linux-kernel - Re: [PATCH] f2fs: fix data corruption issue with hardware encryption

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Message-ID: <20181010213402.GA52406@jaegeuk-macbookpro.roam.corp.google.com>
Date:   Wed, 10 Oct 2018 14:34:02 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Sahitya Tummala <stummala@...eaurora.org>
Cc:     Chao Yu <yuchao0@...wei.com>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: fix data corruption issue with hardware encryption

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@...eaurora.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.

> +		}
>  		if (map->m_next_extent)
>  			*map->m_next_extent = pgofs + map->m_len;
>  		goto out;
> @@ -1188,6 +1194,12 @@ 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) {
> +		blkaddr = map->m_pblk;
> +		for (; blkaddr < map->m_pblk + map->m_len; blkaddr++)
> +			f2fs_wait_on_block_writeback(sbi, blkaddr);
> +	}
>  	if (flag == F2FS_GET_BLOCK_PRECACHE) {
>  		if (map->m_flags & F2FS_MAP_MAPPED) {
>  			unsigned int ofs = start_pgofs - map->m_lblk;
> -- 
> Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.