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CzK/3EaeadWXsI5/Bx4tG8vMtpHVhD9JghnvwzONOGsVb8JaEvkyARIdwaZwUUVtdy/nooPjUKLvp+T0/G9AK6O0EQZe6M+3wgVMaIM/TYo+Ejy5oN5FD+VwEHBe2ZAaHfKTB3+8f6ObuA2PWafIDWmIPW+m4xkmOOODeVceZm/H/Vxvyb0WGGFEC0LMZBfI3Uo/T9GkuKtp8qTFN1thPJ0GiXXiZZRi9MGCMGqC/tLlD+BrgyMuQJjSfMMtSXQxws1387rV1keJFzmQO66QAtiSGwuiGoJDGxAaSj4WvpCBlW1SD33NzA5xiYpK2V2r1m1ics1fS2fXBCms4DW2lMVTHpMqSy12lpdcJOf5m2NU/MDu+WgCGbPXqkne9+aKuK9yuIbQbn7vC+Atq+TMMO4ZsWOX0KoXYd1kDBOQuhcstlR8lBOijvLYzB66/1AJIqdtJ/A+AJltme78= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 mm-stable is usually out of date until very close to 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 ]--- ----------------- On mm-new (without my patches): [ 394.144770] get_swap_device: Bad swap offset entry 3ffffffffffff dmesg | grep "get_swap_device: Bad swap offset entry" | wc -l 359 Additionally, kexec triggers an oops and crash during swapoff: Deactivating swap 704.854238] BUG: unable to handle page fault for address: ffffcbe2de8dffe8 [ 704.861524] #PF: supervisor read access in kernel mode ;39mswap.img.swa[ 704.866666] #PF: error_code(0x0000) - not-present page [ 704.873253] PGD 0 P4D 0 p - /swap.im[ 704.875790] Oops: Oops: 0000 [#1] SMP NOPTI g... [ 704.881354] CPU: 122 UID: 0 PID: 107680 Comm: swapoff Kdump: loaded Not tainted 6.18.0-rc5+ #11 NONE [ 704.891283] Hardware name: Dell Inc. PowerEdge R6525/024PW1, BIOS 2.16.2 07/09/2024 [ 704.898930] RIP: 0010:swap_cache_get_folio+0x2d/0xc0 [ 704.903907] 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 7b 95 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 [ 704.922720] RSP: 0018:ffffcf1227b1fc08 EFLAGS: 00010282 [ 704.928035] RAX: ffff8be2cefb3c00 RBX: 0000555c65a5c000 RCX: 00003fffffffffe0 [ 704.928036] RDX: 0003ffffffffffff RSI: 0003ffffffffffff RDI: ffffcbe2de8dffe0 [ 704.928037] RBP: 0000000000000000 R08: ffff8be2de8e0520 R09: 0000000000000000 Unmount[ 704.928038] R10: 000000000000ffff R11: ffffcf12236f4000 R12: ffff8be2d5b8d968 [ 704.928039] R13: 0003ffffffffffff R14: fffff3eec85eb000 R15: 0000555c65a51000 [ 704.928039] FS: 00007f41fcab3800(0000) GS:ffff8c602b6fe000(0000) knlGS:0000000000000000 [ 704.928040] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 704.928041] CR2: ffffcbe2de8dffe8 CR3: 00000074981af004 CR4: 0000000000770ef0 [ 704.928041] PKRU: 55555554 [ 704.928042] Call Trace: [ 704.928043] [ 704.928044] unuse_pte_range+0x10b/0x290 [ 704.928047] unuse_pud_range.isra.0+0x149/0x190 [ 704.928048] unuse_vma+0x1a6/0x220 [ 704.928050] unuse_mm+0x9b/0x110 [ 704.928052] try_to_unuse+0xc5/0x260 [ 704.928053] __do_sys_swapoff+0x244/0x670 ing boo[ 705.016662] do_syscall_64+0x67/0xc50 [ 705.016667] ? do_user_addr_fault+0x15b/0x6c0 t.mount - /b[ 705.026100] ? exc_page_fault+0x60/0x100 [ 705.031498] ? irqentry_exit_to_user_mode+0x20/0xe0 oot... [ 705.036377] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 705.042200] RIP: 0033:0x7f41fc9271bb [ 705.045780] Code: 0f 1e fa 48 83 fe 01 48 8b 15 59 bc 0d 00 19 c0 83 e0 f0 83 c0 26 64 89 02 b8 ff ff ff ff c3 f3 0f 1e fa b8 a8 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 2d bc 0d 00 f7 d8 64 89 01 48 [ 705.064807] RSP: 002b:00007ffd14b5b6e8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a8 [ 705.064809] RAX: ffffffffffffffda RBX: 00007ffd14b5cf30 RCX: 00007f41fc9271bb [ 705.064810] RDX: 0000000000000001 RSI: 0000000000000c00 RDI: 000055d48f533a40 [ 705.064810] RBP: 00007ffd14b5b750 R08: 00007f41fca03b20 R09: 0000000000000000 [ 705.064811] R10: 0000000000000001 R11: 0000000000000202 R12: 0000000000000000 [ 705.064811] R13: 0000000000000000 R14: 000055d4584f1479 R15: 000055d4584f2b20 [ 705.064813] [ 705.064814] 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 rapl mgag200 drm_client_lib i2c_algo_bit drm_shmem_helper drm_kms_helper acpi_cpufreq i2c_piix4 ptdma ipmi_si k10temp i2c_smbus acpi_power_meter wmi acpi_ipmi ipmi_msghandler sg dm_multipath fuse drm 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 sd_mod kvm_amd ahci libahci kvm nvme tg3 libata ccp irqbypass nvme_core megaraid_sas [last unloaded: ipmi_devintf] [ 705.180420] CR2: ffffcbe2de8dffe8 [ 705.183852] ---[ end trace 0000000000000000 ]--- I haven't had cycles to dig into this yet and been swamped with other things. >> + if (!is_shmem && cc && !cc->is_khugepaged && mapping_can_writeback(mapping)) { >> + range_start = (loff_t)start << PAGE_SHIFT; >> + range_end = ((loff_t)end << PAGE_SHIFT) - 1; >> + if (filemap_write_and_wait_range(mapping, range_start, range_end)) { >> + result = SCAN_FAIL; >> + goto out; >> + } >> + } > > I feel this is the wrong level of abstraction. > > We explicitly invoke this oth from khugepaged and madvise(..., MADV_COLLAPSE): > > > khugepaged_scan_mm_slot() / madvise_collapse() > -> hpage_collapse_scan_file() > -> collapse_file() > > ofc you are addressing this with the !cc->is_khugepaged, but feels like we'd be > better off just doing it in madvise_collapse(). > > I wonder also if doing I/O without getting the mmap lock again and revalidating > is wise, as the state of things might have changed significantly. > > So maybe need a hugepage_vma_revalidate() as well? Thanks for the feedback. I'll incorporate these comments for v2. Thanks, Shivank