Re: [PATCH 2/9] xfs: xfs_buf_ioend and xfs_buf_iodone_work duplicate functionality

[Brian Foster <bfoster@redhat.com>]

On Fri, Aug 15, 2014 at 04:39:00PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> We do some work in xfs_buf_ioend, and some work in
> xfs_buf_iodone_work, but much of that functionality is the same.
> This work can all be done in a single function, leaving
> xfs_buf_iodone just a wrapper to determine if we should execute it
> by workqueue or directly. hence rename xfs_buf_iodone_work to
> xfs_buf_ioend(), and add a new xfs_buf_ioend_async() for places that
> need async processing.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
>  fs/xfs/xfs_buf.c         | 79 +++++++++++++++++++++---------------------------
>  fs/xfs/xfs_buf.h         |  2 +-
>  fs/xfs/xfs_buf_item.c    |  4 +--
>  fs/xfs/xfs_inode.c       |  2 +-
>  fs/xfs/xfs_log.c         |  2 +-
>  fs/xfs/xfs_log_recover.c |  2 +-
>  6 files changed, 40 insertions(+), 51 deletions(-)
> 
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index 5d86bbd..1b7f0bc 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -999,54 +999,49 @@ xfs_buf_wait_unpin(
>   */
>  
>  STATIC void
> -xfs_buf_iodone_work(
> -	struct work_struct	*work)
> +xfs_buf_ioend(
> +	struct xfs_buf	*bp)

Compile failure here due to STATIC.

>  {
> -	struct xfs_buf		*bp =
> -		container_of(work, xfs_buf_t, b_iodone_work);
> -	bool			read = !!(bp->b_flags & XBF_READ);
> +	bool		read = !!(bp->b_flags & XBF_READ);
> +
> +	trace_xfs_buf_iodone(bp, _RET_IP_);
>  
>  	bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
>  
> -	/* only validate buffers that were read without errors */
> -	if (read && bp->b_ops && !bp->b_error && (bp->b_flags & XBF_DONE))
> -		bp->b_ops->verify_read(bp);
> +	if (!bp->b_error) {
> +		bp->b_flags |= XBF_DONE;
> +
> +		/* only validate buffers that were read without errors */
> +		if (read && bp->b_ops)
> +			bp->b_ops->verify_read(bp);
> +	}

Probably not a cause of errors, but this code is now executed twice for
I/O with b_iodone callbacks. Once for the initial call from bio_end_io,
again from the callback via the b_iodone handler. The flags bits are
probably fine, but we don't want to be running the verifiers multiple
times unnecessarily.

>  
>  	if (bp->b_iodone)
>  		(*(bp->b_iodone))(bp);
>  	else if (bp->b_flags & XBF_ASYNC)
>  		xfs_buf_relse(bp);
>  	else {
> -		ASSERT(read && bp->b_ops);
>  		complete(&bp->b_iowait);
>  		xfs_buf_rele(bp);
>  	}
>  }
>  
> -void
> -xfs_buf_ioend(
> -	struct xfs_buf	*bp,
> -	int		schedule)
> +static void
> +xfs_buf_ioend_work(
> +	struct work_struct	*work)
>  {
> -	bool		read = !!(bp->b_flags & XBF_READ);
> -
> -	trace_xfs_buf_iodone(bp, _RET_IP_);
> +	struct xfs_buf		*bp =
> +		container_of(work, xfs_buf_t, b_iodone_work);
>  
> -	if (bp->b_error == 0)
> -		bp->b_flags |= XBF_DONE;
> +	xfs_buf_ioend(bp);
> +}
>  
> -	if (bp->b_iodone || (read && bp->b_ops) || (bp->b_flags & XBF_ASYNC)) {
> -		if (schedule) {
> -			INIT_WORK(&bp->b_iodone_work, xfs_buf_iodone_work);
> -			queue_work(xfslogd_workqueue, &bp->b_iodone_work);
> -		} else {
> -			xfs_buf_iodone_work(&bp->b_iodone_work);
> -		}
> -	} else {
> -		bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
> -		complete(&bp->b_iowait);
> -		xfs_buf_rele(bp);
> -	}
> +void
> +xfs_buf_ioend_async(
> +	struct xfs_buf	*bp)
> +{
> +	INIT_WORK(&bp->b_iodone_work, xfs_buf_ioend_work);
> +	queue_work(xfslogd_workqueue, &bp->b_iodone_work);
>  }
>  
>  void
> @@ -1094,7 +1089,7 @@ xfs_bioerror(
>  	XFS_BUF_UNDONE(bp);
>  	xfs_buf_stale(bp);
>  
> -	xfs_buf_ioend(bp, 0);
> +	xfs_buf_ioend(bp);
>  
>  	return -EIO;
>  }
> @@ -1181,15 +1176,6 @@ xfs_bwrite(
>  }
>  
>  STATIC void
> -_xfs_buf_ioend(
> -	xfs_buf_t		*bp,
> -	int			schedule)
> -{
> -	if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
> -		xfs_buf_ioend(bp, schedule);
> -}
> -
> -STATIC void
>  xfs_buf_bio_end_io(
>  	struct bio		*bio,
>  	int			error)
> @@ -1206,7 +1192,8 @@ xfs_buf_bio_end_io(
>  	if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
>  		invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
>  
> -	_xfs_buf_ioend(bp, 1);
> +	if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
> +		xfs_buf_ioend_async(bp);
>  	bio_put(bio);
>  }
>  
> @@ -1425,10 +1412,12 @@ xfs_buf_iorequest(
>  	 * waiting, and in the synchronous IO case it avoids unnecessary context
>  	 * switches an latency for high-peformance devices.
>  	 */
> -	if (bp->b_error || !(bp->b_flags & XBF_ASYNC))
> -		_xfs_buf_ioend(bp, 0);
> -	else
> -		_xfs_buf_ioend(bp, 1);
> +	if (atomic_dec_and_test(&bp->b_io_remaining) == 1) {
> +		if (bp->b_error || !(bp->b_flags & XBF_ASYNC))
> +			xfs_buf_ioend(bp);
> +		else
> +			xfs_buf_ioend_async(bp);
> +	}

This looks cleaner, but the comment is out of whack at this point.

Brian

>  
>  	xfs_buf_rele(bp);
>  }
> diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
> index c753183..4585c15 100644
> --- a/fs/xfs/xfs_buf.h
> +++ b/fs/xfs/xfs_buf.h
> @@ -286,7 +286,7 @@ extern void xfs_buf_unlock(xfs_buf_t *);
>  
>  /* Buffer Read and Write Routines */
>  extern int xfs_bwrite(struct xfs_buf *bp);
> -extern void xfs_buf_ioend(xfs_buf_t *,	int);
> +extern void xfs_buf_ioend(struct xfs_buf *bp);
>  extern void xfs_buf_ioerror(xfs_buf_t *, int);
>  extern void xfs_buf_ioerror_alert(struct xfs_buf *, const char *func);
>  extern void xfs_buf_iorequest(xfs_buf_t *);
> diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
> index 76007de..4fd41b5 100644
> --- a/fs/xfs/xfs_buf_item.c
> +++ b/fs/xfs/xfs_buf_item.c
> @@ -491,7 +491,7 @@ xfs_buf_item_unpin(
>  		xfs_buf_ioerror(bp, -EIO);
>  		XFS_BUF_UNDONE(bp);
>  		xfs_buf_stale(bp);
> -		xfs_buf_ioend(bp, 0);
> +		xfs_buf_ioend(bp);
>  	}
>  }
>  
> @@ -1115,7 +1115,7 @@ do_callbacks:
>  	xfs_buf_do_callbacks(bp);
>  	bp->b_fspriv = NULL;
>  	bp->b_iodone = NULL;
> -	xfs_buf_ioend(bp, 0);
> +	xfs_buf_ioend(bp);
>  }
>  
>  /*
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index fea3c92..00d210b 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -3056,7 +3056,7 @@ cluster_corrupt_out:
>  			XFS_BUF_UNDONE(bp);
>  			xfs_buf_stale(bp);
>  			xfs_buf_ioerror(bp, -EIO);
> -			xfs_buf_ioend(bp, 0);
> +			xfs_buf_ioend(bp);
>  		} else {
>  			xfs_buf_stale(bp);
>  			xfs_buf_relse(bp);
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index 8eaa8f5..e4665db 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -1689,7 +1689,7 @@ xlog_bdstrat(
>  	if (iclog->ic_state & XLOG_STATE_IOERROR) {
>  		xfs_buf_ioerror(bp, -EIO);
>  		xfs_buf_stale(bp);
> -		xfs_buf_ioend(bp, 0);
> +		xfs_buf_ioend(bp);
>  		/*
>  		 * It would seem logical to return EIO here, but we rely on
>  		 * the log state machine to propagate I/O errors instead of
> diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> index 1fd5787..4ba19bf 100644
> --- a/fs/xfs/xfs_log_recover.c
> +++ b/fs/xfs/xfs_log_recover.c
> @@ -383,7 +383,7 @@ xlog_recover_iodone(
>  					SHUTDOWN_META_IO_ERROR);
>  	}
>  	bp->b_iodone = NULL;
> -	xfs_buf_ioend(bp, 0);
> +	xfs_buf_ioend(bp);
>  }
>  
>  /*
> -- 
> 2.0.0
> 
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