lkml.org 
[lkml]   [2018]   [Jul]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: [PATCH v1 2/2] mm: soft-offline: close the race against page allocation
    Date
    On Fri, Jul 13, 2018 at 01:40:02PM -0700, Andrew Morton wrote:
    > On Fri, 13 Jul 2018 12:26:06 +0900 Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote:
    >
    > > A process can be killed with SIGBUS(BUS_MCEERR_AR) when it tries to
    > > allocate a page that was just freed on the way of soft-offline.
    > > This is undesirable because soft-offline (which is about corrected error)
    > > is less aggressive than hard-offline (which is about uncorrected error),
    > > and we can make soft-offline fail and keep using the page for good reason
    > > like "system is busy."
    > >
    > > Two main changes of this patch are:
    > >
    > > - setting migrate type of the target page to MIGRATE_ISOLATE. As done
    > > in free_unref_page_commit(), this makes kernel bypass pcplist when
    > > freeing the page. So we can assume that the page is in freelist just
    > > after put_page() returns,
    > >
    > > - setting PG_hwpoison on free page under zone->lock which protects
    > > freelists, so this allows us to avoid setting PG_hwpoison on a page
    > > that is decided to be allocated soon.
    > >
    > >
    > > ...
    > >
    > > +
    > > +#ifdef CONFIG_MEMORY_FAILURE
    > > +/*
    > > + * Set PG_hwpoison flag if a given page is confirmed to be a free page
    > > + * within zone lock, which prevents the race against page allocation.
    > > + */
    >
    > I think this is clearer?
    >
    > --- a/mm/page_alloc.c~mm-soft-offline-close-the-race-against-page-allocation-fix
    > +++ a/mm/page_alloc.c
    > @@ -8039,8 +8039,9 @@ bool is_free_buddy_page(struct page *pag
    >
    > #ifdef CONFIG_MEMORY_FAILURE
    > /*
    > - * Set PG_hwpoison flag if a given page is confirmed to be a free page
    > - * within zone lock, which prevents the race against page allocation.
    > + * Set PG_hwpoison flag if a given page is confirmed to be a free page. This
    > + * test is performed under the zone lock to prevent a race against page
    > + * allocation.

    Yes, I like it.

    Thanks,
    Naoya Horiguchi

    \
     
     \ /
      Last update: 2018-07-17 02:34    [W:4.439 / U:0.200 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site