Re: [PATCH] Btrfs: allow compressed extents to be merged during defragment

[Miao Xie <miaox@cn.fujitsu.com>]

On fri, 2 Aug 2013 14:49:54 +0800, Liu Bo wrote:
> The rule originally comes from nocow writing, but snapshot-aware
> defrag is a different case, the extent has been writen and we're
> not going to change the extent but add a reference on the data.
> 
> So we're able to allow such compressed extents to be merged into
> one bigger extent if they're pointing to the same data.
> 
> Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
> ---
>  fs/btrfs/inode.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 55dda87..a7aeecc 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -2229,7 +2229,7 @@ static noinline bool record_extent_backrefs(struct btrfs_path *path,
>  
>  static int relink_is_mergable(struct extent_buffer *leaf,
>  			      struct btrfs_file_extent_item *fi,
> -			      u64 disk_bytenr)
> +			      u64 disk_bytenr, u8 compress)
>  {
>  	if (btrfs_file_extent_disk_bytenr(leaf, fi) != disk_bytenr)
>  		return 0;
> @@ -2237,8 +2237,10 @@ static int relink_is_mergable(struct extent_buffer *leaf,
>  	if (btrfs_file_extent_type(leaf, fi) != BTRFS_FILE_EXTENT_REG)
>  		return 0;
>  
> -	if (btrfs_file_extent_compression(leaf, fi) ||
> -	    btrfs_file_extent_encryption(leaf, fi) ||
> +	if (btrfs_file_extent_compression(leaf, fi) != compress)
> +		return 0;
> +
> +	if (btrfs_file_extent_encryption(leaf, fi) ||
>  	    btrfs_file_extent_other_encoding(leaf, fi))
>  		return 0;
>  
> @@ -2382,8 +2384,9 @@ again:
>  				    struct btrfs_file_extent_item);
>  		extent_len = btrfs_file_extent_num_bytes(leaf, fi);
>  
> -		if (relink_is_mergable(leaf, fi, new->bytenr) &&
> -		    extent_len + found_key.offset == start) {
> +		if (extent_len + found_key.offset == start &&
> +		    relink_is_mergable(leaf, fi, new->bytenr,
> +				       new->compress_type)) {

There is a petty comment: Why not pass "new" to relink_is_mergable() directly?

The other code is OK.

Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>

>  			btrfs_set_file_extent_num_bytes(leaf, fi,
>  							extent_len + len);
>  			btrfs_mark_buffer_dirty(leaf);
>