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SubjectRe: [PATCH v2 2/2] mm/memory-failure.c: Don't access uninitialized memmaps in memory_failure()
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On Wed, Oct 09, 2019 at 04:24:35PM +0200, David Hildenbrand wrote:
> We should check for pfn_to_online_page() to not access uninitialized
> memmaps. Reshuffle the code so we don't have to duplicate the error
> message.
>
> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@kernel.org>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> mm/memory-failure.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 7ef849da8278..e866e6e5660b 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1253,17 +1253,19 @@ int memory_failure(unsigned long pfn, int flags)
> if (!sysctl_memory_failure_recovery)
> panic("Memory failure on page %lx", pfn);
>
> - if (!pfn_valid(pfn)) {
> + p = pfn_to_online_page(pfn);
> + if (!p) {
> + if (pfn_valid(pfn)) {
> + pgmap = get_dev_pagemap(pfn, NULL);
> + if (pgmap)
> + return memory_failure_dev_pagemap(pfn, flags,
> + pgmap);
> + }
> pr_err("Memory failure: %#lx: memory outside kernel control\n",
> pfn);
> return -ENXIO;
> }
>
> - pgmap = get_dev_pagemap(pfn, NULL);
> - if (pgmap)
> - return memory_failure_dev_pagemap(pfn, flags, pgmap);
> -
> - p = pfn_to_page(pfn);

This change seems to assume that memory_failure_dev_pagemap() is never
called for online pages. Is it an intended behavior?
Or the concept "online pages" is not applicable to zone device pages?

Thanks,
Naoya Horiguchi

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