linux-kernel - RE: [PATCH 1/3] f2fs: backup raw

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Date:	Tue, 15 Dec 2015 17:40:51 +0800
From:	Chao Yu <chao2.yu@...sung.com>
To:	Jaegeuk Kim <jaegeuk@...nel.org>, Yunlei He <heyunlei@...wei.com>
Cc:	linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: RE: [PATCH 1/3] f2fs: backup raw_super in sbi

Hi Jaegeuk, Yunlei,

I help do some edits and send it out as my patch's base. :)

But if you want to send patch by yourself, please ignore this patch.

Thanks,

> -----Original Message-----
> From: Chao Yu [mailto:chao2.yu@...sung.com]
> Sent: Tuesday, December 15, 2015 5:17 PM
> To: Jaegeuk Kim (jaegeuk@...nel.org); Yunlei He (heyunlei@...wei.com)
> Cc: linux-f2fs-devel@...ts.sourceforge.net; linux-kernel@...r.kernel.org
> Subject: [PATCH 1/3] f2fs: backup raw_super in sbi
> 
> From: Yunlei He <heyunlei@...wei.com>
> 
> f2fs use fields of f2fs_super_block struct directly in a grabbed buffer.
> 
> Once the buffer happen to be destroyed (e.g. through dd), it may bring
> in unpredictable effect on f2fs.
> 
> This patch fixes to allocate additional buffer to store datas of super
> block rather than using grabbed block buffer directly.
> 
> Signed-off-by: Yunlei He <heyunlei@...wei.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> Signed-off-by: Chao Yu <chao2.yu@...sung.com>
> ---
>  fs/f2fs/super.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 694e092..a6eb79a 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -578,6 +578,7 @@ static void f2fs_put_super(struct super_block *sb)
> 
>  	sb->s_fs_info = NULL;
>  	brelse(sbi->raw_super_buf);
> +	kfree(sbi->raw_super);
>  	kfree(sbi);
>  }
> 
> @@ -1153,6 +1154,9 @@ static int read_raw_super_block(struct super_block *sb,
>  	struct f2fs_super_block *super;
>  	int err = 0;
> 
> +	super = kzalloc(sizeof(struct f2fs_super_block), GFP_KERNEL);
> +	if (!super)
> +		return -ENOMEM;
>  retry:
>  	buffer = sb_bread(sb, block);
>  	if (!buffer) {
> @@ -1168,8 +1172,7 @@ retry:
>  		}
>  	}
> 
> -	super = (struct f2fs_super_block *)
> -		((char *)(buffer)->b_data + F2FS_SUPER_OFFSET);
> +	memcpy(super, buffer->b_data + F2FS_SUPER_OFFSET, sizeof(*super));
> 
>  	/* sanity checking of raw super */
>  	if (sanity_check_raw_super(sb, super)) {
> @@ -1203,14 +1206,17 @@ retry:
> 
>  out:
>  	/* No valid superblock */
> -	if (!*raw_super)
> +	if (!*raw_super) {
> +		kfree(super);
>  		return err;
> +	}
> 
>  	return 0;
>  }
> 
>  int f2fs_commit_super(struct f2fs_sb_info *sbi, bool recover)
>  {
> +	struct f2fs_super_block *super = F2FS_RAW_SUPER(sbi);
>  	struct buffer_head *sbh = sbi->raw_super_buf;
>  	struct buffer_head *bh;
>  	int err;
> @@ -1221,7 +1227,7 @@ int f2fs_commit_super(struct f2fs_sb_info *sbi, bool recover)
>  		return -EIO;
> 
>  	lock_buffer(bh);
> -	memcpy(bh->b_data, sbh->b_data, sbh->b_size);
> +	memcpy(bh->b_data + F2FS_SUPER_OFFSET, super, sizeof(*super));
>  	WARN_ON(sbh->b_size != F2FS_BLKSIZE);
>  	set_buffer_uptodate(bh);
>  	set_buffer_dirty(bh);
> @@ -1237,6 +1243,10 @@ int f2fs_commit_super(struct f2fs_sb_info *sbi, bool recover)
> 
>  	/* write current valid superblock */
>  	lock_buffer(sbh);
> +	if (memcmp(sbh->b_data + F2FS_SUPER_OFFSET, super, sizeof(*super))) {
> +		f2fs_msg(sbi->sb, KERN_INFO, "Write modified valid superblock");
> +		memcpy(sbh->b_data + F2FS_SUPER_OFFSET, super, sizeof(*super));
> +	}
>  	set_buffer_dirty(sbh);
>  	unlock_buffer(sbh);
> 
> @@ -1513,6 +1523,7 @@ free_options:
>  	kfree(options);
>  free_sb_buf:
>  	brelse(raw_super_buf);
> +	kfree(raw_super);
>  free_sbi:
>  	kfree(sbi);
> 
> --
> 2.6.3


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