RE: [PATCH] f2fs crypto: fix racing of accessing encrypted page among different competitors

[Chao Yu <chao2.yu@samsung.com>]

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> Sent: Tuesday, October 13, 2015 5:00 AM
> To: Chao Yu
> Cc: linux-f2fs-devel@lists.sourceforge.net; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH] f2fs crypto: fix racing of accessing encrypted page among different
> competitors
> 
> On Thu, Oct 08, 2015 at 08:50:39PM +0800, Chao Yu wrote:
> > >From 0211c6ed82440891b3369851d079f6c69b432b6c Mon Sep 17 00:00:00 2001
> > From: Chao Yu <chao2.yu@samsung.com>
> > Date: Thu, 8 Oct 2015 13:27:34 +0800
> > Subject: [PATCH] f2fs crypto: fix racing of accessing encrypted page among
> >  different competitors
> >
> > Since we use different page cache (normally inode's page cache for R/W
> > and meta inode's page cache for GC) to cache the same physical block
> > which is belong to an encrypted inode. Writeback of these two page
> > cache should be exclusive, but now we didn't handle writeback state
> > well, so there may be potential racing problem:
> >
> > a)
> > kworker:				f2fs_gc:
> >  - f2fs_write_data_pages
> >   - f2fs_write_data_page
> >    - do_write_data_page
> >     - write_data_page
> >      - f2fs_submit_page_mbio
> > (page#1 in inode's page cache was queued
> > in f2fs bio cache, and be ready to write
> > to new blkaddr)
> > 					 - gc_data_segment
> > 					  - move_encrypted_block
> > 					   - pagecache_get_page
> > 					(page#2 in meta inode's page cache
> > 					was cached with the invalid datas
> > 					of physical block located in new
> > 					blkaddr)
> > 					   - f2fs_submit_page_mbio
> > 					(page#1 was submitted, later, page#2
> > 					with invalid data will be submitted)
> >
> > b)
> > f2fs_gc:
> >  - gc_data_segment
> >   - move_encrypted_block
> >    - f2fs_submit_page_mbio
> > (page#1 in meta inode's page cache was
> > queued in f2fs bio cache, and be ready
> > to write to new blkaddr)
> > 					user thread:
> > 					 - f2fs_write_begin
> > 					  - f2fs_submit_page_bio
> > 					(we submit the request to block layer
> > 					to update page#2 in inode's page cache
> > 					with physical block located in new
> > 					blkaddr, so here we may read gabbage
> > 					data from new blkaddr since GC hasn't
> > 					writebacked the page#1 yet)
> >
> > This patch fixes above potential racing problem for encrypted inode.
> >
> > Signed-off-by: Chao Yu <chao2.yu@samsung.com>
> > ---
> >  fs/f2fs/data.c    | 20 +++++++++++---------
> >  fs/f2fs/f2fs.h    |  1 +
> >  fs/f2fs/file.c    |  5 +++++
> >  fs/f2fs/gc.c      | 13 ++++++++++---
> >  fs/f2fs/segment.c | 17 +++++++++++++++++
> >  5 files changed, 44 insertions(+), 12 deletions(-)
> >
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 40a0102..d791bd3 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -954,21 +954,14 @@ submit_and_realloc:
> >
> >  			if (f2fs_encrypted_inode(inode) &&
> >  					S_ISREG(inode->i_mode)) {
> > -				struct page *cpage;
> >
> >  				ctx = f2fs_get_crypto_ctx(inode);
> >  				if (IS_ERR(ctx))
> >  					goto set_error_page;
> >
> >  				/* wait the page to be moved by cleaning */
> > -				cpage = find_lock_page(
> > -						META_MAPPING(F2FS_I_SB(inode)),
> > -						block_nr);
> > -				if (cpage) {
> > -					f2fs_wait_on_page_writeback(cpage,
> > -									DATA);
> > -					f2fs_put_page(cpage, 1);
> > -				}
> > +				f2fs_wait_on_encrypted_page_writeback(
> > +						F2FS_I_SB(inode), block_nr);
> >  			}
> >
> >  			bio = bio_alloc(GFP_KERNEL,
> > @@ -1059,6 +1052,11 @@ int do_write_data_page(struct f2fs_io_info *fio)
> >  	}
> >
> >  	if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode)) {
> > +
> > +		/* wait for GCed encrypted page writeback */
> > +		f2fs_wait_on_encrypted_page_writeback(F2FS_I_SB(inode),
> > +							fio->blk_addr);
> > +
> >  		fio->encrypted_page = f2fs_encrypt(inode, fio->page);
> >  		if (IS_ERR(fio->encrypted_page)) {
> >  			err = PTR_ERR(fio->encrypted_page);
> > @@ -1446,6 +1444,10 @@ put_next:
> >
> >  	f2fs_wait_on_page_writeback(page, DATA);
> >
> > +	/* wait for GCed encrypted page writeback */
> > +	if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
> > +		f2fs_wait_on_encrypted_page_writeback(sbi, dn.data_blkaddr);
> > +
> >  	if (len == PAGE_CACHE_SIZE)
> >  		goto out_update;
> >  	if (PageUptodate(page))
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index a7522a4..dc4d30b 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -1778,6 +1778,7 @@ void f2fs_replace_block(struct f2fs_sb_info *, struct dnode_of_data
> *,
> >  void allocate_data_block(struct f2fs_sb_info *, struct page *,
> >  		block_t, block_t *, struct f2fs_summary *, int);
> >  void f2fs_wait_on_page_writeback(struct page *, enum page_type);
> > +void f2fs_wait_on_encrypted_page_writeback(struct f2fs_sb_info *, block_t);
> >  void write_data_summaries(struct f2fs_sb_info *, block_t);
> >  void write_node_summaries(struct f2fs_sb_info *, block_t);
> >  int lookup_journal_in_cursum(struct f2fs_summary_block *,
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index e2d9910..1d2df88 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -87,6 +87,11 @@ static int f2fs_vm_page_mkwrite(struct vm_area_struct *vma,
> >  mapped:
> >  	/* fill the page */
> >  	f2fs_wait_on_page_writeback(page, DATA);
> > +
> > +	/* wait for GCed encrypted page writeback */
> > +	if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
> > +		f2fs_wait_on_encrypted_page_writeback(sbi, dn.data_blkaddr);
> > +
> >  	/* if gced page is attached, don't write to cold segment */
> >  	clear_cold_data(page);
> >  out:
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index e7cec86..2493fd6 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -559,14 +559,21 @@ static void move_encrypted_block(struct inode *inode, block_t bidx)
> >  	if (err)
> >  		goto out;
> >
> > -	if (unlikely(dn.data_blkaddr == NULL_ADDR))
> > +	if (unlikely(dn.data_blkaddr == NULL_ADDR)) {
> > +		ClearPageUptodate(page);
> >  		goto put_out;
> > +	}
> > +
> > +	/*
> > +	 * don't cache encrypted data into meta inode until previous dirty
> > +	 * data were writebacked to avoid racing between GC and flush.
> > +	 */
> > +	f2fs_wait_on_page_writeback(page, DATA);
> >
> >  	get_node_info(fio.sbi, dn.nid, &ni);
> >  	set_summary(&sum, dn.nid, dn.ofs_in_node, ni.version);
> >
> >  	/* read page */
> > -	fio.page = page;
> 
> Let's remain just to make sure.

OK.

> 
> >  	fio.blk_addr = dn.data_blkaddr;
> >
> >  	fio.encrypted_page = pagecache_get_page(META_MAPPING(fio.sbi),
> > @@ -589,7 +596,7 @@ static void move_encrypted_block(struct inode *inode, block_t bidx)
> >  		goto put_page_out;
> >
> >  	set_page_dirty(fio.encrypted_page);
> > -	f2fs_wait_on_page_writeback(fio.encrypted_page, META);
> > +	f2fs_wait_on_page_writeback(fio.encrypted_page, DATA);
> 
> Why DATA?

This is because we only submit the encrypted page in to DATA type bio
cache, so we should check whether the page is cached or not in DATA
type bio, rather than META type cache. Right?

Thanks,

> 
> >  	if (clear_page_dirty_for_io(fio.encrypted_page))
> >  		dec_page_count(fio.sbi, F2FS_DIRTY_META);
> >
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 3c546eb..d5d760c 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -1462,6 +1462,23 @@ void f2fs_wait_on_page_writeback(struct page *page,
> >  	}
> >  }
> >
> > +void f2fs_wait_on_encrypted_page_writeback(struct f2fs_sb_info *sbi,
> > +							block_t blkaddr)
> > +{
> > +	struct page *cpage;
> > +
> > +	if (blkaddr == NEW_ADDR)
> > +		return;
> > +
> > +	f2fs_bug_on(sbi, blkaddr == NULL_ADDR);
> > +
> > +	cpage = find_lock_page(META_MAPPING(sbi), blkaddr);
> > +	if (cpage) {
> > +		f2fs_wait_on_page_writeback(cpage, DATA);
> > +		f2fs_put_page(cpage, 1);
> > +	}
> > +}
> > +
> >  static int read_compacted_summaries(struct f2fs_sb_info *sbi)
> >  {
> >  	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
> > --
> > 2.5.2