f2fs: allocate hot_data for atomic write more strictly

If a file not set type as hot, has dirty pages more than
threshold 64 before starting atomic write, may be lose hot
flag.

v1->v2: move set FI_ATOMIC_FILE flag behind flush dirty pages too,
in case of dirty pages before starting atomic use atomic mode to
write back.

Signed-off-by: Yunlei He <heyunlei@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/file.c

@@ -1686,24 +1686,20 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
 	if (ret)
 		goto out;
 
-	set_inode_flag(inode, FI_ATOMIC_FILE);
-	set_inode_flag(inode, FI_HOT_DATA);
-	f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
-
 	if (!get_dirty_pages(inode))
-		goto inc_stat;
+		goto skip_flush;
 
 	f2fs_msg(F2FS_I_SB(inode)->sb, KERN_WARNING,
 		"Unexpected flush for atomic writes: ino=%lu, npages=%u",
 					inode->i_ino, get_dirty_pages(inode));
 	ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX);
-	if (ret) {
-		clear_inode_flag(inode, FI_ATOMIC_FILE);
-		clear_inode_flag(inode, FI_HOT_DATA);
+	if (ret)
 		goto out;
-	}
+skip_flush:
+	set_inode_flag(inode, FI_HOT_DATA);
+	set_inode_flag(inode, FI_ATOMIC_FILE);
+	f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
 
-inc_stat:
 	F2FS_I(inode)->inmem_task = current;
 	stat_inc_atomic_write(inode);
 	stat_update_max_atomic_write(inode);