Re: [PATCH 06/10] xfs: change xfs_iwalk_grab_ichunk to use startino, not lastino

[Brian Foster <bfoster@redhat.com>]

On Tue, Jun 04, 2019 at 02:50:06PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Now that the inode chunk grabbing function is a static function in the
> iwalk code, change its behavior so that @agino is the inode where we
> want to /start/ the iteration.  This reduces cognitive friction with the
> callers and simplifes the code.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

>  fs/xfs/xfs_iwalk.c |   37 +++++++++++++++++--------------------
>  1 file changed, 17 insertions(+), 20 deletions(-)
> 
> 
> diff --git a/fs/xfs/xfs_iwalk.c b/fs/xfs/xfs_iwalk.c
> index bef0c4907781..9ad017ddbae7 100644
> --- a/fs/xfs/xfs_iwalk.c
> +++ b/fs/xfs/xfs_iwalk.c
> @@ -99,10 +99,10 @@ xfs_iwalk_ichunk_ra(
>  }
>  
>  /*
> - * Lookup the inode chunk that the given inode lives in and then get the record
> - * if we found the chunk.  If the inode was not the last in the chunk and there
> - * are some left allocated, update the data for the pointed-to record as well as
> - * return the count of grabbed inodes.
> + * Lookup the inode chunk that the given @agino lives in and then get the
> + * record if we found the chunk.  Set the bits in @irec's free mask that
> + * correspond to the inodes before @agino so that we skip them.  This is how we
> + * restart an inode walk that was interrupted in the middle of an inode record.
>   */
>  STATIC int
>  xfs_iwalk_grab_ichunk(
> @@ -113,6 +113,7 @@ xfs_iwalk_grab_ichunk(
>  {
>  	int				idx;	/* index into inode chunk */
>  	int				stat;
> +	int				i;
>  	int				error = 0;
>  
>  	/* Lookup the inode chunk that this inode lives in */
> @@ -136,24 +137,20 @@ xfs_iwalk_grab_ichunk(
>  		return 0;
>  	}
>  
> -	idx = agino - irec->ir_startino + 1;
> -	if (idx < XFS_INODES_PER_CHUNK &&
> -	    (xfs_inobt_maskn(idx, XFS_INODES_PER_CHUNK - idx) & ~irec->ir_free)) {
> -		int	i;
> +	idx = agino - irec->ir_startino;
>  
> -		/* We got a right chunk with some left inodes allocated at it.
> -		 * Grab the chunk record.  Mark all the uninteresting inodes
> -		 * free -- because they're before our start point.
> -		 */
> -		for (i = 0; i < idx; i++) {
> -			if (XFS_INOBT_MASK(i) & ~irec->ir_free)
> -				irec->ir_freecount++;
> -		}
> -
> -		irec->ir_free |= xfs_inobt_maskn(0, idx);
> -		*icount = irec->ir_count - irec->ir_freecount;
> +	/*
> +	 * We got a right chunk with some left inodes allocated at it.  Grab
> +	 * the chunk record.  Mark all the uninteresting inodes free because
> +	 * they're before our start point.
> +	 */
> +	for (i = 0; i < idx; i++) {
> +		if (XFS_INOBT_MASK(i) & ~irec->ir_free)
> +			irec->ir_freecount++;
>  	}
>  
> +	irec->ir_free |= xfs_inobt_maskn(0, idx);
> +	*icount = irec->ir_count - irec->ir_freecount;
>  	return 0;
>  }
>  
> @@ -281,7 +278,7 @@ xfs_iwalk_ag_start(
>  	 * We require a lookup cache of at least two elements so that we don't
>  	 * have to deal with tearing down the cursor to walk the records.
>  	 */
> -	error = xfs_iwalk_grab_ichunk(*curpp, agino - 1, &icount,
> +	error = xfs_iwalk_grab_ichunk(*curpp, agino, &icount,
>  			&iwag->recs[iwag->nr_recs]);
>  	if (error)
>  		return error;
>