Messages in this thread | | | Subject | Re: arm32: panic in move_freepages (Was [PATCH v2 0/4] arm64: drop pfn_valid_within() and simplify pfn_valid()) | From | Kefeng Wang <> | Date | Fri, 14 May 2021 10:18:21 +0800 |
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On 2021/5/13 18:55, Mike Rapoport wrote: > On Thu, May 13, 2021 at 11:44:00AM +0800, Kefeng Wang wrote: >> On 2021/5/12 16:26, Mike Rapoport wrote: >>> On Wed, May 12, 2021 at 11:08:14AM +0800, Kefeng Wang wrote: >>>> >>>> On 2021/5/11 16:48, Mike Rapoport wrote: >>>>> On Mon, May 10, 2021 at 11:10:20AM +0800, Kefeng Wang wrote: >>>>>> >>>>>>>> The memory is not continuous, see MEMBLOCK: >>>>>>>> memory size = 0x4c0fffff reserved size = 0x027ef058 >>>>>>>> memory.cnt = 0xa >>>>>>>> memory[0x0] [0x80a00000-0x855fffff], 0x04c00000 bytes flags: 0x0 >>>>>>>> memory[0x1] [0x86a00000-0x87dfffff], 0x01400000 bytes flags: 0x0 >>>>>>>> memory[0x2] [0x8bd00000-0x8c4fffff], 0x00800000 bytes flags: 0x0 >>>>>>>> memory[0x3] [0x8e300000-0x8ecfffff], 0x00a00000 bytes flags: 0x0 >>>>>>>> memory[0x4] [0x90d00000-0xbfffffff], 0x2f300000 bytes flags: 0x0 >>>>>>>> memory[0x5] [0xcc000000-0xdc9fffff], 0x10a00000 bytes flags: 0x0 >>>>>>>> memory[0x6] [0xde700000-0xde9fffff], 0x00300000 bytes flags: 0x0 >>>>>>>> ... >>>>>>>> >>>>>>>> The pfn_range [0xde600,0xde700] => addr_range [0xde600000,0xde700000] >>>>>>>> is not available memory, and we won't create memmap , so with or without >>>>>>>> your patch, we can't see the range in free_memmap(), right? >>>>>>> >>>>>>> This is not available memory and we won't see the reange in free_memmap(), >>>>>>> but we still should create memmap for it and that's what my patch tried to >>>>>>> do. >>>>>>> >>>>>>> There are a lot of places in core mm that operate on pageblocks and >>>>>>> free_unused_memmap() should make sure that any pageblock has a valid memory >>>>>>> map. >>>>>>> >>>>>>> Currently, that's not the case when SPARSEMEM=y and my patch tried to fix >>>>>>> it. >>>>>>> >>>>>>> Can you please send log with my patch applied and with the printing of >>>>>>> ranges that are freed in free_unused_memmap() you've used in previous >>>>>>> mails? >>>>> >>>>>> with your patch[1] and debug print in free_memmap, >>>>>> ----> free_memmap, start_pfn = 85800, 85800000 end_pfn = 86800, 86800000 >>>>>> ----> free_memmap, start_pfn = 8c800, 8c800000 end_pfn = 8e000, 8e000000 >>>>>> ----> free_memmap, start_pfn = 8f000, 8f000000 end_pfn = 90000, 90000000 >>>>>> ----> free_memmap, start_pfn = dcc00, dcc00000 end_pfn = de400, de400000 >>>>>> ----> 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 >>>>> >>>>> It seems that freeing of the memory map is suboptimal still because that >>>>> code was not designed for memory layout that has more holes than Swiss >>>>> cheese. >>>>> >>>>> Still, the range [0xde600,0xde700] is not freed and there should be struct >>>>> pages for this range. >>>>> >>>>> Can you add >>>>> >>>>> dump_page(pfn_to_page(0xde600), ""); >>>>> >>>>> say, in the end of memblock_free_all()? >>>>> >>>> The range [0xde600,0xde700] is not memory, so it won't create struct page >>>> for it when sparse_init? >>> >>> sparse_init() indeed does not create memory map for unpopulated memory, but >>> it has pretty coarse granularity, i.e. 64M in your configuration. A hole >>> should be at least 64M in order to skip allocation of the memory map for >>> it. >>> >>> For example, your memory layout has a hole of 192M at pfn 0xc0000 and this >>> hole won't have the memory map. >>> >>> However the hole 0xdca00 - 0xde70 will still have a memory map in the >>> section that covers 0xdc000 - 0xe0000. >>> >>> I've tried outline this in a sketch below, hope it helps. >>> >>> Memory: >>> c0000 cc000 dca00 >>> --------------------------+ +--------------------------+ +----+ >>> memory bank |<- hole ->| memory bank | | mb | >>> --------------------------+ +--------------------------+ +----+ >>> de700 dea00 >>> >>> Memory map: >>> >>> b0000 b4000 c0000 cc000 d0000 d8000 dc000 >>> +--------+--------+- ... -+ +--------+- ... -+--------+---------+ >>> | memmap | memmap | ... |<- hole ->| memmap | ... | memmap | memmap | >>> +--------+--------+- ... -+ +--------+- ... -+--------+---------+ >>> >>> >> Thanks for the sketch, it is more clear, >> >>>> After apply patch[1], the dump_page log, >>>> >>>> page:ef3cc000 is uninitialized and poisoned >>>> raw: ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff >>>> page dumped because: >>> >>> This means that there is a memory map entry, and it got poisoned during the >>> initialization and never got reinitialized to sensible values, which would >>> be PageReserved() in this case. >>> >>> I believe this was fixed by commit 0740a50b9baa ("mm/page_alloc.c: refactor >>> initialization of struct page for holes in memory layout") in the mainline >>> tree. >>> >>> Can you backport it to your 5.10 tree and check if it helps? >> Hi Mike, the 0740a50b9baa is already in 5.10, tags/v5.10.24~5 > > Ah, you are using stable 5.10.y. > >> commit 4c84191cbc3eff49568d3c5cccb628fa382cf7fb >> Author: Mike Rapoport <rppt@kernel.org> >> Date: Fri Mar 12 21:07:12 2021 -0800 >> >> mm/page_alloc.c: refactor initialization of struct page for holes in >> memory layout >> >> commit 0740a50b9baa4472cfb12442df4b39e2712a64a4 upstream. >> >> but check init_unavailable_range(), we need deal with the hole in the >> range of one pageblock. >> >> For our scene, pageblock range: 0xde600,0xde7ff, but the available pfn begin >> with 0xde700. >> >> If pfn(eg, 0xde600) is not valid, the step in init_unavailable_range is >> pageblock_nr_pages, and ALIGN_DOWN(pfn, pageblock_nr_pages) from 0xde600 >> to 0xde700 is same, so the page range for pfn [0xde600,0xde700] won't be >> initialized. > > The pfn 0xde600 is valid in the sense that there is a memory map for that > pfn. Yet, with ARM's custom pfn_valid() will treat it as invalid because > there is a hole. > >> After add the following patch, the oom test could passed, > >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index aaa1655cf682..0c7e04f86f9f 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -6484,13 +6484,14 @@ static u64 __meminit init_unavailable_range(unsigned >> long spfn, >> unsigned long epfn, >> int zone, int node) >> { >> - unsigned long pfn; >> + unsigned long pfn, pfn_down; >> + unsigned long epfn_down = ALIGN_DOWN(epfn, pageblock_nr_pages); >> u64 pgcnt = 0; >> >> for (pfn = spfn; pfn < epfn; pfn++) { >> - if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) { >> - pfn = ALIGN_DOWN(pfn, pageblock_nr_pages) >> - + pageblock_nr_pages - 1; >> + pfn_down = ALIGN_DOWN(pfn, pageblock_nr_pages); >> + if (!pfn_valid(pfn_down) && pfn_down != epfn_down) { >> + pfn = pfn_down + pageblock_nr_pages - 1; >> continue; >> } >> __init_single_page(pfn_to_page(pfn), pfn, zone, node); > > I'd rather prefer to keep init_unavailable_range() and the assumption that > the memory map always covers an entire pageblock. > > Can you please try the below hack. Essentially, it makes arm with SPARSEMEM > to use the generic pfn_valid() and updates the freeing of the memory map to > have the entire pageblocks covered. > > If this works I'll send formal patches for those changes. > > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index 24804f11302d..86ee711a3fdb 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -73,7 +73,7 @@ config ARM > select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU > select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL > select HAVE_ARCH_MMAP_RND_BITS if MMU > - select HAVE_ARCH_PFN_VALID > +# select HAVE_ARCH_PFN_VALID > select HAVE_ARCH_SECCOMP > select HAVE_ARCH_SECCOMP_FILTER if AEABI && !OABI_COMPAT > select HAVE_ARCH_THREAD_STRUCT_WHITELIST > diff --git a/mm/memblock.c b/mm/memblock.c > index 504435753259..0d7bef1b49c3 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -1928,9 +1928,11 @@ static void __init free_unused_memmap(void) > unsigned long start, end, prev_end = 0; > int i; > > +#ifndef CONFIG_ARM > if (!IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID) || > IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)) > return; > +#endif > > /* > * This relies on each bank being in address order. > @@ -1943,14 +1945,13 @@ static void __init free_unused_memmap(void) > * due to SPARSEMEM sections which aren't present. > */ > start = min(start, ALIGN(prev_end, PAGES_PER_SECTION)); > -#else > +#endif > /* > * Align down here since the VM subsystem insists that the > * memmap entries are valid from the bank start aligned to > * MAX_ORDER_NR_PAGES. > */ > start = round_down(start, MAX_ORDER_NR_PAGES); > -#endif > > /* > * If we had a previous bank, and there is a space > >
Without HAVE_ARCH_PFN_VALID, init_unavailable_range will set those page with Reserved flag, and yes, it works for oom test.
On node 0 totalpages: 311551 Normal zone: 1230 pages used for memmap Normal zone: 0 pages reserved Normal zone: 157440 pages, LIFO batch:31 Normal zone: 55552 pages in unavailable ranges HighMem zone: 154111 pages, LIFO batch:31 HighMem zone: 41985 pages in unavailable ranges
Thanks for your kindly guidance.
>> Before: >> On node 0 totalpages: 311551 >> Normal zone: 1230 pages used for memmap >> Normal zone: 0 pages reserved >> Normal zone: 157440 pages, LIFO batch:31 >> Normal zone: 16384 pages in unavailable ranges >> HighMem zone: 154111 pages, LIFO batch:31 >> HighMem zone: 1 pages in unavailable ranges >> >> page:ef3cc000 is uninitialized and poisoned >> raw: ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff >> >> After: >> On node 0 totalpages: 311551 >> Normal zone: 1230 pages used for memmap >> Normal zone: 0 pages reserved >> Normal zone: 157440 pages, LIFO batch:31 >> Normal zone: 17152 pages in unavailable ranges >> HighMem zone: 154111 pages, LIFO batch:31 >> HighMem zone: 513 pages in unavailable ranges >> ... >> page:(ptrval) refcount:1 mapcount:0 mapping:00000000 index:0x0 pfn:0xde600 >> flags: 0xdd001000(reserved) >> raw: dd001000 ef3cc004 ef3cc004 00000000 00000000 00000000 ffffffff 00000001 >> >
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