powerpc/64s/slice: Use addr limit when computing slice mask

While computing slice mask for the free area we need make sure we only
search in the addr limit applicable for this mmap. We update the
slb_addr_limit after we request for a mmap above 128TB. But the
following mmap request with hint addr below 128TB should still limit
its search to below 128TB. ie. we should not use slb_addr_limit to
compute slice mask in this case. Instead, we should derive high addr
limit based on the mmap hint addr value.

Fixes: f4ea6dcb08ea ("powerpc/mm: Enable mappings above 128TB")
Cc: stable@vger.kernel.org # v4.12+
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/slice.c

@@ -122,7 +122,8 @@ static int slice_high_has_vma(struct mm_struct *mm, unsigned long slice)
 	return !slice_area_is_free(mm, start, end - start);
 }
 
-static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret)
+static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret,
+				unsigned long high_limit)
 {
 	unsigned long i;
 
@@ -133,15 +134,16 @@ static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret)
 		if (!slice_low_has_vma(mm, i))
 			ret->low_slices |= 1u << i;
 
-	if (mm->context.slb_addr_limit <= SLICE_LOW_TOP)
+	if (high_limit <= SLICE_LOW_TOP)
 		return;
 
-	for (i = 0; i < GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit); i++)
+	for (i = 0; i < GET_HIGH_SLICE_INDEX(high_limit); i++)
 		if (!slice_high_has_vma(mm, i))
 			__set_bit(i, ret->high_slices);
 }
 
-static void slice_mask_for_size(struct mm_struct *mm, int psize, struct slice_mask *ret)
+static void slice_mask_for_size(struct mm_struct *mm, int psize, struct slice_mask *ret,
+				unsigned long high_limit)
 {
 	unsigned char *hpsizes;
 	int index, mask_index;
@@ -156,8 +158,11 @@ static void slice_mask_for_size(struct mm_struct *mm, int psize, struct slice_ma
 		if (((lpsizes >> (i * 4)) & 0xf) == psize)
 			ret->low_slices |= 1u << i;
 
+	if (high_limit <= SLICE_LOW_TOP)
+		return;
+
 	hpsizes = mm->context.high_slices_psize;
-	for (i = 0; i < GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit); i++) {
+	for (i = 0; i < GET_HIGH_SLICE_INDEX(high_limit); i++) {
 		mask_index = i & 0x1;
 		index = i >> 1;
 		if (((hpsizes[index] >> (mask_index * 4)) & 0xf) == psize)
@@ -169,6 +174,10 @@ static int slice_check_fit(struct mm_struct *mm,
 			   struct slice_mask mask, struct slice_mask available)
 {
 	DECLARE_BITMAP(result, SLICE_NUM_HIGH);
+	/*
+	 * Make sure we just do bit compare only to the max
+	 * addr limit and not the full bit map size.
+	 */
 	unsigned long slice_count = GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit);
 
 	bitmap_and(result, mask.high_slices,
@@ -472,7 +481,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
 	/* First make up a "good" mask of slices that have the right size
 	 * already
 	 */
-	slice_mask_for_size(mm, psize, &good_mask);
+	slice_mask_for_size(mm, psize, &good_mask, high_limit);
 	slice_print_mask(" good_mask", good_mask);
 
 	/*
@@ -497,7 +506,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
 #ifdef CONFIG_PPC_64K_PAGES
 	/* If we support combo pages, we can allow 64k pages in 4k slices */
 	if (psize == MMU_PAGE_64K) {
-		slice_mask_for_size(mm, MMU_PAGE_4K, &compat_mask);
+		slice_mask_for_size(mm, MMU_PAGE_4K, &compat_mask, high_limit);
 		if (fixed)
 			slice_or_mask(&good_mask, &compat_mask);
 	}
@@ -530,11 +539,11 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
 			return newaddr;
 		}
 	}
-
-	/* We don't fit in the good mask, check what other slices are
+	/*
+	 * We don't fit in the good mask, check what other slices are
 	 * empty and thus can be converted
 	 */
-	slice_mask_for_free(mm, &potential_mask);
+	slice_mask_for_free(mm, &potential_mask, high_limit);
 	slice_or_mask(&potential_mask, &good_mask);
 	slice_print_mask(" potential", potential_mask);
 
@@ -744,17 +753,18 @@ int is_hugepage_only_range(struct mm_struct *mm, unsigned long addr,
 {
 	struct slice_mask mask, available;
 	unsigned int psize = mm->context.user_psize;
+	unsigned long high_limit = mm->context.slb_addr_limit;
 
 	if (radix_enabled())
 		return 0;
 
 	slice_range_to_mask(addr, len, &mask);
-	slice_mask_for_size(mm, psize, &available);
+	slice_mask_for_size(mm, psize, &available, high_limit);
 #ifdef CONFIG_PPC_64K_PAGES
 	/* We need to account for 4k slices too */
 	if (psize == MMU_PAGE_64K) {
 		struct slice_mask compat_mask;
-		slice_mask_for_size(mm, MMU_PAGE_4K, &compat_mask);
+		slice_mask_for_size(mm, MMU_PAGE_4K, &compat_mask, high_limit);
 		slice_or_mask(&available, &compat_mask);
 	}
 #endif