[PATCH 4.17 075/336] f2fs: fix race in between GC and atomic open

From: Greg Kroah-Hartman
Date: Wed Aug 01 2018 - 13:40:00 EST


4.17-stable review patch. If anyone has any objections, please let me know.

------------------

From: Chao Yu <yuchao0@xxxxxxxxxx>

[ Upstream commit 27319ba4044c0c67d62ae39e53c0118c89f0a029 ]

Thread GC thread
- f2fs_ioc_start_atomic_write
- get_dirty_pages
- filemap_write_and_wait_range
- f2fs_gc
- do_garbage_collect
- gc_data_segment
- move_data_page
- f2fs_is_atomic_file
- set_page_dirty
- set_inode_flag(, FI_ATOMIC_FILE)

Dirty data page can still be generated by GC in race condition as
above call stack.

This patch adds fi->dio_rwsem[WRITE] in f2fs_ioc_start_atomic_write
to avoid such race.

Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/f2fs/file.c | 3 +++
1 file changed, 3 insertions(+)

--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1670,6 +1670,8 @@ static int f2fs_ioc_start_atomic_write(s

inode_lock(inode);

+ down_write(&F2FS_I(inode)->dio_rwsem[WRITE]);
+
if (f2fs_is_atomic_file(inode))
goto out;

@@ -1699,6 +1701,7 @@ inc_stat:
stat_inc_atomic_write(inode);
stat_update_max_atomic_write(inode);
out:
+ up_write(&F2FS_I(inode)->dio_rwsem[WRITE]);
inode_unlock(inode);
mnt_drop_write_file(filp);
return ret;