[PATCH v2] powerpc/64s/radix: Fix huge vmap false positive

[Nicholas Piggin]

pmd_huge() is defined to false when HUGETLB_PAGE is not configured, but
the vmap code still installs huge PMDs. This leads to false bad PMD
errors when vunmapping because it is not seen as a huge PTE, and the bad
PMD check catches it. The end result may not be much more serious than
some bad pmd warning messages, because the pmd_none_or_clear_bad() does
what we wanted and clears the huge PTE anyway.

Fix this by checking pmd_is_leaf(), which checks for a PTE regardless of
config options. The whole huge/large/leaf stuff is a tangled mess but
that's kernel-wide and not something we can improve much in arch/powerpc
code.

pmd_page(), pud_page(), etc., called by vmalloc_to_page() on huge vmaps
can similarly trigger a false VM_BUG_ON when CONFIG_HUGETLB_PAGE=n, so
those checks are adjusted. The checks were added by commit d6eacedd1f0e
("powerpc/book3s: Use config independent helpers for page table walk"),
while implementing a similar fix for other page table walking functions.

Fixes: d909f9109c30 ("powerpc/64s/radix: Enable HAVE_ARCH_HUGE_VMAP")
Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
---
Since v1:
- Also fix some false positive warnings spotted by Daniel.
- Rename the patch slightly to account for the new changes.

 arch/powerpc/mm/book3s64/radix_pgtable.c |  4 ++--
 arch/powerpc/mm/pgtable_64.c             | 14 +++++++++++---
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
index 3c4f0ebe5df8..ca23f5d1883a 100644
--- a/arch/powerpc/mm/book3s64/radix_pgtable.c
+++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -1076,7 +1076,7 @@ int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
 
 int pud_clear_huge(pud_t *pud)
 {
-	if (pud_huge(*pud)) {
+	if (pud_is_leaf(*pud)) {
 		pud_clear(pud);
 		return 1;
 	}
@@ -1123,7 +1123,7 @@ int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
 
 int pmd_clear_huge(pmd_t *pmd)
 {
-	if (pmd_huge(*pmd)) {
+	if (pmd_is_leaf(*pmd)) {
 		pmd_clear(pmd);
 		return 1;
 	}
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index 78c8cf01db5f..175aabf101e8 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -102,7 +102,8 @@ EXPORT_SYMBOL(__pte_frag_size_shift);
 struct page *p4d_page(p4d_t p4d)
 {
 	if (p4d_is_leaf(p4d)) {
-		VM_WARN_ON(!p4d_huge(p4d));
+		if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMAP))
+			VM_WARN_ON(!p4d_huge(p4d));
 		return pte_page(p4d_pte(p4d));
 	}
 	return virt_to_page(p4d_pgtable(p4d));
@@ -112,7 +113,8 @@ struct page *p4d_page(p4d_t p4d)
 struct page *pud_page(pud_t pud)
 {
 	if (pud_is_leaf(pud)) {
-		VM_WARN_ON(!pud_huge(pud));
+		if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMAP))
+			VM_WARN_ON(!pud_huge(pud));
 		return pte_page(pud_pte(pud));
 	}
 	return virt_to_page(pud_pgtable(pud));
@@ -125,7 +127,13 @@ struct page *pud_page(pud_t pud)
 struct page *pmd_page(pmd_t pmd)
 {
 	if (pmd_is_leaf(pmd)) {
-		VM_WARN_ON(!(pmd_large(pmd) || pmd_huge(pmd)));
+		/*
+		 * vmalloc_to_page may be called on any vmap address (not only
+		 * vmalloc), and it uses pmd_page() etc., when huge vmap is
+		 * enabled so these checks can't be used.
+		 */
+		if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMAP))
+			VM_WARN_ON(!(pmd_large(pmd) || pmd_huge(pmd)));
 		return pte_page(pmd_pte(pmd));
 	}
 	return virt_to_page(pmd_page_vaddr(pmd));
-- 
2.23.0