f2fs: avoid clear valid page

In f2fs_delete_entry, if last dirent is remove from the dentry page,
we will try to punch that page since it has no valid date in it.

But truncate_hole which is used for punching could fail because of
no memory or IO error, if that happened, we'd better skip clearing
this valid dentry page.
Signed-off-by: NChao Yu <chao2.yu@samsung.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/dir.c

@@ -718,8 +718,8 @@ void f2fs_delete_entry(struct f2fs_dir_entry *dentry, struct page *page,
 	if (inode)
 		f2fs_drop_nlink(dir, inode, NULL);
 
-	if (bit_pos == NR_DENTRY_IN_BLOCK) {
-		truncate_hole(dir, page->index, page->index + 1);
+	if (bit_pos == NR_DENTRY_IN_BLOCK &&
+			!truncate_hole(dir, page->index, page->index + 1)) {
 		clear_page_dirty_for_io(page);
 		ClearPagePrivate(page);
 		ClearPageUptodate(page);