linux-ext4 - Re: [PATCH 1/3] ext4: Don't look at buffer_heads outside i

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Message-ID: <20090527162736.GE14035@dhcp231-156.rdu.redhat.com>
Date:	Wed, 27 May 2009 12:27:36 -0400
From:	Josef Bacik <josef@...hat.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	cmm@...ibm.com, tytso@....edu, sandeen@...hat.com, jack@...e.cz,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/3] ext4: Don't look at buffer_heads outside i_size.

On Wed, May 27, 2009 at 09:28:06PM +0530, Aneesh Kumar K.V wrote:
> Buffer heads outside i_size will be unmapped. So when we
> are doing "walk_page_buffers" limit ourself to i_size.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> ---
>  fs/ext4/inode.c |   29 ++++++++++++++++++-----------
>  1 files changed, 18 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 3b07a6c..f0f0065 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2514,7 +2514,7 @@ static int ext4_da_writepage(struct page *page,
>  		 * all are mapped and non delay. We don't want to
>  		 * do block allocation here.
>  		 */
> -		ret = block_prepare_write(page, 0, PAGE_CACHE_SIZE,
> +		ret = block_prepare_write(page, 0, len,
>  					  noalloc_get_block_write);
>  		if (!ret) {
>  			page_bufs = page_buffers(page);
> @@ -2536,7 +2536,7 @@ static int ext4_da_writepage(struct page *page,
>  			return 0;
>  		}
>  		/* now mark the buffer_heads as dirty and uptodate */
> -		block_commit_write(page, 0, PAGE_CACHE_SIZE);
> +		block_commit_write(page, 0, len);
>  	}
>  
>  	if (test_opt(inode->i_sb, NOBH) && ext4_should_writeback_data(inode))
> @@ -3210,6 +3210,8 @@ static int ext4_normal_writepage(struct page *page,
>  static int __ext4_journalled_writepage(struct page *page,
>  				struct writeback_control *wbc)
>  {
> +	loff_t size;
> +	unsigned int len;
>  	struct address_space *mapping = page->mapping;
>  	struct inode *inode = mapping->host;
>  	struct buffer_head *page_bufs;
> @@ -3217,14 +3219,19 @@ static int __ext4_journalled_writepage(struct page *page,
>  	int ret = 0;
>  	int err;
>  
> -	ret = block_prepare_write(page, 0, PAGE_CACHE_SIZE,
> +	size = i_size_read(inode);
> +	if (page->index == size >> PAGE_CACHE_SHIFT)
> +		len = size & ~PAGE_CACHE_MASK;
> +	else
> +		len = PAGE_CACHE_SIZE;
> +
> +	ret = block_prepare_write(page, 0, len,
>  				  noalloc_get_block_write);
>  	if (ret != 0)
>  		goto out_unlock;
>  
>  	page_bufs = page_buffers(page);
> -	walk_page_buffers(handle, page_bufs, 0, PAGE_CACHE_SIZE, NULL,
> -								bget_one);
> +	walk_page_buffers(handle, page_bufs, 0, len, NULL, bget_one);
>  	/* As soon as we unlock the page, it can go away, but we have
>  	 * references to buffers so we are safe */
>  	unlock_page(page);
> @@ -3235,19 +3242,19 @@ static int __ext4_journalled_writepage(struct page *page,
>  		goto out;
>  	}
>  
> -	ret = walk_page_buffers(handle, page_bufs, 0,
> -			PAGE_CACHE_SIZE, NULL, do_journal_get_write_access);
> +	ret = walk_page_buffers(handle, page_bufs, 0, len,
> +				NULL, do_journal_get_write_access);
>  
> -	err = walk_page_buffers(handle, page_bufs, 0,
> -				PAGE_CACHE_SIZE, NULL, write_end_fn);
> +	err = walk_page_buffers(handle, page_bufs, 0, len,
> +				NULL, write_end_fn);
>  	if (ret == 0)
>  		ret = err;
>  	err = ext4_journal_stop(handle);
>  	if (!ret)
>  		ret = err;
>  
> -	walk_page_buffers(handle, page_bufs, 0,
> -				PAGE_CACHE_SIZE, NULL, bput_one);
> +	walk_page_buffers(handle, page_bufs, 0, len,
> +				NULL, bput_one);
>  	EXT4_I(inode)->i_state |= EXT4_STATE_JDATA;
>  	goto out;
>  

This feels a bit silly since its a pretty simple patch, but I took time to
review it so,

Reviewed-by: Josef Bacik <jbacik@...hat.com>
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