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

[Mike Rapoport]

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)

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@xxxxxxxxx/

> 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.