From patchwork Sun Nov 29 00:45:39 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nadav Amit X-Patchwork-Id: 11938875 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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 E678CC83014 for ; Sun, 29 Nov 2020 00:50:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B76AC208CA for ; Sun, 29 Nov 2020 00:50:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Uq3Na595" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729700AbgK2Au3 (ORCPT ); Sat, 28 Nov 2020 19:50:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40684 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725616AbgK2Au0 (ORCPT ); Sat, 28 Nov 2020 19:50:26 -0500 Received: from mail-pg1-x541.google.com (mail-pg1-x541.google.com [IPv6:2607:f8b0:4864:20::541]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 34BB3C0617A7; Sat, 28 Nov 2020 16:50:01 -0800 (PST) Received: by mail-pg1-x541.google.com with SMTP id t21so7391894pgl.3; Sat, 28 Nov 2020 16:50:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=pLO/Dm5aFg8h/isH2BDIjhNLAvIImEOy4o6l0iht6RI=; b=Uq3Na5959zjHT7zlMKGk03UxrU8zJxP7eRY742Q33BmNMujMif/ZsQnVVaWeZE8I0B TUUMUVhsGOUUj1IGJAY+A/VqbT330oGghAQqZbr8EQMFzkYwpGBecRM4VkBfAKEVNY/D 50xUF4uQxyWN0SG+snoLEuPHMi/X9IEthoWmsLGlC4stOdIh+Z+natl07aqHeaDinAsE K5nkqAOIB+SPkEIpZgkC1B7573INdvewtxEmAsrPOEmqxtjD22S9S1X1VnL67PFle+ei CY8lCbvTZ223ZsuxSU/4XsGE3qjZZY30qHZ/yg9AscOe6JQQjzdjjhKOIgFBj2fR17cM gjEQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=pLO/Dm5aFg8h/isH2BDIjhNLAvIImEOy4o6l0iht6RI=; b=iNVMfBowZOLhi/Dt+snrtAPPa8gYmYUhVB3UyJ1yRSaXzgUiImIniVA8D40s9RqInF om1rsPfNlZk6DEfThioc68h1vx/255faGVF9syUwZL0ZpZ30ZA6jCEjKm9w8RM9XvqLL doe9IC38s6xipeUX0Kg7lJN2nHoTHmuQ3w9/U8BdVHAWYARp3+ldkgcS/hfn7Y8hvaK4 9TcEid6nLO06Yrw/0/Xt+FsEOtNjzEtAM/XQhDHg60WPuLvqGIYHBmzKWXIITqwjD1f/ Te4qATtRPCLSoNkRZkyd9MpKWHRCjJrn5x07d/Whl9o5mdOkRXUeQ5YT6SfOu8dXCN+J GgwA== X-Gm-Message-State: AOAM532DJZ5ewagMJrY0ujV24+YDNuGXCQtJZeC61A1Lf4y5PsSR8s4c Bi0kw3VZiHKSaqCEP0+/otMdPcwU26gSNQ== X-Google-Smtp-Source: ABdhPJxaY9DxLDKGnkGFs9A9oqkbO/fjTGIBVHcLBTu9hXYx/XXtNjBNR1mCzr6//0a7w+5LsYbWMw== X-Received: by 2002:a63:eb4b:: with SMTP id b11mr12181060pgk.351.1606611000280; Sat, 28 Nov 2020 16:50:00 -0800 (PST) Received: from sc2-haas01-esx0118.eng.vmware.com ([66.170.99.1]) by smtp.gmail.com with ESMTPSA id gg19sm16444871pjb.21.2020.11.28.16.49.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 28 Nov 2020 16:49:59 -0800 (PST) From: Nadav Amit X-Google-Original-From: Nadav Amit To: linux-fsdevel@vger.kernel.org Cc: Nadav Amit , Jens Axboe , Andrea Arcangeli , Peter Xu , Alexander Viro , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH 04/13] fs/userfaultfd: simplify locks in userfaultfd_ctx_read Date: Sat, 28 Nov 2020 16:45:39 -0800 Message-Id: <20201129004548.1619714-5-namit@vmware.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201129004548.1619714-1-namit@vmware.com> References: <20201129004548.1619714-1-namit@vmware.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Nadav Amit Small refactoring to reduce the number of locations in which locks are released in userfaultfd_ctx_read(), as this makes the understanding of the code and its changes harder. No functional change intended. Cc: Jens Axboe Cc: Andrea Arcangeli Cc: Peter Xu Cc: Alexander Viro Cc: io-uring@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org Signed-off-by: Nadav Amit --- fs/userfaultfd.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 4fe07c1a44c6..fedf7c1615d5 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1039,6 +1039,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, set_current_state(TASK_INTERRUPTIBLE); spin_lock(&ctx->fault_pending_wqh.lock); uwq = find_userfault(ctx); + ret = -EAGAIN; if (uwq) { /* * Use a seqcount to repeat the lockless check @@ -1077,11 +1078,11 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, /* careful to always initialize msg if ret == 0 */ *msg = uwq->msg; - spin_unlock(&ctx->fault_pending_wqh.lock); ret = 0; - break; } spin_unlock(&ctx->fault_pending_wqh.lock); + if (!ret) + break; spin_lock(&ctx->event_wqh.lock); uwq = find_userfault_evt(ctx); @@ -1099,17 +1100,14 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, * reference on it. */ userfaultfd_ctx_get(fork_nctx); - spin_unlock(&ctx->event_wqh.lock); - ret = 0; - break; + } else { + userfaultfd_event_complete(ctx, uwq); } - - userfaultfd_event_complete(ctx, uwq); - spin_unlock(&ctx->event_wqh.lock); ret = 0; - break; } spin_unlock(&ctx->event_wqh.lock); + if (!ret) + break; if (signal_pending(current)) { ret = -ERESTARTSYS;