Re: [PATCH 4/7] xfs: treat CoW fork operations as delalloc for quota accounting

[Brian Foster <bfoster@redhat.com>]

On Fri, Jan 26, 2018 at 05:10:34PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Since the CoW fork only exists in memory, it is incorrect to update the
> on-disk quota block counts when we modify the CoW fork.  Unlike the data
> fork, even real extents in the CoW fork are only delalloc-style
> reservations (on-disk they're owned by the refcountbt) so they must not
> be tracked in the on disk quota info.  Ensure the i_delayed_blks
> accounting reflects this too.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

Patch doesn't apply.. I'm guessing because xfs_bmap_btalloc_accounting()
doesn't exist. Is this series incomplete, or perhaps not consistent with
for-next..?

Brian

>  fs/xfs/libxfs/xfs_bmap.c |   32 ++++++++++++++++++++++++++++++--
>  fs/xfs/xfs_reflink.c     |   15 +++++++++++----
>  2 files changed, 41 insertions(+), 6 deletions(-)
> 
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 4582f55..cad21fd 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -3343,8 +3343,35 @@ xfs_bmap_btalloc_accounting(
>  	struct xfs_bmalloca	*ap,
>  	struct xfs_alloc_arg	*args)
>  {
> -	if (!(ap->flags & XFS_BMAPI_COWFORK))
> -		ap->ip->i_d.di_nblocks += args->len;
> +	if (ap->flags & XFS_BMAPI_COWFORK) {
> +		/*
> +		 * COW fork blocks are in-core only and thus are treated as
> +		 * in-core quota reservation (like delalloc blocks) even when
> +		 * converted to real blocks. The quota reservation is not
> +		 * accounted to disk until blocks are remapped to the data
> +		 * fork. So if these blocks were previously delalloc, we
> +		 * already have quota reservation and there's nothing to do
> +		 * yet.
> +		 */
> +		if (ap->wasdel)
> +			return;
> +
> +		/*
> +		 * Otherwise, we've allocated blocks in a hole. The transaction
> +		 * has acquired in-core quota reservation for this extent.
> +		 * Rather than account these as real blocks, however, we reduce
> +		 * the transaction quota reservation based on the allocation.
> +		 * This essentially transfers the transaction quota reservation
> +		 * to that of a delalloc extent.
> +		 */
> +		ap->ip->i_delayed_blks += args->len;
> +		xfs_trans_mod_dquot_byino(ap->tp, ap->ip, XFS_TRANS_DQ_RES_BLKS,
> +				-(long)args->len);
> +		return;
> +	}
> +
> +	/* data/attr fork only */
> +	ap->ip->i_d.di_nblocks += args->len;
>  	xfs_trans_log_inode(ap->tp, ap->ip, XFS_ILOG_CORE);
>  	if (ap->wasdel)
>  		ap->ip->i_delayed_blks -= args->len;
> @@ -4820,6 +4847,7 @@ xfs_bmap_del_extent_cow(
>  		xfs_iext_insert(ip, icur, &new, state);
>  		break;
>  	}
> +	ip->i_delayed_blks -= del->br_blockcount;
>  }
>  
>  /*
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 85a119e..c4f0aff 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -599,10 +599,6 @@ xfs_reflink_cancel_cow_blocks(
>  					del.br_startblock, del.br_blockcount,
>  					NULL);
>  
> -			/* Update quota accounting */
> -			xfs_trans_mod_dquot_byino(*tpp, ip, XFS_TRANS_DQ_BCOUNT,
> -					-(long)del.br_blockcount);
> -
>  			/* Roll the transaction */
>  			xfs_defer_ijoin(&dfops, ip);
>  			error = xfs_defer_finish(tpp, &dfops);
> @@ -613,6 +609,13 @@ xfs_reflink_cancel_cow_blocks(
>  
>  			/* Remove the mapping from the CoW fork. */
>  			xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
> +
> +			/* Remove the quota reservation */
> +			error = xfs_trans_reserve_quota_nblks(NULL, ip,
> +					-(long)del.br_blockcount, 0,
> +					XFS_QMOPT_RES_REGBLKS);
> +			if (error)
> +				break;
>  		} else {
>  			/* Didn't do anything, push cursor back. */
>  			xfs_iext_prev(ifp, &icur);
> @@ -795,6 +798,10 @@ xfs_reflink_end_cow(
>  		if (error)
>  			goto out_defer;
>  
> +		/* Charge this new data fork mapping to the on-disk quota. */
> +		xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_DELBCOUNT,
> +				(long)del.br_blockcount);
> +
>  		/* Remove the mapping from the CoW fork. */
>  		xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
>  
> 
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