Re: [PATCH 09/22] HWPOISON: Handle hardware poisoned pages intry_to_unmap

[Minchan Kim]

On Mon, 15 Jun 2009 23:26:12 +0800
Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:

> On Mon, Jun 15, 2009 at 09:09:03PM +0800, Minchan Kim wrote:
> > On Mon, Jun 15, 2009 at 11:45 AM, Wu Fengguang<fengguang.wu@xxxxxxxxx> wrote:
> > > From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> > >
> > > When a page has the poison bit set replace the PTE with a poison entry.
> > > This causes the right error handling to be done later when a process runs
> > > into it.
> > >
> > > Also add a new flag to not do that (needed for the memory-failure handler
> > > later)
> > >
> > > Reviewed-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> > > Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> > >
> > > ---
> > > Âinclude/linux/rmap.h | Â Â1 +
> > > Âmm/rmap.c      Â|  Â9 ++++++++-
> > > Â2 files changed, 9 insertions(+), 1 deletion(-)
> > >
> > > --- sound-2.6.orig/mm/rmap.c
> > > +++ sound-2.6/mm/rmap.c
> > > @@ -958,7 +958,14 @@ static int try_to_unmap_one(struct page
> > > Â Â Â Â/* Update high watermark before we lower rss */
> > > Â Â Â Âupdate_hiwater_rss(mm);
> > >
> > > - Â Â Â if (PageAnon(page)) {
> > > + Â Â Â if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
> > > + Â Â Â Â Â Â Â if (PageAnon(page))
> > > + Â Â Â Â Â Â Â Â Â Â Â dec_mm_counter(mm, anon_rss);
> > > + Â Â Â Â Â Â Â else if (!is_migration_entry(pte_to_swp_entry(*pte)))
> > 
> > Isn't it straightforward to use !is_hwpoison_entry ?
> 
> Good catch!  It looks like a redundant check: the
> page_check_address() at the beginning of the function guarantees that 
> !is_migration_entry() or !is_migration_entry() tests will all be TRUE.
> So let's do this?
It seems you expand my sight :)

I don't know migration well.
How page_check_address guarantee it's not migration entry ? 

In addtion, If the page is poison while we are going to migration((PAGE_MIGRATION && migration) == TRUE), we should decrease file_rss ?

> 
> - Â Â Â Â Â Â Â else if (!is_migration_entry(pte_to_swp_entry(*pte)))
> + Â Â Â Â Â Â Â else
> 
> 
> Thanks,
> Fengguang


-- 
Kinds Regards
Minchan Kim
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