x86/mm: provide pmdp_establish() helper
We need an atomic way to setup pmd page table entry, avoiding races with
CPU setting dirty/accessed bits. This is required to implement
pmdp_invalidate() that doesn't lose these bits.
On PAE we can avoid expensive cmpxchg8b for cases when new page table
entry is not present. If it's present, fallback to cpmxchg loop.
[akpm@linux-foundation.org: add missing `do' to do-while loop]
Link: http://lkml.kernel.org/r/20171213105756.69879-10-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index e42b894..63c2552 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1109,6 +1109,21 @@ static inline int pud_write(pud_t pud)
return pud_flags(pud) & _PAGE_RW;
}
+#ifndef pmdp_establish
+#define pmdp_establish pmdp_establish
+static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
+ unsigned long address, pmd_t *pmdp, pmd_t pmd)
+{
+ if (IS_ENABLED(CONFIG_SMP)) {
+ return xchg(pmdp, pmd);
+ } else {
+ pmd_t old = *pmdp;
+ *pmdp = pmd;
+ return old;
+ }
+}
+#endif
+
/*
* clone_pgd_range(pgd_t *dst, pgd_t *src, int count);
*