f2fs: fix race in between GC and atomic open

BugLink: http://bugs.launchpad.net/bugs/1815234
[ 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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index c0ec81016a07983a9bee63d2ab0e81272c57a5ed..729dba0cc210e5a2ad1eb001df47321f415153d1 100644 (file)
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1669,6 +1669,8 @@ 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;
 
@@ -1698,6 +1700,7 @@ 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;