linux-kernel - RE: [PATCH V2] fork: Improve error message for corrupted page tables

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Message-ID: <FFF73D592F13FD46B8700F0A279B802F4FA16F3E@ORSMSX114.amr.corp.intel.com>
Date:   Tue, 6 Aug 2019 16:11:34 +0000
From:   "Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>
To:     Anshuman Khandual <anshuman.khandual@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
CC:     "Hansen, Dave" <dave.hansen@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: RE: [PATCH V2] fork: Improve error message for corrupted page tables

> >> Without patch:
> >> --------------
> >> [  204.836425] mm/pgtable-generic.c:29: bad p4d
> >> 0000000089eb4e92(800000025f941467)
> >> [  204.836544] BUG: Bad rss-counter state mm:00000000f75895ea idx:0
> >> val:2 [  204.836615] BUG: Bad rss-counter state mm:00000000f75895ea
> >> idx:1 val:5 [  204.836685] BUG: non-zero pgtables_bytes on freeing
> >> mm: 20480
> >>
> >> With patch:
> >> -----------
> >> [   69.815453] mm/pgtable-generic.c:29: bad p4d
> 0000000084653642(800000025ca37467)
> >> [   69.815872] BUG: Bad rss-counter state mm:00000000014a6c03
> type:MM_FILEPAGES val:2
> >> [   69.815962] BUG: Bad rss-counter state mm:00000000014a6c03
> type:MM_ANONPAGES val:5
> >> [   69.816050] BUG: non-zero pgtables_bytes on freeing mm: 20480
> >>
> >> Also, change print function (from printk(KERN_ALERT, ..) to
> >> pr_alert()) so that it matches the other print statement.
> >>
> >> Cc: Ingo Molnar <mingo@...nel.org>
> >> Cc: Vlastimil Babka <vbabka@...e.cz>
> >> Cc: Peter Zijlstra <peterz@...radead.org>
> >> Cc: Andrew Morton <akpm@...ux-foundation.org>
> >> Cc: Anshuman Khandual <anshuman.khandual@....com>
> >> Acked-by: Dave Hansen <dave.hansen@...el.com>
> >> Suggested-by: Dave Hansen <dave.hansen@...el.com>
> >> Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
> >
> > Acked-by: Vlastimil Babka <vbabka@...e.cz>
> >
> > I would also add something like this to reduce risk of breaking it in
> > the
> > future:
> >
> > ----8<----
> > diff --git a/include/linux/mm_types_task.h
> > b/include/linux/mm_types_task.h index d7016dcb245e..a6f83cbe4603
> > 100644
> > --- a/include/linux/mm_types_task.h
> > +++ b/include/linux/mm_types_task.h
> > @@ -36,6 +36,9 @@ struct vmacache {
> >  	struct vm_area_struct *vmas[VMACACHE_SIZE];  };
> >
> > +/*
> > + * When touching this, update also resident_page_types in
> > +kernel/fork.c  */
> >  enum {
> >  	MM_FILEPAGES,	/* Resident file mapping pages */
> >  	MM_ANONPAGES,	/* Resident anonymous pages */
> >
> 
> Agreed and with that
> 
> Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>

Thanks for the review and helping me in improving the patch :)

Regards,
Sai