[PATCH] f2fs: simplify the way of calulating next nat address

[PATCH] f2fs: simplify the way of calulating next nat address

[Fan Li]

The index of segment which the next nat block is in has only one different
bit than the current one, so to get the next nat address, we can simply
alter that one bit.

Signed-off-by: Fan Li <fanofcode.li@samsung.com>
---
 fs/f2fs/node.h | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
index 558048e..da0b21b 100644
--- a/fs/f2fs/node.h
+++ b/fs/f2fs/node.h
@@ -224,10 +224,7 @@ static inline pgoff_t next_nat_addr(struct f2fs_sb_info *sbi,
        struct f2fs_nm_info *nm_i = NM_I(sbi);

        block_addr -= nm_i->nat_blkaddr;
-       if ((block_addr >> sbi->log_blocks_per_seg) % 2)
-               block_addr -= sbi->blocks_per_seg;
-       else
-               block_addr += sbi->blocks_per_seg;
+       block_addr ^= 1 << sbi->log_blocks_per_seg;

        return block_addr + nm_i->nat_blkaddr;
 }
--
2.7.4


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Re: [PATCH] f2fs: simplify the way of calulating next nat address

[Chao Yu]

On 2017/6/2 15:45, Fan Li wrote:
> The index of segment which the next nat block is in has only one different
> bit than the current one, so to get the next nat address, we can simply
> alter that one bit.
> 
> Signed-off-by: Fan Li <fanofcode.li@samsung.com>

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

Thanks,

> ---
>  fs/f2fs/node.h | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
> index 558048e..da0b21b 100644
> --- a/fs/f2fs/node.h
> +++ b/fs/f2fs/node.h
> @@ -224,10 +224,7 @@ static inline pgoff_t next_nat_addr(struct f2fs_sb_info *sbi,
>         struct f2fs_nm_info *nm_i = NM_I(sbi);
> 
>         block_addr -= nm_i->nat_blkaddr;
> -       if ((block_addr >> sbi->log_blocks_per_seg) % 2)
> -               block_addr -= sbi->blocks_per_seg;
> -       else
> -               block_addr += sbi->blocks_per_seg;
> +       block_addr ^= 1 << sbi->log_blocks_per_seg;
> 
>         return block_addr + nm_i->nat_blkaddr;
>  }
> --
> 2.7.4
> 
> 
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> 

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