4 files changed, 68 insertions, 38 deletions

diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 7a81e86..8452316 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -1180,13 +1180,25 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
 	pgdir = mm->pgd;
 	if (pgdir == NULL)
 		return;
+
+	/* Get VSID */
+	ssize = user_segment_size(ea);
+	vsid = get_vsid(mm->context.id, ea, ssize);
+	if (!vsid)
+		return;
+	/*
+	 * Hash doesn't like irqs. Walking linux page table with irq disabled
+	 * saves us from holding multiple locks.
+	 */
+	local_irq_save(flags);
+
 	/*
 	 * THP pages use update_mmu_cache_pmd. We don't do
 	 * hash preload there. Hence can ignore THP here
 	 */
 	ptep = find_linux_pte_or_hugepte(pgdir, ea, &hugepage_shift);
 	if (!ptep)
-		return;
+		goto out_exit;
 
 	WARN_ON(hugepage_shift);
 #ifdef CONFIG_PPC_64K_PAGES
@@ -1197,18 +1209,9 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
 	 * page size demotion here
 	 */
 	if (pte_val(*ptep) & (_PAGE_4K_PFN | _PAGE_NO_CACHE))
-		return;
+		goto out_exit;
 #endif /* CONFIG_PPC_64K_PAGES */
 
-	/* Get VSID */
-	ssize = user_segment_size(ea);
-	vsid = get_vsid(mm->context.id, ea, ssize);
-	if (!vsid)
-		return;
-
-	/* Hash doesn't like irqs */
-	local_irq_save(flags);
-
 	/* Is that local to this CPU ? */
 	if (cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id())))
 		local = 1;
@@ -1230,7 +1233,7 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
 				   mm->context.user_psize,
 				   mm->context.user_psize,
 				   pte_val(*ptep));
-
+out_exit:
 	local_irq_restore(flags);
 }
 
diff --git a/arch/powerpc/mm/hugepage-hash64.c b/arch/powerpc/mm/hugepage-hash64.c
index 3c22fa3..34de9e0 100644
--- a/arch/powerpc/mm/hugepage-hash64.c
+++ b/arch/powerpc/mm/hugepage-hash64.c
@@ -37,6 +37,9 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
 		/* If PMD busy, retry the access */
 		if (unlikely(old_pmd & _PAGE_BUSY))
 			return 0;
+		/* If PMD is trans splitting retry the access */
+		if (unlikely(old_pmd & _PAGE_SPLITTING))
+			return 0;
 		/* If PMD permissions don't match, take page fault */
 		if (unlikely(access & ~old_pmd))
 			return 1;
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 8add580..e9e6882 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -925,12 +925,16 @@ void flush_dcache_icache_hugepage(struct page *page)
  * (2) pointer to next table, as normal; bottom 6 bits == 0
  * (3) leaf pte for huge page, bottom two bits != 00
  * (4) hugepd pointer, bottom two bits == 00, next 4 bits indicate size of table
+ *
+ * So long as we atomically load page table pointers we are safe against teardown,
+ * we can follow the address down to the the page and take a ref on it.
  */
+
 pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, unsigned *shift)
 {
-	pgd_t *pg;
-	pud_t *pu;
-	pmd_t *pm;
+	pgd_t pgd, *pgdp;
+	pud_t pud, *pudp;
+	pmd_t pmd, *pmdp;
 	pte_t *ret_pte;
 	hugepd_t *hpdp = NULL;
 	unsigned pdshift = PGDIR_SHIFT;
@@ -938,34 +942,42 @@ pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, unsigned *shift
 	if (shift)
 		*shift = 0;
 
-	pg = pgdir + pgd_index(ea);
-
+	pgdp = pgdir + pgd_index(ea);
+	pgd  = ACCESS_ONCE(*pgdp);
 	/*
-	 * we should first check for none. That takes care of a
-	 * a parallel hugetlb or THP pagefault moving none entries
-	 * to respective types.
+	 * Always operate on the local stack value. This make sure the
+	 * value don't get updated by a parallel THP split/collapse,
+	 * page fault or a page unmap. The return pte_t * is still not
+	 * stable. So should be checked there for above conditions.
 	 */
-	if (pgd_none(*pg))
+	if (pgd_none(pgd))
 		return NULL;
-	else if (pgd_huge(*pg)) {
-		ret_pte = (pte_t *) pg;
+	else if (pgd_huge(pgd)) {
+		ret_pte = (pte_t *) pgdp;
 		goto out;
-	} else if (is_hugepd(pg))
-		hpdp = (hugepd_t *)pg;
+	} else if (is_hugepd(&pgd))
+		hpdp = (hugepd_t *)&pgd;
 	else {
+		/*
+		 * Even if we end up with an unmap, the pgtable will not
+		 * be freed, because we do an rcu free and here we are
+		 * irq disabled
+		 */
 		pdshift = PUD_SHIFT;
-		pu = pud_offset(pg, ea);
+		pudp = pud_offset(&pgd, ea);
+		pud  = ACCESS_ONCE(*pudp);
 
-		if (pud_none(*pu))
+		if (pud_none(pud))
 			return NULL;
-		else if (pud_huge(*pu)) {
-			ret_pte = (pte_t *) pu;
+		else if (pud_huge(pud)) {
+			ret_pte = (pte_t *) pudp;
 			goto out;
-		} else if (is_hugepd(pu))
-			hpdp = (hugepd_t *)pu;
+		} else if (is_hugepd(&pud))
+			hpdp = (hugepd_t *)&pud;
 		else {
 			pdshift = PMD_SHIFT;
-			pm = pmd_offset(pu, ea);
+			pmdp = pmd_offset(&pud, ea);
+			pmd  = ACCESS_ONCE(*pmdp);
 			/*
 			 * A hugepage collapse is captured by pmd_none, because
 			 * it mark the pmd none and do a hpte invalidate.
@@ -975,16 +987,16 @@ pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, unsigned *shift
 			 * hpte invalidate
 			 *
 			 */
-			if (pmd_none(*pm) || pmd_trans_splitting(*pm))
+			if (pmd_none(pmd) || pmd_trans_splitting(pmd))
 				return NULL;
 
-			if (pmd_huge(*pm) || pmd_large(*pm)) {
-				ret_pte = (pte_t *) pm;
+			if (pmd_huge(pmd) || pmd_large(pmd)) {
+				ret_pte = (pte_t *) pmdp;
 				goto out;
-			} else if (is_hugepd(pm))
-				hpdp = (hugepd_t *)pm;
+			} else if (is_hugepd(&pmd))
+				hpdp = (hugepd_t *)&pmd;
 			else
-				return pte_offset_kernel(pm, ea);
+				return pte_offset_kernel(&pmd, ea);
 		}
 	}
 	if (!hpdp)
@@ -1020,6 +1032,14 @@ int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
 	if ((pte_val(pte) & mask) != mask)
 		return 0;
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	/*
+	 * check for splitting here
+	 */
+	if (pmd_trans_splitting(pte_pmd(pte)))
+		return 0;
+#endif
+
 	/* hugepages are never "special" */
 	VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 0988a26..ccd49f9 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -508,6 +508,10 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
 		      pte_t *ptep)
 {
 #ifdef CONFIG_PPC_STD_MMU
+	/*
+	 * We don't need to worry about _PAGE_PRESENT here because we are
+	 * called with either mm->page_table_lock held or ptl lock held
+	 */
 	unsigned long access = 0, trap;
 
 	/* We only want HPTEs for linux PTEs that have _PAGE_ACCESSED set */