Re: [PATCH 2/4] xfs: calculate minleft correctly for bmap allocations

[Brian Foster <bfoster@redhat.com>]

On Tue, Dec 13, 2016 at 04:59:25PM +0100, Christoph Hellwig wrote:
> We need to take into account the worst possible number of bmap and rmap
> btree block allocations.  Use the helper we have to calculate it instead
> of doing an overly optimistic estimate.  Also move the call to calculate
> it into the function that sets the allocation parameters, as we have
> more accurate information about the allocation there.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---

Seems reasonable:

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

>  fs/xfs/libxfs/xfs_bmap.c | 16 ++++++----------
>  fs/xfs/libxfs/xfs_bmap.h |  1 -
>  2 files changed, 6 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 44773c9..2126ecc 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -3764,7 +3764,12 @@ xfs_bmap_btalloc(
>  		args.alignment = 1;
>  		args.minalignslop = 0;
>  	}
> -	args.minleft = ap->minleft;
> +
> +	/*
> +	 * Ensure we have enough blocks left in the AG to satisfy all possible
> +	 * bmap and rmap tree block allocations.
> +	 */
> +	args.minleft = xfs_bmap_worst_indlen(ap->ip, args.maxlen);
>  	args.wasdel = ap->wasdel;
>  	args.resv = XFS_AG_RESV_NONE;
>  	args.datatype = ap->datatype;
> @@ -4572,15 +4577,6 @@ xfs_bmapi_write(
>  
>  	XFS_STATS_INC(mp, xs_blk_mapw);
>  
> -	if (*firstblock == NULLFSBLOCK) {
> -		if (XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_BTREE)
> -			bma.minleft = be16_to_cpu(ifp->if_broot->bb_level) + 1;
> -		else
> -			bma.minleft = 1;
> -	} else {
> -		bma.minleft = 0;
> -	}
> -
>  	if (!(ifp->if_flags & XFS_IFEXTENTS)) {
>  		error = xfs_iread_extents(tp, ip, whichfork);
>  		if (error)
> diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
> index cecd094..92e6755 100644
> --- a/fs/xfs/libxfs/xfs_bmap.h
> +++ b/fs/xfs/libxfs/xfs_bmap.h
> @@ -49,7 +49,6 @@ struct xfs_bmalloca {
>  
>  	xfs_extlen_t		total;	/* total blocks needed for xaction */
>  	xfs_extlen_t		minlen;	/* minimum allocation size (blocks) */
> -	xfs_extlen_t		minleft; /* amount must be left after alloc */
>  	bool			eof;	/* set if allocating past last extent */
>  	bool			wasdel;	/* replacing a delayed allocation */
>  	bool			aeof;	/* allocated space at eof */
> -- 
> 2.1.4
> 
> --
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