mm: remove remnants of SPLIT_RSS_COUNTING

The feature got retired in f1a7941 ("mm: convert mm's rss stats into
percpu_counter"), but the patch failed to fully clean it up.

Link: https://lkml.kernel.org/r/20230823170556.2281747-1-mjguzik@gmail.com
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: mjguzik

fs/exec.c

@@ -986,8 +986,6 @@ static int exec_mmap(struct mm_struct *mm)
 	tsk = current;
 	old_mm = current->mm;
 	exec_mm_release(tsk, old_mm);
-	if (old_mm)
-		sync_mm_rss(old_mm);
 
 	ret = down_write_killable(&tsk->signal->exec_update_lock);
 	if (ret)

include/linux/mm.h

@@ -2628,14 +2628,6 @@ static inline void setmax_mm_hiwater_rss(unsigned long *maxrss,
 		*maxrss = hiwater_rss;
 }
 
-#if defined(SPLIT_RSS_COUNTING)
-void sync_mm_rss(struct mm_struct *mm);
-#else
-static inline void sync_mm_rss(struct mm_struct *mm)
-{
-}
-#endif
-
 #ifndef CONFIG_ARCH_HAS_PTE_SPECIAL
 static inline int pte_special(pte_t pte)
 {

kernel/exit.c

@@ -539,7 +539,6 @@ static void exit_mm(void)
 	exit_mm_release(current, mm);
 	if (!mm)
 		return;
-	sync_mm_rss(mm);
 	mmap_read_lock(mm);
 	mmgrab_lazy_tlb(mm);
 	BUG_ON(mm != current->active_mm);
@@ -829,9 +828,6 @@ void __noreturn do_exit(long code)
 	io_uring_files_cancel();
 	exit_signals(tsk);  /* sets PF_EXITING */
 
-	/* sync mm's RSS info before statistics gathering */
-	if (tsk->mm)
-		sync_mm_rss(tsk->mm);
 	acct_update_integrals(tsk);
 	group_dead = atomic_dec_and_test(&tsk->signal->live);
 	if (group_dead) {

kernel/fork.c

@@ -2406,10 +2406,6 @@ __latent_entropy struct task_struct *copy_process(
 	p->io_uring = NULL;
 #endif
 
-#if defined(SPLIT_RSS_COUNTING)
-	memset(&p->rss_stat, 0, sizeof(p->rss_stat));
-#endif
-
 	p->default_timer_slack_ns = current->timer_slack_ns;
 
 #ifdef CONFIG_PSI

kernel/kthread.c

@@ -1469,7 +1469,6 @@ void kthread_unuse_mm(struct mm_struct *mm)
 	 * clearing tsk->mm.
 	 */
 	smp_mb__after_spinlock();
-	sync_mm_rss(mm);
 	local_irq_disable();
 	tsk->mm = NULL;
 	membarrier_update_current_mm(NULL);

mm/madvise.c

@@ -746,11 +746,8 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 		folio_mark_lazyfree(folio);
 	}
 
-	if (nr_swap) {
-		if (current->mm == mm)
-			sync_mm_rss(mm);
+	if (nr_swap)
 		add_mm_counter(mm, MM_SWAPENTS, nr_swap);
-	}
 	if (start_pte) {
 		arch_leave_lazy_mmu_mode();
 		pte_unmap_unlock(start_pte, ptl);

mm/memory.c

@@ -471,8 +471,6 @@ static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
 {
 	int i;
 
-	if (current->mm == mm)
-		sync_mm_rss(mm);
 	for (i = 0; i < NR_MM_COUNTERS; i++)
 		if (rss[i])
 			add_mm_counter(mm, i, rss[i]);