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Date: Mon, 14 Oct 2013 18:44:03 +0300 (EEST)
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Max Filippov <jcmvbkbc@...il.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Peter Zijlstra <peterz@...radead.org>,
Chris Zankel <chris@...kel.net>,
Christoph Lameter <cl@...ux-foundation.org>,
Pekka Enberg <penberg@...nel.org>,
Matt Mackall <mpm@...enic.com>,
LKML <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
Linux-Arch <linux-arch@...r.kernel.org>,
"linux-xtensa@...ux-xtensa.org" <linux-xtensa@...ux-xtensa.org>
Subject: Re: [PATCHv2 2/2] xtensa: use buddy allocator for PTE table
Max Filippov wrote:
> On Mon, Oct 14, 2013 at 6:32 PM, Kirill A. Shutemov
> <kirill.shutemov@...ux.intel.com> wrote:
> > At the moment xtensa uses slab allocator for PTE table. It doesn't work
> > with enabled split page table lock: slab uses page->slab_cache and
> > page->first_page for its pages. These fields share stroage with
> > page->ptl.
> >
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > Cc: Chris Zankel <chris@...kel.net>
> > Cc: Max Filippov <jcmvbkbc@...il.com>
> > ---
> > v2:
> > - add missed return in pte_alloc_one_kernel;
> >
> > arch/xtensa/include/asm/pgalloc.h | 20 ++++++++++++--------
> > arch/xtensa/include/asm/pgtable.h | 3 +--
> > arch/xtensa/mm/mmu.c | 20 --------------------
> > 3 files changed, 13 insertions(+), 30 deletions(-)
> >
> > diff --git a/arch/xtensa/include/asm/pgalloc.h b/arch/xtensa/include/asm/pgalloc.h
> > index b8774f1e21..8507b32d6e 100644
> > --- a/arch/xtensa/include/asm/pgalloc.h
> > +++ b/arch/xtensa/include/asm/pgalloc.h
> > @@ -38,14 +38,18 @@ static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
> > free_page((unsigned long)pgd);
> > }
> >
> > -/* Use a slab cache for the pte pages (see also sparc64 implementation) */
> > -
> > -extern struct kmem_cache *pgtable_cache;
> > -
> > static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm,
> > unsigned long address)
> > {
> > - return kmem_cache_alloc(pgtable_cache, GFP_KERNEL|__GFP_REPEAT);
> > + pte_t *ptep;
> > + int i;
> > +
> > + ptep = (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT);
> > + if (!ptep)
> > + return NULL;
> > + for (i = 0; i < 1024; i++, ptep++)
> > + pte_clear(NULL, 0, ptep);
> > + return ptep;
>
> You're returning modified ptep, not the allocated one.
Erghh.. Stupid me.
Corrected patch below.
>From 0ba2ac687321f5ad7bac5f5c141da5b65b957fdc Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Date: Mon, 14 Oct 2013 13:38:21 +0300
Subject: [PATCHv3] xtensa: use buddy allocator for PTE table
At the moment xtensa uses slab allocator for PTE table. It doesn't work
with enabled split page table lock: slab uses page->slab_cache and
page->first_page for its pages. These fields share stroage with
page->ptl.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Chris Zankel <chris@...kel.net>
Cc: Max Filippov <jcmvbkbc@...il.com>
---
v3:
- return correct value from pte_alloc_one_kernel();
v2:
- add missed return in pte_alloc_one_kernel();
arch/xtensa/include/asm/pgalloc.h | 20 ++++++++++++--------
arch/xtensa/include/asm/pgtable.h | 3 +--
arch/xtensa/mm/mmu.c | 20 --------------------
3 files changed, 13 insertions(+), 30 deletions(-)
diff --git a/arch/xtensa/include/asm/pgalloc.h b/arch/xtensa/include/asm/pgalloc.h
index b8774f1e21..d38eb9237e 100644
--- a/arch/xtensa/include/asm/pgalloc.h
+++ b/arch/xtensa/include/asm/pgalloc.h
@@ -38,14 +38,18 @@ static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
free_page((unsigned long)pgd);
}
-/* Use a slab cache for the pte pages (see also sparc64 implementation) */
-
-extern struct kmem_cache *pgtable_cache;
-
static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm,
unsigned long address)
{
- return kmem_cache_alloc(pgtable_cache, GFP_KERNEL|__GFP_REPEAT);
+ pte_t *ptep;
+ int i;
+
+ ptep = (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT);
+ if (!ptep)
+ return NULL;
+ for (i = 0; i < 1024; i++)
+ pte_clear(NULL, 0, ptep + i);
+ return ptep;
}
static inline pgtable_t pte_alloc_one(struct mm_struct *mm,
@@ -59,7 +63,7 @@ static inline pgtable_t pte_alloc_one(struct mm_struct *mm,
return NULL;
page = virt_to_page(pte);
if (!pgtable_page_ctor(page)) {
- kmem_cache_free(pgtable_cache, pte);
+ __free_page(page);
return NULL;
}
return page;
@@ -67,13 +71,13 @@ static inline pgtable_t pte_alloc_one(struct mm_struct *mm,
static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
{
- kmem_cache_free(pgtable_cache, pte);
+ free_page((unsigned long)pte);
}
static inline void pte_free(struct mm_struct *mm, pgtable_t pte)
{
pgtable_page_dtor(pte);
- kmem_cache_free(pgtable_cache, page_address(pte));
+ __free_page(pte);
}
#define pmd_pgtable(pmd) pmd_page(pmd)
diff --git a/arch/xtensa/include/asm/pgtable.h b/arch/xtensa/include/asm/pgtable.h
index 0fdf5d043f..216446295a 100644
--- a/arch/xtensa/include/asm/pgtable.h
+++ b/arch/xtensa/include/asm/pgtable.h
@@ -220,12 +220,11 @@ extern unsigned long empty_zero_page[1024];
#ifdef CONFIG_MMU
extern pgd_t swapper_pg_dir[PAGE_SIZE/sizeof(pgd_t)];
extern void paging_init(void);
-extern void pgtable_cache_init(void);
#else
# define swapper_pg_dir NULL
static inline void paging_init(void) { }
-static inline void pgtable_cache_init(void) { }
#endif
+static inline void pgtable_cache_init(void) { }
/*
* The pmd contains the kernel virtual address of the pte page.
diff --git a/arch/xtensa/mm/mmu.c b/arch/xtensa/mm/mmu.c
index a1077570e3..c43771c974 100644
--- a/arch/xtensa/mm/mmu.c
+++ b/arch/xtensa/mm/mmu.c
@@ -50,23 +50,3 @@ void __init init_mmu(void)
*/
set_ptevaddr_register(PGTABLE_START);
}
-
-struct kmem_cache *pgtable_cache __read_mostly;
-
-static void pgd_ctor(void *addr)
-{
- pte_t *ptep = (pte_t *)addr;
- int i;
-
- for (i = 0; i < 1024; i++, ptep++)
- pte_clear(NULL, 0, ptep);
-
-}
-
-void __init pgtable_cache_init(void)
-{
- pgtable_cache = kmem_cache_create("pgd",
- PAGE_SIZE, PAGE_SIZE,
- SLAB_HWCACHE_ALIGN,
- pgd_ctor);
-}
--
Kirill A. Shutemov
--
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