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 X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C00CCC433E0 for ; Sun, 31 May 2020 14:15:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9461B20723 for ; Sun, 31 May 2020 14:15:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727971AbgEaOPQ (ORCPT ); Sun, 31 May 2020 10:15:16 -0400 Received: from out30-133.freemail.mail.aliyun.com ([115.124.30.133]:58044 "EHLO out30-133.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725889AbgEaOPQ (ORCPT ); Sun, 31 May 2020 10:15:16 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07484;MF=xiaoguang.wang@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0U-74R55_1590934328; Received: from 30.15.192.46(mailfrom:xiaoguang.wang@linux.alibaba.com fp:SMTPD_---0U-74R55_1590934328) by smtp.aliyun-inc.com(127.0.0.1); Sun, 31 May 2020 22:12:08 +0800 Subject: Re: [PATCH v4 1/2] io_uring: avoid whole io_wq_work copy for requests completed inline To: Jens Axboe , io-uring@vger.kernel.org Cc: asml.silence@gmail.com, joseph.qi@linux.alibaba.com References: <20200530143947.21224-1-xiaoguang.wang@linux.alibaba.com> <8c361177-c0b0-b08c-e0a5-141f7fd948f0@kernel.dk> <27e264ec-2707-495f-3d24-4e9e20b86032@kernel.dk> From: Xiaoguang Wang Message-ID: <32d0768e-f7d7-1281-e9ff-e95329db9dc5@linux.alibaba.com> Date: Sun, 31 May 2020 22:12:08 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.1 MIME-Version: 1.0 In-Reply-To: <27e264ec-2707-495f-3d24-4e9e20b86032@kernel.dk> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org hi jens, > On 5/30/20 11:14 AM, Jens Axboe wrote: >> On 5/30/20 10:44 AM, Jens Axboe wrote: >>> On 5/30/20 8:39 AM, Xiaoguang Wang wrote: >>>> If requests can be submitted and completed inline, we don't need to >>>> initialize whole io_wq_work in io_init_req(), which is an expensive >>>> operation, add a new 'REQ_F_WORK_INITIALIZED' to control whether >>>> io_wq_work is initialized. >>>> >>>> I use /dev/nullb0 to evaluate performance improvement in my physical >>>> machine: >>>> modprobe null_blk nr_devices=1 completion_nsec=0 >>>> sudo taskset -c 60 fio -name=fiotest -filename=/dev/nullb0 -iodepth=128 >>>> -thread -rw=read -ioengine=io_uring -direct=1 -bs=4k -size=100G -numjobs=1 >>>> -time_based -runtime=120 >>>> >>>> before this patch: >>>> Run status group 0 (all jobs): >>>> READ: bw=724MiB/s (759MB/s), 724MiB/s-724MiB/s (759MB/s-759MB/s), >>>> io=84.8GiB (91.1GB), run=120001-120001msec >>>> >>>> With this patch: >>>> Run status group 0 (all jobs): >>>> READ: bw=761MiB/s (798MB/s), 761MiB/s-761MiB/s (798MB/s-798MB/s), >>>> io=89.2GiB (95.8GB), run=120001-120001msec >>>> >>>> About 5% improvement. >>> >>> There's something funky going on here. I ran the liburing test >>> suite on this, and get a lot of left behind workers: >>> >>> Tests _maybe_ failed: ring-leak open-close open-close file-update file-update accept-reuse accept-reuse poll-v-poll poll-v-poll fadvise fadvise madvise madvise short-read short-read openat2 openat2 probe probe shared-wq shared-wq personality personality eventfd eventfd send_recv send_recv eventfd-ring eventfd-ring across-fork across-fork sq-poll-kthread sq-poll-kthread splice splice lfs-openat lfs-openat lfs-openat-write lfs-openat-write iopoll iopoll d4ae271dfaae-test d4ae271dfaae-test eventfd-disable eventfd-disable write-file write-file buf-rw buf-rw statx statx >>> >>> and also saw this: >>> >>> [ 168.208940] ================================================================== >>> [ 168.209311] BUG: KASAN: use-after-free in __lock_acquire+0x8bf/0x3000 >>> [ 168.209626] Read of size 8 at addr ffff88806801c0d8 by task io_wqe_worker-0/41761 >>> [ 168.209987] >>> [ 168.210069] CPU: 0 PID: 41761 Comm: io_wqe_worker-0 Not tainted 5.7.0-rc7+ #6318 >>> [ 168.210424] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 >>> [ 168.210857] Call Trace: >>> [ 168.210991] dump_stack+0x97/0xe0 >>> [ 168.211164] print_address_description.constprop.0+0x1a/0x210 >>> [ 168.211446] ? __lock_acquire+0x8bf/0x3000 >>> [ 168.211649] __kasan_report.cold+0x20/0x39 >>> [ 168.211851] ? __lock_acquire+0x8bf/0x3000 >>> [ 168.212051] kasan_report+0x30/0x40 >>> [ 168.212226] __lock_acquire+0x8bf/0x3000 >>> [ 168.212432] ? ret_from_fork+0x24/0x30 >>> [ 168.212623] ? stack_trace_save+0x81/0xa0 >>> [ 168.212821] ? lockdep_hardirqs_on+0x270/0x270 >>> [ 168.213039] ? save_stack+0x32/0x40 >>> [ 168.213212] lock_acquire+0x122/0x570 >>> [ 168.213398] ? __close_fd_get_file+0x40/0x150 >>> [ 168.213615] ? lock_release+0x3f0/0x3f0 >>> [ 168.213814] ? __lock_acquire+0x87e/0x3000 >>> [ 168.214016] _raw_spin_lock+0x2c/0x40 >>> [ 168.214196] ? __close_fd_get_file+0x40/0x150 >>> [ 168.214408] __close_fd_get_file+0x40/0x150 >>> [ 168.214618] io_issue_sqe+0x57f/0x22f0 >>> [ 168.214803] ? lockdep_hardirqs_on+0x270/0x270 >>> [ 168.215019] ? mark_held_locks+0x24/0x90 >>> [ 168.215211] ? quarantine_put+0x6f/0x190 >>> [ 168.215404] ? io_assign_current_work+0x59/0x80 >>> [ 168.215623] ? __ia32_sys_io_uring_setup+0x30/0x30 >>> [ 168.215855] ? find_held_lock+0xcb/0x100 >>> [ 168.216054] ? io_worker_handle_work+0x289/0x980 >>> [ 168.216280] ? lock_downgrade+0x340/0x340 >>> [ 168.216476] ? io_wq_submit_work+0x5d/0x140 >>> [ 168.216679] ? _raw_spin_unlock_irq+0x24/0x40 >>> [ 168.216890] io_wq_submit_work+0x5d/0x140 >>> [ 168.217087] io_worker_handle_work+0x30a/0x980 >>> [ 168.217305] ? io_wqe_dec_running.isra.0+0x70/0x70 >>> [ 168.217537] ? do_raw_spin_lock+0x100/0x180 >>> [ 168.217742] ? rwlock_bug.part.0+0x60/0x60 >>> [ 168.217943] io_wqe_worker+0x5fd/0x780 >>> [ 168.218126] ? lock_downgrade+0x340/0x340 >>> [ 168.218323] ? io_worker_handle_work+0x980/0x980 >>> [ 168.218546] ? lockdep_hardirqs_on+0x17d/0x270 >>> [ 168.218765] ? __kthread_parkme+0xca/0xe0 >>> [ 168.218961] ? io_worker_handle_work+0x980/0x980 >>> [ 168.219186] kthread+0x1f0/0x220 >>> [ 168.219346] ? kthread_create_worker_on_cpu+0xb0/0xb0 >>> [ 168.219590] ret_from_fork+0x24/0x30 >>> [ 168.219768] >>> [ 168.219846] Allocated by task 41758: >>> [ 168.220021] save_stack+0x1b/0x40 >>> [ 168.220185] __kasan_kmalloc.constprop.0+0xc2/0xd0 >>> [ 168.220416] kmem_cache_alloc+0xe0/0x290 >>> [ 168.220607] dup_fd+0x4e/0x5a0 >>> [ 168.220758] copy_process+0xe35/0x2bf0 >>> [ 168.220942] _do_fork+0xd8/0x550 >>> [ 168.221102] __do_sys_clone+0xb5/0xe0 >>> [ 168.221282] do_syscall_64+0x5e/0xe0 >>> [ 168.221457] entry_SYSCALL_64_after_hwframe+0x49/0xb3 >>> [ 168.221729] >>> [ 168.221848] Freed by task 41759: >>> [ 168.222088] save_stack+0x1b/0x40 >>> [ 168.222336] __kasan_slab_free+0x12f/0x180 >>> [ 168.222632] slab_free_freelist_hook+0x4d/0x120 >>> [ 168.222959] kmem_cache_free+0x90/0x2e0 >>> [ 168.223239] do_exit+0x5d2/0x12e0 >>> [ 168.223482] do_group_exit+0x6f/0x130 >>> [ 168.223754] __x64_sys_exit_group+0x28/0x30 >>> [ 168.224061] do_syscall_64+0x5e/0xe0 >>> [ 168.224326] entry_SYSCALL_64_after_hwframe+0x49/0xb3 >>> [ 168.224686] >>> >>> which indicates that current->files is no longer valid. >> >> Narrowed it down to the test/open-close test, and in particular where >> it closes the ring itself: >> >> ret = test_close(&ring, ring.ring_fd, 1); >> >> This seems to be because you do io_req_init_async() after calling >> io_issue_sqe(), and the command handler may have set something >> else for ->func at that point. Hence we never call the right >> handler if the close needs to be deferred, as it needs to for >> the io_uring as it has ->flush() defined. >> >> Why isn't io_req_init_async() just doing: >> >> static inline void io_req_init_async(struct io_kiocb *req, >> void (*func)(struct io_wq_work **)) >> { >> if (!(req->flags & REQ_F_WORK_INITIALIZED)) { >> req->work = (struct io_wq_work){ .func = func }; >> req->flags |= REQ_F_WORK_INITIALIZED; >> } >> } >> >> ? > > I guess that won't always work, if the request has been deferred and > we're now setting a new work func. So we really want the 'reset to > io_wq_submit_work' to only happen if the opcode hasn't already set > a private handler. Can you make that change? > > Also please fix up missing braces. The cases of: > > if (something) { > line 1 > line 2 > } else > line 3 > > should always includes braces, if one clause has it. > > A v5 with those two things would be ready to commit. First thanks for figuring out this bug. Indeed, I had run test cases in liburing/test multiple rounds before sending V4 patches, and all test cases pass, no kernel issues occurred, here is my kernel build config, seems that I had kasan enabled. [lege@localhost linux]$ cat .config | grep KASAN CONFIG_KASAN_SHADOW_OFFSET=0xdffffc0000000000 CONFIG_HAVE_ARCH_KASAN=y CONFIG_HAVE_ARCH_KASAN_VMALLOC=y CONFIG_CC_HAS_KASAN_GENERIC=y CONFIG_KASAN=y CONFIG_KASAN_GENERIC=y CONFIG_KASAN_OUTLINE=y # CONFIG_KASAN_INLINE is not set CONFIG_KASAN_STACK=1 # CONFIG_KASAN_VMALLOC is not set # CONFIG_TEST_KASAN is not set But I don't know why I did't reproduce the bug, sorry. Are you fine below changes? diff --git a/fs/io_uring.c b/fs/io_uring.c index 12296ce3e8b9..2a3a02838f7b 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -907,9 +907,10 @@ static void io_file_put_work(struct work_struct *work); static inline void io_req_init_async(struct io_kiocb *req, void (*func)(struct io_wq_work **)) { - if (req->flags & REQ_F_WORK_INITIALIZED) - req->work.func = func; - else { + if (req->flags & REQ_F_WORK_INITIALIZED) { + if (!req->work.func) + req->work.func = func; + } else { req->work = (struct io_wq_work){ .func = func }; req->flags |= REQ_F_WORK_INITIALIZED; } @@ -2920,6 +2921,8 @@ static int __io_splice_prep(struct io_kiocb *req, return ret; req->flags |= REQ_F_NEED_CLEANUP; + /* Splice will be punted aync, so initialize io_wq_work firstly_*/ + io_req_init_async(req, io_wq_submit_work); if (!S_ISREG(file_inode(sp->file_in)->i_mode)) req->work.flags |= IO_WQ_WORK_UNBOUND; @@ -3592,6 +3595,9 @@ static int io_statx(struct io_kiocb *req, bool force_nonblock) static int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) { + /* Close may be punted aync, so initialize io_wq_work firstly */ + io_req_init_async(req, io_wq_submit_work); + /* * If we queue this for async, it must not be cancellable. That would * leave the 'file' in an undeterminate state. Regards, Xiaoguang Wang >