linux-kernel - Re: [PATCH 6/7] xfs: propagate issue-flush error code

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Message-Id: <200903301720.48260.bzolnier@gmail.com>
Date:	Mon, 30 Mar 2009 17:20:43 +0200
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	Fernando Luis Vázquez Cao 
	<fernando@....ntt.co.jp>
Cc:	Jeff Garzik <jeff@...zik.org>,
	Christoph Hellwig <hch@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Theodore Tso <tytso@....edu>, Ingo Molnar <mingo@...e.hu>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arjan van de Ven <arjan@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Nick Piggin <npiggin@...e.de>, David Rees <drees76@...il.com>,
	Jesper Krogh <jesper@...gh.cc>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	chris.mason@...cle.com, david@...morbit.com, tj@...nel.org
Subject: Re: [PATCH 6/7] xfs: propagate issue-flush error code

On Monday 30 March 2009, Fernando Luis Vázquez Cao wrote:
> blkdev_issue_flush() may fail (i.e. due to media error on FLUSH CACHE
> command execution) so its users should check for the return value.
> 
> (This issues was first spotted Bartlomiej Zolnierkiewicz)
> 
> Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
> Signed-off-by: Fernando Luis Vazquez Cao <fernando@....ntt.co.jp>
> ---
> 
> diff -urNp linux-2.6.29-orig/fs/xfs/linux-2.6/xfs_buf.c linux-2.6.29/fs/xfs/linux-2.6/xfs_buf.c
> --- linux-2.6.29-orig/fs/xfs/linux-2.6/xfs_buf.c	2009-03-24 08:12:14.000000000 +0900
> +++ linux-2.6.29/fs/xfs/linux-2.6/xfs_buf.c	2009-03-30 14:44:34.000000000 +0900
> @@ -1446,6 +1446,7 @@ xfs_free_buftarg(
>   {
>   	xfs_flush_buftarg(btp, 1);
>   	if (mp->m_flags & XFS_MOUNT_BARRIER)
> +		/* FIXME: check return value */
>   		xfs_blkdev_issue_flush(btp);
>   	xfs_free_bufhash(btp);
>   	iput(btp->bt_mapping->host);
> diff -urNp linux-2.6.29-orig/fs/xfs/linux-2.6/xfs_super.c linux-2.6.29/fs/xfs/linux-2.6/xfs_super.c
> --- linux-2.6.29-orig/fs/xfs/linux-2.6/xfs_super.c	2009-03-24 08:12:14.000000000 +0900
> +++ linux-2.6.29/fs/xfs/linux-2.6/xfs_super.c	2009-03-30 15:16:42.000000000 +0900
> @@ -721,11 +721,11 @@ xfs_mountfs_check_barriers(xfs_mount_t *
>   	}
>   }
> 
> -void
> +int
>   xfs_blkdev_issue_flush(
>   	xfs_buftarg_t		*buftarg)
>   {
> -	blkdev_issue_flush(buftarg->bt_bdev, NULL);
> +	return block_flush_device(buftarg->bt_bdev);
>   }
> 
>   STATIC void
> diff -urNp linux-2.6.29-orig/fs/xfs/linux-2.6/xfs_super.h linux-2.6.29/fs/xfs/linux-2.6/xfs_super.h
> --- linux-2.6.29-orig/fs/xfs/linux-2.6/xfs_super.h	2009-03-24 08:12:14.000000000 +0900
> +++ linux-2.6.29/fs/xfs/linux-2.6/xfs_super.h	2009-03-30 14:46:31.000000000 +0900
> @@ -89,7 +89,7 @@ struct block_device;
> 
>   extern __uint64_t xfs_max_file_offset(unsigned int);
> 
> -extern void xfs_blkdev_issue_flush(struct xfs_buftarg *);
> +extern int xfs_blkdev_issue_flush(struct xfs_buftarg *);
> 
>   extern const struct export_operations xfs_export_operations;
>   extern struct xattr_handler *xfs_xattr_handlers[];
> diff -urNp linux-2.6.29-orig/fs/xfs/xfs_vnodeops.c linux-2.6.29/fs/xfs/xfs_vnodeops.c
> --- linux-2.6.29-orig/fs/xfs/xfs_vnodeops.c	2009-03-24 08:12:14.000000000 +0900
> +++ linux-2.6.29/fs/xfs/xfs_vnodeops.c	2009-03-30 15:08:21.000000000 +0900
> @@ -678,20 +678,20 @@ xfs_fsync(
>   		xfs_iunlock(ip, XFS_ILOCK_EXCL);
>   	}
> 
> -	if ((ip->i_mount->m_flags & XFS_MOUNT_BARRIER) && changed) {
> +	if (!error && (ip->i_mount->m_flags & XFS_MOUNT_BARRIER) && changed) {
>   		/*
>   		 * If the log write didn't issue an ordered tag we need
>   		 * to flush the disk cache for the data device now.
>   		 */
>   		if (!log_flushed)
> -			xfs_blkdev_issue_flush(ip->i_mount->m_ddev_targp);
> +			error = xfs_blkdev_issue_flush(ip->i_mount->m_ddev_targp);

This is different from my original patch which preserved the original
error value...

>   		/*
>   		 * If this inode is on the RT dev we need to flush that
>   		 * cache as well.
>   		 */
> -		if (XFS_IS_REALTIME_INODE(ip))
> -			xfs_blkdev_issue_flush(ip->i_mount->m_rtdev_targp);
> +		if (!error && XFS_IS_REALTIME_INODE(ip))
> +			error = xfs_blkdev_issue_flush(ip->i_mount->m_rtdev_targp);

This is also different and is a change in behavior
(it makes sense IMHO but please document it).

Thanks,
Bart
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