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 099CFC25B72 for ; Wed, 25 Oct 2023 14:39:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234992AbjJYOj4 (ORCPT ); Wed, 25 Oct 2023 10:39:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57798 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344790AbjJYOEA (ORCPT ); Wed, 25 Oct 2023 10:04:00 -0400 Received: from mail-io1-xd35.google.com (mail-io1-xd35.google.com [IPv6:2607:f8b0:4864:20::d35]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17DB8189 for ; Wed, 25 Oct 2023 07:03:57 -0700 (PDT) Received: by mail-io1-xd35.google.com with SMTP id ca18e2360f4ac-7a6643ba679so40446139f.1 for ; Wed, 25 Oct 2023 07:03:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20230601.gappssmtp.com; s=20230601; t=1698242636; x=1698847436; darn=vger.kernel.org; h=content-transfer-encoding:subject:from:cc:to:content-language :user-agent:mime-version:date:message-id:from:to:cc:subject:date :message-id:reply-to; bh=xmmBJe4qx/Z0FecJmP2HKoWoGSGv5MNLqFmWTEvkhKI=; b=a/8qgnaEyPA2+d8L9scDYh0UYOxTJMS3BK0vc5+KINadxbd8jQdWq6+LEwx98nOVly QYPXB7WikXnW7AijKNEUhH3X3mNTwxws0+hr9itZeAWfE7zkEv+j0sQaEQyDGjTfPI5m Z63kUysNIdyjWSZS7XeBfu+j3muxPa0v1WQoll8aqn8y9vFZVyrvshAYBcKoxkC03yT9 Jsl+Syxfw0fyhDGofGoSgoVI/H2VyOu0CF4ILccExRaYfztxPUiyBg3E20syJ87UiipT ubsIRvA5ZZO5cfEixyMI9Idhv53GILJcjwqxvJauCzg0yB9iWlMK+e/gRdweVnuXGgAv jqOw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1698242636; x=1698847436; h=content-transfer-encoding:subject:from:cc:to:content-language :user-agent:mime-version:date:message-id:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=xmmBJe4qx/Z0FecJmP2HKoWoGSGv5MNLqFmWTEvkhKI=; b=Rh3SdhFLb+6x4OMxzSn3+YcP9jHQ77xLazrBzdjgYclLH2F8FLkf3Y2tjExit9vJCG DWOTmmSO2WLUgwN9IxcbQTfI/HVKJNzNcyffJjMRbK1XHDURUflcuWTDYvEauJxJXye+ 4PiG65ceKafFDRCdjvs7o0z1gMN1C9tJS41GZFqQIgp29Ojspk4mRAGlXuJG7M/DeCsN ZuE3f9WkFkrGiav3xoJpx+2Lvi2Ec4BlrhWYbia/e9RoZ1ALvRM2n760WVF9GiDKjsi6 boXEPDwC/qFdZkbrKNG6d/BXTjqtDzgTQEoyozjBSbLZfUxOsENQGQxfQG5VjJ7iV32e 8qqw== X-Gm-Message-State: AOJu0YwQSpEiQ7nesrQ3xU9zLyJQ9Uf2SFFUdhmry3Z92LH0VbGYL5QC 42KxFqfftsEaDpn0gMZj8xnXFQ5FuQBac4hDW9SmZA== X-Google-Smtp-Source: AGHT+IFYmFywKXAzWWhg4qfxKE9/pCPls+VDtDPHa5McGJtGQk0XUmWH7jSIpHWbdFzkwKTT1x9JWg== X-Received: by 2002:a05:6e02:ec1:b0:357:a986:18ee with SMTP id i1-20020a056e020ec100b00357a98618eemr12760905ilk.1.1698242635601; Wed, 25 Oct 2023 07:03:55 -0700 (PDT) Received: from [192.168.1.94] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id y13-20020a92090d000000b0034fccc27c11sm3735496ilg.76.2023.10.25.07.03.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 25 Oct 2023 07:03:55 -0700 (PDT) Message-ID: <48d0ea0b-af74-4a2e-9961-0286466050a9@kernel.dk> Date: Wed, 25 Oct 2023 08:03:54 -0600 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US To: io-uring Cc: Andres Freund , Dave Chinner , "linux-ext4@vger.kernel.org" From: Jens Axboe Subject: [PATCH] io_uring/rw: disable IOCB_DIO_CALLER_COMP Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org If an application does O_DIRECT writes with io_uring and the file system supports IOCB_DIO_CALLER_COMP, then completions of the dio write side is done from the task_work that will post the completion event for said write as well. Whenever a dio write is done against a file, the inode i_dio_count is elevated. This enables other callers to use inode_dio_wait() to wait for previous writes to complete. If we defer the full dio completion to task_work, we are dependent on that task_work being run before the inode i_dio_count can be decremented. If the same task that issues io_uring dio writes with IOCB_DIO_CALLER_COMP performs a synchronous system call that calls inode_dio_wait(), then we can deadlock as we're blocked sleeping on the event to become true, but not processing the completions that will result in the inode i_dio_count being decremented. Until we can guarantee that this is the case, then disable the deferred caller completions. Fixes: 099ada2c8726 ("io_uring/rw: add write support for IOCB_DIO_CALLER_COMP") Reported-by: Andres Freund Signed-off-by: Jens Axboe --- diff --git a/io_uring/rw.c b/io_uring/rw.c index c8c822fa7980..807d83ab756e 100644 --- a/io_uring/rw.c +++ b/io_uring/rw.c @@ -913,15 +913,6 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags) kiocb_start_write(kiocb); kiocb->ki_flags |= IOCB_WRITE; - /* - * For non-polled IO, set IOCB_DIO_CALLER_COMP, stating that our handler - * groks deferring the completion to task context. This isn't - * necessary and useful for polled IO as that can always complete - * directly. - */ - if (!(kiocb->ki_flags & IOCB_HIPRI)) - kiocb->ki_flags |= IOCB_DIO_CALLER_COMP; - if (likely(req->file->f_op->write_iter)) ret2 = call_write_iter(req->file, kiocb, &s->iter); else if (req->file->f_op->write) -- Jens Axboe