if (!df) return; 
void global_flush_tlb(void){ 	struct deferred_page *df, *next_df;	down_read(&init_mm.mmap_sem);	df = xchg(&df_list, NULL);	up_read(&init_mm.mmap_sem);	if (!df)		return;	flush_map((df && !df->next) ? df->address : 0);	for (; df; df = next_df) { 		next_df = df->next;		if (df->fpage) 			__free_page(df->fpage);		kfree(df);	} } 
10457	/local/tlutelli/issta_data/temp/c/2005_temp/2005/10457/094804c5a132f04c12dd4902ee15c64362e5c1af/pageattr.c/buggy/arch/x86_64/mm/pageattr.c