linux-kernel - Re: [PATCH] Fix regression in O_DIRECT|O

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Date:	Thu, 22 Apr 2010 21:25:00 +0200
From:	Jan Kara <jack@...e.cz>
To:	Anton Blanchard <anton@...ba.org>
Cc:	Jan Kara <jack@...e.cz>, Christoph Hellwig <hch@....de>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jens Axboe <jens.axboe@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix regression in O_DIRECT|O_SYNC writes to block
 devices

On Tue 20-04-10 12:30:47, Anton Blanchard wrote:
<snip>
> Signed-off-by: Anton Blanchard <anton@...ba.org>
  The patch looks good to me now.

Acked-by: Jan Kara <jack@...e.cz>

> Index: linux-2.6/fs/block_dev.c
> ===================================================================
> --- linux-2.6.orig/fs/block_dev.c	2010-04-20 11:28:32.000000000 +1000
> +++ linux-2.6/fs/block_dev.c	2010-04-20 11:36:46.000000000 +1000
> @@ -406,16 +406,23 @@ static loff_t block_llseek(struct file *
>   
>  int blkdev_fsync(struct file *filp, struct dentry *dentry, int datasync)
>  {
> -	struct block_device *bdev = I_BDEV(filp->f_mapping->host);
> +	struct inode *bd_inode = filp->f_mapping->host;
> +	struct block_device *bdev = I_BDEV(bd_inode);
>  	int error;
>  
> -	error = sync_blockdev(bdev);
> -	if (error)
> -		return error;
> -	
> +	/*
> +	 * There is no need to serialise calls to blkdev_issue_flush with
> +	 * i_mutex and doing so causes performance issues with concurrent
> +	 * O_SYNC writers to a block device.
> +	 */
> +	mutex_unlock(&bd_inode->i_mutex);
> +
>  	error = blkdev_issue_flush(bdev, NULL);
>  	if (error == -EOPNOTSUPP)
>  		error = 0;
> +
> +	mutex_lock(&bd_inode->i_mutex);
> +
>  	return error;
>  }
>  EXPORT_SYMBOL(blkdev_fsync);
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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