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: https://git.stricted.de/?a=commitdiff_plain;h=9e222d7ca5d535d524e92ff303b6f1e61f5ec4d5;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git

f2fs: fix race in between GC and atomic open

[ 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@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 249f917a494b..7d0e8d6bf009 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1512,6 +1512,8 @@ 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;
 
@@ -1532,6 +1534,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
 	if (ret)
 		clear_inode_flag(inode, FI_ATOMIC_FILE);
 out:
+	up_write(&F2FS_I(inode)->dio_rwsem[WRITE]);
 	inode_unlock(inode);
 	mnt_drop_write_file(filp);
 	return ret;