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 09:08:11 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Ira Weiny <ira.weiny@...el.com>, 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 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 ...

Guenter

> I've tried to bisect mmotm and I've got the first bad commits in
> different places in the middle of arch/kmap series [1] so I've added Ira
> to CC as well :)
> 
> I'll continue to look into "bad page" on sparc32
> 
> [1] https://lore.kernel.org/dri-devel/20200507150004.1423069-11-ira.weiny@intel.com/
> 
> > Here are the bisect results for ppc:
> > 
> > # bad: [bdecf38f228bcca73b31ada98b5b7ba1215eb9c9] Add linux-next specific files for 20200515
> > # good: [2ef96a5bb12be62ef75b5828c0aab838ebb29cb8] Linux 5.7-rc5
> > git bisect start 'HEAD' 'v5.7-rc5'
> 
> ...
> 
> > # good: [9b5aa5b43f957f03a1f4a9aff5f7924e2ebbc011] arch-kmap_atomic-consolidate-duplicate-code-checkpatch-fixes
> > git bisect good 9b5aa5b43f957f03a1f4a9aff5f7924e2ebbc011
> > # bad: [89194ba5ee31567eeee9c81101b334c8e3248198] arch/kmap: define kmap_atomic_prot() for all arch's
> > git bisect bad 89194ba5ee31567eeee9c81101b334c8e3248198
> > # good: [022785d2bea99f8bc2a37b7b6c525eea26f6ac59] arch-kunmap_atomic-consolidate-duplicate-code-checkpatch-fixes
> > git bisect good 022785d2bea99f8bc2a37b7b6c525eea26f6ac59
> > # good: [a13c2f39e3f0519ddee57d26cc66ec70e3546106] arch/kmap: don't hard code kmap_prot values
> > git bisect good a13c2f39e3f0519ddee57d26cc66ec70e3546106
> > # first bad commit: [89194ba5ee31567eeee9c81101b334c8e3248198] arch/kmap: define kmap_atomic_prot() for all arch's
> > 
> > I don't know if that is accurate either. Maybe things are so broken
> > that bisect gets confused, or the problem is due to interaction
> > between different patch series.
> 
> My results with the workaround for sparc32 boot look similar:
> 
> # bad: [2bbf0589bfeb27800c730b76eacf34528eee5418] pci: test for unexpectedly disabled bridges
> git bisect bad 2bbf0589bfeb27800c730b76eacf34528eee5418
> # good: [2ef96a5bb12be62ef75b5828c0aab838ebb29cb8] Linux 5.7-rc5
> git bisect good 2ef96a5bb12be62ef75b5828c0aab838ebb29cb8
> # bad: [e4592f53440c6fd2288e2dcb8c6f5b4d9d40fd35] mm-add-debug_wx-support-fix
> git bisect bad e4592f53440c6fd2288e2dcb8c6f5b4d9d40fd35
> # bad: [e4592f53440c6fd2288e2dcb8c6f5b4d9d40fd35] mm-add-debug_wx-support-fix
> git bisect bad e4592f53440c6fd2288e2dcb8c6f5b4d9d40fd35
> # good: [e27369856a2d42ae4d84bc2c4ddac1e696c40d7c] mm: remove the prot argument from vm_map_ram
> git bisect good e27369856a2d42ae4d84bc2c4ddac1e696c40d7c
> # good: [6911f2b29f6daae2c4b51e6a37f794056d8afabd] mm/page_alloc.c: clear out zone->lowmem_reserve[] if the zone is empty
> git bisect good 6911f2b29f6daae2c4b51e6a37f794056d8afabd
> # good: [8cef4726f20ae37c3cf3f7a449f5b8a088247a27] hugetlbfs: clean up command line processing
> git bisect good 8cef4726f20ae37c3cf3f7a449f5b8a088247a27
> # good: [94f38895e0a68ceac3ceece6528123ed3129cedd] arch/kmap: ensure kmap_prot visibility
> git bisect good 94f38895e0a68ceac3ceece6528123ed3129cedd
> # skip: [fcc77c28bf9155c681712b25c0f5e6125d10ba2e] kmap: consolidate kmap_prot definitions
> git bisect skip fcc77c28bf9155c681712b25c0f5e6125d10ba2e
> # bad: [175a67be7ee750b2aa2a4a2fedeff18fdce787ac] kmap-consolidate-kmap_prot-definitions-checkpatch-fixes
> git bisect bad 175a67be7ee750b2aa2a4a2fedeff18fdce787ac
> # bad: [54db8ed321d66a00b6c69bbd5bf7c59809b3fd42] drm: vmwgfx: include linux/highmem.h
> git bisect bad 54db8ed321d66a00b6c69bbd5bf7c59809b3fd42
> # bad: [6671299c829d19c6ceb0fd1a14b690f6115c6d3d] arch/kmap: define kmap_atomic_prot() for all arch's
> git bisect bad 6671299c829d19c6ceb0fd1a14b690f6115c6d3d
> # bad: [f800fb6e517710e04391821e4b1908606c8a6b24] arch/kmap: don't hard code kmap_prot values
> git bisect bad f800fb6e517710e04391821e4b1908606c8a6b24
> # first bad commit: [f800fb6e517710e04391821e4b1908606c8a6b24] arch/kmap: don't hard code kmap_prot values
> 
> 
> > Guenter
> 
> -- 
> Sincerely yours,
> Mike.