Subject: [PATCH] powerpc/64s/slice: Use addr limit when computing slice mask

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Fri, 10 Nov 2017 10:25:07 +0530

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.

Signed-off-by: Aneesh Kumar K.V <[email-masked]>
---
 arch/powerpc/mm/slice.c | 34 ++++++++++++++++++++++------------
 1 file changed, 22 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index 564fff06f5c1..23ec2c5e3b78 100644
--- a/arch/powerpc/mm/slice.c
+++ b/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
-- 
2.13.6