Re: [PATCH] Revert "mm: page_alloc: skip over regions of invalid pfns where possible"

From: Michal Hocko
Date: Fri Mar 16 2018 - 11:14:40 EST

On Fri 16-03-18 15:38:55, Daniel Vacek wrote:
> This reverts commit b92df1de5d289c0b5d653e72414bf0850b8511e0. The commit
> is meant to be a boot init speed up skipping the loop in memmap_init_zone()
> for invalid pfns. But given some specific memory mapping on x86_64 (or more
> generally theoretically anywhere but on arm with CONFIG_HAVE_ARCH_PFN_VALID)
> the implementation also skips valid pfns which is plain wrong and causes
> 'kernel BUG at mm/page_alloc.c:1389!'
>
> crash> log | grep -e BUG -e RIP -e Call.Trace -e move_freepages_block -e rmqueue -e freelist -A1
> kernel BUG at mm/page_alloc.c:1389!
> invalid opcode: 0000 [#1] SMP
> --
> RIP: 0010:[<ffffffff8118833e>] [<ffffffff8118833e>] move_freepages+0x15e/0x160
> RSP: 0018:ffff88054d727688 EFLAGS: 00010087
> --
> Call Trace:
> [<ffffffff811883b3>] move_freepages_block+0x73/0x80
> [<ffffffff81189e63>] __rmqueue+0x263/0x460
> [<ffffffff8118c781>] get_page_from_freelist+0x7e1/0x9e0
> [<ffffffff8118caf6>] __alloc_pages_nodemask+0x176/0x420
> --
> RIP [<ffffffff8118833e>] move_freepages+0x15e/0x160
> RSP <ffff88054d727688>
>
> crash> page_init_bug -v | grep RAM
> <struct resource 0xffff88067fffd2f8> 1000 - 9bfff System RAM (620.00 KiB)
> <struct resource 0xffff88067fffd3a0> 100000 - 430bffff System RAM ( 1.05 GiB = 1071.75 MiB = 1097472.00 KiB)
> <struct resource 0xffff88067fffd410> 4b0c8000 - 4bf9cfff System RAM ( 14.83 MiB = 15188.00 KiB)
> <struct resource 0xffff88067fffd480> 4bfac000 - 646b1fff System RAM (391.02 MiB = 400408.00 KiB)
> <struct resource 0xffff88067fffd560> 7b788000 - 7b7fffff System RAM (480.00 KiB)
> <struct resource 0xffff88067fffd640> 100000000 - 67fffffff System RAM ( 22.00 GiB)
>
> crash> page_init_bug | head -6
> <struct resource 0xffff88067fffd560> 7b788000 - 7b7fffff System RAM (480.00 KiB)
> <struct page 0xffffea0001ede200> 1fffff00000000 0 <struct pglist_data 0xffff88047ffd9000> 1 <struct zone 0xffff88047ffd9800> DMA32 4096 1048575
> <struct page 0xffffea0001ede200> 505736 505344 <struct page 0xffffea0001ed8000> 505855 <struct page 0xffffea0001edffc0>
> <struct page 0xffffea0001ed8000> 0 0 <struct pglist_data 0xffff88047ffd9000> 0 <struct zone 0xffff88047ffd9000> DMA 1 4095
> <struct page 0xffffea0001edffc0> 1fffff00000400 0 <struct pglist_data 0xffff88047ffd9000> 1 <struct zone 0xffff88047ffd9800> DMA32 4096 1048575
> BUG, zones differ!
>
> crash> kmem -p 77fff000 78000000 7b5ff000 7b600000 7b787000 7b788000
> PAGE PHYSICAL MAPPING INDEX CNT FLAGS
> ffffea0001e00000 78000000 0 0 0 0
> ffffea0001ed7fc0 7b5ff000 0 0 0 0
> ffffea0001ed8000 7b600000 0 0 0 0 <<<<
> ffffea0001ede1c0 7b787000 0 0 0 0
> ffffea0001ede200 7b788000 0 0 1 1fffff00000000
>
> Fixes: b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns where possible")
> Signed-off-by: Daniel Vacek <neelx@xxxxxxxxxx>
> Acked-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
> Cc: Paul Burton <paul.burton@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

Yes, this looks like the most simple way for now before a proper
solution is found
Acked-by: Michal Hocko <mhocko@xxxxxxxx>

> ---
> include/linux/memblock.h | 1 -
> mm/memblock.c | 28 ----------------------------
> mm/page_alloc.c | 11 +----------
> 3 files changed, 1 insertion(+), 39 deletions(-)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 8be5077efb5f..f92ea7783652 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -187,7 +187,6 @@ int memblock_search_pfn_nid(unsigned long pfn, unsigned long *start_pfn,
> unsigned long *end_pfn);
> void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
> unsigned long *out_end_pfn, int *out_nid);
> -unsigned long memblock_next_valid_pfn(unsigned long pfn, unsigned long max_pfn);
>
> /**
> * for_each_mem_pfn_range - early memory pfn range iterator
> diff --git a/mm/memblock.c b/mm/memblock.c
> index b6ba6b7adadc..48376bd33274 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1101,34 +1101,6 @@ void __init_memblock __next_mem_pfn_range(int *idx, int nid,
> *out_nid = r->nid;
> }
>
> -unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn,
> - unsigned long max_pfn)
> -{
> - struct memblock_type *type = &memblock.memory;
> - unsigned int right = type->cnt;
> - unsigned int mid, left = 0;
> - phys_addr_t addr = PFN_PHYS(++pfn);
> -
> - do {
> - mid = (right + left) / 2;
> -
> - if (addr < type->regions[mid].base)
> - right = mid;
> - else if (addr >= (type->regions[mid].base +
> - type->regions[mid].size))
> - left = mid + 1;
> - else {
> - /* addr is within the region, so pfn is valid */
> - return pfn;
> - }
> - } while (left < right);
> -
> - if (right == type->cnt)
> - return -1UL;
> - else
> - return PHYS_PFN(type->regions[right].base);
> -}
> -
> /**
> * memblock_set_node - set node ID on memblock regions
> * @base: base of area to set node ID for
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 635d7dd29d7f..e4566a3f8083 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5356,17 +5356,8 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
> if (context != MEMMAP_EARLY)
> goto not_early;
>
> - if (!early_pfn_valid(pfn)) {
> -#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
> - /*
> - * Skip to the pfn preceding the next valid one (or
> - * end_pfn), such that we hit a valid pfn (or end_pfn)
> - * on our next iteration of the loop.
> - */
> - pfn = memblock_next_valid_pfn(pfn, end_pfn) - 1;
> -#endif
> + if (!early_pfn_valid(pfn))
> continue;
> - }
> if (!early_pfn_in_nid(pfn, nid))
> continue;
> if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised))
> --
> 2.16.2
>

--
Michal Hocko
SUSE Labs