[PATCH 1/5] f2fs: fix race in between GC and atomic open

[Chao Yu]

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 <yuch...@huawei.com>
---
 fs/f2fs/file.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 78b3a58cfe21..408471bf4799 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;
 
@@ -1702,6 +1704,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
        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;
-- 
2.15.0.55.gc2ece9dc4de6