Re: [PATCH 17/18] xfs: refactor xfs_trans_apply_dquot_deltas

From: Chandan Babu R <chandanrlinux@gmail.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH 17/18] xfs: refactor xfs_trans_apply_dquot_deltas
Date: Mon, 06 Jul 2020 19:10:16 +0530	[thread overview]
Message-ID: <2009509.OecK6LfPaT@garuda> (raw)
In-Reply-To: <159353181889.2864738.7577728127911412217.stgit@magnolia>

On Tuesday 30 June 2020 9:13:38 PM IST Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Hoist the code that adjusts the incore quota reservation count
> adjustments into a separate function, both to reduce the level of
> indentation and also to reduce the amount of open-coded logic.
>

The changes are logically consistent with the previous behaviour.

Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>

> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/xfs/xfs_trans_dquot.c |  103 +++++++++++++++++++++-------------------------
>  1 file changed, 46 insertions(+), 57 deletions(-)
> 
> 
> diff --git a/fs/xfs/xfs_trans_dquot.c b/fs/xfs/xfs_trans_dquot.c
> index 30a011dc9828..701923ea6c04 100644
> --- a/fs/xfs/xfs_trans_dquot.c
> +++ b/fs/xfs/xfs_trans_dquot.c
> @@ -293,6 +293,37 @@ xfs_trans_dqlockedjoin(
>  	}
>  }
>  
> +/* Apply dqtrx changes to the quota reservation counters. */
> +static inline void
> +xfs_apply_quota_reservation_deltas(
> +	struct xfs_dquot_res	*res,
> +	uint64_t		reserved,
> +	int64_t			res_used,
> +	int64_t			count_delta)
> +{
> +	if (reserved != 0) {
> +		/*
> +		 * Subtle math here: If reserved > res_used (the normal case),
> +		 * we're simply subtracting the unused transaction quota
> +		 * reservation from the dquot reservation.
> +		 *
> +		 * If, however, res_used > reserved, then we have allocated
> +		 * more quota blocks than were reserved for the transaction.
> +		 * We must add that excess to the dquot reservation since it
> +		 * tracks (usage + resv) and by definition we didn't reserve
> +		 * that excess.
> +		 */
> +		res->reserved -= abs(reserved - res_used);
> +	} else if (count_delta != 0) {
> +		/*
> +		 * These blks were never reserved, either inside a transaction
> +		 * or outside one (in a delayed allocation). Also, this isn't
> +		 * always a negative number since we sometimes deliberately
> +		 * skip quota reservations.
> +		 */
> +		res->reserved += count_delta;
> +	}
> +}
>  
>  /*
>   * Called by xfs_trans_commit() and similar in spirit to
> @@ -327,6 +358,8 @@ xfs_trans_apply_dquot_deltas(
>  		xfs_trans_dqlockedjoin(tp, qa);
>  
>  		for (i = 0; i < XFS_QM_TRANS_MAXDQS; i++) {
> +			uint64_t	blk_res_used;
> +
>  			qtrx = &qa[i];
>  			/*
>  			 * The array of dquots is filled
> @@ -396,71 +429,27 @@ xfs_trans_apply_dquot_deltas(
>  			 * In case of delayed allocations, there's no
>  			 * reservation that a transaction structure knows of.
>  			 */
> -			if (qtrx->qt_blk_res != 0) {
> -				uint64_t	blk_res_used = 0;
> +			blk_res_used = max_t(int64_t, 0, qtrx->qt_bcount_delta);
> +			xfs_apply_quota_reservation_deltas(&dqp->q_blk,
> +					qtrx->qt_blk_res, blk_res_used,
> +					qtrx->qt_bcount_delta);
>  
> -				if (qtrx->qt_bcount_delta > 0)
> -					blk_res_used = qtrx->qt_bcount_delta;
> -
> -				if (qtrx->qt_blk_res != blk_res_used) {
> -					if (qtrx->qt_blk_res > blk_res_used)
> -						dqp->q_blk.reserved -= (xfs_qcnt_t)
> -							(qtrx->qt_blk_res -
> -							 blk_res_used);
> -					else
> -						dqp->q_blk.reserved -= (xfs_qcnt_t)
> -							(blk_res_used -
> -							 qtrx->qt_blk_res);
> -				}
> -			} else {
> -				/*
> -				 * These blks were never reserved, either inside
> -				 * a transaction or outside one (in a delayed
> -				 * allocation). Also, this isn't always a
> -				 * negative number since we sometimes
> -				 * deliberately skip quota reservations.
> -				 */
> -				if (qtrx->qt_bcount_delta) {
> -					dqp->q_blk.reserved +=
> -					      (xfs_qcnt_t)qtrx->qt_bcount_delta;
> -				}
> -			}
>  			/*
>  			 * Adjust the RT reservation.
>  			 */
> -			if (qtrx->qt_rtblk_res != 0) {
> -				if (qtrx->qt_rtblk_res != qtrx->qt_rtblk_res_used) {
> -					if (qtrx->qt_rtblk_res >
> -					    qtrx->qt_rtblk_res_used)
> -					       dqp->q_rtb.reserved -= (xfs_qcnt_t)
> -						       (qtrx->qt_rtblk_res -
> -							qtrx->qt_rtblk_res_used);
> -					else
> -					       dqp->q_rtb.reserved -= (xfs_qcnt_t)
> -						       (qtrx->qt_rtblk_res_used -
> -							qtrx->qt_rtblk_res);
> -				}
> -			} else {
> -				if (qtrx->qt_rtbcount_delta)
> -					dqp->q_rtb.reserved +=
> -					    (xfs_qcnt_t)qtrx->qt_rtbcount_delta;
> -			}
> +			xfs_apply_quota_reservation_deltas(&dqp->q_rtb,
> +					qtrx->qt_rtblk_res,
> +					qtrx->qt_rtblk_res_used,
> +					qtrx->qt_rtbcount_delta);
>  
>  			/*
>  			 * Adjust the inode reservation.
>  			 */
> -			if (qtrx->qt_ino_res != 0) {
> -				ASSERT(qtrx->qt_ino_res >=
> -				       qtrx->qt_ino_res_used);
> -				if (qtrx->qt_ino_res > qtrx->qt_ino_res_used)
> -					dqp->q_ino.reserved -= (xfs_qcnt_t)
> -						(qtrx->qt_ino_res -
> -						 qtrx->qt_ino_res_used);
> -			} else {
> -				if (qtrx->qt_icount_delta)
> -					dqp->q_ino.reserved +=
> -					    (xfs_qcnt_t)qtrx->qt_icount_delta;
> -			}
> +			ASSERT(qtrx->qt_ino_res >= qtrx->qt_ino_res_used);
> +			xfs_apply_quota_reservation_deltas(&dqp->q_ino,
> +					qtrx->qt_ino_res,
> +					qtrx->qt_ino_res_used,
> +					qtrx->qt_icount_delta);
>  
>  			ASSERT(dqp->q_blk.reserved >= dqp->q_blk.count);
>  			ASSERT(dqp->q_ino.reserved >= dqp->q_ino.count);
> 
> 

-- 
chandan