f2fs: optimize error handling in redirty_blocks

Current error handling is at risk of page leaks. However, we dot't seek
any failure scenarios, just use f2fs_bug_on.
Signed-off-by: Jack Qiu <jack.qiu@huawei.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/file.c

@@ -3903,10 +3903,10 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len)
 
 	for (i = 0; i < page_len; i++, redirty_idx++) {
 		page = find_lock_page(mapping, redirty_idx);
-		if (!page) {
-			ret = -ENOMEM;
-			break;
-		}
+
+		/* It will never fail, when page has pinned above */
+		f2fs_bug_on(F2FS_I_SB(inode), !page);
+
 		set_page_dirty(page);
 		f2fs_put_page(page, 1);
 		f2fs_put_page(page, 0);