linux-kernel - Re: [PATCH 5/13] ext4: use zero_user

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Date:	Tue, 10 Apr 2007 22:14:30 -0600
From:	Andreas Dilger <adilger@...sterfs.com>
To:	Nate Diller <nate.diller@...il.com>
Cc:	Andrew Morton <akpm@...l.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 5/13] ext4: use zero_user_page

On Apr 10, 2007  20:36 -0700, Nate Diller wrote:
> Use zero_user_page() instead of open-coding it. 
> 
> Signed-off-by: Nate Diller <nate.diller@...il.com>

> To: Andrew Morton <akpm@...l.org>,
>        Alexander Viro <viro@...iv.linux.org.uk>
>Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org

Would have been better to CC the filesystem maintainers directly
(which was one of the reasons Andrew wanted per-fs patches so they
can be Ack/Nack independently.

Looks good in any case,

Signed-off-by: Andreas Dilger <adilger@...sterfs.com>

> diff -urpN -X dontdiff linux-2.6.21-rc6-mm1/fs/ext4/inode.c linux-2.6.21-rc6-mm1-test/fs/ext4/inode.c
> --- linux-2.6.21-rc6-mm1/fs/ext4/inode.c	2007-04-10 17:15:04.000000000 -0700
> +++ linux-2.6.21-rc6-mm1-test/fs/ext4/inode.c	2007-04-10 18:33:04.000000000 -0700
> @@ -1791,7 +1791,6 @@ int ext4_block_truncate_page(handle_t *h
>  	struct inode *inode = mapping->host;
>  	struct buffer_head *bh;
>  	int err = 0;
> -	void *kaddr;
>  
>  	if ((EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) &&
>  			test_opt(inode->i_sb, EXTENTS) &&
> @@ -1808,10 +1807,7 @@ int ext4_block_truncate_page(handle_t *h
>  	 */
>  	if (!page_has_buffers(page) && test_opt(inode->i_sb, NOBH) &&
>  	     ext4_should_writeback_data(inode) && PageUptodate(page)) {
> -		kaddr = kmap_atomic(page, KM_USER0);
> -		memset(kaddr + offset, 0, length);
> -		flush_dcache_page(page);
> -		kunmap_atomic(kaddr, KM_USER0);
> +		zero_user_page(page, offset, length);
>  		set_page_dirty(page);
>  		goto unlock;
>  	}
> @@ -1864,11 +1860,7 @@ int ext4_block_truncate_page(handle_t *h
>  			goto unlock;
>  	}
>  
> -	kaddr = kmap_atomic(page, KM_USER0);
> -	memset(kaddr + offset, 0, length);
> -	flush_dcache_page(page);
> -	kunmap_atomic(kaddr, KM_USER0);
> -
> +	zero_user_page(page, offset, length);
>  	BUFFER_TRACE(bh, "zeroed end of block");
>  
>  	err = 0;
> diff -urpN -X dontdiff linux-2.6.21-rc6-mm1/fs/ext4/writeback.c linux-2.6.21-rc6-mm1-test/fs/ext4/writeback.c
> --- linux-2.6.21-rc6-mm1/fs/ext4/writeback.c	2007-04-10 18:05:52.000000000 -0700
> +++ linux-2.6.21-rc6-mm1-test/fs/ext4/writeback.c	2007-04-10 18:33:04.000000000 -0700
> @@ -961,7 +961,6 @@ int ext4_wb_writepage(struct page *page,
>  	loff_t i_size = i_size_read(inode);
>  	pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
>  	unsigned offset;
> -	void *kaddr;
>  
>  	wb_debug("writepage %lu from inode %lu\n", page->index, inode->i_ino);
>  
> @@ -1011,10 +1010,7 @@ int ext4_wb_writepage(struct page *page,
>  	 * the  page size, the remaining memory is zeroed when mapped, and
>  	 * writes to that region are not written out to the file."
>  	 */
> -	kaddr = kmap_atomic(page, KM_USER0);
> -	memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
> -	flush_dcache_page(page);
> -	kunmap_atomic(kaddr, KM_USER0);
> +	zero_user_page(page, offset, PAGE_CACHE_SIZE - offset);
>  	return ext4_wb_write_single_page(page, wbc);
>  }
>  
> @@ -1065,7 +1061,6 @@ int ext4_wb_block_truncate_page(handle_t
>  	struct inode *inode = mapping->host;
>  	struct buffer_head bh, *bhw = &bh;
>  	unsigned blocksize, length;
> -	void *kaddr;
>  	int err = 0;
>  
>  	wb_debug("partial truncate from %lu on page %lu from inode %lu\n",
> @@ -1104,10 +1099,7 @@ int ext4_wb_block_truncate_page(handle_t
>  		}
>  	}
>  
> -	kaddr = kmap_atomic(page, KM_USER0);
> -	memset(kaddr + offset, 0, length);
> -	flush_dcache_page(page);
> -	kunmap_atomic(kaddr, KM_USER0);
> +	zero_user_page(page, offset, length);
>  	SetPageUptodate(page);
>  	__set_page_dirty_nobuffers(page);
>  
> -
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Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

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