linux-kernel - Re: [PATCH v2] f2fs crypto: fix incorrect positioning for GCing encrypted data page

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Message-ID: <20160226195044.GA54334@jaegeuk.gateway>
Date:	Fri, 26 Feb 2016 11:50:44 -0800
From:	Jaegeuk Kim <jaegeuk@...nel.org>
To:	Chao Yu <chao2.yu@...sung.com>
Cc:	linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] f2fs crypto: fix incorrect positioning for GCing
 encrypted data page

Hi Chao,

On Tue, Feb 23, 2016 at 05:52:43PM +0800, Chao Yu wrote:
> For now, flow of GCing an encrypted data page:
> 1) try to grab meta page in meta inode's mapping with index of old block
> address of that data page
> 2) load data of ciphertext into meta page
> 3) allocate new block address
> 4) write the meta page into new block address
> 5) update block address pointer in direct node page.
> 
> Other reader/writer will use f2fs_wait_on_encrypted_page_writeback to
> check and wait on GCed encrypted data cached in meta page writebacked
> in order to avoid inconsistence among data page cache, meta page cache
> and data on-disk when updating.
> 
> However, we will use new block address updated in step 5) as an index to
> lookup meta page in inner bio buffer. That would be wrong, and we will
> never find the GCing meta page, since we use the old block address as
> index of that page in step 1).
> 
> This patch fixes the issue by adjust the order of step 1) and step 3),
> and in step 1) grab page with index generated in step 3).
> 
> Signed-off-by: Chao Yu <chao2.yu@...sung.com>
> ---
>  v2:
>  - fix to recover data page to old block address when error occurs.
> 
>  fs/f2fs/f2fs.h    |  2 ++
>  fs/f2fs/gc.c      | 25 +++++++++++++++++--------
>  fs/f2fs/segment.c |  3 +--
>  3 files changed, 20 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index b57dee6..a7197b3 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1821,6 +1821,8 @@ void write_meta_page(struct f2fs_sb_info *, struct page *);
>  void write_node_page(unsigned int, struct f2fs_io_info *);
>  void write_data_page(struct dnode_of_data *, struct f2fs_io_info *);
>  void rewrite_data_page(struct f2fs_io_info *);
> +void __f2fs_replace_block(struct f2fs_sb_info *, struct f2fs_summary *,
> +					block_t, block_t, bool, bool);
>  void f2fs_replace_block(struct f2fs_sb_info *, struct dnode_of_data *,
>  				block_t, block_t, unsigned char, bool, bool);
>  void allocate_data_block(struct f2fs_sb_info *, struct page *,
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 4af3d80..c7cb1e6 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -549,6 +549,7 @@ static void move_encrypted_block(struct inode *inode, block_t bidx)
>  	struct f2fs_summary sum;
>  	struct node_info ni;
>  	struct page *page;
> +	block_t newaddr;
>  	int err;
>  
>  	/* do not read out */
> @@ -579,12 +580,15 @@ static void move_encrypted_block(struct inode *inode, block_t bidx)
>  	fio.page = page;
>  	fio.new_blkaddr = fio.old_blkaddr = dn.data_blkaddr;
>  
> -	fio.encrypted_page = pagecache_get_page(META_MAPPING(fio.sbi),
> -					fio.new_blkaddr,
> -					FGP_LOCK|FGP_CREAT,
> -					GFP_NOFS);
> -	if (!fio.encrypted_page)
> -		goto put_out;
> +	allocate_data_block(fio.sbi, NULL, fio.old_blkaddr, &newaddr,
> +							&sum, CURSEG_COLD_DATA);
> +
> +	fio.encrypted_page = pagecache_get_page(META_MAPPING(fio.sbi), newaddr,
> +					FGP_LOCK | FGP_CREAT, GFP_NOFS);
> +	if (!fio.encrypted_page) {
> +		err = -ENOMEM;
> +		goto recover_block;
> +	}
>  
>  	err = f2fs_submit_page_bio(&fio);
>  	if (err)
> @@ -593,6 +597,7 @@ static void move_encrypted_block(struct inode *inode, block_t bidx)
>  	/* write page */
>  	lock_page(fio.encrypted_page);
>  
> +	err = -EIO;

I found out that this will trigger error all the time, even in the successful
case.
I'll move assigning this to the below error cases only.

Thanks,


>  	if (unlikely(!PageUptodate(fio.encrypted_page)))
>  		goto put_page_out;
>  	if (unlikely(fio.encrypted_page->mapping != META_MAPPING(fio.sbi)))
> @@ -607,9 +612,9 @@ static void move_encrypted_block(struct inode *inode, block_t bidx)
>  
>  	/* allocate block address */
>  	f2fs_wait_on_page_writeback(dn.node_page, NODE, true);
> -	allocate_data_block(fio.sbi, NULL, fio.old_blkaddr, &fio.new_blkaddr,
> -							&sum, CURSEG_COLD_DATA);
> +
>  	fio.rw = WRITE_SYNC;
> +	fio.new_blkaddr = newaddr;
>  	f2fs_submit_page_mbio(&fio);
>  
>  	dn.data_blkaddr = fio.new_blkaddr;
> @@ -620,6 +625,10 @@ static void move_encrypted_block(struct inode *inode, block_t bidx)
>  		set_inode_flag(F2FS_I(inode), FI_FIRST_BLOCK_WRITTEN);
>  put_page_out:
>  	f2fs_put_page(fio.encrypted_page, 1);
> +recover_block:
> +	if (err)
> +		__f2fs_replace_block(fio.sbi, &sum, newaddr, fio.old_blkaddr,
> +								true, true);
>  put_out:
>  	f2fs_put_dnode(&dn);
>  out:
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index d8e13b0..639c4ff 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1439,8 +1439,7 @@ void rewrite_data_page(struct f2fs_io_info *fio)
>  	f2fs_submit_page_mbio(fio);
>  }
>  
> -static void __f2fs_replace_block(struct f2fs_sb_info *sbi,
> -				struct f2fs_summary *sum,
> +void __f2fs_replace_block(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>  				block_t old_blkaddr, block_t new_blkaddr,
>  				bool recover_curseg, bool recover_newaddr)
>  {
> -- 
> 2.7.0
>