thp: add x86 32bit support
Add support for transparent hugepages to x86 32bit.
Share the same VM_ bitflag for VM_MAPPED_COPY. mm/nommu.c will never
support transparent hugepages.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
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-3level.h b/arch/x86/include/asm/pgtable-3level.h
index 177b016..94b979d 100644
--- a/arch/x86/include/asm/pgtable-3level.h
+++ b/arch/x86/include/asm/pgtable-3level.h
@@ -104,6 +104,29 @@
#define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
#endif
+#ifdef CONFIG_SMP
+union split_pmd {
+ struct {
+ u32 pmd_low;
+ u32 pmd_high;
+ };
+ pmd_t pmd;
+};
+static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
+{
+ union split_pmd res, *orig = (union split_pmd *)pmdp;
+
+ /* xchg acts as a barrier before setting of the high bits */
+ res.pmd_low = xchg(&orig->pmd_low, 0);
+ res.pmd_high = orig->pmd_high;
+ orig->pmd_high = 0;
+
+ return res.pmd;
+}
+#else
+#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
+#endif
+
/*
* Bits 0, 6 and 7 are taken in the low part of the pte,
* put the 32 bits of offset into the high part.