Rewind v3.13-rc3+ (78fd82238d0e5716) to v3.12

1 files changed, 59 insertions, 24 deletions

diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
index 639fce46..5d758db 100644
--- a/arch/s390/mm/gup.c
+++ b/arch/s390/mm/gup.c
@@ -180,15 +180,9 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
 	addr = start;
 	len = (unsigned long) nr_pages << PAGE_SHIFT;
 	end = start + len;
-	if ((end <= start) || (end > TASK_SIZE))
+	if ((end < start) || (end > TASK_SIZE))
 		return 0;
-	/*
-	 * local_irq_save() doesn't prevent pagetable teardown, but does
-	 * prevent the pagetables from being freed on s390.
-	 *
-	 * So long as we atomically load page table pointers versus teardown,
-	 * we can follow the address down to the the page and take a ref on it.
-	 */
+
 	local_irq_save(flags);
 	pgdp = pgd_offset(mm, addr);
 	do {
@@ -225,22 +219,63 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write,
 			struct page **pages)
 {
 	struct mm_struct *mm = current->mm;
-	int nr, ret;
+	unsigned long addr, len, end;
+	unsigned long next;
+	pgd_t *pgdp, pgd;
+	int nr = 0;
 
 	start &= PAGE_MASK;
-	nr = __get_user_pages_fast(start, nr_pages, write, pages);
-	if (nr == nr_pages)
-		return nr;
-
-	/* Try to get the remaining pages with get_user_pages */
-	start += nr << PAGE_SHIFT;
-	pages += nr;
-	down_read(&mm->mmap_sem);
-	ret = get_user_pages(current, mm, start,
-			     nr_pages - nr, write, 0, pages, NULL);
-	up_read(&mm->mmap_sem);
-	/* Have to be a bit careful with return values */
-	if (nr > 0)
-		ret = (ret < 0) ? nr : ret + nr;
-	return ret;
+	addr = start;
+	len = (unsigned long) nr_pages << PAGE_SHIFT;
+	end = start + len;
+	if ((end < start) || (end > TASK_SIZE))
+		goto slow_irqon;
+
+	/*
+	 * local_irq_disable() doesn't prevent pagetable teardown, but does
+	 * prevent the pagetables from being freed on s390.
+	 *
+	 * So long as we atomically load page table pointers versus teardown,
+	 * we can follow the address down to the the page and take a ref on it.
+	 */
+	local_irq_disable();
+	pgdp = pgd_offset(mm, addr);
+	do {
+		pgd = *pgdp;
+		barrier();
+		next = pgd_addr_end(addr, end);
+		if (pgd_none(pgd))
+			goto slow;
+		if (!gup_pud_range(pgdp, pgd, addr, next, write, pages, &nr))
+			goto slow;
+	} while (pgdp++, addr = next, addr != end);
+	local_irq_enable();
+
+	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
+	return nr;
+
+	{
+		int ret;
+slow:
+		local_irq_enable();
+slow_irqon:
+		/* Try to get the remaining pages with get_user_pages */
+		start += nr << PAGE_SHIFT;
+		pages += nr;
+
+		down_read(&mm->mmap_sem);
+		ret = get_user_pages(current, mm, start,
+			(end - start) >> PAGE_SHIFT, write, 0, pages, NULL);
+		up_read(&mm->mmap_sem);
+
+		/* Have to be a bit careful with return values */
+		if (nr > 0) {
+			if (ret < 0)
+				ret = nr;
+			else
+				ret += nr;
+		}
+
+		return ret;
+	}
 }