Re: cgroup and FALLOC_FL_PUNCH_HOLE: WARNING: CPU: 13 PID: 2438 at mm/page_counter.c:57 page_counter_uncharge+0x4b/0x5

From: David Hildenbrand
Date: Wed Oct 21 2020 - 09:34:27 EST

On 21.10.20 15:11, David Hildenbrand wrote:
> On 21.10.20 14:57, Michal Privoznik wrote:
>> On 10/21/20 5:35 AM, Mike Kravetz wrote:
>>> On 10/20/20 6:38 AM, David Hildenbrand wrote:
>>>>
>>>> I'm bisecting the warning right now. Looks like it was introduced in v5.7.
>>>
>>> I found the following bugs in the cgroup reservation accounting. The ones
>>> in region_del are pretty obvious as the number of pages to uncharge would
>>> always be zero. The one on alloc_huge_page needs racing code to expose.
>>>
>>> With these fixes, my testing is showing consistent/correct results for
>>> hugetlb reservation cgroup accounting.
>>>
>>> It would be good if Mina (at least) would look these over. Would also
>>> be interesting to know if these fixes address the bug seen with the qemu
>>> use case.
>>>
>>> I'm still doing more testing and code inspection to look for other issues.
>>>
>>> From 861bcd7d0443f18a5fed3c3ddc5f1c71e78c4ef4 Mon Sep 17 00:00:00 2001
>>> From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
>>> Date: Tue, 20 Oct 2020 20:21:42 -0700
>>> Subject: [PATCH] hugetlb_cgroup: fix reservation accounting
>>>
>>> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
>>> ---
>>> mm/hugetlb.c | 15 +++++++++------
>>> 1 file changed, 9 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>>> index 67fc6383995b..c92366313780 100644
>>> --- a/mm/hugetlb.c
>>> +++ b/mm/hugetlb.c
>>> @@ -685,17 +685,17 @@ static long region_del(struct resv_map *resv, long f, long t)
>>> }
>>>
>>> if (f <= rg->from) { /* Trim beginning of region */
>>> - del += t - rg->from;
>>> - rg->from = t;
>>> -
>>> hugetlb_cgroup_uncharge_file_region(resv, rg,
>>> t - rg->from);
>>> - } else { /* Trim end of region */
>>> - del += rg->to - f;
>>> - rg->to = f;
>>>
>>> + del += t - rg->from;
>>> + rg->from = t;
>>> + } else { /* Trim end of region */
>>> hugetlb_cgroup_uncharge_file_region(resv, rg,
>>> rg->to - f);
>>> +
>>> + del += rg->to - f;
>>> + rg->to = f;
>>> }
>>> }
>>>
>>> @@ -2454,6 +2454,9 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
>>>
>>> rsv_adjust = hugepage_subpool_put_pages(spool, 1);
>>> hugetlb_acct_memory(h, -rsv_adjust);
>>> + if (deferred_reserve)
>>> + hugetlb_cgroup_uncharge_page_rsvd(hstate_index(h),
>>> + pages_per_huge_page(h), page);
>>> }
>>> return page;
>>>
>>>
>>
>> I've applied, rebuilt and tested, but unfortunately I still hit the problem:
>> [ 6472.719047] ------------[ cut here ]------------
>> [ 6472.719052] WARNING: CPU: 6 PID: 11773 at mm/page_counter.c:57
>> page_counter_uncharge+0x33/0x40
>> [ 6472.719052] Modules linked in: kvm_amd amdgpu kvm btusb sp5100_tco
>> btrtl watchdog k10temp btbcm btintel mfd_core gpu_sched ttm
>> [ 6472.719057] CPU: 6 PID: 11773 Comm: CPU 3/KVM Not tainted
>> 5.9.1-gentoo-x86_64 #1
>> [ 6472.719057] Hardware name: System manufacturer System Product
>> Name/PRIME X570-PRO, BIOS 1005 08/01/2019
>> [ 6472.719059] RIP: 0010:page_counter_uncharge+0x33/0x40
>> [ 6472.719060] Code: 48 85 ff 74 24 4c 89 c8 f0 48 0f c1 07 4c 29 c0 48
>> 89 c1 48 89 c6 e8 7c fe ff ff 48 85 c9 78 0a 48 8b 7f 28 48 85 ff 75 dc
>> c3 <0f> 0b eb f2 66 0f 1f 84 00 00 00 00 00 48 8b 17 48 39 d6 72 41 41
>> [ 6472.719061] RSP: 0018:ffffc90000b77b40 EFLAGS: 00010286
>> [ 6472.719061] RAX: fffffffffffe9200 RBX: ffff888fb3b97b40 RCX:
>> fffffffffffe9200
>> [ 6472.719062] RDX: 0000000000000221 RSI: fffffffffffe9200 RDI:
>> ffff888fd8451dd0
>> [ 6472.719062] RBP: ffff888fb6990420 R08: 0000000000044200 R09:
>> fffffffffffbbe00
>> [ 6472.719062] R10: ffff888fb3b97b40 R11: 000000000000000a R12:
>> 0000000000000001
>> [ 6472.719063] R13: 00000000000005df R14: 00000000000005de R15:
>> ffff888fb3b97b40
>> [ 6472.719063] FS: 00007fbd175fe700(0000) GS:ffff888fde980000(0000)
>> knlGS:0000000000000000
>> [ 6472.719064] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [ 6472.719064] CR2: 00007fbd825101f0 CR3: 0000000fb5e41000 CR4:
>> 0000000000350ee0
>> [ 6472.719065] Call Trace:
>> [ 6472.719067] hugetlb_cgroup_uncharge_file_region+0x46/0x70
>> [ 6472.719069] region_del+0x1ae/0x270
>> [ 6472.719070] hugetlb_unreserve_pages+0x32/0xa0
>> [ 6472.719072] remove_inode_hugepages+0x19d/0x3a0
>> [ 6472.719079] ? writeback_registers+0x45/0x60 [kvm]
>> [ 6472.719080] hugetlbfs_fallocate+0x3f2/0x4a0
>> [ 6472.719081] ? __mod_lruvec_state+0x1d/0x40
>> [ 6472.719081] ? __mod_memcg_lruvec_state+0x1b/0xe0
>> [ 6472.719083] ? __seccomp_filter+0x75/0x6a0
>> [ 6472.719084] vfs_fallocate+0x122/0x260
>> [ 6472.719085] __x64_sys_fallocate+0x39/0x60
>> [ 6472.719086] do_syscall_64+0x2d/0x40
>> [ 6472.719088] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>> [ 6472.719089] RIP: 0033:0x7fbe3cefcde7
>> [ 6472.719089] Code: 89 7c 24 08 48 89 4c 24 18 e8 45 fc f8 ff 41 89 c0
>> 4c 8b 54 24 18 48 8b 54 24 10 b8 1d 01 00 00 8b 74 24 0c 8b 7c 24 08 0f
>> 05 <48> 3d 00 f0 ff ff 77 41 44 89 c7 89 44 24 08 e8 75 fc f8 ff 8b 44
>> [ 6472.719090] RSP: 002b:00007fbd175fc7a0 EFLAGS: 00000293 ORIG_RAX:
>> 000000000000011d
>> [ 6472.719090] RAX: ffffffffffffffda RBX: 00000000bbe00000 RCX:
>> 00007fbe3cefcde7
>> [ 6472.719091] RDX: 00000000bbc00000 RSI: 0000000000000003 RDI:
>> 000000000000001d
>> [ 6472.719091] RBP: 00007fbd175fc800 R08: 0000000000000000 R09:
>> 0000000000000000
>> [ 6472.719091] R10: 0000000000200000 R11: 0000000000000293 R12:
>> 00007ffeea066d2e
>> [ 6472.719092] R13: 00007ffeea066d2f R14: 00007fbd175fe700 R15:
>> 00007fbd175fcdc0
>> [ 6472.719092] ---[ end trace c97dc6281a861980 ]---
>
> Agreed, same over here. :(
>

I *think* the following on top makes it fly

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 67fc6383995b..5cf7f6a6c1a6 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -656,6 +656,9 @@ static long region_del(struct resv_map *resv, long
f, long t)

del += t - f;

+ hugetlb_cgroup_uncharge_file_region(
+ resv, rg, t - f);
+
/* New entry for end of split region */
nrg->from = t;
nrg->to = rg->to;
@@ -667,9 +670,6 @@ static long region_del(struct resv_map *resv, long
f, long t)
/* Original entry is trimmed */
rg->to = f;

- hugetlb_cgroup_uncharge_file_region(
- resv, rg, nrg->to - nrg->from);
-
list_add(&nrg->link, &rg->link);
nrg = NULL;
break;


--
Thanks,

David / dhildenb