linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: optimize __update_nat

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Date:   Mon, 30 Oct 2017 17:39:20 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Fan Li <fanofcode.li@...sung.com>, <jaegeuk@...nel.org>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH] f2fs: optimize __update_nat_bits

On 2017/10/30 15:19, Fan Li wrote:
> Make three modification for __update_nat_bits:
> 1. Take the codes of dealing the nat with nid 0 out of the loop
>     Such nat only needs to be dealt with once at beginning.
> 2. Use " nat_index == 0" instead of " start_nid == 0" to decide if it's the first nat block
>     It's better that we don't assume @start_nid is the first nid of the nat block it's in.
> 3. Use " if (nat_blk->entries[i].block_addr != NULL_ADDR)" to explicitly comfirm the value of block_addr
>     use constant to make sure the codes is right, even if the value of NULL_ADDR changes.
> 
> Signed-off-by: Fan li <fanofcode.li@...sung.com>

Reviewed-by: Chao Yu <yuchao0@...wei.com>

Thanks,

> ---
>  fs/f2fs/node.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index ac629d6..b97a031 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -2407,15 +2407,17 @@ static void __update_nat_bits(struct f2fs_sb_info *sbi, nid_t start_nid,
>         unsigned int nat_index = start_nid / NAT_ENTRY_PER_BLOCK;
>         struct f2fs_nat_block *nat_blk = page_address(page);
>         int valid = 0;
> -       int i;
> +       int i = 0;
> 
>         if (!enabled_nat_bits(sbi, NULL))
>                 return;
> 
> -       for (i = 0; i < NAT_ENTRY_PER_BLOCK; i++) {
> -               if (start_nid == 0 && i == 0)
> -                       valid++;
> -               if (nat_blk->entries[i].block_addr)
> +       if (nat_index == 0) {
> +               valid = 1;
> +               i = 1;
> +       }
> +       for (; i < NAT_ENTRY_PER_BLOCK; i++) {
> +               if (nat_blk->entries[i].block_addr != NULL_ADDR)
>                         valid++;
>         }
>         if (valid == 0) {
> --
> 2.7.4
> 
> 
>