From patchwork Wed Dec 1 04:23:23 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kumar Kartikeya Dwivedi X-Patchwork-Id: 12649023 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 BA440C433EF for ; Wed, 1 Dec 2021 04:23:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346513AbhLAE1D (ORCPT ); Tue, 30 Nov 2021 23:27:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49398 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229590AbhLAE06 (ORCPT ); Tue, 30 Nov 2021 23:26:58 -0500 Received: from mail-pl1-x641.google.com (mail-pl1-x641.google.com [IPv6:2607:f8b0:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8305FC061574; Tue, 30 Nov 2021 20:23:37 -0800 (PST) Received: by mail-pl1-x641.google.com with SMTP id u17so16655408plg.9; Tue, 30 Nov 2021 20:23:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=bUNS+Sa8lyKiGCkA+yHXnwWVJUVBTnwtTeWAMPi77yU=; b=AUPrMX2FYEVyWVtXZF8Mq1+JnAUt7vxT1USS8RlM6Y2qeM16AaTrc1LIFFqXIgH4Xz n1yXFrn/zYsO1AoQxcHdf6JkD80NRfgEfAOsnaTPwHuh0eDXvRSG7T5PBFRjPuHBKfDv Gc/cjpeyzTZ3QDnDN3Yi0rkmgdN+CUqnD/rmIWm8CZvFvAAOLLYvF5oq8pHZ1C6iS8Hj Ly5gnVIEcmIHcUunnj90/EQ4OPhQqPO+C/FnAV5Sa3s6nrK1rP+63zI6Jlcm8GMsO3/T nwQeEvOWakHYjhC/3/PBxxFXQAg2xHQ6zukKYBeGygsu0bluatriZC2BSNV2l9HwcKDW mUlA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=bUNS+Sa8lyKiGCkA+yHXnwWVJUVBTnwtTeWAMPi77yU=; b=wdgg3h6JmXOVBQKYciN5XwaY/wepIhq7TXoGAdeR1eMKxBYsk/u9CThE+KRqfBkzsY wXRQjb+XLyHQBmIIG3+6AZM2z9pbUDzKZ27OxqtrZjWGvpsekiuSa6Y431tiX4HeSB+3 t0Tx49jAMAiSDlnygc/le6pQKGNiEwnsLIjBfNeIO/J0+CqMUH2UAmL0ECwuoPQgFDLQ MfmGAcSHkMyGoxTr/k6RcxAkoZE2xADjFUxApPiwxs8q0CMyRPbKZVx1kS3J6Bd7W+xr XQ+k5j2ZMgJnbRIzVsuh6gx9ZnYOMdzoPbbmjVWYGzBqInXwCZBVfUDNt+WIEm3tWYM8 ABzw== X-Gm-Message-State: AOAM533ob83kg48/bVLDbEJCdLECdSUnB9mx2zRM3M7pZGJo/r8JCY9W GV+6PbF7bdQu8S+ag0CM2RMjMcVWlgU= X-Google-Smtp-Source: ABdhPJzsEXToPhYGsoz+kClFoqPOupoKGXO57zQ2W/4x2taxvfdw8IUT5ugl1N7Eikqqyz19bTyVKg== X-Received: by 2002:a17:90a:fe0a:: with SMTP id ck10mr4400247pjb.216.1638332616806; Tue, 30 Nov 2021 20:23:36 -0800 (PST) Received: from localhost ([2405:201:6014:d064:3d4e:6265:800c:dc84]) by smtp.gmail.com with ESMTPSA id j1sm21330637pfe.158.2021.11.30.20.23.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Nov 2021 20:23:36 -0800 (PST) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Yonghong Song , Pavel Emelyanov , Alexander Mikhalitsyn , Andrei Vagin , criu@openvz.org, io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH bpf-next v3 00/10] Introduce BPF iterators for io_uring and epoll Date: Wed, 1 Dec 2021 09:53:23 +0530 Message-Id: <20211201042333.2035153-1-memxor@gmail.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5748; h=from:subject; bh=78j4YRjD1ivrtgADq/aBU0z1jmIS5yDNBh6P6aC15iE=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBhpvYxUM1Dy/xAourqI/VAL5JiyFeJL5BD/eBYJet/ +XPkbeeJAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCYab2MQAKCRBM4MiGSL8Rysc5D/ 47yUGjwZcGdDvkiIfUKjBSxSB+C6/R6f1rwOWZyp/13XsPvJkppU06j5+yKLATMPTfFiBt7zG7ONzS IXsLB4Fi3o6HkPt+Y4X0q9/BaECD34r/0+wCnz+q/Hq4JnUsRRej9ZOOdNjDs+4zHCfvFDcxsLYTxg jCecWe/sP2JcXzUbQxtK9V/aa700Q5hl92a6v8zwEjKFpC36NrB/njmlYMk+udgBR0P4yFsdhiqzxI QhaK6DS6mMdKLR7+XNs4egILTLlVT///H3np0SK2t3w0E2w9AaTUvEnCJtFbZuDAhhQE0RiN9E9mog 1/RNi3/0jUqq+WzI+tTpnGQyQknPKW19OQTAywWE4ndj02XIySQfGEbReIRDfCwCum0MQymlyRy1P2 xf9yXH2fZSy+hGQu4Sh04MUaXOfvVd1oZfKLz7luh7HSRVP86OsKZtGSmHAcRbhkKWU1Zr71/n9Ohv bZ7MPV5H8qhU0Nl9K4u1VRVfL3KWw8V/JqPNH1S/1RzI/70x5UMBnZimAGipu/L5HJ2HYYT0/2zyYB sBQNxkVZoDGar4AG8GfpMbEkRXlFQkhmJHXP3URPu8gwaZK95mtQCzYM6YZaXWXXOo1N8BnFxn3s+D iFDaDAZxLg3pLXKD4Qpt0MZRmdTAclqoUeYYkvED+FPDlWMg+91gxRFoexDw== X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=4BBE2A7E06ECF9D5823C61114CE0C88648BF11CA Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org The CRIU [0] project developers are exploring potential uses of the BPF subsystem to do complicated tasks that are difficult to add support for in the kernel using existing interfaces. Even if they are implemented using procfs, or kcmp, it is difficult to make it perform well without having some kind of programmable introspection into the kernel data structures. Moreover, for procfs based state inspection, the output format once agreed upon is set in stone and hard to extend, and at the same time inefficient to consume from programs (where it is first converted from machine readable form to human readable form, only to be converted again to machine readable form). In addition to this, kcmp based file set matching algorithm performs poorly since each file in one set needs to be compared to each file in another set, to determine struct file equivalence. This set adds a io_uring file iterator (for registered files), a io_uring ubuf iterator (for registered buffers), and a epoll iterator (for registered items (files, registered using EPOLL_CTL_ADD)) to overcome these limitations. Using existing task, task_file, task_vma iterators, all of these can be combined together to significantly enhance and speed up the task dumping procedure. The two immediate use cases are io_uring checkpoint/restore support and epoll checkpoint/restore support. The first is unimplemented, and the second is being expedited using a new epoll iterator. In the future, more stages of the checkpointing sequence can be offloaded to eBPF programs to reduce process downtime, e.g. in pre-dump stage, before task is seized. The io_uring file iterator is even more important now due to the advent of descriptorless files in io_uring [1], which makes dumping a task's files a lot more harder for CRIU, since there is no visibility into these hidden descriptors that the task depends upon for operation. Similarly, the io_uring_ubuf iterator is useful in case original VMA used in registering a buffer has been destroyed. The set includes an example sample showing how these iterator(s) along with task_file iterator can be useful to restore an io_uring instance, implementing a simplified version of the code we are planning to adopt for CRIU. Patch 10 is not meant for submission, only exposition, hence explicitly marked RFC. It implements the missing features noted in [2]. Please see the individual patches for more details. [ Note (for Yonghong): I am still unusure what will be useful in show_fdinfo, fill_link_info for epoll, so that has been left out. I was reminded that io_uring now uses anon_inode_getfile_secure, which we also use in CRIU to determine source fd of ring mapping, so this should be enough to identify the io_uring fd in userspace, hence I implemented it for io_uring in v2. ] [0]: https://criu.org/Main_Page [1]: https://lwn.net/Articles/863071 [2]: https://github.com/checkpoint-restore/criu/pull/1597 Changelog: ---------- v2 -> v3: v2: https://lore.kernel.org/bpf/20211122225352.618453-1-memxor@gmail.com * Make show_fdinfo/fill_link_info functions static (Kernel Test Robot) * Minor memory leak fixes for bpf_cr * Use proper names instead of -2, -1 for denoting epoll iterator state v1 -> v2: v1: https://lore.kernel.org/bpf/20211116054237.100814-1-memxor@gmail.com * Add example showing how iterator is useful in C/R of io_uring (Alexei) * Change type of index from unsigned long to u64 (Yonghong) * Fix build error for CONFIG_IO_URING=n (Kernel Test Robot) * Move bpf_page_to_pfn out of CONFIG_IO_URING (Yonghong) * Add comment to bpf_iter_aux_info for map member (Yonghong) * show_fdinfo/fill_link_info for io_uring (Yonghong) * Fix other nits Kumar Kartikeya Dwivedi (10): io_uring: Implement eBPF iterator for registered buffers bpf: Add bpf_page_to_pfn helper io_uring: Implement eBPF iterator for registered files epoll: Implement eBPF iterator for registered items bpftool: Output io_uring iterator info selftests/bpf: Add test for io_uring BPF iterators selftests/bpf: Add test for epoll BPF iterator selftests/bpf: Test partial reads for io_uring, epoll iterators selftests/bpf: Fix btf_dump test for bpf_iter_link_info samples/bpf: Add example to checkpoint/restore io_uring fs/eventpoll.c | 201 ++++- fs/io_uring.c | 345 +++++++++ include/linux/bpf.h | 16 + include/uapi/linux/bpf.h | 18 + kernel/trace/bpf_trace.c | 19 + samples/bpf/.gitignore | 1 + samples/bpf/Makefile | 8 +- samples/bpf/bpf_cr.bpf.c | 185 +++++ samples/bpf/bpf_cr.c | 688 ++++++++++++++++++ samples/bpf/bpf_cr.h | 48 ++ samples/bpf/hbm_kern.h | 2 - scripts/bpf_doc.py | 2 + tools/bpf/bpftool/link.c | 10 + tools/include/uapi/linux/bpf.h | 18 + .../selftests/bpf/prog_tests/bpf_iter.c | 387 +++++++++- .../selftests/bpf/prog_tests/btf_dump.c | 4 +- .../selftests/bpf/progs/bpf_iter_epoll.c | 33 + .../selftests/bpf/progs/bpf_iter_io_uring.c | 50 ++ 18 files changed, 2027 insertions(+), 8 deletions(-) create mode 100644 samples/bpf/bpf_cr.bpf.c create mode 100644 samples/bpf/bpf_cr.c create mode 100644 samples/bpf/bpf_cr.h create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_epoll.c create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_io_uring.c