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Date:   Thu, 11 Oct 2018 09:15:09 +0530
From:   Sahitya Tummala <stummala@codeaurora.org>
To:     Jaegeuk Kim <jaegeuk@kernel.org>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix data corruption issue with hardware
 encryption
Message-ID: <20181011034509.GB24669@codeaurora.org>
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On Wed, Oct 10, 2018 at 08:05:44PM -0700, Jaegeuk Kim wrote:
> On 10/10, Jaegeuk Kim wrote:
> > On 10/11, Sahitya Tummala wrote:
> > > On Wed, Oct 10, 2018 at 02:34:02PM -0700, Jaegeuk Kim wrote:
> > > > On 10/10, Sahitya Tummala wrote:
> > > > > Direct IO can be used in case of hardware encryption. The following
> > > > > scenario results into data corruption issue in this path -
> > > > > 
> > > > > Thread A -                          Thread B-
> > > > > -> write file#1 in direct IO
> > > > >                                     -> GC gets kicked in
> > > > >                                     -> GC submitted bio on meta mapping
> > > > > 				       for file#1, but pending completion
> > > > > -> write file#1 again with new data
> > > > >    in direct IO
> > > > >                                     -> GC bio gets completed now
> > > > >                                     -> GC writes old data to the new
> > > > >                                        location and thus file#1 is
> > > > > 				       corrupted.
> > > > > 
> > > > > Fix this by submitting and waiting for pending io on meta mapping
> > > > > for direct IO case in f2fs_map_blocks().
> > > > > 
> > > > > Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
> > > > > ---
> > > > >  fs/f2fs/data.c | 12 ++++++++++++
> > > > >  1 file changed, 12 insertions(+)
> > > > > 
> > > > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > > > > index 9ef6f1f..7b2fef0 100644
> > > > > --- a/fs/f2fs/data.c
> > > > > +++ b/fs/f2fs/data.c
> > > > > @@ -1028,6 +1028,12 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
> > > > >  		map->m_pblk = ei.blk + pgofs - ei.fofs;
> > > > >  		map->m_len = min((pgoff_t)maxblocks, ei.fofs + ei.len - pgofs);
> > > > >  		map->m_flags = F2FS_MAP_MAPPED;
> > > > > +		/* for HW encryption, but to avoid potential issue in future */
> > > > > +		if (flag == F2FS_GET_BLOCK_DIO) {
> > > > > +			blkaddr = map->m_pblk;
> > > > > +			for (; blkaddr < map->m_pblk + map->m_len; blkaddr++)
> > > > > +				f2fs_wait_on_block_writeback(sbi, blkaddr);
> > > > 
> > > > Do we need this? IIRC, DIO would give create=1.
> > > 
> > > Yes, we need it. When we are overwriting an existing file, DIO calls
> > > f2fs_map_blocks() with create=0. From the DIO code, I see that this happens
> > > because blockdev_direct_IO() passes this dio flag DIO_SKIP_HOLES. And then
> > > in get_more_blocks(), below code updates create=0, when we are overwriting
> > > an existing file.
> > > 
> > >                 create = dio->op == REQ_OP_WRITE;
> > >                 if (dio->flags & DIO_SKIP_HOLES) {
> > >                         if (fs_startblk <= ((i_size_read(dio->inode) - 1) >>
> > >                                                         i_blkbits))
> > >                                 create = 0;
> > >                 }
> > > 
> > >                 ret = (*sdio->get_block)(dio->inode, fs_startblk,
> > >                                                 map_bh, create);
> > > 
> > 
> > Got it.
> > How about this?
> > 
> 
> Sorry, this is v2.

Looks good to me. Thanks for updating it :)

> 
> From b78dd7b2e0317be18716b9496269e9792829f63e Mon Sep 17 00:00:00 2001
> From: Sahitya Tummala <stummala@codeaurora.org>
> Date: Wed, 10 Oct 2018 10:56:22 +0530
> Subject: [PATCH] f2fs: fix data corruption issue with hardware encryption
> 
> Direct IO can be used in case of hardware encryption. The following
> scenario results into data corruption issue in this path -
> 
> Thread A -                          Thread B-
> -> write file#1 in direct IO
>                                     -> GC gets kicked in
>                                     -> GC submitted bio on meta mapping
> 				       for file#1, but pending completion
> -> write file#1 again with new data
>    in direct IO
>                                     -> GC bio gets completed now
>                                     -> GC writes old data to the new
>                                        location and thus file#1 is
> 				       corrupted.
> 
> Fix this by submitting and waiting for pending io on meta mapping
> for direct IO case in f2fs_map_blocks().
> 
> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/data.c    | 11 +++++++++++
>  fs/f2fs/f2fs.h    |  2 ++
>  fs/f2fs/segment.c |  9 +++++++++
>  3 files changed, 22 insertions(+)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index be19257d9e36..8952f2d610a6 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1030,6 +1030,11 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
>  		map->m_flags = F2FS_MAP_MAPPED;
>  		if (map->m_next_extent)
>  			*map->m_next_extent = pgofs + map->m_len;
> +
> +		/* for hardware encryption, but to avoid potential issue in future */
> +		if (flag == F2FS_GET_BLOCK_DIO)
> +			f2fs_wait_on_block_writeback_range(inode,
> +						map->m_pblk, map->m_len);
>  		goto out;
>  	}
>  
> @@ -1188,6 +1193,12 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
>  	goto next_dnode;
>  
>  sync_out:
> +
> +	/* for hardware encryption, but to avoid potential issue in future */
> +	if (flag == F2FS_GET_BLOCK_DIO && map->m_flags & F2FS_MAP_MAPPED)
> +		f2fs_wait_on_block_writeback_range(inode,
> +						map->m_pblk, map->m_len);
> +
>  	if (flag == F2FS_GET_BLOCK_PRECACHE) {
>  		if (map->m_flags & F2FS_MAP_MAPPED) {
>  			unsigned int ofs = start_pgofs - map->m_lblk;
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 7693b1a2072e..4a608a71c360 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2986,6 +2986,8 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
>  void f2fs_wait_on_page_writeback(struct page *page,
>  			enum page_type type, bool ordered);
>  void f2fs_wait_on_block_writeback(struct inode *inode, block_t blkaddr);
> +void f2fs_wait_on_block_writeback_range(struct inode *inode, block_t blkaddr,
> +								block_t len);
>  void f2fs_write_data_summaries(struct f2fs_sb_info *sbi, block_t start_blk);
>  void f2fs_write_node_summaries(struct f2fs_sb_info *sbi, block_t start_blk);
>  int f2fs_lookup_journal_in_cursum(struct f2fs_journal *journal, int type,
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 805c8310d7b0..f306d8946d99 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -3301,6 +3301,15 @@ void f2fs_wait_on_block_writeback(struct inode *inode, block_t blkaddr)
>  	}
>  }
>  
> +void f2fs_wait_on_block_writeback_range(struct inode *inode, block_t blkaddr,
> +								block_t len)
> +{
> +	block_t i;
> +
> +	for (i = 0; i < len; i++)
> +		f2fs_wait_on_block_writeback(inode, blkaddr + i);
> +}
> +
>  static int read_compacted_summaries(struct f2fs_sb_info *sbi)
>  {
>  	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
> -- 
> 2.19.0.605.g01d371f741-goog
> 

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