X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=mm%2Fmemory.c;h=2b73dbde2274a535aadf90bb3ca2873347ef66f9;hb=26935fb06ee88f1188789807687c03041f3c70d9;hp=b3c6bf9a398e9b13f7c5bb1130a72e67034faf75;hpb=ec5b103ecfde929004b691f29183255aeeadecd5;p=firefly-linux-kernel-4.4.55.git

diff --git a/mm/memory.c b/mm/memory.c
index b3c6bf9a398e..2b73dbde2274 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -372,30 +372,6 @@ void tlb_remove_table(struct mmu_gather *tlb, void *table)
 
 #endif /* CONFIG_HAVE_RCU_TABLE_FREE */
 
-/*
- * If a p?d_bad entry is found while walking page tables, report
- * the error, before resetting entry to p?d_none.  Usually (but
- * very seldom) called out from the p?d_none_or_clear_bad macros.
- */
-
-void pgd_clear_bad(pgd_t *pgd)
-{
-	pgd_ERROR(*pgd);
-	pgd_clear(pgd);
-}
-
-void pud_clear_bad(pud_t *pud)
-{
-	pud_ERROR(*pud);
-	pud_clear(pud);
-}
-
-void pmd_clear_bad(pmd_t *pmd)
-{
-	pmd_ERROR(*pmd);
-	pmd_clear(pmd);
-}
-
 /*
  * Note: this doesn't free the actual pages themselves. That
  * has been handled earlier when unmapping all the memory regions.
@@ -1505,7 +1481,8 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
 	if (pud_none(*pud))
 		goto no_page_table;
 	if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
-		BUG_ON(flags & FOLL_GET);
+		if (flags & FOLL_GET)
+			goto out;
 		page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
 		goto out;
 	}
@@ -1516,8 +1493,20 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
 	if (pmd_none(*pmd))
 		goto no_page_table;
 	if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
-		BUG_ON(flags & FOLL_GET);
 		page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
+		if (flags & FOLL_GET) {
+			/*
+			 * Refcount on tail pages are not well-defined and
+			 * shouldn't be taken. The caller should handle a NULL
+			 * return when trying to follow tail pages.
+			 */
+			if (PageHead(page))
+				get_page(page);
+			else {
+				page = NULL;
+				goto out;
+			}
+		}
 		goto out;
 	}
 	if ((flags & FOLL_NUMA) && pmd_numa(*pmd))