Revert "mm: Perform PID map reads on the little CPU cluster"

Our little cores are not that fast; moreover, they are inefficient.
Therefore, it's not a good idea to perform PID map reads on this cluster.
We can presumably get better jitter by doing this.

This reverts commit d46ff2c.

Signed-off-by: Tashfin Shakeer Rhythm <tashfinshakeerrhythm@gmail.com>

fs/proc/internal.h

@@ -298,7 +298,6 @@ struct proc_maps_private {
 #ifdef CONFIG_NUMA
 	struct mempolicy *task_mempolicy;
 #endif
-	unsigned long old_cpus_allowed;
 } __randomize_layout;
 
 struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode);

fs/proc/task_mmu.c

@@ -182,9 +182,6 @@ static void vma_stop(struct proc_maps_private *priv)
 	release_task_mempolicy(priv);
 	up_read(&mm->mmap_sem);
 	mmput(mm);
-
-	sched_migrate_to_cpumask_end(to_cpumask(&priv->old_cpus_allowed),
-				     cpu_lp_mask);
 }
 
 static struct vm_area_struct *
@@ -221,9 +218,6 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
 	if (!mm || !mmget_not_zero(mm))
 		return NULL;
 
-	sched_migrate_to_cpumask_start(to_cpumask(&priv->old_cpus_allowed),
-				       cpu_lp_mask);
-
 	if (down_read_killable(&mm->mmap_sem)) {
 		mmput(mm);
 		return ERR_PTR(-EINTR);