[PATCH 2/2] arch/powerpc: Switch to generic RCU get_user_pages

Discussion:

[PATCH 2/2] arch/powerpc: Switch to generic RCU get_user_pages_fast

Aneesh Kumar K.V

2014-10-15 16:34:48 UTC

This patch switch the ppc arch to use the generic RCU based
gup implementation.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/hugetlb.h | 8 +-
arch/powerpc/include/asm/page.h | 4 +-
arch/powerpc/include/asm/pgtable-ppc64.h | 1 -
arch/powerpc/include/asm/pgtable.h | 5 -
arch/powerpc/mm/Makefile | 2 +-
arch/powerpc/mm/gup.c | 235 -------------------------------
arch/powerpc/mm/hugetlbpage.c | 27 ++--
8 files changed, 21 insertions(+), 262 deletions(-)
delete mode 100644 arch/powerpc/mm/gup.c

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 88eace4e28c3..7af887dc6aed 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -148,6 +148,7 @@ config PPC
select HAVE_ARCH_AUDITSYSCALL
select ARCH_SUPPORTS_ATOMIC_RMW
select DCACHE_WORD_ACCESS if PPC64 && CPU_LITTLE_ENDIAN
+ select HAVE_GENERIC_RCU_GUP

config GENERIC_CSUM
def_bool CPU_LITTLE_ENDIAN
diff --git a/arch/powerpc/include/asm/hugetlb.h b/arch/powerpc/include/asm/hugetlb.h
index 623f2971ce0e..7855cce9c969 100644
--- a/arch/powerpc/include/asm/hugetlb.h
+++ b/arch/powerpc/include/asm/hugetlb.h
@@ -48,7 +48,7 @@ static inline unsigned int hugepd_shift(hugepd_t hpd)
#endif /* CONFIG_PPC_BOOK3S_64 */

-static inline pte_t *hugepte_offset(hugepd_t *hpdp, unsigned long addr,
+static inline pte_t *hugepte_offset(hugepd_t hpd, unsigned long addr,
unsigned pdshift)
{
/*
@@ -58,9 +58,9 @@ static inline pte_t *hugepte_offset(hugepd_t *hpdp, unsigned long addr,
*/
unsigned long idx = 0;

- pte_t *dir = hugepd_page(*hpdp);
+ pte_t *dir = hugepd_page(hpd);
#ifndef CONFIG_PPC_FSL_BOOK3E
- idx = (addr & ((1UL << pdshift) - 1)) >> hugepd_shift(*hpdp);
+ idx = (addr & ((1UL << pdshift) - 1)) >> hugepd_shift(hpd);
#endif

return dir + idx;
@@ -193,7 +193,7 @@ static inline void flush_hugetlb_page(struct vm_area_struct *vma,
}

#define hugepd_shift(x) 0
-static inline pte_t *hugepte_offset(hugepd_t *hpdp, unsigned long addr,
+static inline pte_t *hugepte_offset(hugepd_t hpd, unsigned long addr,
unsigned pdshift)
{
return 0;
diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
index 26fe1ae15212..aa430ec14895 100644
--- a/arch/powerpc/include/asm/page.h
+++ b/arch/powerpc/include/asm/page.h
@@ -379,12 +379,12 @@ static inline int hugepd_ok(hugepd_t hpd)
}
#endif

-#define is_hugepd(pdep) (hugepd_ok(*((hugepd_t *)(pdep))))
+#define is_hugepd(hpd) (hugepd_ok(hpd))
int pgd_huge(pgd_t pgd);
#else /* CONFIG_HUGETLB_PAGE */
#define is_hugepd(pdep) 0
-#define pgd_huge(pgd) 0
#endif /* CONFIG_HUGETLB_PAGE */
+#define __hugepd(x) ((hugepd_t) { (x) })

struct page;
extern void clear_user_page(void *page, unsigned long vaddr, struct page *pg);
diff --git a/arch/powerpc/include/asm/pgtable-ppc64.h b/arch/powerpc/include/asm/pgtable-ppc64.h
index ae153c40ab7c..29c36242cc6a 100644
--- a/arch/powerpc/include/asm/pgtable-ppc64.h
+++ b/arch/powerpc/include/asm/pgtable-ppc64.h
@@ -575,6 +575,5 @@ static inline int pmd_move_must_withdraw(struct spinlock *new_pmd_ptl,
*/
return true;
}
-
#endif /* __ASSEMBLY__ */
#endif /* _ASM_POWERPC_PGTABLE_PPC64_H_ */
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 316f9a5da173..4a67c1ddb91b 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -274,11 +274,6 @@ extern void paging_init(void);
*/
extern void update_mmu_cache(struct vm_area_struct *, unsigned long, pte_t *);

-extern int gup_hugepd(hugepd_t *hugepd, unsigned pdshift, unsigned long addr,
- unsigned long end, int write, struct page **pages, int *nr);
-
-extern int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
- unsigned long end, int write, struct page **pages, int *nr);
#ifndef CONFIG_TRANSPARENT_HUGEPAGE
#define pmd_large(pmd) 0
#define has_transparent_hugepage() 0
diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile
index 325e861616a1..438dcd3fd0d1 100644
--- a/arch/powerpc/mm/Makefile
+++ b/arch/powerpc/mm/Makefile
@@ -6,7 +6,7 @@ subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror

ccflags-$(CONFIG_PPC64) := $(NO_MINIMAL_TOC)

-obj-y := fault.o mem.o pgtable.o gup.o mmap.o \
+obj-y := fault.o mem.o pgtable.o mmap.o \
init_$(CONFIG_WORD_SIZE).o \
pgtable_$(CONFIG_WORD_SIZE).o
obj-$(CONFIG_PPC_MMU_NOHASH) += mmu_context_nohash.o tlb_nohash.o \
diff --git a/arch/powerpc/mm/gup.c b/arch/powerpc/mm/gup.c
deleted file mode 100644
index d8746684f606..000000000000
--- a/arch/powerpc/mm/gup.c
+++ /dev/null
@@ -1,235 +0,0 @@
-/*
- * Lockless get_user_pages_fast for powerpc
- *
- * Copyright (C) 2008 Nick Piggin
- * Copyright (C) 2008 Novell Inc.
- */
-#undef DEBUG
-
-#include <linux/sched.h>
-#include <linux/mm.h>
-#include <linux/hugetlb.h>
-#include <linux/vmstat.h>
-#include <linux/pagemap.h>
-#include <linux/rwsem.h>
-#include <asm/pgtable.h>
-
-#ifdef __HAVE_ARCH_PTE_SPECIAL
-
-/*
- * The performance critical leaf functions are made noinline otherwise gcc
- * inlines everything into a single function which results in too much
- * register pressure.
- */
-static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
- unsigned long end, int write, struct page **pages, int *nr)
-{
- unsigned long mask, result;
- pte_t *ptep;
-
- result = _PAGE_PRESENT|_PAGE_USER;
- if (write)
- result |= _PAGE_RW;
- mask = result | _PAGE_SPECIAL;
-
- ptep = pte_offset_kernel(&pmd, addr);
- do {
- pte_t pte = ACCESS_ONCE(*ptep);
- struct page *page;
- /*
- * Similar to the PMD case, NUMA hinting must take slow path
- */
- if (pte_numa(pte))
- return 0;
-
- if ((pte_val(pte) & mask) != result)
- return 0;
- VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
- page = pte_page(pte);
- if (!page_cache_get_speculative(page))
- return 0;
- if (unlikely(pte_val(pte) != pte_val(*ptep))) {
- put_page(page);
- return 0;
- }
- pages[*nr] = page;
- (*nr)++;
-
- } while (ptep++, addr += PAGE_SIZE, addr != end);
-
- return 1;
-}
-
-static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
- int write, struct page **pages, int *nr)
-{
- unsigned long next;
- pmd_t *pmdp;
-
- pmdp = pmd_offset(&pud, addr);
- do {
- pmd_t pmd = ACCESS_ONCE(*pmdp);
-
- next = pmd_addr_end(addr, end);
- /*
- * If we find a splitting transparent hugepage we
- * return zero. That will result in taking the slow
- * path which will call wait_split_huge_page()
- * if the pmd is still in splitting state
- */
- if (pmd_none(pmd) || pmd_trans_splitting(pmd))
- return 0;
- if (pmd_huge(pmd) || pmd_large(pmd)) {
- /*
- * NUMA hinting faults need to be handled in the GUP
- * slowpath for accounting purposes and so that they
- * can be serialised against THP migration.
- */
- if (pmd_numa(pmd))
- return 0;
-
- if (!gup_hugepte((pte_t *)pmdp, PMD_SIZE, addr, next,
- write, pages, nr))
- return 0;
- } else if (is_hugepd(pmdp)) {
- if (!gup_hugepd((hugepd_t *)pmdp, PMD_SHIFT,
- addr, next, write, pages, nr))
- return 0;
- } else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
- return 0;
- } while (pmdp++, addr = next, addr != end);
-
- return 1;
-}
-
-static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
- int write, struct page **pages, int *nr)
-{
- unsigned long next;
- pud_t *pudp;
-
- pudp = pud_offset(&pgd, addr);
- do {
- pud_t pud = ACCESS_ONCE(*pudp);
-
- next = pud_addr_end(addr, end);
- if (pud_none(pud))
- return 0;
- if (pud_huge(pud)) {
- if (!gup_hugepte((pte_t *)pudp, PUD_SIZE, addr, next,
- write, pages, nr))
- return 0;
- } else if (is_hugepd(pudp)) {
- if (!gup_hugepd((hugepd_t *)pudp, PUD_SHIFT,
- addr, next, write, pages, nr))
- return 0;
- } else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
- return 0;
- } while (pudp++, addr = next, addr != end);
-
- return 1;
-}
-
-int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
- struct page **pages)
-{
- struct mm_struct *mm = current->mm;
- unsigned long addr, len, end;
- unsigned long next;
- unsigned long flags;
- pgd_t *pgdp;
- int nr = 0;
-
- pr_devel("%s(%lx,%x,%s)\n", __func__, start, nr_pages, write ? "write" : "read");
-
- start &= PAGE_MASK;
- addr = start;
- len = (unsigned long) nr_pages << PAGE_SHIFT;
- end = start + len;
-
- if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
- start, len)))
- return 0;
-
- pr_devel(" aligned: %lx .. %lx\n", start, end);
-
- /*
- * XXX: batch / limit 'nr', to avoid large irq off latency
- * needs some instrumenting to determine the common sizes used by
- * important workloads (eg. DB2), and whether limiting the batch size
- * will decrease performance.
- *
- * It seems like we're in the clear for the moment. Direct-IO is
- * the main guy that batches up lots of get_user_pages, and even
- * they are limited to 64-at-a-time which is not so many.
- */
- /*
- * This doesn't prevent pagetable teardown, but does prevent
- * the pagetables from being freed on powerpc.
- *
- * So long as we atomically load page table pointers versus teardown,
- * we can follow the address down to the the page and take a ref on it.
- */
- local_irq_save(flags);
-
- pgdp = pgd_offset(mm, addr);
- do {
- pgd_t pgd = ACCESS_ONCE(*pgdp);
-
- pr_devel(" %016lx: normal pgd %p\n", addr,
- (void *)pgd_val(pgd));
- next = pgd_addr_end(addr, end);
- if (pgd_none(pgd))
- break;
- if (pgd_huge(pgd)) {
- if (!gup_hugepte((pte_t *)pgdp, PGDIR_SIZE, addr, next,
- write, pages, &nr))
- break;
- } else if (is_hugepd(pgdp)) {
- if (!gup_hugepd((hugepd_t *)pgdp, PGDIR_SHIFT,
- addr, next, write, pages, &nr))
- break;
- } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
- break;
- } while (pgdp++, addr = next, addr != end);
-
- local_irq_restore(flags);
-
- return nr;
-}
-
-int get_user_pages_fast(unsigned long start, int nr_pages, int write,
- struct page **pages)
-{
- struct mm_struct *mm = current->mm;
- int nr, ret;
-
- start &= PAGE_MASK;
- nr = __get_user_pages_fast(start, nr_pages, write, pages);
- ret = nr;
-
- if (nr < nr_pages) {
- pr_devel(" slow path ! nr = %d\n", nr);
-
- /* Try to get the remaining pages with get_user_pages */
- start += nr << PAGE_SHIFT;
- pages += nr;
-
- down_read(&mm->mmap_sem);
- ret = get_user_pages(current, mm, start,
- nr_pages - nr, write, 0, pages, NULL);
- up_read(&mm->mmap_sem);
-
- /* Have to be a bit careful with return values */
- if (nr > 0) {
- if (ret < 0)
- ret = nr;
- else
- ret += nr;
- }
- }
-
- return ret;
-}
-
-#endif /* __HAVE_ARCH_PTE_SPECIAL */
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 7e70ae968e5f..b8d228ca50fd 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -230,7 +230,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz
if (hugepd_none(*hpdp) && __hugepte_alloc(mm, hpdp, addr, pdshift, pshift))
return NULL;

- return hugepte_offset(hpdp, addr, pdshift);
+ return hugepte_offset(*hpdp, addr, pdshift);
}

#else
@@ -270,7 +270,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz
if (hugepd_none(*hpdp) && __hugepte_alloc(mm, hpdp, addr, pdshift, pshift))
return NULL;

- return hugepte_offset(hpdp, addr, pdshift);
+ return hugepte_offset(*hpdp, addr, pdshift);
}
#endif

@@ -538,7 +538,7 @@ static void hugetlb_free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
do {
pmd = pmd_offset(pud, addr);
next = pmd_addr_end(addr, end);
- if (!is_hugepd(pmd)) {
+ if (!is_hugepd(__hugepd(pmd_val(*pmd)))) {
/*
* if it is not hugepd pointer, we should already find
* it cleared.
@@ -587,7 +587,7 @@ static void hugetlb_free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
do {
pud = pud_offset(pgd, addr);
next = pud_addr_end(addr, end);
- if (!is_hugepd(pud)) {
+ if (!is_hugepd(__hugepd(pud_val(*pud)))) {
if (pud_none_or_clear_bad(pud))
continue;
hugetlb_free_pmd_range(tlb, pud, addr, next, floor,
@@ -653,7 +653,7 @@ void hugetlb_free_pgd_range(struct mmu_gather *tlb,
do {
next = pgd_addr_end(addr, end);
pgd = pgd_offset(tlb->mm, addr);
- if (!is_hugepd(pgd)) {
+ if (!is_hugepd(__hugepd(pgd_val(*pgd)))) {
if (pgd_none_or_clear_bad(pgd))
continue;
hugetlb_free_pud_range(tlb, pgd, addr, next, floor, ceiling);
@@ -713,18 +713,17 @@ static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
return (__boundary - 1 < end - 1) ? __boundary : end;
}

-int gup_hugepd(hugepd_t *hugepd, unsigned pdshift,
- unsigned long addr, unsigned long end,
- int write, struct page **pages, int *nr)
+int gup_hugepd(hugepd_t hugepd, unsigned long addr, unsigned pdshift,
+ unsigned long end, int write, struct page **pages, int *nr)
{
pte_t *ptep;
- unsigned long sz = 1UL << hugepd_shift(*hugepd);
+ unsigned long sz = 1UL << hugepd_shift(hugepd);
unsigned long next;

ptep = hugepte_offset(hugepd, addr, pdshift);
do {
next = hugepte_addr_end(addr, end, sz);
- if (!gup_hugepte(ptep, sz, addr, end, write, pages, nr))
+ if (!gup_huge_pte(*ptep, ptep, addr, sz, end, write, pages, nr))
return 0;
} while (ptep++, addr = next, addr != end);

@@ -961,7 +960,7 @@ pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, unsigned *shift
else if (pgd_huge(pgd)) {
ret_pte = (pte_t *) pgdp;
goto out;
- } else if (is_hugepd(&pgd))
+ } else if (is_hugepd(__hugepd(pgd_val(pgd))))
hpdp = (hugepd_t *)&pgd;
else {
/*
@@ -978,7 +977,7 @@ pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, unsigned *shift
else if (pud_huge(pud)) {
ret_pte = (pte_t *) pudp;
goto out;
- } else if (is_hugepd(&pud))
+ } else if (is_hugepd(__hugepd(pud_val(pud))))
hpdp = (hugepd_t *)&pud;
else {
pdshift = PMD_SHIFT;
@@ -999,7 +998,7 @@ pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, unsigned *shift
if (pmd_huge(pmd) || pmd_large(pmd)) {
ret_pte = (pte_t *) pmdp;
goto out;
- } else if (is_hugepd(&pmd))
+ } else if (is_hugepd(__hugepd(pmd_val(pmd))))
hpdp = (hugepd_t *)&pmd;
else
return pte_offset_kernel(&pmd, ea);
@@ -1008,7 +1007,7 @@ pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea, unsigned *shift
if (!hpdp)
return NULL;

- ret_pte = hugepte_offset(hpdp, ea, pdshift);
+ ret_pte = hugepte_offset(*hpdp, ea, pdshift);
pdshift = hugepd_shift(*hpdp);
out:
if (shift)

--
1.9.1

Steve Capper

2014-10-16 09:25:30 UTC

Permalink

Update generic gup implementation with powerpc specific details.
On powerpc at pmd level we can have hugepte, normal pmd pointer
or a pointer to the hugepage directory.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>

Hi,
This patch causes compiler errors on arm and arm64 due to pgd_huge
being undefined. I've attached a fixup below, this fixup will require
that #define pgd_huge(pgd) 0 be added back into:
arch/powerpc/include/asm/page.h
For the second patch in this series.

Another avenue would be to do something like:
#ifndef pgd_huge
#define pgd_huge(pgd) (0)
#endif

Then no changes would be required to arm and arm64 (or other
architectures).

To help with bisectability, could we please have a suitable fix applied
to the two patches in the -mm tree:
http://ozlabs.org/~akpm/mmots/broken-out/mm-update-generic-gup-implementation-to-handle-hugepage-directory.patch
http://ozlabs.org/~akpm/mmots/broken-out/arch-powerpc-switch-to-generic-rcu-get_user_pages_fast.patch

rather than applied afterwards?

With pgd_huge(x) defined, this patch passes my futex test on arm
(Arndale platform) and arm64(Juno).

Cheers,

--
Steve

Aneesh Kumar K.V

2014-10-16 15:18:20 UTC

Permalink

Post by Steve Capper

Hi,
This patch causes compiler errors on arm and arm64 due to pgd_huge
being undefined. I've attached a fixup below, this fixup will require
arch/powerpc/include/asm/page.h
For the second patch in this series.
#ifndef pgd_huge
#define pgd_huge(pgd) (0)
#endif
Then no changes would be required to arm and arm64 (or other
architectures).
To help with bisectability, could we please have a suitable fix applied
http://ozlabs.org/~akpm/mmots/broken-out/mm-update-generic-gup-implementation-to-handle-hugepage-directory.patch
http://ozlabs.org/~akpm/mmots/broken-out/arch-powerpc-switch-to-generic-rcu-get_user_pages_fast.patch
rather than applied afterwards?
With pgd_huge(x) defined, this patch passes my futex test on arm
(Arndale platform) and arm64(Juno).
Cheers,
--
Steve
From 2fb7b0308f0aca94c50611257ba82d656abb0768 Mon Sep 17 00:00:00 2001
From: Steve Capper <steve.capper at linaro.org>
Date: Thu, 16 Oct 2014 09:09:48 +0100
Subject: [PATCH] Fixup for Update generic gup implementation
mm: Update generic gup implementation to handle hugepage directory
will not compile for arm or arm64 due to pgd_huge being undefined.
Signed-off-by: Steve Capper <steve.capper at linaro.org>
---
arch/arm/include/asm/pgtable.h | 2 ++
arch/arm64/include/asm/pgtable.h | 2 ++
include/linux/hugetlb.h | 1 -
3 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index 90aa4583..46f81fb 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -181,6 +181,8 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
/* to find an entry in a kernel page-table-directory */
#define pgd_offset_k(addr) pgd_offset(&init_mm, addr)
+#define pgd_huge(pgd) (0)
+
#define pmd_none(pmd) (!pmd_val(pmd))
#define pmd_present(pmd) (pmd_val(pmd))
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 464c5ce..d4462ca 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -462,6 +462,8 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
extern pgd_t idmap_pg_dir[PTRS_PER_PGD];
+#define pgd_huge(pgd) (0)
+
/*
* bits 0-1: present (must be zero)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 65e12a2..6e6d338 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -138,7 +138,6 @@ static inline void hugetlb_show_meminfo(void)
#define prepare_hugepage_range(file, addr, len) (-EINVAL)
#define pmd_huge(x) 0
#define pud_huge(x) 0
-#define pgd_huge(x) 0
#define is_hugepage_only_range(mm, addr, len) 0
#define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) ({BUG(); 0; })
#define hugetlb_fault(mm, vma, addr, flags) ({ BUG(); 0; })

don't do the last hunk, that will result in build failures on sub
platforms on ppc64. can you do the arm patch without making the change
to hugetlb.h ?

-aneesh

Steve Capper

2014-10-16 15:42:29 UTC

Permalink

Post by Aneesh Kumar K.V

Post by Steve Capper

don't do the last hunk, that will result in build failures on sub
platforms on ppc64. can you do the arm patch without making the change
to hugetlb.h ?

Hi Aneesh,

The problem with leaving the empty pgd_huge in hugetlb.h is that we
would then have to resort to patterns like this for both arm and arm64:

#ifdef CONFIG_HUGETLB_PAGE
#define pgd_huge(pgd) (0)
#endif

If possible, I'd much rather just have:
#define pgd_huge(pgd) (0)

After the second patch in this series we already have the following
code pattern in arch/powerpc/include/asm/page.h:

#define is_hugepd(hpd) (hugepd_ok(hpd))
int pgd_huge(pgd_t pgd);
#else /* CONFIG_HUGETLB_PAGE */
#define is_hugepd(pdep) 0
#endif /* CONFIG_HUGETLB_PAGE */
#define __hugepd(x) ((hugepd_t) { (x) })

Can we not just add a:
#define pgd_huge(pgd) (0)
above the "#endif /* CONFIG_HUGETLB_PAGE */" line in the second patch?
(or, more precisely, prevent the second patch from removing this line).

That way we get a clearer code overall?

Cheers,

--
Steve

Aneesh Kumar K.V

2014-10-16 18:05:10 UTC

Permalink

Post by Steve Capper
#define pgd_huge(pgd) (0)
above the "#endif /* CONFIG_HUGETLB_PAGE */" line in the second patch?
(or, more precisely, prevent the second patch from removing this line).
That way we get a clearer code overall?

it is strange to have both pmd_huge and pud_huge in hugetlb.h and
pgd_huge in page.h. But if that is what we want then we may need.

diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
index aa430ec14895..aeca81947dc6 100644
--- a/arch/powerpc/include/asm/page.h
+++ b/arch/powerpc/include/asm/page.h
@@ -383,6 +383,7 @@ static inline int hugepd_ok(hugepd_t hpd)
int pgd_huge(pgd_t pgd);
#else /* CONFIG_HUGETLB_PAGE */
#define is_hugepd(pdep) 0
+#define pgd_huge(pgd) 0
#endif /* CONFIG_HUGETLB_PAGE */
#define __hugepd(x) ((hugepd_t) { (x) })