linux-kernel - Re: [PATCH 2/9] f2fs: avoid unneeded initializing when converting inline dentry

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Date:	Thu, 20 Aug 2015 10:17:18 -0700
From:	Jaegeuk Kim <jaegeuk@...nel.org>
To:	Chao Yu <chao2.yu@...sung.com>
Cc:	linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/9] f2fs: avoid unneeded initializing when converting
 inline dentry

Hi Chao,

On Wed, Aug 19, 2015 at 07:10:19PM +0800, Chao Yu wrote:
> When converting inline dentry, we will zero out target dentry page before
> duplicating data of inline dentry into target page, it become overhead
> since inline dentry size is not small.
> 
> So this patch tries to remove unneeded initializing in the space of target
> dentry page.
> 
> Signed-off-by: Chao Yu <chao2.yu@...sung.com>
> ---
>  fs/f2fs/inline.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
> index 79d18d5..e4da0d7 100644
> --- a/fs/f2fs/inline.c
> +++ b/fs/f2fs/inline.c
> @@ -384,17 +384,30 @@ static int f2fs_convert_inline_dir(struct inode *dir, struct page *ipage,
>  		goto out;
>  
>  	f2fs_wait_on_page_writeback(page, DATA);
> -	zero_user_segment(page, 0, PAGE_CACHE_SIZE);
> +	zero_user_segment(page, MAX_INLINE_DATA, PAGE_CACHE_SIZE);
>  
>  	dentry_blk = kmap_atomic(page);
>  
>  	/* copy data from inline dentry block to new dentry block */
>  	memcpy(dentry_blk->dentry_bitmap, inline_dentry->dentry_bitmap,
>  					INLINE_DENTRY_BITMAP_SIZE);
> +	memset(dentry_blk->dentry_bitmap + INLINE_DENTRY_BITMAP_SIZE, 0,
> +			SIZE_OF_DENTRY_BITMAP - INLINE_DENTRY_BITMAP_SIZE);

Setting zeros for bitmap would be enough.
It doesn't need to copy or set zeros for reserved, dentries, and filename slots.

Thanks,

> +	/*
> +	 * reserved space size of inline dentry is larger than the one of
> +	 * regular dentry, here we just copy with the size of reserved space
> +	 * in regular dentry.
> +	 */
> +	memcpy(dentry_blk->reserved, inline_dentry->reserved, SIZE_OF_RESERVED);
>  	memcpy(dentry_blk->dentry, inline_dentry->dentry,
>  			sizeof(struct f2fs_dir_entry) * NR_INLINE_DENTRY);
> +	memset(dentry_blk->dentry + NR_INLINE_DENTRY, 0,
> +			sizeof (struct f2fs_dir_entry) *
> +			(NR_DENTRY_IN_BLOCK - NR_INLINE_DENTRY));
>  	memcpy(dentry_blk->filename, inline_dentry->filename,
>  					NR_INLINE_DENTRY * F2FS_SLOT_LEN);
> +	memset(&dentry_blk->filename[NR_INLINE_DENTRY][0], 0,
> +		F2FS_SLOT_LEN * (NR_DENTRY_IN_BLOCK - NR_INLINE_DENTRY));
>  
>  	kunmap_atomic(dentry_blk);
>  	SetPageUptodate(page);
> -- 
> 2.4.2
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