arm64: fix erroneous warnings in page freeing functions

In pmd_free_pte_page() and pud_free_pmd_page() we try to warn if they
hit a present non-table entry. In both cases we'll warn for non-present
entries, as the VM_WARN_ON() only checks the entry is not a table entry.

This has been observed to result in warnings when booting a v4.19-rc2
kernel under qemu.

Fix this by bailing out earlier for non-present entries.

Fixes: 63b12f86ba9d1548 ("arm64: Implement page table free interfaces")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 65f86271f02bc1bf71a44b07fba51aefee49d381..8080c9f489c3e43af385066514f3f60cca629141 100644 (file)
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -985,8 +985,9 @@ int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr)
 
        pmd = READ_ONCE(*pmdp);
 
-       /* No-op for empty entry and WARN_ON for valid entry */
-       if (!pmd_present(pmd) || !pmd_table(pmd)) {
+       if (!pmd_present(pmd))
+               return 1;
+       if (!pmd_table(pmd)) {
                VM_WARN_ON(!pmd_table(pmd));
                return 1;
        }
@@ -1007,8 +1008,9 @@ int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
 
        pud = READ_ONCE(*pudp);
 
-       /* No-op for empty entry and WARN_ON for valid entry */
-       if (!pud_present(pud) || !pud_table(pud)) {
+       if (!pud_present(pud))
+               return 1;
+       if (!pud_table(pud)) {
                VM_WARN_ON(!pud_table(pud));
                return 1;
        }