linux-kernel - Re: [PATCH] f2fs: correct cp_ver for compatibility to old image

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Date:   Thu, 2 Mar 2017 10:55:18 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH] f2fs: correct cp_ver for compatibility to old image

On 03/02, Chao Yu wrote:
> There is no CP_CRC_RECOVERY_FLAG tagged in checkpoint pack, calculate
> cp_version as old format.
> 
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> ---
>  fs/f2fs/node.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 6c027b6833f4..0d46404ca769 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -2507,7 +2507,9 @@ static int __get_nat_bitmaps(struct f2fs_sb_info *sbi)
>  		f2fs_put_page(page, 1);
>  	}
>  
> -	cp_ver |= (cur_cp_crc(ckpt) << 32);
> +	if (__is_set_ckpt_flags(ckpt, CP_CRC_RECOVERY_FLAG))
> +		cp_ver |= (cur_cp_crc(ckpt) << 32);

Well, we always write nat_bits with crc. So if it's different, something is
wrong and we need to drop it. CP-CRC_RECOVERY_FLAG is used for roll-forward
recovery, which is a different context.

> +
>  	if (cpu_to_le64(cp_ver) != *(__le64 *)nm_i->nat_bits) {
>  		disable_nat_bits(sbi, true);
>  		return 0;
> -- 
> 2.8.2.295.g3f1c1d0