Re: [PATCH v8 2/5] xfs: hoist out xfs_resizefs_init_new_ags()

[Brian Foster <bfoster@redhat.com>]

On Fri, Mar 05, 2021 at 10:57:00AM +0800, Gao Xiang wrote:
> Move out related logic for initializing new added AGs to a new helper
> in preparation for shrinking. No logic changes.
> 
> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
> ---
>  fs/xfs/xfs_fsops.c | 107 +++++++++++++++++++++++++++------------------
>  1 file changed, 64 insertions(+), 43 deletions(-)
> 
> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> index 9f9ba8bd0213..fc9e799b2ae3 100644
> --- a/fs/xfs/xfs_fsops.c
> +++ b/fs/xfs/xfs_fsops.c
> @@ -20,6 +20,64 @@
>  #include "xfs_ag.h"
>  #include "xfs_ag_resv.h"
>  
> +/*
> + * 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.
> + */
> +static int
> +xfs_resizefs_init_new_ags(
> +	struct xfs_trans	*tp,
> +	struct aghdr_init_data	*id,
> +	xfs_agnumber_t		oagcount,
> +	xfs_agnumber_t		nagcount,
> +	xfs_rfsblock_t		delta,
> +	bool			*lastag_resetagres)

Nit: I'd just call this lastag_extended or something that otherwise
indicates what this function reports (as opposed to trying to tell the
caller what to do).

> +{
> +	struct xfs_mount	*mp = tp->t_mountp;
> +	xfs_rfsblock_t		nb = mp->m_sb.sb_dblocks + delta;
> +	int			error;
> +
> +	*lastag_resetagres = false;
> +
> +	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;
> +		}
> +	}
> +
> +	error = xfs_buf_delwri_submit(&id->buffer_list);
> +	if (error)
> +		return error;
> +
> +	xfs_trans_agblocks_delta(tp, id->nfree);
> +
> +	if (delta) {
> +		*lastag_resetagres = true;
> +		error = xfs_ag_extend_space(mp, tp, id, delta);
> +	}
> +	return error;
> +}
> +
>  /*
>   * growfs operations
>   */
...
> @@ -123,9 +145,8 @@ xfs_growfs_data_private(
>  	 */
>  	if (nagcount > oagcount)
>  		xfs_trans_mod_sb(tp, XFS_TRANS_SB_AGCOUNT, nagcount - oagcount);
> -	if (nb > mp->m_sb.sb_dblocks)
> -		xfs_trans_mod_sb(tp, XFS_TRANS_SB_DBLOCKS,
> -				 nb - mp->m_sb.sb_dblocks);
> +	if (delta > 0)
> +		xfs_trans_mod_sb(tp, XFS_TRANS_SB_DBLOCKS, delta);

Hm.. isn't delta still unsigned as of this patch?

Brian

>  	if (id.nfree)
>  		xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, id.nfree);
>  
> @@ -152,7 +173,7 @@ xfs_growfs_data_private(
>  	 * If we expanded the last AG, free the per-AG reservation
>  	 * so we can reinitialize it with the new size.
>  	 */
> -	if (delta) {
> +	if (lastag_resetagres) {
>  		struct xfs_perag	*pag;
>  
>  		pag = xfs_perag_get(mp, id.agno);
> -- 
> 2.27.0
>