Re: [PATCH] Revert "mm/memblock.c: hardcode the end_pfn being -1"

From: Michal Hocko
Date: Fri Mar 16 2018 - 06:27:35 EST


On Fri 16-03-18 17:26:57, Jia He wrote:
>
>
> On 3/16/2018 5:06 PM, Michal Hocko Wrote:
> > On Thu 15-03-18 19:56:06, Jia He wrote:
> > > This reverts commit 379b03b7fa05f7db521b7732a52692448a3c34fe.
> > >
> > > Commit 864b75f9d6b0 ("mm/page_alloc: fix memmap_init_zone pageblock
> > > alignment") introduced boot hang issues in arm/arm64 machines, so
> > > Ard Biesheuvel reverted in commit 3e04040df6d4. But there is a
> > > preparation patch for commit 864b75f9d6b0. So just revert it for
> > > the sake of caution.
> > Why? Is there anything wrong with this one?
> I don't think there might be anything wrong. Justin for the sake of caution.
> Please ignore this patch if you prefer to keep 379b03b7fa.

We do not revert just if the patch is correct. I do not have strong
preference for the patch but I also do not see anything wrong with it.

> But seems parameter *max_pfn* is useless and can be removed in this case?

A patch for that is already sitting in mmotm tree

> Cheers,
> Jia
> > > Signed-off-by: Jia He <jia.he@xxxxxxxxxxxxxxxx>
> > > ---
> > > mm/memblock.c | 10 +++++-----
> > > 1 file changed, 5 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/mm/memblock.c b/mm/memblock.c
> > > index b6ba6b7..5a9ca2a 100644
> > > --- a/mm/memblock.c
> > > +++ b/mm/memblock.c
> > > @@ -1107,7 +1107,7 @@ unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn,
> > > struct memblock_type *type = &memblock.memory;
> > > unsigned int right = type->cnt;
> > > unsigned int mid, left = 0;
> > > - phys_addr_t addr = PFN_PHYS(++pfn);
> > > + phys_addr_t addr = PFN_PHYS(pfn + 1);
> > > do {
> > > mid = (right + left) / 2;
> > > @@ -1118,15 +1118,15 @@ unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn,
> > > type->regions[mid].size))
> > > left = mid + 1;
> > > else {
> > > - /* addr is within the region, so pfn is valid */
> > > - return pfn;
> > > + /* addr is within the region, so pfn + 1 is valid */
> > > + return min(pfn + 1, max_pfn);
> > > }
> > > } while (left < right);
> > > if (right == type->cnt)
> > > - return -1UL;
> > > + return max_pfn;
> > > else
> > > - return PHYS_PFN(type->regions[right].base);
> > > + return min(PHYS_PFN(type->regions[right].base), max_pfn);
> > > }
> > > /**
> > > --
> > > 2.7.4
> > >

--
Michal Hocko
SUSE Labs