linux-ext4 - Re: [PATCH 2/3] ext2: Merge loops in ext2_xattr

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Message-ID: <6340e88cfb57aadef737ba882d342cd922555a95.camel@zoho.com.cn>
Date:   Thu, 16 May 2019 09:13:34 +0800
From:   "cgxu519@...o.com.cn" <cgxu519@...o.com.cn>
To:     Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/3] ext2: Merge loops in ext2_xattr_set()

On Wed, 2019-05-15 at 16:01 +0200, Jan Kara wrote:
> There are two very similar loops when searching xattr to set. Just merge
> them.
> 
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  fs/ext2/xattr.c | 32 +++++++++++---------------------
>  1 file changed, 11 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
> index fb2e008d4406..26a049ca89fb 100644
> --- a/fs/ext2/xattr.c
> +++ b/fs/ext2/xattr.c
> @@ -437,27 +437,7 @@ ext2_xattr_set(struct inode *inode, int name_index, const
> char *name,
>  			goto cleanup;
>  		}
>  		/* Find the named attribute. */
> -		here = FIRST_ENTRY(bh);
> -		while (!IS_LAST_ENTRY(here)) {
> -			struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
> -			if ((char *)next >= end)
> -				goto bad_block;
> -			if (!here->e_value_block && here->e_value_size) {
> -				size_t offs = le16_to_cpu(here->e_value_offs);
> -				if (offs < min_offs)
> -					min_offs = offs;
> -			}
> -			not_found = name_index - here->e_name_index;
> -			if (!not_found)
> -				not_found = name_len - here->e_name_len;
> -			if (!not_found)
> -				not_found = memcmp(name, here->e_name,name_len);
> -			if (not_found <= 0)
> -				break;
> -			here = next;
> -		}
> -		last = here;
> -		/* We still need to compute min_offs and last. */
> +		last = FIRST_ENTRY(bh);
>  		while (!IS_LAST_ENTRY(last)) {
>  			struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
>  			if ((char *)next >= end)
> @@ -467,8 +447,18 @@ ext2_xattr_set(struct inode *inode, int name_index, const
> char *name,
>  				if (offs < min_offs)
>  					min_offs = offs;
>  			}
> +			if (not_found) {
> +				if (name_index == last->e_name_index &&
> +				    name_len == last->e_name_len &&
> +				    !memcmp(name, last->e_name,name_len)) {
> +					not_found = 0;
> +					here = last;
> +				}
> +			}
>  			last = next;
>  		}
> +		if (not_found)
> +			here = last;

Entry name is sorted so I think for new entry we should find right place for it
not just appending to last.

Thanks,
Chengguang

>  
>  		/* Check whether we have enough space left. */
>  		free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);