sparc64: Trim page tables for 8M hugepages

For PMD aligned (8M) hugepages, we currently allocate
all four page table levels which is wasteful. We now
allocate till PMD level only which saves memory usage
from page tables.

Also, when freeing page table for 8M hugepage backed region,
make sure we don't try to access non-existent PTE level.

Orabug: 22630259

Signed-off-by: Nitin Gupta <nitin.m.gupta@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 112 insertions, 54 deletions

diff --git a/arch/sparc/mm/hugetlbpage.c b/arch/sparc/mm/hugetlbpage.c
index d69b66e01b84..988acc8b1b80 100644
--- a/arch/sparc/mm/hugetlbpage.c
+++ b/arch/sparc/mm/hugetlbpage.c
@@ -12,6 +12,7 @@
 
 #include <asm/mman.h>
 #include <asm/pgalloc.h>
+#include <asm/pgtable.h>
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
 #include <asm/cacheflush.h>
@@ -131,23 +132,13 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
 {
 	pgd_t *pgd;
 	pud_t *pud;
-	pmd_t *pmd;
 	pte_t *pte = NULL;
 
-	/* We must align the address, because our caller will run
-	 * set_huge_pte_at() on whatever we return, which writes out
-	 * all of the sub-ptes for the hugepage range.  So we have
-	 * to give it the first such sub-pte.
-	 */
-	addr &= HPAGE_MASK;
-
 	pgd = pgd_offset(mm, addr);
 	pud = pud_alloc(mm, pgd, addr);
-	if (pud) {
-		pmd = pmd_alloc(mm, pud, addr);
-		if (pmd)
-			pte = pte_alloc_map(mm, pmd, addr);
-	}
+	if (pud)
+		pte = (pte_t *)pmd_alloc(mm, pud, addr);
+
 	return pte;
 }
 
@@ -155,19 +146,13 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
 {
 	pgd_t *pgd;
 	pud_t *pud;
-	pmd_t *pmd;
 	pte_t *pte = NULL;
 
-	addr &= HPAGE_MASK;
-
 	pgd = pgd_offset(mm, addr);
 	if (!pgd_none(*pgd)) {
 		pud = pud_offset(pgd, addr);
-		if (!pud_none(*pud)) {
-			pmd = pmd_offset(pud, addr);
-			if (!pmd_none(*pmd))
-				pte = pte_offset_map(pmd, addr);
-		}
+		if (!pud_none(*pud))
+			pte = (pte_t *)pmd_offset(pud, addr);
 	}
 	return pte;
 }
@@ -175,70 +160,143 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
 void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
 		     pte_t *ptep, pte_t entry)
 {
-	int i;
-	pte_t orig[2];
-	unsigned long nptes;
+	pte_t orig;
 
 	if (!pte_present(*ptep) && pte_present(entry))
 		mm->context.hugetlb_pte_count++;
 
 	addr &= HPAGE_MASK;
-
-	nptes = 1 << HUGETLB_PAGE_ORDER;
-	orig[0] = *ptep;
-	orig[1] = *(ptep + nptes / 2);
-	for (i = 0; i < nptes; i++) {
-		*ptep = entry;
-		ptep++;
-		addr += PAGE_SIZE;
-		pte_val(entry) += PAGE_SIZE;
-	}
+	orig = *ptep;
+	*ptep = entry;
 
 	/* Issue TLB flush at REAL_HPAGE_SIZE boundaries */
-	addr -= REAL_HPAGE_SIZE;
-	ptep -= nptes / 2;
-	maybe_tlb_batch_add(mm, addr, ptep, orig[1], 0);
-	addr -= REAL_HPAGE_SIZE;
-	ptep -= nptes / 2;
-	maybe_tlb_batch_add(mm, addr, ptep, orig[0], 0);
+	maybe_tlb_batch_add(mm, addr, ptep, orig, 0);
+	maybe_tlb_batch_add(mm, addr + REAL_HPAGE_SIZE, ptep, orig, 0);
 }
 
 pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
 			      pte_t *ptep)
 {
 	pte_t entry;
-	int i;
-	unsigned long nptes;
 
 	entry = *ptep;
 	if (pte_present(entry))
 		mm->context.hugetlb_pte_count--;
 
 	addr &= HPAGE_MASK;
-	nptes = 1 << HUGETLB_PAGE_ORDER;
-	for (i = 0; i < nptes; i++) {
-		*ptep = __pte(0UL);
-		addr += PAGE_SIZE;
-		ptep++;
-	}
+	*ptep = __pte(0UL);
 
 	/* Issue TLB flush at REAL_HPAGE_SIZE boundaries */
-	addr -= REAL_HPAGE_SIZE;
-	ptep -= nptes / 2;
-	maybe_tlb_batch_add(mm, addr, ptep, entry, 0);
-	addr -= REAL_HPAGE_SIZE;
-	ptep -= nptes / 2;
 	maybe_tlb_batch_add(mm, addr, ptep, entry, 0);
+	maybe_tlb_batch_add(mm, addr + REAL_HPAGE_SIZE, ptep, entry, 0);
 
 	return entry;
 }
 
 int pmd_huge(pmd_t pmd)
 {
-	return 0;
+	return !pmd_none(pmd) &&
+		(pmd_val(pmd) & (_PAGE_VALID|_PAGE_PMD_HUGE)) != _PAGE_VALID;
 }
 
 int pud_huge(pud_t pud)
 {
 	return 0;
 }
+
+static void hugetlb_free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
+			   unsigned long addr)
+{
+	pgtable_t token = pmd_pgtable(*pmd);
+
+	pmd_clear(pmd);
+	pte_free_tlb(tlb, token, addr);
+	atomic_long_dec(&tlb->mm->nr_ptes);
+}
+
+static void hugetlb_free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
+				   unsigned long addr, unsigned long end,
+				   unsigned long floor, unsigned long ceiling)
+{
+	pmd_t *pmd;
+	unsigned long next;
+	unsigned long start;
+
+	start = addr;
+	pmd = pmd_offset(pud, addr);
+	do {
+		next = pmd_addr_end(addr, end);
+		if (pmd_none(*pmd))
+			continue;
+		if (is_hugetlb_pmd(*pmd))
+			pmd_clear(pmd);
+		else
+			hugetlb_free_pte_range(tlb, pmd, addr);
+	} while (pmd++, addr = next, addr != end);
+
+	start &= PUD_MASK;
+	if (start < floor)
+		return;
+	if (ceiling) {
+		ceiling &= PUD_MASK;
+		if (!ceiling)
+			return;
+	}
+	if (end - 1 > ceiling - 1)
+		return;
+
+	pmd = pmd_offset(pud, start);
+	pud_clear(pud);
+	pmd_free_tlb(tlb, pmd, start);
+	mm_dec_nr_pmds(tlb->mm);
+}
+
+static void hugetlb_free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
+				   unsigned long addr, unsigned long end,
+				   unsigned long floor, unsigned long ceiling)
+{
+	pud_t *pud;
+	unsigned long next;
+	unsigned long start;
+
+	start = addr;
+	pud = pud_offset(pgd, addr);
+	do {
+		next = pud_addr_end(addr, end);
+		if (pud_none_or_clear_bad(pud))
+			continue;
+		hugetlb_free_pmd_range(tlb, pud, addr, next, floor,
+				       ceiling);
+	} while (pud++, addr = next, addr != end);
+
+	start &= PGDIR_MASK;
+	if (start < floor)
+		return;
+	if (ceiling) {
+		ceiling &= PGDIR_MASK;
+		if (!ceiling)
+			return;
+	}
+	if (end - 1 > ceiling - 1)
+		return;
+
+	pud = pud_offset(pgd, start);
+	pgd_clear(pgd);
+	pud_free_tlb(tlb, pud, start);
+}
+
+void hugetlb_free_pgd_range(struct mmu_gather *tlb,
+			    unsigned long addr, unsigned long end,
+			    unsigned long floor, unsigned long ceiling)
+{
+	pgd_t *pgd;
+	unsigned long next;
+
+	pgd = pgd_offset(tlb->mm, addr);
+	do {
+		next = pgd_addr_end(addr, end);
+		if (pgd_none_or_clear_bad(pgd))
+			continue;
+		hugetlb_free_pud_range(tlb, pgd, addr, next, floor, ceiling);
+	} while (pgd++, addr = next, addr != end);
+}