Messages in this thread | | | Date | Thu, 6 Oct 2016 15:01:03 -0600 | From | Chris Friesen <> | Subject | "swap_free: Bad swap file entry" and "BUG: Bad page map in process" but no swap configured |
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I have Linux host running as a kvm hypervisor. It's running CentOS. (So the kernel is based on 3.10 but with loads of stuff backported by RedHat.) I realize this is not a mainline kernel, but I was wondering if anyone is aware of similar issues that had been fixed in mainline.
When doing a bunch of live migrations eventually I hit a bunch of errors that look like this.
2016-10-03T23:13:54.017 controller-1 kernel: err [247517.457614] swap_free: Bad swap file entry 001fe858 2016-10-03T23:13:54.017 controller-1 kernel: alert [247517.463191] BUG: Bad page map in process qemu-kvm pte:3fd0b000 pmd:4557cb067 2016-10-03T23:13:54.017 controller-1 kernel: alert [247517.471352] addr:00007fefa9be4000 vm_flags:00100073 anon_vma:ffff88043f87ff80 mapping: (null) index:7fefa9be4 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483510] CPU: 0 PID: 154525 Comm: qemu-kvm Tainted: G OE ------------ 3.10.0-327.28.3.7.tis.x86_64 #1 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483513] Hardware name: Intel Corporation S2600WT2R/S2600WT2R, BIOS SE5C610.86B.01.01.0016.033120161139 03/31/2016 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483516] 00007fefa9be4000 0000000007795eb9 ffff88044007bc60 ffffffff81670503 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483524] ffff88044007bca8 ffffffff8115e70f 000000003fd0b000 00000007fefa9be4 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483531] ffff8804557cbf20 000000003fd0b000 00007fefa9c00000 00007fefa9be4000 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483538] Call Trace: 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483548] [<ffffffff81670503>] dump_stack+0x19/0x1b 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483553] [<ffffffff8115e70f>] print_bad_pte+0x1af/0x250 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483557] [<ffffffff81160000>] unmap_page_range+0x5a0/0x7f0 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483561] [<ffffffff811602a9>] unmap_single_vma+0x59/0xd0 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483564] [<ffffffff81161595>] zap_page_range+0x105/0x170 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483568] [<ffffffff8115dd7c>] SyS_madvise+0x3bc/0x7d0 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483573] [<ffffffff810ca1e0>] ? SyS_futex+0x80/0x180 2016-10-03T23:13:54.017 controller-1 kernel: warning [247517.483577] [<ffffffff81678f89>] system_call_fastpath+0x16/0x1b
One interesting thing about the "Bad swap file entry" error is that these hosts do not have any swap configured:
compute-4:~$ free total used free shared buff/cache available Mem: 131805464 122187644 8815864 245456 801956 9193644 Swap: 0 0 0
So why is the kernel calling swap_info_get()?
In the second error, the offset in the SyS_madvise routine is here: 0xffffffff8115dd77 <+951>: callq 0xffffffff81161490 <zap_page_range> 0xffffffff8115dd7c <+956>: xor %eax,%eax
this maps to the second zap_page_range() call below in madvise_dontneed():
if (unlikely(vma->vm_flags & VM_NONLINEAR)) { struct zap_details details = { .nonlinear_vma = vma, .last_index = ULONG_MAX, }; zap_page_range(vma, start, end - start, &details); } else zap_page_range(vma, start, end - start, NULL);
print_bad_pte() is called from this code in zap_pte_range():
if (pte_file(ptent)) { if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) print_bad_pte(vma, addr, ptent, NULL);
Here's the interesting bit...we're calling print_bad_pte() here if "vma->vm_flags & VM_NONLINEAR" is not true...but we called zap_page_range() with a "details" of NULL specifically because it was not true. So probably pte_file(ptent) should not be true--but it is.
Any of this sound familiar to anyone? Anyone have suggestions on how to bottom it out?
Chris
PS: Please CC me on replies.
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