Re: [PATCH] xfs: revert "xfs: factor rmap btree size into the indlen calculations"

[Brian Foster <bfoster@redhat.com>]

On Sat, Sep 23, 2017 at 12:11:42AM -0700, Darrick J. Wong wrote:
> In commit fd26a88093ba we added a worst case estimate for rmapbt blocks
> needed to satisfy the block mapping request.  Since then, we added the
> ability to reserve enough space in each AG such that we should never run
> out of blocks to grow the rmapbt, which makes this calculation
> unnecessary.  Revert the commit because it makes the extra delalloc
> indlen accounting unnecessary and incorrect.
> 
> Reported-by: Eryu Guan <eguan@redhat.com>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

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

>  fs/xfs/libxfs/xfs_bmap.c |   17 ++---------------
>  1 file changed, 2 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 459f4b4f0..044a363 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -49,7 +49,6 @@
>  #include "xfs_rmap.h"
>  #include "xfs_ag_resv.h"
>  #include "xfs_refcount.h"
> -#include "xfs_rmap_btree.h"
>  #include "xfs_icache.h"
>  
>  
> @@ -192,12 +191,8 @@ xfs_bmap_worst_indlen(
>  	int		maxrecs;	/* maximum record count at this level */
>  	xfs_mount_t	*mp;		/* mount structure */
>  	xfs_filblks_t	rval;		/* return value */
> -	xfs_filblks_t   orig_len;
>  
>  	mp = ip->i_mount;
> -
> -	/* Calculate the worst-case size of the bmbt. */
> -	orig_len = len;
>  	maxrecs = mp->m_bmap_dmxr[0];
>  	for (level = 0, rval = 0;
>  	     level < XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK);
> @@ -205,20 +200,12 @@ xfs_bmap_worst_indlen(
>  		len += maxrecs - 1;
>  		do_div(len, maxrecs);
>  		rval += len;
> -		if (len == 1) {
> -			rval += XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) -
> +		if (len == 1)
> +			return rval + XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) -
>  				level - 1;
> -			break;
> -		}
>  		if (level == 0)
>  			maxrecs = mp->m_bmap_dmxr[1];
>  	}
> -
> -	/* Calculate the worst-case size of the rmapbt. */
> -	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
> -		rval += 1 + xfs_rmapbt_calc_size(mp, orig_len) +
> -				mp->m_rmap_maxlevels;
> -
>  	return rval;
>  }
>  
> --
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