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

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Date:   Mon, 18 May 2020 11:14:39 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Mike Rapoport <rppt@...nel.org>, Will Deacon <will@...nel.org>,
        linux-kernel@...r.kernel.org, elver@...gle.com, tglx@...utronix.de,
        paulmck@...nel.org, mingo@...nel.org, peterz@...radead.org,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v5 04/18] sparc32: mm: Reduce allocation size for PMD and
 PTE tables

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@...emloft.net>
> > > >>>> Cc: Peter Zijlstra <peterz@...radead.org>
> > > >>>> Signed-off-by: Will Deacon <will@...nel.org>
> > > >>>
> > > >>> 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 ...

Sparc had the same problem...


commit 6e5c523370c510f5fae3436b193ab5dabe0fef06 (HEAD -> lm-kmap17)
Author: Ira Weiny <ira.weiny@...el.com>
Date:   Mon May 18 11:13:16 2020 -0700

    arch/sparc: 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@...el.com>

diff --git a/arch/sparc/mm/highmem.c b/arch/sparc/mm/highmem.c
index d237d902f9c3..13fb197bb26c 100644
--- a/arch/sparc/mm/highmem.c
+++ b/arch/sparc/mm/highmem.c
@@ -86,11 +86,8 @@ void kunmap_atomic_high(void *kvaddr)
        unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
        int type;
 
-       if (vaddr < FIXADDR_START) { // FIXME
-               pagefault_enable();
-               preempt_enable();
+       if (vaddr < FIXADDR_START) // FIXME
                return;
-       }
 
        type = kmap_atomic_idx();