linux-kernel - [f2fs-dev] [PATCH 1/2] f2fs: fix wrong extent

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Message-ID: <20250910135835.2751574-1-wangzijie1@honor.com>
Date: Wed, 10 Sep 2025 21:58:34 +0800
From: wangzijie <wangzijie1@...or.com>
To: <jaegeuk@...nel.org>, <chao@...nel.org>
CC: <bintian.wang@...or.com>, <feng.han@...or.com>,
	<linux-kernel@...r.kernel.org>, <linux-f2fs-devel@...ts.sourceforge.net>,
	wangzijie <wangzijie1@...or.com>
Subject: [f2fs-dev] [PATCH 1/2] f2fs: fix wrong extent_info data for precache extents

When the data layout is like this:
dnode1:                     dnode2:
[0]      A                  [0]    NEW_ADDR
[1]      A+1                [1]    0x0
...                         ....
[1016]   A+1016
[1017]   B (B!=A+1017)      [1017] 0x0

We can build this kind of layout by following steps(with i_extra_isize:36):
./f2fs_io write 1 0 1881 rand dsync testfile
./f2fs_io write 1 1881 1 rand buffered testfile
./f2fs_io fallocate 0 7708672 4096 testfile

And when we map first data block in dnode2, we will get wrong extent_info data:
map->m_len = 1
ofs = start_pgofs - map->m_lblk = 1882 - 1881 = 1

ei.fofs = start_pgofs = 1882
ei.len = map->m_len - ofs = 1 - 1 = 0

Fix it by skipping updating this kind of extent info.

Signed-off-by: wangzijie <wangzijie1@...or.com>
---
 fs/f2fs/data.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 7961e0ddf..b8bb71852 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1649,6 +1649,9 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag)
 
 		switch (flag) {
 		case F2FS_GET_BLOCK_PRECACHE:
+			if (__is_valid_data_blkaddr(map->m_pblk) &&
+				start_pgofs - map->m_lblk == map->m_len)
+				map->m_flags &= ~F2FS_MAP_MAPPED;
 			goto sync_out;
 		case F2FS_GET_BLOCK_BMAP:
 			map->m_pblk = 0;
-- 
2.25.1