powerpc/mm: Fix bug in pagetable cache cleanup with CONFIG_PPC_SUBPAGE_PROT

Commit a0668cdc154e54bf0c85182e0535eea237d53146 cleans up the handling
of kmem_caches for allocating various levels of pagetables.
Unfortunately, it conflicts badly with CONFIG_PPC_SUBPAGE_PROT, due to
the latter's cleverly hidden technique of adding some extra allocation
space to the top level page directory to store the extra information
it needs.

Since that extra allocation really doesn't fit into the cleaned up
page directory allocating scheme, this patch alters
CONFIG_PPC_SUBPAGE_PROT to instead allocate its struct
subpage_prot_table as part of the mm_context_t.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

3 files changed, 16 insertions, 7 deletions

diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 6810128..50f867d 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -835,9 +835,9 @@ void demote_segment_4k(struct mm_struct *mm, unsigned long addr)
  * Result is 0: full permissions, _PAGE_RW: read-only,
  * _PAGE_USER or _PAGE_USER|_PAGE_RW: no access.
  */
-static int subpage_protection(pgd_t *pgdir, unsigned long ea)
+static int subpage_protection(struct mm_struct *mm, unsigned long ea)
 {
-	struct subpage_prot_table *spt = pgd_subpage_prot(pgdir);
+	struct subpage_prot_table *spt = &mm->context.spt;
 	u32 spp = 0;
 	u32 **sbpm, *sbpp;
 
@@ -865,7 +865,7 @@ static int subpage_protection(pgd_t *pgdir, unsigned long ea)
 }
 
 #else /* CONFIG_PPC_SUBPAGE_PROT */
-static inline int subpage_protection(pgd_t *pgdir, unsigned long ea)
+static inline int subpage_protection(struct mm_struct *mm, unsigned long ea)
 {
 	return 0;
 }
diff --git a/arch/powerpc/mm/mmu_context_hash64.c b/arch/powerpc/mm/mmu_context_hash64.c
index b9e4cc2..b910d37 100644
--- a/arch/powerpc/mm/mmu_context_hash64.c
+++ b/arch/powerpc/mm/mmu_context_hash64.c
@@ -76,6 +76,7 @@ int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
 	 */
 	if (slice_mm_new_context(mm))
 		slice_set_user_psize(mm, mmu_virtual_psize);
+	subpage_prot_init_new_context(mm);
 	mm->context.id = index;
 
 	return 0;
@@ -92,5 +93,6 @@ EXPORT_SYMBOL_GPL(__destroy_context);
 void destroy_context(struct mm_struct *mm)
 {
 	__destroy_context(mm->context.id);
+	subpage_prot_free(mm);
 	mm->context.id = NO_CONTEXT;
 }
diff --git a/arch/powerpc/mm/subpage-prot.c b/arch/powerpc/mm/subpage-prot.c
index 4cafc0c..a040b81 100644
--- a/arch/powerpc/mm/subpage-prot.c
+++ b/arch/powerpc/mm/subpage-prot.c
@@ -24,9 +24,9 @@
  * Also makes sure that the subpage_prot_table structure is
  * reinitialized for the next user.
  */
-void subpage_prot_free(pgd_t *pgd)
+void subpage_prot_free(struct mm_struct *mm)
 {
-	struct subpage_prot_table *spt = pgd_subpage_prot(pgd);
+	struct subpage_prot_table *spt = &mm->context.spt;
 	unsigned long i, j, addr;
 	u32 **p;
 
@@ -51,6 +51,13 @@ void subpage_prot_free(pgd_t *pgd)
 	spt->maxaddr = 0;
 }
 
+void subpage_prot_init_new_context(struct mm_struct *mm)
+{
+	struct subpage_prot_table *spt = &mm->context.spt;
+
+	memset(spt, 0, sizeof(*spt));
+}
+
 static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
 			     int npages)
 {
@@ -87,7 +94,7 @@ static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
 static void subpage_prot_clear(unsigned long addr, unsigned long len)
 {
 	struct mm_struct *mm = current->mm;
-	struct subpage_prot_table *spt = pgd_subpage_prot(mm->pgd);
+	struct subpage_prot_table *spt = &mm->context.spt;
 	u32 **spm, *spp;
 	int i, nw;
 	unsigned long next, limit;
@@ -136,7 +143,7 @@ static void subpage_prot_clear(unsigned long addr, unsigned long len)
 long sys_subpage_prot(unsigned long addr, unsigned long len, u32 __user *map)
 {
 	struct mm_struct *mm = current->mm;
-	struct subpage_prot_table *spt = pgd_subpage_prot(mm->pgd);
+	struct subpage_prot_table *spt = &mm->context.spt;
 	u32 **spm, *spp;
 	int i, nw;
 	unsigned long next, limit;