linux-kernel - Re: [PATCH 06/28] xfs: factor common AIL item deletion code

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Date:   Mon, 4 Nov 2019 15:16:32 -0800
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     Dave Chinner <david@...morbit.com>
Cc:     linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/28] xfs: factor common AIL item deletion code

On Fri, Nov 01, 2019 at 10:45:56AM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@...hat.com>
> 
> Factor the common AIL deletion code that does all the wakeups into a
> helper so we only have one copy of this somewhat tricky code to
> interface with all the wakeups necessary when the LSN of the log
> tail changes.
> 
> Signed-off-by: Dave Chinner <dchinner@...hat.com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> ---
>  fs/xfs/xfs_inode_item.c | 12 +----------
>  fs/xfs/xfs_trans_ail.c  | 48 ++++++++++++++++++++++-------------------
>  fs/xfs/xfs_trans_priv.h |  4 +++-
>  3 files changed, 30 insertions(+), 34 deletions(-)
> 
> diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
> index bb8f076805b9..ab12e526540a 100644
> --- a/fs/xfs/xfs_inode_item.c
> +++ b/fs/xfs/xfs_inode_item.c
> @@ -743,17 +743,7 @@ xfs_iflush_done(
>  				xfs_clear_li_failed(blip);
>  			}
>  		}
> -
> -		if (mlip_changed) {
> -			if (!XFS_FORCED_SHUTDOWN(ailp->ail_mount))
> -				xlog_assign_tail_lsn_locked(ailp->ail_mount);
> -			if (list_empty(&ailp->ail_head))
> -				wake_up_all(&ailp->ail_empty);
> -		}
> -		spin_unlock(&ailp->ail_lock);
> -
> -		if (mlip_changed)
> -			xfs_log_space_wake(ailp->ail_mount);
> +		xfs_ail_update_finish(ailp, mlip_changed);
>  	}
>  
>  	/*
> diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
> index 6ccfd75d3c24..656819523bbd 100644
> --- a/fs/xfs/xfs_trans_ail.c
> +++ b/fs/xfs/xfs_trans_ail.c
> @@ -678,6 +678,27 @@ xfs_ail_push_all_sync(
>  	finish_wait(&ailp->ail_empty, &wait);
>  }
>  
> +void
> +xfs_ail_update_finish(
> +	struct xfs_ail		*ailp,
> +	bool			do_tail_update) __releases(ailp->ail_lock)
> +{
> +	struct xfs_mount	*mp = ailp->ail_mount;
> +
> +	if (!do_tail_update) {
> +		spin_unlock(&ailp->ail_lock);
> +		return;
> +	}
> +
> +	if (!XFS_FORCED_SHUTDOWN(mp))
> +		xlog_assign_tail_lsn_locked(mp);
> +
> +	if (list_empty(&ailp->ail_head))
> +		wake_up_all(&ailp->ail_empty);
> +	spin_unlock(&ailp->ail_lock);
> +	xfs_log_space_wake(mp);
> +}
> +
>  /*
>   * xfs_trans_ail_update - bulk AIL insertion operation.
>   *
> @@ -737,15 +758,7 @@ xfs_trans_ail_update_bulk(
>  	if (!list_empty(&tmp))
>  		xfs_ail_splice(ailp, cur, &tmp, lsn);
>  
> -	if (mlip_changed) {
> -		if (!XFS_FORCED_SHUTDOWN(ailp->ail_mount))
> -			xlog_assign_tail_lsn_locked(ailp->ail_mount);
> -		spin_unlock(&ailp->ail_lock);
> -
> -		xfs_log_space_wake(ailp->ail_mount);

This call site didn't have a wake_up_all and now it does; is that going
to make a difference?  I /think/ the answer is that this function
usually puts things on the AIL so we won't trigger the ail_empty wakeup;
and if the AIL was previously empty and we didn't match any log items
(such that it's still empty) then it's fine to wake up anyone who was
waiting for the ail to clear out?

--D

> -	} else {
> -		spin_unlock(&ailp->ail_lock);
> -	}
> +	xfs_ail_update_finish(ailp, mlip_changed);
>  }
>  
>  bool
> @@ -789,10 +802,10 @@ void
>  xfs_trans_ail_delete(
>  	struct xfs_ail		*ailp,
>  	struct xfs_log_item	*lip,
> -	int			shutdown_type) __releases(ailp->ail_lock)
> +	int			shutdown_type)
>  {
>  	struct xfs_mount	*mp = ailp->ail_mount;
> -	bool			mlip_changed;
> +	bool			need_update;
>  
>  	if (!test_bit(XFS_LI_IN_AIL, &lip->li_flags)) {
>  		spin_unlock(&ailp->ail_lock);
> @@ -805,17 +818,8 @@ xfs_trans_ail_delete(
>  		return;
>  	}
>  
> -	mlip_changed = xfs_ail_delete_one(ailp, lip);
> -	if (mlip_changed) {
> -		if (!XFS_FORCED_SHUTDOWN(mp))
> -			xlog_assign_tail_lsn_locked(mp);
> -		if (list_empty(&ailp->ail_head))
> -			wake_up_all(&ailp->ail_empty);
> -	}
> -
> -	spin_unlock(&ailp->ail_lock);
> -	if (mlip_changed)
> -		xfs_log_space_wake(ailp->ail_mount);
> +	need_update = xfs_ail_delete_one(ailp, lip);
> +	xfs_ail_update_finish(ailp, need_update);
>  }
>  
>  int
> diff --git a/fs/xfs/xfs_trans_priv.h b/fs/xfs/xfs_trans_priv.h
> index 2e073c1c4614..64ffa746730e 100644
> --- a/fs/xfs/xfs_trans_priv.h
> +++ b/fs/xfs/xfs_trans_priv.h
> @@ -92,8 +92,10 @@ xfs_trans_ail_update(
>  }
>  
>  bool xfs_ail_delete_one(struct xfs_ail *ailp, struct xfs_log_item *lip);
> +void xfs_ail_update_finish(struct xfs_ail *ailp, bool do_tail_update)
> +			__releases(ailp->ail_lock);
>  void xfs_trans_ail_delete(struct xfs_ail *ailp, struct xfs_log_item *lip,
> -		int shutdown_type) __releases(ailp->ail_lock);
> +		int shutdown_type);
>  
>  static inline void
>  xfs_trans_ail_remove(
> -- 
> 2.24.0.rc0
>