Re: [Bug 203715] BUG: unable to handle kernel NULL pointer dereference under stress (possibly related to https://lkml.org/lkml/2019/5/24/292 ?)

[balducci@units.it]

> Please try the following on top of 5.2-rc3
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 9e1b9acb116b..69f4ddfddfa4 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -277,8 +277,7 @@ __reset_isolation_pfn(struct zone *zone, unsigned long pf
> n,
> bool check_source,
>         }
>
>         /* Ensure the end of the pageblock or zone is online and valid */
> -       block_pfn += pageblock_nr_pages;
> -       block_pfn = min(block_pfn, zone_end_pfn(zone) - 1);
> +       block_pfn = min(pageblock_end_pfn(block_pfn), zone_end_pfn(zone) - 1)
> ;
>         end_page = pfn_to_online_page(block_pfn);
>         if (!end_page)
>                 return false;
> @@ -289,7 +288,7 @@ __reset_isolation_pfn(struct zone *zone, unsigned long pf
> n,
> bool check_source,
>          * is necessary for the block to be a migration source/target.
>          */
>         do {
> -               if (pfn_valid_within(pfn)) {
> +               if (pfn_valid(pfn)) {
>                         if (check_source && PageLRU(page)) {
>                                 clear_pageblock_skip(page);
>                                 return true;
>

no joy; I left the FF build running and found the machine frozen this
morning; however, firefox build could apparently complete successfully;
I can't say when exactly the problem happened, as I haven't found any
message in the logs

thanks
ciao
-g