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

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Message-ID: <20151215220625.GD66113@jaegeuk.local>
Date:	Tue, 15 Dec 2015 14:06:25 -0800
From:	Jaegeuk Kim <jaegeuk@...nel.org>
To:	Chao Yu <chao2.yu@...sung.com>
Cc:	Yunlei He <heyunlei@...wei.com>,
	linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] f2fs: backup raw_super in sbi

On Tue, Dec 15, 2015 at 05:40:51PM +0800, Chao Yu wrote:
> 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.

No problem to merge this patch.
Thanks Chao.

> 
> 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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