Don't use __GFP_CLEAR for user pages.

It doesn't do the virtual cache synchronization that clear_user_highpage()
does.

Pointed out by Hugh Dickins.

include/linux/gfp.h

@@ -53,7 +53,6 @@ struct vm_area_struct;
 #define GFP_KERNEL	(__GFP_WAIT | __GFP_IO | __GFP_FS)
 #define GFP_USER	(__GFP_WAIT | __GFP_IO | __GFP_FS)
 #define GFP_HIGHUSER	(__GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_HIGHMEM)
-#define GFP_HIGHZERO	(__GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_HIGHMEM | __GFP_ZERO)
 
 /* Flag - indicates that the buffer will be suitable for DMA.  Ignored on some
    platforms, used as appropriate on others */

mm/memory.c

@@ -1795,9 +1795,10 @@ do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 
 		if (unlikely(anon_vma_prepare(vma)))
 			goto no_mem;
-		page = alloc_page_vma(GFP_HIGHZERO, vma, addr);
+		page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
 		if (!page)
 			goto no_mem;
+		clear_user_highpage(page, addr);
 
 		spin_lock(&mm->page_table_lock);
 		page_table = pte_offset_map(pmd, addr);