[PATCH v3 4/6] mm: Change vunmap to tear down huge KVA mappings

[Toshi Kani <toshi.kani@hp.com>]

Changed vunmap_pmd_range() and vunmap_pud_range() to tear down
huge KVA mappings when they are set.  pud_clear_huge() and
pmd_clear_huge() return zero when no-operation is performed,
i.e. huge page mapping was not used.

These changes are only enabled when CONFIG_HAVE_ARCH_HUGE_VMAP
is defined on the architecture.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 include/asm-generic/pgtable.h |    4 ++++
 mm/vmalloc.c                  |    4 ++++
 2 files changed, 8 insertions(+)

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index bf6e86c..b583235 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -701,6 +701,8 @@ static inline int pmd_protnone(pmd_t pmd)
 #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
 int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot);
 int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot);
+int pud_clear_huge(pud_t *pud);
+int pmd_clear_huge(pmd_t *pmd);
 #else	/* !CONFIG_HAVE_ARCH_HUGE_VMAP */
 static inline int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
 {
@@ -710,6 +712,8 @@ static inline int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
 {
 	return 0;
 }
+static inline int pud_clear_huge(pud_t *pud) { return 0; }
+static inline int pmd_clear_huge(pmd_t *pmd) { return 0; }
 #endif	/* CONFIG_HAVE_ARCH_HUGE_VMAP */
 
 #endif /* _ASM_GENERIC_PGTABLE_H */
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index fe1672d..9184cf7 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -75,6 +75,8 @@ static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end)
 	pmd = pmd_offset(pud, addr);
 	do {
 		next = pmd_addr_end(addr, end);
+		if (pmd_clear_huge(pmd))
+			continue;
 		if (pmd_none_or_clear_bad(pmd))
 			continue;
 		vunmap_pte_range(pmd, addr, next);
@@ -89,6 +91,8 @@ static void vunmap_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end)
 	pud = pud_offset(pgd, addr);
 	do {
 		next = pud_addr_end(addr, end);
+		if (pud_clear_huge(pud))
+			continue;
 		if (pud_none_or_clear_bad(pud))
 			continue;
 		vunmap_pmd_range(pud, addr, next);