On 11/10/2025 10:25 PM, Zi Yan wrote:
> On 10 Nov 2025, at 11:06, Lorenzo Stoakes wrote:
>
>> On Mon, Nov 10, 2025 at 01:22:16PM +0000, Lorenzo Stoakes wrote:
>>> On Mon, Nov 10, 2025 at 06:37:58PM +0530, Garg, Shivank wrote:
>>>>
>>>>
>>>> On 11/10/2025 5:31 PM, Lorenzo Stoakes wrote:
>>>>> On Mon, Nov 10, 2025 at 11:32:53AM +0000, Shivank Garg wrote:
>>>>>> When MADV_COLLAPSE is called on file-backed mappings (e.g., executable
>>>>
>>>>>> ---
>>>>>> Applies cleanly on:
>>>>>> 6.18-rc5
>>>>>> mm-stable:e9a6fb0bc
>>>>>
>>>>> Please base on mm-unstable. mm-stable is usually out of date until very close to
>>>>> merge window.
>>>>
>>>> I'm observing issues when testing with kselftest on mm-unstable and mm-new branches that prevent
>>>> proper testing for my patches:
>>>>
>>>> On mm-unstable (without my patches):
>>>>
>>>> # # running ./transhuge-stress -d 20
>>>> # # --------------------------------
>>>> # # TAP version 13
>>>> # # 1..1
>>>> # # transhuge-stress: allocate 220271 transhuge pages, using 440543 MiB virtual memory and 1720 MiB of ram
>>>>
>>>>
>>>> [ 367.225667] RIP: 0010:swap_cache_get_folio+0x2d/0xc0
>>>> [ 367.230635] Code: 00 00 48 89 f9 49 89 f9 48 89 fe 48 c1 e1 06 49 c1 e9 3a 48 c1 e9 0f 48 c1 e1 05 4a 8b 04 cd c0 2e 5b 99 48 8b 78 60 48 01 cf <48> 8b 47 08 48 85 c0 74 20 48 89 f2 81 e2 ff 01 00 00 48 8d 04 d0
>>>> [ 367.249378] RSP: 0000:ffffcde32943fba8 EFLAGS: 00010282
>>>> [ 367.254605] RAX: ffff8bd1668fdc00 RBX: 00007ffc15df5000 RCX: 00003fffffffffe0
>>>> [ 367.261736] RDX: ffffffff995cb530 RSI: 0003ffffffffffff RDI: ffffcbd1560dffe0
>>>> [ 367.268862] RBP: 0003ffffffffffff R08: ffffcde32943fc47 R09: 0000000000000000
>>>> [ 367.275994] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
>>>> [ 367.283129] R13: 0000000000000000 R14: ffff8bd1668fdc00 R15: 0000000000100cca
>>>> [ 367.290260] FS: 00007ff600af5b80(0000) GS:ffff8c4e9ec7e000(0000) knlGS:0000000000000000
>>>> [ 367.298344] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [ 367.304083] CR2: ffffcbd1560dffe8 CR3: 00000001280e9001 CR4: 0000000000770ef0
>>>> [ 367.311216] PKRU: 55555554
>>>> [ 367.313929] Call Trace:
>>>> [ 367.316375]
>>>> [ 367.318479] __read_swap_cache_async+0x8e/0x1b0
>>>> [ 367.323014] swap_vma_readahead+0x23d/0x430
>>>> [ 367.327198] swapin_readahead+0xb0/0xc0
>>>> [ 367.331039] do_swap_page+0x5bc/0x1260
>>>> [ 367.334789] ? rseq_ip_fixup+0x6f/0x190
>>>> [ 367.338631] ? __pfx_default_wake_function+0x10/0x10
>>>> [ 367.343596] __handle_mm_fault+0x49a/0x760
>>>> [ 367.347696] handle_mm_fault+0x188/0x300
>>>> [ 367.351620] do_user_addr_fault+0x15b/0x6c0
>>>> [ 367.355807] exc_page_fault+0x60/0x100
>>>> [ 367.359562] asm_exc_page_fault+0x22/0x30
>>>> [ 367.363574] RIP: 0033:0x7ff60091ba99
>>>> [ 367.367153] Code: f7 d8 64 89 02 b8 ff ff ff ff eb bd e8 40 c4 01 00 f3 0f 1e fa 80 3d b5 f5 0e 00 00 74 13 31 c0 0f 05 48 3d 00 f0 ff ff 77 4f 66 0f 1f 44 00 00 55 48 89 e5 48 83 ec 20 48 89 55 e8 48 89 75
>>>> [ 367.385897] RSP: 002b:00007ffc15df1118 EFLAGS: 00010203
>>>> [ 367.391124] RAX: 0000000000000001 RBX: 000055941fb672a0 RCX: 00007ff60091ba91
>>>> [ 367.398256] RDX: 0000000000000001 RSI: 000055941fb813e0 RDI: 0000000000000000
>>>> [ 367.405387] RBP: 00007ffc15df21e0 R08: 0000000000000000 R09: 0000000000000007
>>>> [ 367.412513] R10: 000055941fb97cb0 R11: 0000000000000246 R12: 000055941fb813e0
>>>> [ 367.419646] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>>>> [ 367.426781]
>>>> [ 367.428970] Modules linked in: xfrm_user xfrm_algo xt_addrtype xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT nf_reject_ipv4 nft_compat nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables overlay bridge stp llc cfg80211 rfkill binfmt_misc ipmi_ssif amd_atl intel_rapl_msr intel_rapl_common wmi_bmof amd64_edac edac_mce_amd mgag200 rapl drm_client_lib i2c_algo_bit drm_shmem_helper drm_kms_helper acpi_cpufreq i2c_piix4 ptdma k10temp i2c_smbus wmi acpi_power_meter ipmi_si acpi_ipmi ipmi_devintf ipmi_msghandler sg dm_multipath drm fuse dm_mod nfnetlink ext4 crc16 mbcache jbd2 raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor xor async_tx raid6_pq raid1 raid0 kvm_amd sd_mod ahci nvme libahci kvm libata nvme_core tg3 ccp megaraid_sas irqbypass
>>>> [ 367.497528] CR2: ffffcbd1560dffe8
>>>> [ 367.500846] ---[ end trace 0000000000000000 ]---
>>>
>>> Yikes, oopsies!
>>>
>>> I'll try running tests locally on threadripper, but ran tests against yours
>>> previously and seemed fine, strange. Maybe fixed since but let me try, maybe
>>> because swap is not enabled locally for me?
>>>
>>> Likely this actually...
>>
>> I have tried on swap-enabled setup and no issue with mm-unstable.
>>
>> So this is odd, I know you have limited time (_totally sympathise_) but is it at
>> all possible if you get a moment to bisect against tip mm-unstable/mm-new?
>>
>> Obviously we want to make sure buggy swap code doesn't get merged to mainline!
>
> I could not reproduce locally either.
>
> Shivank, can you share your config file and machine config?
I bisected the crash on mm-unstable
b14d61d8fe442b1cc2d7591cf040a6dcd7fe2dd8 is the first bad commit
commit b14d61d8fe442b1cc2d7591cf040a6dcd7fe2dd8
Author: Lorenzo Stoakes
Date: Sat Nov 8 17:08:18 2025 +0000
mm: eliminate is_swap_pte() when softleaf_from_pte() suffices
In cases where we can simply utilise the fact that softleaf_from_pte()
treats present entries as if they were none entries and thus eliminate
spurious uses of is_swap_pte(), do so.
No functional change intended.
Got delayed because I did a wrong step in git bisect and wanted to double confirm bisection.
No worries on time. Happy to test whenever you have a patch.
AMD Zen 3 EPYC server (7713) (2-sockets, 32 cores, SMT Enabled), 1 NUMA node per socket
total used free shared buff/cache available
Mem: 430Gi 183Gi 248Gi 5.5Mi 489Mi 246Gi
Swap: 8.0Gi 84Ki 8.0Gi
/proc/cmdline options:
init_on_alloc=0 console=ttyS0,115200n8 earlyprintk mitigations=off nohz_full= nohz=off amd_pstate=disable preempt=none
config attached.
Let me know if you need any other information:
Thanks,
Shivank