f2fs: avoid to allocate when inline_data was written

The sceanrio is like this.
inline_data   i_size     page                 write_begin/vm_page_mkwrite
  X             30       dirty_page
  X             30                            write to #4096 position
  X             30       get_dnode_of_data    wait for get_dnode_of_data
  O             30       write inline_data
  O             30                            get_dnode_of_data
  O             30                            reserve data block
..

In this case, we have #0 = NEW_ADDR and inline_data as well.
We should not allow this condition for further access.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 543d8c6..456df07 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -35,12 +35,13 @@
 	struct inode *inode = file_inode(vma->vm_file);
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	struct dnode_of_data dn;
+	struct page *ipage;
 	int err;
 
 	f2fs_balance_fs(sbi);
 
 	sb_start_pagefault(inode->i_sb);
-
+retry:
 	/* force to convert with normal data indices */
 	err = f2fs_convert_inline_data(inode, MAX_INLINE_DATA + 1, page);
 	if (err)
@@ -48,11 +49,28 @@
 
 	/* block allocation */
 	f2fs_lock_op(sbi);
-	set_new_dnode(&dn, inode, NULL, NULL, 0);
-	err = f2fs_reserve_block(&dn, page->index);
-	f2fs_unlock_op(sbi);
-	if (err)
+
+	/* check inline_data */
+	ipage = get_node_page(sbi, inode->i_ino);
+	if (IS_ERR(ipage)) {
+		f2fs_unlock_op(sbi);
 		goto out;
+	}
+
+	if (f2fs_has_inline_data(inode)) {
+		f2fs_put_page(ipage, 1);
+		f2fs_unlock_op(sbi);
+		goto retry;
+	}
+
+	set_new_dnode(&dn, inode, ipage, NULL, 0);
+	err = f2fs_reserve_block(&dn, page->index);
+	if (err) {
+		f2fs_unlock_op(sbi);
+		goto out;
+	}
+	f2fs_put_dnode(&dn);
+	f2fs_unlock_op(sbi);
 
 	file_update_time(vma->vm_file);
 	lock_page(page);