Hi Baoquan, On Thu, May 21, 2020 at 09:44:07AM +0800, Baoquan He wrote: > Qian reported that a crash happened in compaction. > http://lkml.kernel.org/r/8C537EB7-85EE-4DCF-943E-3CC0ED0DF56D@xxxxxx > V> LTP: starting swapping01 (swapping01 -i 5) > page:ffffea0000aa0000 refcount:1 mapcount:0 mapping:000000002243743b index:0x0 > flags: 0x1fffe000001000(reserved) > raw: 001fffe000001000 ffffea0000aa0008 ffffea0000aa0008 0000000000000000 > raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 > page dumped because: VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn)) > page_owner info is not present (never set?) > ------------[ cut here ]------------ > kernel BUG at mm/page_alloc.c:533! ... > After investigation, it turns out that this is introduced by commit of > linux-next: commit f6edbdb71877 ("mm: memmap_init: iterate over memblock > regions rather that check each PFN"). > > After investigation, it turns out that this is introduced by commit of > linux-next, the patch subject is: > "mm: memmap_init: iterate over memblock regions rather that check each PFN". > > Qian added debugging code. The debugging log shows that the fault page is > 0x2a800000. From the system e820 map which is pasted at bottom, the page > is in e820 reserved range: > BIOS-e820: [mem 0x0000000029ffe000-0x000000002a80afff] reserved > And it's in section [0x28000000, 0x2fffffff]. In that secion, there are > several usable ranges and some e820 reserved ranges. > > For this kind of e820 reserved range, it won't be added to memblock allocator. > However, init_unavailable_mem() will initialize to add them into node 0, > zone 0. Before that commit, later, memmap_init() will add e820 reserved > ranges into the zone where they are contained, because it can pass > the checking of early_pfn_valid() and early_pfn_in_nid(). In this case, > the e820 reserved range where fault page 0x2a800000 is located is added > into DMA32 zone. After that commit, the e820 reserved rgions are kept > in node 0, zone 0, since we iterate over memblock regions to iniatialize > in memmap_init() instead, their node and zone won't be changed. I wonder why woudn't we add the reserved memory to memblock from the very beginning... I've tried to undestand why this was not done, but I couldn't find the reasoning behind that. Can you please try the below patch and see if it helps or, on the contrary, breaks anything else :) diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c index c5399e80c59c..b0940c618ed9 100644 --- a/arch/x86/kernel/e820.c +++ b/arch/x86/kernel/e820.c @@ -1301,8 +1301,11 @@ void __init e820__memblock_setup(void) if (end != (resource_size_t)end) continue; - if (entry->type == E820_TYPE_SOFT_RESERVED) + if (entry->type == E820_TYPE_SOFT_RESERVED || + entry->type == E820_TYPE_RESERVED) { + memblock_add(entry->addr, entry->size); memblock_reserve(entry->addr, entry->size); + } if (entry->type != E820_TYPE_RAM && entry->type != E820_TYPE_RESERVED_KERN) continue; > Now, fast_isolate_freepages() will use min mark directly as the migration > target if no page is found from buddy. However, the min mark is not checked > carefully, it could be in e820 reserved range, and trigger the > VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn)) when try to mark it > as skip. > > Here, let's call pageblock_pfn_to_page() to get page of min_pfn, since it > will do careful checks and return NULL if the pfn is not qualified. > > [ 0.000000] BIOS-provided physical RAM map: > [ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000008bfff] usable > [ 0.000000] BIOS-e820: [mem 0x000000000008c000-0x000000000009ffff] reserved > [ 0.000000] BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved > [ 0.000000] BIOS-e820: [mem 0x0000000000100000-0x0000000028328fff] usable > [ 0.000000] BIOS-e820: [mem 0x0000000028329000-0x0000000028568fff] reserved > [ 0.000000] BIOS-e820: [mem 0x0000000028569000-0x0000000028d85fff] usable > [ 0.000000] BIOS-e820: [mem 0x0000000028d86000-0x0000000028ee5fff] reserved > [ 0.000000] BIOS-e820: [mem 0x0000000028ee6000-0x0000000029a04fff] usable > [ 0.000000] BIOS-e820: [mem 0x0000000029a05000-0x0000000029a08fff] reserved > [ 0.000000] BIOS-e820: [mem 0x0000000029a09000-0x0000000029ee4fff] usable > [ 0.000000] BIOS-e820: [mem 0x0000000029ee5000-0x0000000029ef2fff] ACPI data > [ 0.000000] BIOS-e820: [mem 0x0000000029ef3000-0x0000000029f22fff] usable > [ 0.000000] BIOS-e820: [mem 0x0000000029f23000-0x0000000029f23fff] ACPI data > [ 0.000000] BIOS-e820: [mem 0x0000000029f24000-0x0000000029f24fff] usable > [ 0.000000] BIOS-e820: [mem 0x0000000029f25000-0x0000000029f28fff] ACPI data > [ 0.000000] BIOS-e820: [mem 0x0000000029f29000-0x0000000029f29fff] ACPI NVS > [ 0.000000] BIOS-e820: [mem 0x0000000029f2a000-0x0000000029f2bfff] ACPI data > [ 0.000000] BIOS-e820: [mem 0x0000000029f2c000-0x0000000029f2cfff] reserved > [ 0.000000] BIOS-e820: [mem 0x0000000029f2d000-0x0000000029f2ffff] ACPI data > [ 0.000000] BIOS-e820: [mem 0x0000000029f30000-0x0000000029ffdfff] usable > [ 0.000000] BIOS-e820: [mem 0x0000000029ffe000-0x000000002a80afff] reserved > [ 0.000000] BIOS-e820: [mem 0x000000002a80b000-0x000000002a80efff] ACPI NVS > [ 0.000000] BIOS-e820: [mem 0x000000002a80f000-0x000000002a81ffff] reserved > [ 0.000000] BIOS-e820: [mem 0x000000002a820000-0x000000002a822fff] ACPI NVS > [ 0.000000] BIOS-e820: [mem 0x000000002a823000-0x0000000033a22fff] usable > [ 0.000000] BIOS-e820: [mem 0x0000000033a23000-0x0000000033a32fff] reserved > [ 0.000000] BIOS-e820: [mem 0x0000000033a33000-0x0000000033a42fff] ACPI NVS > [ 0.000000] BIOS-e820: [mem 0x0000000033a43000-0x0000000033a52fff] ACPI data > [ 0.000000] BIOS-e820: [mem 0x0000000033a53000-0x0000000077ffffff] usable > [ 0.000000] BIOS-e820: [mem 0x0000000078000000-0x000000008fffffff] reserved > [ 0.000000] BIOS-e820: [mem 0x00000000fed80000-0x00000000fed80fff] reserved > [ 0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000087effffff] usable > [ 0.000000] BIOS-e820: [mem 0x000000087f000000-0x000000087fffffff] reserved > > Reported-by: Qian Cai <cai@xxxxxx> > Signed-off-by: Baoquan He <bhe@xxxxxxxxxx> > --- > mm/compaction.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 67fd317f78db..9ce4cff4d407 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1418,7 +1418,9 @@ fast_isolate_freepages(struct compact_control *cc) > cc->free_pfn = highest; > } else { > if (cc->direct_compaction && pfn_valid(min_pfn)) { > - page = pfn_to_page(min_pfn); > + page = pageblock_pfn_to_page(min_pfn, > + pageblock_end_pfn(min_pfn), > + cc->zone); > cc->free_pfn = min_pfn; > } > } > -- > 2.17.2 > -- Sincerely yours, Mike.
