Messages in this thread |  | | | Date | Thu, 7 Jan 2010 14:39:02 +0900 | | From | KAMEZAWA Hiroyuki <> | | Subject | Re: [RFC][PATCH] vmalloc: simplify vread()/vwrite() |
| |
On Thu, 7 Jan 2010 13:24:03 +0800 Wu Fengguang <fengguang.wu@intel.com> wrote:
> On Thu, Jan 07, 2010 at 11:23:04AM +0800, KAMEZAWA Hiroyuki wrote: > > On Thu, 07 Jan 2010 11:15:41 +0800 > > Huang Ying <ying.huang@intel.com> wrote: > > > > > > > > > > > > > The page_is_ram() check is necessary because kmap_atomic() is not > > > > > > designed to work with non-RAM pages. > > > > > > > > > > > I think page_is_ram() is not a complete method...on x86, it just check > > > > > e820's memory range. checking VM_IOREMAP is better, I think. > > > > > > > > (double check) Not complete or not safe? > > > > > > > > EFI seems to not update e820 table by default. Ying, do you know why? > > > > > > In EFI system, E820 table is constructed from EFI memory map in boot > > > loader, so I think you can rely on E820 table. > > > > > Yes, we can rely on. But concerns here is that we cannot get any > > information of ioremap via e820 map. > > > > But yes, > > == ioremap() > > 140 for (pfn = phys_addr >> PAGE_SHIFT; > > 141 (pfn << PAGE_SHIFT) < (last_addr & PAGE_MASK); > > 142 pfn++) { > > 143 > > 144 int is_ram = page_is_ram(pfn); > > 145 > > 146 if (is_ram && pfn_valid(pfn) && !PageReserved(pfn_to_page(pfn))) > > 147 return NULL; > > 148 WARN_ON_ONCE(is_ram); > > 149 } > > == > > you'll get warned before access if "ram" area is remapped... > > Right. > > > But, about this patch, it seems that page_is_ram() is not free from architecture > > dependecy. > > Yes this is a problem. We can provide a generic page_is_ram() as below. > And could further convert the existing x86 (and others) page_is_ram() > to be resource-based -- since at least for now the e820 table won't be > updated on memory hotplug. > > Thanks, > Fengguang
seems nice :)
Thanks, -Kame
> --- > include/linux/ioport.h | 2 ++ > kernel/resource.c | 18 ++++++++++++++++++ > 2 files changed, 20 insertions(+) > > --- linux-mm.orig/kernel/resource.c 2010-01-07 12:40:55.000000000 +0800 > +++ linux-mm/kernel/resource.c 2010-01-07 13:13:46.000000000 +0800 > @@ -297,6 +297,24 @@ int walk_system_ram_range(unsigned long > > #endif > > +static int __page_is_ram(unsigned long pfn, unsigned long nr_pages, void *arg) > +{ > + int *is_ram = arg; > + > + *is_ram = 1; > + > + return 1; > +} > + > +int __attribute__((weak)) page_is_ram(unsigned long pagenr) > +{ > + int is_ram = 0; > + > + walk_system_ram_range(pagenr, 1, &is_ram, __page_is_ram); > + > + return is_ram; > +} > + > /* > * Find empty slot in the resource tree given range and alignment. > */ > --- linux-mm.orig/include/linux/ioport.h 2010-01-07 13:11:43.000000000 +0800 > +++ linux-mm/include/linux/ioport.h 2010-01-07 13:12:37.000000000 +0800 > @@ -188,5 +188,7 @@ extern int > walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages, > void *arg, int (*func)(unsigned long, unsigned long, void *)); > > +extern int page_is_ram(unsigned long pagenr); > + > #endif /* __ASSEMBLY__ */ > #endif /* _LINUX_IOPORT_H */ >
|  |