tmpfs: restore missing clear_highpage

tmpfs was misconverted to __GFP_ZERO in 2.6.11.  There's an unusual case in
which shmem_getpage receives the page from its caller instead of allocating.
We must cover this case by clear_highpage before SetPageUptodate, as before.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/shmem.c

@@ -1072,7 +1072,7 @@ shmem_alloc_page(gfp_t gfp, struct shmem_inode_info *info,
 	pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
 	pvma.vm_pgoff = idx;
 	pvma.vm_end = PAGE_SIZE;
-	page = alloc_page_vma(gfp | __GFP_ZERO, &pvma, 0);
+	page = alloc_page_vma(gfp, &pvma, 0);
 	mpol_free(pvma.vm_policy);
 	return page;
 }
@@ -1093,7 +1093,7 @@ shmem_swapin(struct shmem_inode_info *info,swp_entry_t entry,unsigned long idx)
 static inline struct page *
 shmem_alloc_page(gfp_t gfp,struct shmem_inode_info *info, unsigned long idx)
 {
-	return alloc_page(gfp | __GFP_ZERO);
+	return alloc_page(gfp);
 }
 #endif
 
@@ -1306,6 +1306,7 @@ static int shmem_getpage(struct inode *inode, unsigned long idx,
 
 		info->alloced++;
 		spin_unlock(&info->lock);
+		clear_highpage(filepage);
 		flush_dcache_page(filepage);
 		SetPageUptodate(filepage);
 	}