Re: + x86-add-support-for-pud-sized-transparent-hugepages-checkpatch-fixes.patch added to -mm tree

[Matthew Wilcox]

On Wed, Mar 09, 2016 at 01:45:40PM -0500, Matthew Wilcox wrote:
> > In fact even before starting to fix the comment, I would recommend to
> > try again to call native_local_pmdp_get_and_clear and
> > native_local_ptep_get_and_clear to verify if it still breaks, just in
> > case the include ordering got fixed by accident in the meanwhile (that
> > was a comment in 2.6.25 when arch/x86/include/asm didn't even exist
> > yet, it was still in include/asm-x86). If it would manage to build
> > without the manual expansion, the comment could go and the duplication
> > as well.
> 
> The ordering problem is still there.  native_local_ptep_get_and_clear()
> is declared at line 726 of asm/pgtable.h and asm/pgtable_64.h is included
> at line 466 of asm/pgtable.h.
> 
> I'll have a little play; see if I can resolve this ...

asm/pgtable.h:466
# include <asm/pgtable_64.h>

asm/pgtable.h:726
static inline pte_t native_local_ptep_get_and_clear(pte_t *ptep)
{
        pte_t res = *ptep;

        /* Pure native function needs no input for mm, addr */
        native_pte_clear(NULL, 0, ptep);
        return res;
}

asm/pgtable_64.h:47
static inline void native_pte_clear(struct mm_struct *mm, unsigned long addr,
                                    pte_t *ptep)
{
        *ptep = native_make_pte(0);
}

asm/pgtable_64.h:73
static inline pte_t native_ptep_get_and_clear(pte_t *xp)
{
#ifdef CONFIG_SMP
        return native_make_pte(xchg(&xp->pte, 0));
#else
        /* native_local_ptep_get_and_clear,
           but duplicated because of cyclic dependency */
        pte_t ret = *xp;
        native_pte_clear(NULL, 0, xp);
        return ret;
#endif
}

Why don't we just convert native_ptep_get_and_clear to work the same way that
pgtable-2level and pgtable-3level work?  ie:

#ifdef CONFIG_SMP
static inline pte_t native_ptep_get_and_clear(pte_t *xp)
{
        return native_make_pte(xchg(&xp->pte, 0));
}
#else
#define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
#endif

Or perhaps better, centralise the non-SMP definitions:

 arch/x86/include/asm/pgtable-2level.h |  6 ------
 arch/x86/include/asm/pgtable-3level.h |  7 +------
 arch/x86/include/asm/pgtable.h        |  5 +++++
 arch/x86/include/asm/pgtable_64.h     | 18 ++----------------
 4 files changed, 8 insertions(+), 28 deletions(-)

diff --git a/arch/x86/include/asm/pgtable-2level.h b/arch/x86/include/asm/pgtable-2level.h
index fd74a11..520318f 100644
--- a/arch/x86/include/asm/pgtable-2level.h
+++ b/arch/x86/include/asm/pgtable-2level.h
@@ -42,17 +42,11 @@ static inline pte_t native_ptep_get_and_clear(pte_t *xp)
 {
 	return __pte(xchg(&xp->pte_low, 0));
 }
-#else
-#define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
-#endif
 
-#ifdef CONFIG_SMP
 static inline pmd_t native_pmdp_get_and_clear(pmd_t *xp)
 {
 	return __pmd(xchg((pmdval_t *)xp, 0));
 }
-#else
-#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
 #endif
 
 /* Bit manipulation helper on pte/pgoff entry */
diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h
index cdaa58c..b1b6412 100644
--- a/arch/x86/include/asm/pgtable-3level.h
+++ b/arch/x86/include/asm/pgtable-3level.h
@@ -149,11 +149,7 @@ static inline pte_t native_ptep_get_and_clear(pte_t *ptep)
 
 	return res;
 }
-#else
-#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;
@@ -161,6 +157,7 @@ union split_pmd {
 	};
 	pmd_t pmd;
 };
+
 static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
 {
 	union split_pmd res, *orig = (union split_pmd *)pmdp;
@@ -172,8 +169,6 @@ static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
 
 	return res.pmd;
 }
-#else
-#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
 #endif
 
 /* Encode and de-code a swap entry */
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 1ff49ec..35306ca 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -740,6 +740,11 @@ static inline pmd_t native_local_pmdp_get_and_clear(pmd_t *pmdp)
 	return res;
 }
 
+#ifndef CONFIG_SMP
+#define native_ptep_get_and_clear(p)	native_local_ptep_get_and_clear(p)
+#define native_pmdp_get_and_clear(p)	native_local_pmdp_get_and_clear(p)
+#endif
+
 static inline void native_set_pte_at(struct mm_struct *mm, unsigned long addr,
 				     pte_t *ptep , pte_t pte)
 {
diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index 2ee7811..a0c0219 100644
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -70,31 +70,17 @@ static inline void native_pmd_clear(pmd_t *pmd)
 	native_set_pmd(pmd, native_make_pmd(0));
 }
 
+#ifdef CONFIG_SMP
 static inline pte_t native_ptep_get_and_clear(pte_t *xp)
 {
-#ifdef CONFIG_SMP
 	return native_make_pte(xchg(&xp->pte, 0));
-#else
-	/* native_local_ptep_get_and_clear,
-	   but duplicated because of cyclic dependency */
-	pte_t ret = *xp;
-	native_pte_clear(NULL, 0, xp);
-	return ret;
-#endif
 }
 
 static inline pmd_t native_pmdp_get_and_clear(pmd_t *xp)
 {
-#ifdef CONFIG_SMP
 	return native_make_pmd(xchg(&xp->pmd, 0));
-#else
-	/* native_local_pmdp_get_and_clear,
-	   but duplicated because of cyclic dependency */
-	pmd_t ret = *xp;
-	native_pmd_clear(xp);
-	return ret;
-#endif
 }
+#endif
 
 static inline void native_set_pud(pud_t *pudp, pud_t pud)
 {