[PATCH v2] xfs: store rmapbt block count in the AGF

[Christoph Hellwig]

On Wed, Aug 03, 2016 at 02:46:13PM -0700, Darrick J. Wong wrote:
> Track the number of blocks used for the rmapbt in the AGF.  When we
> get to the AG reservation code we need this counter to quickly
> make our reservation during mount.
> 
> v2: Actually include growfs support.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong at oracle.com>
> ---
>  fs/xfs/libxfs/xfs_alloc.c      |    1 +
>  fs/xfs/libxfs/xfs_format.h     |   11 ++++++++---
>  fs/xfs/libxfs/xfs_rmap_btree.c |    6 ++++++
>  fs/xfs/xfs_fsops.c             |    1 +
>  4 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index 776ae2f..af1a72e 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -2264,6 +2264,7 @@ xfs_alloc_log_agf(
>  		offsetof(xfs_agf_t, agf_longest),
>  		offsetof(xfs_agf_t, agf_btreeblks),
>  		offsetof(xfs_agf_t, agf_uuid),
> +		offsetof(xfs_agf_t, agf_rmap_blocks),
>  		sizeof(xfs_agf_t)
>  	};
>  
> diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
> index f814d42..e6a8bea 100644
> --- a/fs/xfs/libxfs/xfs_format.h
> +++ b/fs/xfs/libxfs/xfs_format.h
> @@ -640,12 +640,15 @@ typedef struct xfs_agf {
>  	__be32		agf_btreeblks;	/* # of blocks held in AGF btrees */
>  	uuid_t		agf_uuid;	/* uuid of filesystem */
>  
> +	__be32		agf_rmap_blocks;	/* rmapbt blocks used */
> +	__be32		agf_padding;		/* padding */

Now _spare?  It could easily be used by the next new field.

Otherwise this looks fine to me:

Reviewed-by: Christoph Hellwig <hch at lst.de>