Re: [PATCH v5 04/18] sparc32: mm: Reduce allocation size for PMD and PTE tables

From: Ira Weiny
Date: Mon May 18 2020 - 14:12:14 EST


On Mon, May 18, 2020 at 09:08:11AM -0700, Guenter Roeck wrote:
> On Mon, May 18, 2020 at 05:23:10PM +0300, Mike Rapoport wrote:
> > On Mon, May 18, 2020 at 02:48:18AM -0700, Guenter Roeck wrote:
> > > On 5/18/20 1:37 AM, Will Deacon wrote:
> > > > On Sat, May 16, 2020 at 05:07:50PM -0700, Guenter Roeck wrote:
> > > >> On Sat, May 16, 2020 at 05:00:50PM -0700, Guenter Roeck wrote:
> > > >>> On Mon, May 11, 2020 at 09:41:36PM +0100, Will Deacon wrote:
> > > >>>> Now that the page table allocator can free page table allocations
> > > >>>> smaller than PAGE_SIZE, reduce the size of the PMD and PTE allocations
> > > >>>> to avoid needlessly wasting memory.
> > > >>>>
> > > >>>> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> > > >>>> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > > >>>> Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> > > >>>
> > > >>> Something in the sparc32 patches in linux-next causes all my sparc32 emulations
> > > >>> to crash. bisect points to this patch, but reverting it doesn't help, and neither
> > > >>> does reverting the rest of the series.
> > > >>>
> > > >> Actually, turns out I see the same pattern (lots of scheduling while atomic
> > > >> followed by 'killing interrupt handler' in cryptomgr_test) with several
> > > >> powerpc boot tests. I am currently bisecting those crashes. I'll report
> > > >> the results here as well as soon as I have it.
> > > >
> > > > FWIW, I retested my sparc32 patches with PREEMPT=y and I don't see any
> > > > issues. However, linux-next is a different story, where I don't get very far
> > > > at all:
> > > >
> > > > BUG: Bad page state in process swapper pfn:005b4
> >
> > This one seems to be due to commit 24aab577764f ("mm: memmap_init:
> > iterate over memblock regions rather that check each PFN") and reverting
> > it and partially reverting the next cleanup commits makes those
> > dissapear. sparc32 boot still fails on today's linux-next and mmotm for me with
> >
> > Run /sbin/init as init process
> > with arguments:
> > /sbin/init
> > with environment:
> > HOME=/
> > TERM=linux
> > Starting init: /sbin/init exists but couldn't execute it (error -14)
> >
>
> Interesting; that is also seen on microblazeel:petalogix-ml605. Bisect there
> suggests 'arch/kmap_atomic: consolidate duplicate code' as the culprit,
> which is part of Ira's series.
>
> Today's -next is even worse, unfortunately; now all microblaze boot tests
> (both little and big endian) fail, plus everything that failed last
> time, plus new compile failures. Another round of bisects ...

I've found this bug in microblaze for sure still looking through the other archs...

commit 82c284b2bb74ca195dfcd35b70a175f010b9fd46 (HEAD -> lm-kmap17)
Author: Ira Weiny <ira.weiny@xxxxxxxxx>
Date: Mon May 18 11:01:10 2020 -0700

microblaze/kmap: Don't enable pagefault/preempt twice

The kunmap_atomic clean up failed to remove the pagefault/preempt
enables on this path.

Fixes: bee2128a09e6 ("arch/kunmap_atomic: consolidate duplicate code")
Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>

diff --git a/arch/microblaze/mm/highmem.c b/arch/microblaze/mm/highmem.c
index ee8a422b2b76..92e0890416c9 100644
--- a/arch/microblaze/mm/highmem.c
+++ b/arch/microblaze/mm/highmem.c
@@ -57,11 +57,8 @@ void kunmap_atomic_high(void *kvaddr)
int type;
unsigned int idx;

- if (vaddr < __fix_to_virt(FIX_KMAP_END)) {
- pagefault_enable();
- preempt_enable();
+ if (vaddr < __fix_to_virt(FIX_KMAP_END))
return;
- }

type = kmap_atomic_idx();