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Message-ID: <4FEA9A0D.4020000@kernel.org>
Date: Wed, 27 Jun 2012 14:28:45 +0900
From: Minchan Kim <minchan@...nel.org>
To: Seth Jennings <sjenning@...ux.vnet.ibm.com>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
devel@...verdev.osuosl.org,
Dan Magenheimer <dan.magenheimer@...cle.com>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Andrew Morton <akpm@...ux-foundation.org>,
Robert Jennings <rcj@...ux.vnet.ibm.com>,
Nitin Gupta <ngupta@...are.org>
Subject: Re: [PATCH 2/3] zsmalloc: add generic path and remove x86 dependency
On 06/26/2012 01:14 AM, Seth Jennings wrote:
> This patch adds generic pages mapping methods that
> work on all archs in the absence of support for
> local_tlb_flush_kernel_range() advertised by the
> arch through __HAVE_LOCAL_TLB_FLUSH_KERNEL_RANGE
>
> Signed-off-by: Seth Jennings <sjenning@...ux.vnet.ibm.com>
Sorry for handling this issue recently.
I like the patch.
Some comment below.
> ---
> drivers/staging/zsmalloc/Kconfig | 4 -
> drivers/staging/zsmalloc/zsmalloc-main.c | 136 ++++++++++++++++++++++++------
> drivers/staging/zsmalloc/zsmalloc_int.h | 5 +-
> 3 files changed, 115 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/staging/zsmalloc/Kconfig b/drivers/staging/zsmalloc/Kconfig
> index a5ab720..9084565 100644
> --- a/drivers/staging/zsmalloc/Kconfig
> +++ b/drivers/staging/zsmalloc/Kconfig
> @@ -1,9 +1,5 @@
> config ZSMALLOC
> tristate "Memory allocator for compressed pages"
> - # X86 dependency is because of the use of __flush_tlb_one and set_pte
> - # in zsmalloc-main.c.
> - # TODO: convert these to portable functions
> - depends on X86
> default n
> help
> zsmalloc is a slab-based memory allocator designed to store
> diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
> index 10b0d60..14f04d8 100644
> --- a/drivers/staging/zsmalloc/zsmalloc-main.c
> +++ b/drivers/staging/zsmalloc/zsmalloc-main.c
> @@ -470,28 +470,116 @@ static struct page *find_get_zspage(struct size_class *class)
> return page;
> }
>
> +#ifdef __HAVE_LOCAL_FLUSH_TLB_KERNEL_RANGE
As you already mentioned, __HAVE_ARCH_LOCAL_XXX
> +static inline int zs_arch_cpu_up(struct mapping_area *area)
Why should function's name represent arch dependent?
IMHO, it would be better to use just zs_cpu_up.
> +{
> + if (area->vm)
> + return 0;
Just out of curiosity.
When do we need above check?
> + area->vm = alloc_vm_area(PAGE_SIZE * 2, NULL);
> + if (!area->vm)
> + return -ENOMEM;
> + return 0;
> +}
> +
> +static inline void zs_arch_cpu_down(struct mapping_area *area)
Ditto.
> +{
> + if (area->vm)
> + free_vm_area(area->vm);
> + area->vm = NULL;
> +}
> +
> +static inline void zs_arch_map_object(struct mapping_area *area,
> + struct page *pages[2], int off, int size)
> +{
> + BUG_ON(map_vm_area(area->vm, PAGE_KERNEL, &pages));
I think we need some comment about why map_vm_area must not fail.
I used below comment in my patch.
+ /*
+ * map_vm_area never fail because we already allocated
+ * pages for page table in alloc_vm_area.
+ */
> + area->vm_addr = area->vm->addr;
> +}
> +
> +static inline void zs_arch_unmap_object(struct mapping_area *area,
> + struct page *pages[2], int off, int size)
> +{
> + unsigned long addr = (unsigned long)area->vm_addr;
> + unsigned long end = addr + (PAGE_SIZE * 2);
> +
> + flush_cache_vunmap(addr, end);
> + unmap_kernel_range_noflush(addr, PAGE_SIZE * 2);
> + local_flush_tlb_kernel_range(addr, end);
> +}
> +#else
> +static inline int zs_arch_cpu_up(struct mapping_area *area)
> +{
> + if (area->vm_buf)
> + return 0;
> + area->vm_buf = (char *)__get_free_pages(GFP_KERNEL, 1);
> + if (!area->vm_buf)
> + return -ENOMEM;
> + return 0;
> +}
> +
> +static inline void zs_arch_cpu_down(struct mapping_area *area)
> +{
> + if (area->vm_buf)
> + free_pages((unsigned long)area->vm_buf, 1);
> + area->vm_buf = NULL;
> +}
> +
> +static void zs_arch_map_object(struct mapping_area *area,
> + struct page *pages[2], int off, int size)
How about just void __zs_map_object?
Anyway, it's just preference and I am not strong against.
> +{
> + int sizes[2];
> + char *buf = area->vm_buf + off;
> + void *addr;
> +
> + sizes[0] = PAGE_SIZE - off;
> + sizes[1] = size - sizes[0];
> +
> + /* copy object to temp buffer */
> + addr = kmap_atomic(pages[0]);
> + memcpy(buf, addr + off, sizes[0]);
> + kunmap_atomic(addr);
> + addr = kmap_atomic(pages[1]);
> + memcpy(buf + sizes[0], addr, sizes[1]);
> + kunmap_atomic(addr);
> + area->vm_addr = area->vm_buf;
> +}
> +
> +static void zs_arch_unmap_object(struct mapping_area *area,
> + struct page *pages[2], int off, int size)
> +{
> + int sizes[2];
> + char *buf = area->vm_buf + off;
> + void *addr;
> +
> + sizes[0] = PAGE_SIZE - off;
> + sizes[1] = size - sizes[0];
> +
> + /* copy temp buffer to obj*/
> + addr = kmap_atomic(pages[0]);
> + memcpy(addr + off, buf, sizes[0]);
> + kunmap_atomic(addr);
> + addr = kmap_atomic(pages[1]);
> + memcpy(addr, buf + sizes[0], sizes[1]);
> + kunmap_atomic(addr);
> +}
> +#endif
>
> static int zs_cpu_notifier(struct notifier_block *nb, unsigned long action,
> void *pcpu)
> {
> - int cpu = (long)pcpu;
> + int ret, cpu = (long)pcpu;
> struct mapping_area *area;
>
> switch (action) {
> case CPU_UP_PREPARE:
> area = &per_cpu(zs_map_area, cpu);
> - if (area->vm)
> - break;
> - area->vm = alloc_vm_area(2 * PAGE_SIZE, area->vm_ptes);
> - if (!area->vm)
> - return notifier_from_errno(-ENOMEM);
> + ret = zs_arch_cpu_up(area);
> + if (ret)
> + return notifier_from_errno(ret);
> break;
> case CPU_DEAD:
> case CPU_UP_CANCELED:
> area = &per_cpu(zs_map_area, cpu);
> - if (area->vm)
> - free_vm_area(area->vm);
> - area->vm = NULL;
> + zs_arch_cpu_down(area);
> break;
> }
>
> @@ -716,19 +804,14 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle)
> area->vm_addr = kmap_atomic(page);
> } else {
> /* this object spans two pages */
> - struct page *nextp;
> -
> - nextp = get_next_page(page);
> - BUG_ON(!nextp);
> + struct page *pages[2];
>
> + pages[0] = page;
> + pages[1] = get_next_page(page);
> + BUG_ON(!pages[1]);
>
> - set_pte(area->vm_ptes[0], mk_pte(page, PAGE_KERNEL));
> - set_pte(area->vm_ptes[1], mk_pte(nextp, PAGE_KERNEL));
> -
> - /* We pre-allocated VM area so mapping can never fail */
> - area->vm_addr = area->vm->addr;
> + zs_arch_map_object(area, pages, off, class->size);
> }
> -
> return area->vm_addr + off;
> }
> EXPORT_SYMBOL_GPL(zs_map_object);
> @@ -751,13 +834,16 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
> off = obj_idx_to_offset(page, obj_idx, class->size);
>
> area = &__get_cpu_var(zs_map_area);
> - if (off + class->size <= PAGE_SIZE) {
> + if (off + class->size <= PAGE_SIZE)
> kunmap_atomic(area->vm_addr);
> - } else {
> - set_pte(area->vm_ptes[0], __pte(0));
> - set_pte(area->vm_ptes[1], __pte(0));
> - __flush_tlb_one((unsigned long)area->vm_addr);
> - __flush_tlb_one((unsigned long)area->vm_addr + PAGE_SIZE);
> + else {
> + struct page *pages[2];
> +
> + pages[0] = page;
> + pages[1] = get_next_page(page);
> + BUG_ON(!pages[1]);
> +
> + zs_arch_unmap_object(area, pages, off, class->size);
> }
> put_cpu_var(zs_map_area);
> }
> diff --git a/drivers/staging/zsmalloc/zsmalloc_int.h b/drivers/staging/zsmalloc/zsmalloc_int.h
> index 6fd32a9..8a6887e 100644
> --- a/drivers/staging/zsmalloc/zsmalloc_int.h
> +++ b/drivers/staging/zsmalloc/zsmalloc_int.h
> @@ -110,8 +110,11 @@ enum fullness_group {
> static const int fullness_threshold_frac = 4;
>
> struct mapping_area {
> +#ifdef __HAVE_LOCAL_FLUSH_TLB_KERNEL_RANGE
> struct vm_struct *vm;
> - pte_t *vm_ptes[2];
> +#else
> + char *vm_buf;
> +#endif
> char *vm_addr;
> };
Need comment about vm_buf and vm_addr.
Thanks, Seth.
--
Kind regards,
Minchan Kim
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