x86/highmem: add a "already used pte" check

This is a copy from kmap_atomic_prot().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

diff --git a/arch/x86/mm/iomap_32.c b/arch/x86/mm/iomap_32.c
index 63ced61497451c34f89f13b48b22fc48279ef456..b2ffa5c7d3d3c471597eff1136fc178356d64e82 100644 (file)
--- a/arch/x86/mm/iomap_32.c
+++ b/arch/x86/mm/iomap_32.c
@@ -66,6 +66,8 @@ void *kmap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot)
        type = kmap_atomic_idx_push();
        idx = type + KM_TYPE_NR * smp_processor_id();
        vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+       WARN_ON(!pte_none(*(kmap_pte - idx)));
+
 #ifdef CONFIG_PREEMPT_RT_FULL
        current->kmap_pte[type] = pte;
 #endif