From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4760CC04A6A for ; Wed, 9 Aug 2023 15:23:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232046AbjHIPXQ (ORCPT ); Wed, 9 Aug 2023 11:23:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52324 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231643AbjHIPXP (ORCPT ); Wed, 9 Aug 2023 11:23:15 -0400 Received: from mail-wr1-x435.google.com (mail-wr1-x435.google.com [IPv6:2a00:1450:4864:20::435]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9E5A7E7C for ; Wed, 9 Aug 2023 08:23:14 -0700 (PDT) Received: by mail-wr1-x435.google.com with SMTP id ffacd0b85a97d-3176a439606so5338045f8f.3 for ; Wed, 09 Aug 2023 08:23:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1691594593; x=1692199393; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=ELMb6v23f8g+8dGMLdkl9Jyc+EIf9oDO46Nx+EN1fG4=; b=7lapMx26WZNlT/xrrIVJt/a2qO2K1qpR+FsL19quyx5ZstB99UIgHHe73v7ck1WWJr 2E4oOepfMCGcKwfRbCGQkJriZhEg+IjyoX3t1v5+Y62OB4bE9I8KKHtSg6+DglgaPul8 sSIC15ySQHhffaE4E8EslKNwxo9eK/0sW2oVwPEDcyv2Jg6aErBVISmoLBFHpF1pJvGE rCdYYKNTMu3A/Scc945WtkfxzM2fHgu48+2LraEHnTnAHdq09ItUbDdfnhHu6gNhV7Yz mwXTZdjCLSri8Di2ikIcjUac2wz5ptgx8UxaVTFGTzT/NOgVWGaeW2ry0w9tHtzEFs1W J2rQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1691594593; x=1692199393; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=ELMb6v23f8g+8dGMLdkl9Jyc+EIf9oDO46Nx+EN1fG4=; b=EFhSAfgBhJjthMwp15EfvqqBJKt7pBOJ1eDBRfH/SkHVIYG8V9tm2+MFjfdkToWlgS gxCBvnavgbHTgY4n4dMRZrqbqyegxmprmZBJBe1zRyWWRarVb3nS9kGOeGZIVsb9GYL8 VsXiVQZKMzmXm6ARAJz30k7sD9vn9OmvzTlmhqpotlxMmphcv6Pp2hySfhWXwz+UGP8c 0J3LJwZIEYzQX0+jmR4fBRN7seErl2m9zCv5ZUyd/fU5a0A9eF+/rjSVFX8Z0D79ni94 sh04DxHre4wSqgWfjp533CgG3bi2cgKopCGgop50lAVeXHCt27jDw4mmBcGsDwHf/KiK XWTg== X-Gm-Message-State: AOJu0YwqBwpnletUqpq3wVE+Mc6rZOgi7D/7Pkwyrt+bxBoIyx+43J5u bpAf9rbyZUg6MSpZvs2eKy68LFzK+UuNvZ2CTueKDw== X-Google-Smtp-Source: AGHT+IHpMssOOannUeS7r2GRzEdsLMy2aZavOMdGJXQWLiw1L0Oj05rPR/9uwk5jaJB+w5wIUunktWb3O8pHZ6inQFk= X-Received: by 2002:a5d:4dc5:0:b0:309:1532:8287 with SMTP id f5-20020a5d4dc5000000b0030915328287mr2059361wru.19.1691594592883; Wed, 09 Aug 2023 08:23:12 -0700 (PDT) MIME-Version: 1.0 References: <20230630211957.1341547-1-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Wed, 9 Aug 2023 08:22:59 -0700 Message-ID: Subject: Re: [PATCH v7 0/6] Per-VMA lock support for swap and userfaults To: David Hildenbrand Cc: akpm@linux-foundation.org, willy@infradead.org, hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz, minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com, lstoakes@gmail.com, hdanton@sina.com, apopple@nvidia.com, peterx@redhat.com, ying.huang@intel.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, pasha.tatashin@soleen.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Aug 9, 2023 at 7:28=E2=80=AFAM Suren Baghdasaryan wrote: > > On Wed, Aug 9, 2023 at 12:49=E2=80=AFAM David Hildenbrand wrote: > > > > On 30.06.23 23:19, Suren Baghdasaryan wrote: > > > When per-VMA locks were introduced in [1] several types of page fault= s > > > would still fall back to mmap_lock to keep the patchset simple. Among= them > > > are swap and userfault pages. The main reason for skipping those case= s was > > > the fact that mmap_lock could be dropped while handling these faults = and > > > that required additional logic to be implemented. > > > Implement the mechanism to allow per-VMA locks to be dropped for thes= e > > > cases. > > > First, change handle_mm_fault to drop per-VMA locks when returning > > > VM_FAULT_RETRY or VM_FAULT_COMPLETED to be consistent with the way > > > mmap_lock is handled. Then change folio_lock_or_retry to accept vm_fa= ult > > > and return vm_fault_t which simplifies later patches. Finally allow s= wap > > > and uffd page faults to be handled under per-VMA locks by dropping pe= r-VMA > > > and retrying, the same way it's done under mmap_lock. > > > Naturally, once VMA lock is dropped that VMA should be assumed unstab= le > > > and can't be used. > > > > > > Changes since v6 posted at [2] > > > - 4/6 replaced the ternary operation in folio_lock_or_retry, > > > per Matthew Wilcox > > > - 4/6 changed return code description for __folio_lock_or_retry > > > per Matthew Wilcox > > > > > > Note: patch 3/6 will cause a trivial merge conflict in arch/arm64/mm/= fault.c > > > when applied over mm-unstable branch due to a patch from ARM64 tree [= 3] > > > which is missing in mm-unstable. > > > > > > [1] https://lore.kernel.org/all/20230227173632.3292573-1-surenb@googl= e.com/ > > > [2] https://lore.kernel.org/all/20230630020436.1066016-1-surenb@googl= e.com/ > > > [3] https://lore.kernel.org/all/20230524131305.2808-1-jszhang@kernel.= org/ > > > > > > Suren Baghdasaryan (6): > > > swap: remove remnants of polling from read_swap_cache_async > > > mm: add missing VM_FAULT_RESULT_TRACE name for VM_FAULT_COMPLETED > > > mm: drop per-VMA lock when returning VM_FAULT_RETRY or > > > VM_FAULT_COMPLETED > > > mm: change folio_lock_or_retry to use vm_fault directly > > > mm: handle swap page faults under per-VMA lock > > > mm: handle userfaults under VMA lock > > > > On mm/mm-unstable I get running the selftests: > > > > Testing sigbus-wp on shmem... [ 383.215804] mm ffff9666078e5280 task_s= ize 140737488351232 > > [ 383.215804] get_unmapped_area ffffffffad03b980 > > [ 383.215804] mmap_base 140378441285632 mmap_legacy_base 4725435388313= 6 > > [ 383.215804] pgd ffff966608960000 mm_users 1 mm_count 6 pgtables_byte= s 126976 map_count 28 > > [ 383.215804] hiwater_rss 6183 hiwater_vm 8aa7 total_vm 8aa7 locked_vm= 0 > > [ 383.215804] pinned_vm 0 data_vm 844 exec_vm 1a4 stack_vm 21 > > [ 383.215804] start_code 402000 end_code 408f09 start_data 40ce10 end_= data 40d500 > > [ 383.215804] start_brk 17fe000 brk 1830000 start_stack 7ffecbbe08e0 > > [ 383.215804] arg_start 7ffecbbe1c6f arg_end 7ffecbbe1c81 env_start 7f= fecbbe1c81 env_end 7ffecbbe1fe6 > > [ 383.215804] binfmt ffffffffaf3efe40 flags 80000cd > > [ 383.215804] ioctx_table 0000000000000000 > > [ 383.215804] owner ffff96660d4a4000 exe_file ffff966285501a00 > > [ 383.215804] notifier_subscriptions 0000000000000000 > > [ 383.215804] numa_next_scan 4295050919 numa_scan_offset 0 numa_scan_s= eq 0 > > [ 383.215804] tlb_flush_pending 0 > > [ 383.215804] def_flags: 0x0() > > [ 383.236255] ------------[ cut here ]------------ > > [ 383.237537] kernel BUG at include/linux/mmap_lock.h:66! > > [ 383.238897] invalid opcode: 0000 [#1] PREEMPT SMP PTI > > [ 383.240114] CPU: 37 PID: 1482 Comm: uffd-unit-tests Not tainted 6.5.= 0-rc4+ #68 > > [ 383.242513] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS= 1.16.2-1.fc38 04/01/2014 > > [ 383.244936] RIP: 0010:find_vma+0x3a/0x40 > > [ 383.246200] Code: 48 89 34 24 48 85 c0 74 1c 48 83 c7 40 48 c7 c2 ff= ff ff ff 48 89 e6 e8 a4 29 ba 00 > > [ 383.251084] RSP: 0000:ffffae3745b6beb0 EFLAGS: 00010282 > > [ 383.252781] RAX: 0000000000000314 RBX: ffff9666078e5280 RCX: 0000000= 000000000 > > [ 383.255073] RDX: 0000000000000001 RSI: ffffffffae8f69c3 RDI: 0000000= 0ffffffff > > [ 383.257352] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffae3= 745b6bc48 > > [ 383.259369] R10: 0000000000000003 R11: ffff9669fff46fe8 R12: 0000000= 044401028 > > [ 383.261570] R13: ffff9666078e5338 R14: ffffae3745b6bf58 R15: 0000000= 000000400 > > [ 383.263499] FS: 00007fac671c5740(0000) GS:ffff9669efbc0000(0000) kn= lGS:0000000000000000 > > [ 383.265483] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [ 383.266847] CR2: 0000000044401028 CR3: 0000000488960006 CR4: 0000000= 000770ee0 > > [ 383.268532] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000= 000000000 > > [ 383.270206] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000= 000000400 > > [ 383.271905] PKRU: 55555554 > > [ 383.272593] Call Trace: > > [ 383.273215] > > [ 383.273774] ? die+0x32/0x80 > > [ 383.274510] ? do_trap+0xd6/0x100 > > [ 383.275326] ? find_vma+0x3a/0x40 > > [ 383.276152] ? do_error_trap+0x6a/0x90 > > [ 383.277072] ? find_vma+0x3a/0x40 > > [ 383.277899] ? exc_invalid_op+0x4c/0x60 > > [ 383.278846] ? find_vma+0x3a/0x40 > > [ 383.279675] ? asm_exc_invalid_op+0x16/0x20 > > [ 383.280698] ? find_vma+0x3a/0x40 > > [ 383.281527] lock_mm_and_find_vma+0x3f/0x270 > > [ 383.282570] do_user_addr_fault+0x1e4/0x660 > > [ 383.283591] exc_page_fault+0x73/0x170 > > [ 383.284509] asm_exc_page_fault+0x22/0x30 > > [ 383.285486] RIP: 0033:0x404428 > > [ 383.286265] Code: 48 89 85 18 ff ff ff e9 dc 00 00 00 48 8b 15 9f 92= 00 00 48 8b 05 80 92 00 00 48 03 > > [ 383.290566] RSP: 002b:00007ffecbbe05c0 EFLAGS: 00010206 > > [ 383.291814] RAX: 0000000044401028 RBX: 00007ffecbbe08e8 RCX: 00007fa= c66e93c18 > > [ 383.293502] RDX: 0000000044400000 RSI: 0000000000000001 RDI: 0000000= 000000000 > > [ 383.295175] RBP: 00007ffecbbe06c0 R08: 00007ffecbbe05c0 R09: 00007ff= ecbbe06c0 > > [ 383.296857] R10: 0000000000000008 R11: 0000000000000246 R12: 0000000= 000000000 > > [ 383.298533] R13: 00007ffecbbe08f8 R14: 000000000040ce18 R15: 00007fa= c67206000 > > [ 383.300203] > > [ 383.300775] Modules linked in: rfkill intel_rapl_msr intel_rapl_comm= on intel_uncore_frequency_commong > > [ 383.309661] ---[ end trace 0000000000000000 ]--- > > [ 383.310795] RIP: 0010:find_vma+0x3a/0x40 > > [ 383.311771] Code: 48 89 34 24 48 85 c0 74 1c 48 83 c7 40 48 c7 c2 ff= ff ff ff 48 89 e6 e8 a4 29 ba 00 > > [ 383.316081] RSP: 0000:ffffae3745b6beb0 EFLAGS: 00010282 > > [ 383.317346] RAX: 0000000000000314 RBX: ffff9666078e5280 RCX: 0000000= 000000000 > > [ 383.319050] RDX: 0000000000000001 RSI: ffffffffae8f69c3 RDI: 0000000= 0ffffffff > > [ 383.320767] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffae3= 745b6bc48 > > [ 383.322468] R10: 0000000000000003 R11: ffff9669fff46fe8 R12: 0000000= 044401028 > > [ 383.324164] R13: ffff9666078e5338 R14: ffffae3745b6bf58 R15: 0000000= 000000400 > > [ 383.325870] FS: 00007fac671c5740(0000) GS:ffff9669efbc0000(0000) kn= lGS:0000000000000000 > > [ 383.327795] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [ 383.329177] CR2: 0000000044401028 CR3: 0000000488960006 CR4: 0000000= 000770ee0 > > [ 383.330885] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000= 000000000 > > [ 383.332592] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000= 000000400 > > [ 383.334287] PKRU: 55555554 > > > > > > Which ends up being > > > > VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm); > > > > I did not check if this is also the case on mainline, and if this serie= s is responsible. > > Thanks for reporting! I'm checking it now. Hmm. From the code it's not obvious how lock_mm_and_find_vma() ends up calling find_vma() without mmap_lock after successfully completing get_mmap_lock_carefully(). lock_mm_and_find_vma+0x3f/0x270 points to the first invocation of find_vma(), so this is not even the lock upgrade path... I'll try to reproduce this issue and dig up more but from the information I have so far this issue does not seem to be related to this series. > > > > > -- > > Cheers, > > > > David / dhildenb > >