uprobes: Rename the "struct page *" args of __replace_page()

Purely cosmetic, no changes in the compiled code.

Perhaps it is just me but I can hardly read __replace_page() because I can't
distinguish "page" from "kpage" and because I need to look at the caller to
to ensure that, say, kpage is really the new page and the code is correct.
Rename them to old_page and new_page, this matches the caller.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Brenden Blanco <bblanco@plumgrid.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Link: http://lkml.kernel.org/r/20160817153704.GC29724@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/events/uprobes.c

@@ -150,7 +150,7 @@ static loff_t vaddr_to_offset(struct vm_area_struct *vma, unsigned long vaddr)
  * Returns 0 on success, -EFAULT on failure.
  */
 static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
-				struct page *page, struct page *kpage)
+				struct page *old_page, struct page *new_page)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	spinlock_t *ptl;
@@ -161,49 +161,49 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
 	const unsigned long mmun_end   = addr + PAGE_SIZE;
 	struct mem_cgroup *memcg;
 
-	err = mem_cgroup_try_charge(kpage, vma->vm_mm, GFP_KERNEL, &memcg,
+	err = mem_cgroup_try_charge(new_page, vma->vm_mm, GFP_KERNEL, &memcg,
 			false);
 	if (err)
 		return err;
 
 	/* For try_to_free_swap() and munlock_vma_page() below */
-	lock_page(page);
+	lock_page(old_page);
 
 	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
 	err = -EAGAIN;
-	ptep = page_check_address(page, mm, addr, &ptl, 0);
+	ptep = page_check_address(old_page, mm, addr, &ptl, 0);
 	if (!ptep) {
-		mem_cgroup_cancel_charge(kpage, memcg, false);
+		mem_cgroup_cancel_charge(new_page, memcg, false);
 		goto unlock;
 	}
 
-	get_page(kpage);
-	page_add_new_anon_rmap(kpage, vma, addr, false);
-	mem_cgroup_commit_charge(kpage, memcg, false, false);
-	lru_cache_add_active_or_unevictable(kpage, vma);
+	get_page(new_page);
+	page_add_new_anon_rmap(new_page, vma, addr, false);
+	mem_cgroup_commit_charge(new_page, memcg, false, false);
+	lru_cache_add_active_or_unevictable(new_page, vma);
 
-	if (!PageAnon(page)) {
-		dec_mm_counter(mm, mm_counter_file(page));
+	if (!PageAnon(old_page)) {
+		dec_mm_counter(mm, mm_counter_file(old_page));
 		inc_mm_counter(mm, MM_ANONPAGES);
 	}
 
 	flush_cache_page(vma, addr, pte_pfn(*ptep));
 	ptep_clear_flush_notify(vma, addr, ptep);
-	set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
+	set_pte_at_notify(mm, addr, ptep, mk_pte(new_page, vma->vm_page_prot));
 
-	page_remove_rmap(page, false);
-	if (!page_mapped(page))
-		try_to_free_swap(page);
+	page_remove_rmap(old_page, false);
+	if (!page_mapped(old_page))
+		try_to_free_swap(old_page);
 	pte_unmap_unlock(ptep, ptl);
 
 	if (vma->vm_flags & VM_LOCKED)
-		munlock_vma_page(page);
-	put_page(page);
+		munlock_vma_page(old_page);
+	put_page(old_page);
 
 	err = 0;
  unlock:
 	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
-	unlock_page(page);
+	unlock_page(old_page);
 	return err;
 }