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

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]

> I was under the impression that this bug was potentially solved. From openSUS
> E,
> I know that a similar class of bug was fixed by at least 5.1.9 and comment 23
> indicates that for one user at least, this bug has disappeared. Can you confi
> rm
> whether the latest 5.1 -stable kernel is ok for you or are you still seeing
> problems? If so, can you repost the latest oops on a recent kernel so I can t
> ry
> determine if it's a similar or different bug. Thanks.


just tried a firefox build with 5.1.14 and didn't experience any problem

However, I wouldn't close this before I can successfully complete some
more tests, which I plan to do immediately

I'll report both in case I'll find problems again and also if everything
goes well (so that the issue can be closed with reasonable confidence)

thanks a lot

ciao
-g

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]

> That's fine. Thanks for doing the preliminary test and either report a proble
> m
> or close the bug whenever you feel it's appropriate.

OK: I've performed a number of tests and all passed fine, so I close
this

the problem seems to be solved, AFAICS, at least since 5.1.14 (I have
run the tests with both 5.1.14 and 5.1.15)

thanks again for your valuable help and work

ciao
-g

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]

> 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