Messages in this thread | | | Subject | Re: [PATCH V3 2/3] arm64/mm/hotplug: Enable MEM_OFFLINE event handling | From | Gavin Shan <> | Date | Wed, 23 Sep 2020 16:31:34 +1000 |
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Hi Anshuman,
On 9/21/20 10:05 PM, Anshuman Khandual wrote: > This enables MEM_OFFLINE memory event handling. It will help intercept any > possible error condition such as if boot memory some how still got offlined > even after an explicit notifier failure, potentially by a future change in > generic hot plug framework. This would help detect such scenarios and help > debug further. > > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.com> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: Marc Zyngier <maz@kernel.org> > Cc: Steve Capper <steve.capper@arm.com> > Cc: Mark Brown <broonie@kernel.org> > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > ---
I'm not sure if it makes sense since MEM_OFFLINE won't be triggered after NOTIFY_BAD is returned from MEM_GOING_OFFLINE. NOTIFY_BAD means the whole offline process is stopped. It would be guranteed by generic framework from syntax standpoint.
However, this looks good if MEM_OFFLINE is triggered without calling into MEM_GOING_OFFLINE previously, but it would be a bug from generic framework.
> arch/arm64/mm/mmu.c | 37 ++++++++++++++++++++++++++++++++----- > 1 file changed, 32 insertions(+), 5 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index df3b7415b128..6b171bd88bcf 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -1482,13 +1482,40 @@ static int prevent_bootmem_remove_notifier(struct notifier_block *nb, > unsigned long end_pfn = arg->start_pfn + arg->nr_pages; > unsigned long pfn = arg->start_pfn; > > - if (action != MEM_GOING_OFFLINE) > + if ((action != MEM_GOING_OFFLINE) && (action != MEM_OFFLINE)) > return NOTIFY_OK; > > - for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) { > - ms = __pfn_to_section(pfn); > - if (early_section(ms)) > - return NOTIFY_BAD; > + if (action == MEM_GOING_OFFLINE) { > + for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) { > + ms = __pfn_to_section(pfn); > + if (early_section(ms)) { > + pr_warn("Boot memory offlining attempted\n"); > + return NOTIFY_BAD; > + } > + } > + } else if (action == MEM_OFFLINE) { > + for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) { > + ms = __pfn_to_section(pfn); > + if (early_section(ms)) { > + > + /* > + * This should have never happened. Boot memory > + * offlining should have been prevented by this > + * very notifier. Probably some memory removal > + * procedure might have changed which would then > + * require further debug. > + */ > + pr_err("Boot memory offlined\n"); > + > + /* > + * Core memory hotplug does not process a return > + * code from the notifier for MEM_OFFLINE event. > + * Error condition has been reported. Report as > + * ignored. > + */ > + return NOTIFY_DONE; > + } > + } > } > return NOTIFY_OK; > } >
It's pretty much irrelevant comment if the patch doesn't make sense: the logical block for MEM_GOING_OFFLINE would be reused by MEM_OFFLINE as they looks similar except the return value and error message :)
Cheers, Gavin
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