linux-kernel - Re: [PATCH] f2fs: avoid GC causing encrypted file corrupted

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Message-ID: <d2acab58-5f7f-1aed-3719-bc58c5c45b53@huawei.com>
Date:   Wed, 24 Oct 2018 16:07:08 +0800
From:   Yunlong Song <yunlong.song@...wei.com>
To:     <jaegeuk@...nel.org>, <chao@...nel.org>, <yuchao0@...wei.com>,
        <yunlong.song@...oud.com>
CC:     <miaoxie@...wei.com>, <bintian.wang@...wei.com>,
        <shengyong1@...wei.com>, <heyunlei@...wei.com>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: avoid GC causing encrypted file corrupted

ping...

On 2018/9/18 20:39, Yunlong Song wrote:
> The encrypted file may be corrupted by GC in following case:
>
> Time 1: | segment 1 blkaddr = A |  GC -> | segment 2 blkaddr = B |
> Encrypted block 1 is moved from blkaddr A of segment 1 to blkaddr B of
> segment 2,
>
> Time 2: | segment 1 blkaddr = B |  GC -> | segment 3 blkaddr = C |
>
> Before page 1 is written back and if segment 2 become a victim, then
> page 1 is moved from blkaddr B of segment 2 to blkaddr Cof segment 3,
> during the GC process of Time 2, f2fs should wait for page 1 written back
> before reading it, or move_data_block will read a garbage block from
> blkaddr B since page is not written back to blkaddr B yet.
>
> Commit 6aa58d8a ("f2fs: readahead encrypted block during GC") introduce
> ra_data_block to read encrypted block, but it forgets to add
> f2fs_wait_on_page_writeback to avoid racing between GC and flush.
>
> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
> ---
>   fs/f2fs/gc.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index a4c1a41..c55fb62 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -641,6 +641,14 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
>   	fio.page = page;
>   	fio.new_blkaddr = fio.old_blkaddr = dn.data_blkaddr;
>   
> +	/*
> +	 * 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, true);
> +
> +	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
> +
>   	fio.encrypted_page = f2fs_pagecache_get_page(META_MAPPING(sbi),
>   					dn.data_blkaddr,
>   					FGP_LOCK | FGP_CREAT, GFP_NOFS);
> @@ -723,6 +731,8 @@ static void move_data_block(struct inode *inode, block_t bidx,
>   	 */
>   	f2fs_wait_on_page_writeback(page, DATA, true);
>   
> +	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
> +
>   	err = f2fs_get_node_info(fio.sbi, dn.nid, &ni);
>   	if (err)
>   		goto put_out;

-- 
Thanks,
Yunlong Song