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

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@redhat.com Acked-by: Ard Biesheuvel ard.biesheuvel@linaro.org Cc: Andrew Morton akpm@linux-foundation.org Cc: Michal Hocko mhocko@suse.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Mel Gorman mgorman@techsingularity.net Cc: Pavel Tatashin pasha.tatashin@oracle.com Cc: Paul Burton paul.burton@imgtec.com Cc: stable@vger.kernel.org

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

---

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