Re: [PATCH v3 3/4] xfs: hoist out xfs_resizefs_init_new_ags()

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Sat, Jan 09, 2021 at 03:09:18AM +0800, Gao Xiang wrote:
> Move out related logic for initializing new added AGs to a new helper
> in preparation for shrinking. No logic changes.
> 
> Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
> ---
>  fs/xfs/xfs_fsops.c | 74 +++++++++++++++++++++++++++-------------------

Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

>  1 file changed, 44 insertions(+), 30 deletions(-)
> 
> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> index 6c5f6a50da2e..a792d1f0ac55 100644
> --- a/fs/xfs/xfs_fsops.c
> +++ b/fs/xfs/xfs_fsops.c
> @@ -20,6 +20,49 @@
>  #include "xfs_ag.h"
>  #include "xfs_ag_resv.h"
>  
> +static int
> +xfs_resizefs_init_new_ags(
> +	xfs_mount_t		*mp,
> +	struct aghdr_init_data	*id,
> +	xfs_agnumber_t		oagcount,
> +	xfs_agnumber_t		nagcount,
> +	xfs_rfsblock_t		*delta)
> +{
> +	xfs_rfsblock_t		nb = mp->m_sb.sb_dblocks + *delta;
> +	int			error;
> +
> +	/*
> +	 * Write new AG headers to disk. Non-transactional, but need to be
> +	 * written and completed prior to the growfs transaction being logged.
> +	 * To do this, we use a delayed write buffer list and wait for
> +	 * submission and IO completion of the list as a whole. This allows the
> +	 * IO subsystem to merge all the AG headers in a single AG into a single
> +	 * IO and hide most of the latency of the IO from us.
> +	 *
> +	 * This also means that if we get an error whilst building the buffer
> +	 * list to write, we can cancel the entire list without having written
> +	 * anything.
> +	 */
> +	INIT_LIST_HEAD(&id->buffer_list);
> +	for (id->agno = nagcount - 1;
> +	     id->agno >= oagcount;
> +	     id->agno--, *delta -= id->agsize) {
> +
> +		if (id->agno == nagcount - 1)
> +			id->agsize = nb - (id->agno *
> +					(xfs_rfsblock_t)mp->m_sb.sb_agblocks);
> +		else
> +			id->agsize = mp->m_sb.sb_agblocks;
> +
> +		error = xfs_ag_init_headers(mp, id);
> +		if (error) {
> +			xfs_buf_delwri_cancel(&id->buffer_list);
> +			return error;
> +		}
> +	}
> +	return xfs_buf_delwri_submit(&id->buffer_list);
> +}
> +
>  /*
>   * growfs operations
>   */
> @@ -74,36 +117,7 @@ xfs_growfs_data_private(
>  	if (error)
>  		return error;
>  
> -	/*
> -	 * Write new AG headers to disk. Non-transactional, but need to be
> -	 * written and completed prior to the growfs transaction being logged.
> -	 * To do this, we use a delayed write buffer list and wait for
> -	 * submission and IO completion of the list as a whole. This allows the
> -	 * IO subsystem to merge all the AG headers in a single AG into a single
> -	 * IO and hide most of the latency of the IO from us.
> -	 *
> -	 * This also means that if we get an error whilst building the buffer
> -	 * list to write, we can cancel the entire list without having written
> -	 * anything.
> -	 */
> -	INIT_LIST_HEAD(&id.buffer_list);
> -	for (id.agno = nagcount - 1;
> -	     id.agno >= oagcount;
> -	     id.agno--, delta -= id.agsize) {
> -
> -		if (id.agno == nagcount - 1)
> -			id.agsize = nb -
> -				(id.agno * (xfs_rfsblock_t)mp->m_sb.sb_agblocks);
> -		else
> -			id.agsize = mp->m_sb.sb_agblocks;
> -
> -		error = xfs_ag_init_headers(mp, &id);
> -		if (error) {
> -			xfs_buf_delwri_cancel(&id.buffer_list);
> -			goto out_trans_cancel;
> -		}
> -	}
> -	error = xfs_buf_delwri_submit(&id.buffer_list);
> +	error = xfs_resizefs_init_new_ags(mp, &id, oagcount, nagcount, &delta);
>  	if (error)
>  		goto out_trans_cancel;
>  
> -- 
> 2.27.0
>