mm/debug_vm_pgtable: fix kernel crash by checking for THP support

Architectures can have CONFIG_TRANSPARENT_HUGEPAGE enabled but no THP
support enabled based on platforms.  For ex: with 4K PAGE_SIZE ppc64
supports THP only with radix translation.

This results in below crash when running with hash translation and 4K
PAGE_SIZE.

    kernel BUG at arch/powerpc/include/asm/book3s/64/hash-4k.h:140!
    cpu 0x61: Vector: 700 (Program Check) at [c000000ff948f860]
        pc: debug_vm_pgtable+0x480/0x8b0
        lr: debug_vm_pgtable+0x474/0x8b0
    ...
        debug_vm_pgtable+0x374/0x8b0 (unreliable)
        do_one_initcall+0x98/0x4f0
        kernel_init_freeable+0x330/0x3fc
        kernel_init+0x24/0x148

Check for THP support correctly

Link: http://lkml.kernel.org/r/20200608125252.407659-1-aneesh.kumar@linux.ibm.com
Fixes: 1b70849a7884 ("mm/debug: add tests validating architecture page table helpers")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 9ec59c38d6a2b25090919add151b45124823656a..e45623016aea101c4234c0c207b63d76b3ae358f 100644 (file)
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -60,6 +60,9 @@ static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot)
 {
        pmd_t pmd = pfn_pmd(pfn, prot);
 
+       if (!has_transparent_hugepage())
+               return;
+
        WARN_ON(!pmd_same(pmd, pmd));
        WARN_ON(!pmd_young(pmd_mkyoung(pmd_mkold(pmd))));
        WARN_ON(!pmd_dirty(pmd_mkdirty(pmd_mkclean(pmd))));
@@ -79,6 +82,9 @@ static void __init pud_basic_tests(unsigned long pfn, pgprot_t prot)
 {
        pud_t pud = pfn_pud(pfn, prot);
 
+       if (!has_transparent_hugepage())
+               return;
+
        WARN_ON(!pud_same(pud, pud));
        WARN_ON(!pud_young(pud_mkyoung(pud_mkold(pud))));
        WARN_ON(!pud_write(pud_mkwrite(pud_wrprotect(pud))));