Re: arm32: panic in move_freepages (Was [PATCH v2 0/4] arm64: drop pfn_valid_within() and simplify pfn_valid())

[Mike Rapoport]

On Sun, Apr 25, 2021 at 03:51:56PM +0800, Kefeng Wang wrote:
> 
> On 2021/4/25 15:19, Mike Rapoport wrote:
> 
>     On Fri, Apr 23, 2021 at 04:11:16PM +0800, Kefeng Wang wrote:
> 
>         I tested this patchset(plus arm32 change, like arm64 does) based on lts
>         5.10，add
> 
>         some debug log, the useful info shows below, if we enable HOLES_IN_ZONE, no
>         panic,
> 
>         any idea, thanks.
> 
> 
>     Are there any changes on top of 5.10 except for pfn_valid() patch?
>     Do you see this panic on 5.10 without the changes?
> 
> Yes, there are some BSP support for arm board based on 5.10, with or without
> 
> your patch will get same panic, the panic pfn=de600 in the range of
> [dcc00,de00]
> 
> which is freed by free_memmap, start_pfn = dcc00,  dcc00000 end_pfn = de700,
> de700000
> 
> we see the PC is at PageLRU, same reason like arm64 panic log,
> 
>    "PageBuddy in move_freepages returns false
>     Then we call PageLRU, the macro calls PF_HEAD which is compound_page()
>     compound_page reads page->compound_head, it is 0xffffffffffffffff, so it
>     resturns 0xfffffffffffffffe - and accessing this address causes crash"
> 
>     Can you see stack backtrace beyond move_freepages_block?
> 
> I do some oom test, so the log is about memory allocate,
> 
> [<c02383c8>] (move_freepages_block) from [<c0238668>]
> (steal_suitable_fallback+0x174/0x1f4)
> 
> [<c0238668>] (steal_suitable_fallback) from [<c023999c>] (get_page_from_freelist+0x490/0x9a4)

Hmm, this is called with a page from free list, having a page from a freed
part of the memory map passed to steal_suitable_fallback() means that there
is an issue with creation of the free list.

Can you please add "memblock=debug" to the kernel command line and post the
log?

> [<c023999c>] (get_page_from_freelist) from [<c023a4dc>] (__alloc_pages_nodemask+0x188/0xc08)
> [<c023a4dc>] (__alloc_pages_nodemask) from [<c0223078>] (alloc_zeroed_user_highpage_movable+0x14/0x3c)
> [<c0223078>] (alloc_zeroed_user_highpage_movable) from [<c0226768>] (handle_mm_fault+0x254/0xac8)
> [<c0226768>] (handle_mm_fault) from [<c04ba09c>] (do_page_fault+0x228/0x2f4)
> [<c04ba09c>] (do_page_fault) from [<c0111d80>] (do_DataAbort+0x48/0xd0)
> [<c0111d80>] (do_DataAbort) from [<c0100e00>] (__dabt_usr+0x40/0x60)
> 
> 
> 
>         Zone ranges:
>           Normal   [mem 0x0000000080a00000-0x00000000b01fffff]
>           HighMem  [mem 0x00000000b0200000-0x00000000ffffefff]
>         Movable zone start for each node
>         Early memory node ranges
>           node   0: [mem 0x0000000080a00000-0x00000000855fffff]
>           node   0: [mem 0x0000000086a00000-0x0000000087dfffff]
>           node   0: [mem 0x000000008bd00000-0x000000008c4fffff]
>           node   0: [mem 0x000000008e300000-0x000000008ecfffff]
>           node   0: [mem 0x0000000090d00000-0x00000000bfffffff]
>           node   0: [mem 0x00000000cc000000-0x00000000dc9fffff]
>           node   0: [mem 0x00000000de700000-0x00000000de9fffff]
>           node   0: [mem 0x00000000e0800000-0x00000000e0bfffff]
>           node   0: [mem 0x00000000f4b00000-0x00000000f6ffffff]
>           node   0: [mem 0x00000000fda00000-0x00000000ffffefff]
> 
>         ----> free_memmap, start_pfn = 85800,  85800000 end_pfn = 86a00, 86a00000
>         ----> free_memmap, start_pfn = 8c800,  8c800000 end_pfn = 8e300, 8e300000
>         ----> free_memmap, start_pfn = 8f000,  8f000000 end_pfn = 90000, 90000000
>         ----> free_memmap, start_pfn = dcc00,  dcc00000 end_pfn = de700, de700000
>         ----> free_memmap, start_pfn = dec00,  dec00000 end_pfn = e0000, e0000000
>         ----> free_memmap, start_pfn = e0c00,  e0c00000 end_pfn = e4000, e4000000
>         ----> free_memmap, start_pfn = f7000,  f7000000 end_pfn = f8000, f8000000
>         === >move_freepages: start_pfn/end_pfn [de601, de7ff], [de600000, de7ff000]
>         :  pfn =de600 pfn2phy = de600000 , page = ef3cc000, page-flags = ffffffff
>         8<--- cut here ---
>         Unable to handle kernel paging request at virtual address fffffffe
>         pgd = 5dd50df5
>         [fffffffe] *pgd=affff861, *pte=00000000, *ppte=00000000
>         Internal error: Oops: 37 [#1] SMP ARM
>         Modules linked in: gmac(O)
>         CPU: 2 PID: 635 Comm: test-oom Tainted: G           O      5.10.0+ #31
>         Hardware name: Hisilicon A9
>         PC is at move_freepages_block+0x150/0x278
>         LR is at move_freepages_block+0x150/0x278
>         pc : [<c02383a4>]    lr : [<c02383a4>]    psr: 200e0393
>         sp : c4179cf8  ip : 00000000  fp : 00000001
>         r10: c4179d58  r9 : 000de7ff  r8 : 00000000
>         r7 : c0863280  r6 : 000de600  r5 : 000de600  r4 : ef3cc000
>         r3 : ffffffff  r2 : 00000000  r1 : ef5d069c  r0 : fffffffe
>         Flags: nzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment user
>         Control: 1ac5387d  Table: 83b0c04a  DAC: 55555555
>         Process test-oom (pid: 635, stack limit = 0x25d667df)
> 
> 

-- 
Sincerely yours,
Mike.