From: Chao Yu <yuchao0@huawei.com>
Date: Tue, 17 Apr 2018 09:51:28 +0000 (+0800)
Subject: f2fs: fix race in between GC and atomic open
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=27319ba4044c0c67d62ae39e53c0118c89f0a029;p=openwrt%2Fstaging%2Fblogic.git

f2fs: fix race in between GC and atomic open

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@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index f639b5fcd66f..18be18907529 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1677,6 +1677,8 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
 
 	inode_lock(inode);
 
+	down_write(&F2FS_I(inode)->dio_rwsem[WRITE]);
+
 	if (f2fs_is_atomic_file(inode))
 		goto out;
 
@@ -1706,6 +1708,7 @@ 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;