk(struct btrfs_root *root,
>  		return 0;
>  	}
>  
> +	/* stripes filter */
> +	if ((bargs->flags & BTRFS_BALANCE_ARGS_STRIPES) &&
> +	    chunk_stripes_filter(leaf, chunk, bargs)) {
> +		return 0;
> +	}

Ok, I think that this ordering of the filters is right.

> +
>  	/* soft profile changing mode */
>  	if ((bargs->flags & BTRFS_BALANCE_ARGS_SOFT) &&
>  	    chunk_soft_convert_filter(chunk_type, bargs)) {
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 2ca784a..fb6b89a 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -375,6 +375,7 @@ struct map_lookup {
>  #define BTRFS_BALANCE_ARGS_DRANGE	(1ULL << 3)
>  #define BTRFS_BALANCE_ARGS_VRANGE	(1ULL << 4)
>  #define BTRFS_BALANCE_ARGS_LIMIT	(1ULL << 5)
> +#define BTRFS_BALANCE_ARGS_STRIPES	(1ULL << 6)
>  
>  /*
>   * Profile changing flags.  When SOFT is set we won't relocate chunk if
> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
> index b6dec05..a7819d0 100644
> --- a/include/uapi/linux/btrfs.h
> +++ b/include/uapi/linux/btrfs.h
> @@ -218,7 +218,11 @@ struct btrfs_balance_args {
>  	__u64 flags;
>  
>  	__u64 limit;		/* limit number of processed chunks */
> -	__u64 unused[7];

same comment from the ctree.h applies here

> +
> +	__u64 sstart;
> +	__u64 send;
> +
> +	__u64 unused[5];
>  } __attribute__ ((__packed__));
>  
>  /* report balance progress to userspace */