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

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Date:   Tue, 18 Sep 2018 20:39:53 +0800
From:   Yunlong Song <yunlong.song@...wei.com>
To:     <jaegeuk@...nel.org>, <chao@...nel.org>, <yuchao0@...wei.com>,
        <yunlong.song@...oud.com>, <yunlong.song@...wei.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: [PATCH] f2fs: avoid GC causing encrypted file corrupted

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;
-- 
1.8.5.2