[PATCH 4/4] xfs: obey minleft values during extent allocation correctly.

[Dave Chinner]

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On Thu, Apr 21, 2011 at 07:34:28PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner at redhat.com>
> 
> When allocating an extent that is long enough to consume the
> remaining free space in an AG, we need to ensure that the allocation
> leaves enough space in the AG for any subsequent bmap btree blocks
> that are needed to track the new extent. These have to be allocated
> in the same AG as we only reserve enough blocks in an allocation
> transaction for modification of the freespace trees in a single AG.
> 
> xfs_alloc_fix_minleft() has been considering blocks on the AGFL as
> free blocks available for extent and bmbt block allocation, which is
> not correct - blocks on the AGFL are there exclusively for the use
> of the free space btrees. As a result, when minleft is less than the
> number of blocks on the AGFL, xfs_alloc_fix_minleft() does not trim
> the given extent to leave minleft blocks available for bmbt
> allocation, and hence we can fail allocation during bmbt record
> insertion.
> 
> Signed-off-by: Dave Chinner <dchinner at redhat.com>
> ---
>  fs/xfs/xfs_alloc.c |    1 -
>  1 files changed, 0 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
> index 27d64d7..8946464 100644
> --- a/fs/xfs/xfs_alloc.c
> +++ b/fs/xfs/xfs_alloc.c
> @@ -280,7 +280,6 @@ xfs_alloc_fix_minleft(
>  		return 1;
>  	agf = XFS_BUF_TO_AGF(args->agbp);
>  	diff = be32_to_cpu(agf->agf_freeblks)
> -		+ be32_to_cpu(agf->agf_flcount)
>  		- args->len - args->minleft;
>  	if (diff >= 0)
>  		return 1;
> -- 
> 1.7.4.4
> 
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-- 
Dave Chinner
david at fromorbit.com