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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 C1A7BC433E0 for ; Wed, 5 Aug 2020 07:43:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6124A22B40 for ; Wed, 5 Aug 2020 07:43:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=szeredi.hu header.i=@szeredi.hu header.b="G2U85/Sh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726175AbgHEHnv (ORCPT ); Wed, 5 Aug 2020 03:43:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47014 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725809AbgHEHnv (ORCPT ); Wed, 5 Aug 2020 03:43:51 -0400 Received: from mail-ed1-x541.google.com (mail-ed1-x541.google.com [IPv6:2a00:1450:4864:20::541]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0801C06174A for ; Wed, 5 Aug 2020 00:43:50 -0700 (PDT) Received: by mail-ed1-x541.google.com with SMTP id l23so18065600edv.11 for ; Wed, 05 Aug 2020 00:43:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=c7MS/sDmqsu2UeEHE/y1WIBOLGRyoL/hTSKDaerW230=; b=G2U85/Sh33+IcIW0dxhFoe+oW0YUFI67TOMZGh5yXHDRtVNTTIES6+/5ghbYizPlrA NxqWRNYE+WiZQ5x/6V5NBGxTNuIsiyaYdE1+DK4um+EutgPdxUhLgshYgl+AqycDH9vs 4dvJRUCTUHLDjtWW+GCIgH/TbkBbaYm/yDD6c= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=c7MS/sDmqsu2UeEHE/y1WIBOLGRyoL/hTSKDaerW230=; b=qLHkh6rs5DUKGwagqFPgczNQkjkDs2FndE4Nv9EZsBgOyPV6h5pVbCq2MlbbrhYMgx bjRmX/V5Dv9Wdt0Piy08TkBxkMrcWmfHNlg7q8W4vbE9DJZBnF8N5rJMv7bgvEZHm9cY 6msPEZyEjL+hthIv00ngSdahIkLOGROTxpfxrT3slPPryKvyfP54SZRysFiVeIvHkEZU n9bIBnQoVwYIkutzS1Vs8gCHfSnQHORwKcIuZk3EWeMSAsJujlCeizCGHV0qXPV1WzMc KXqGYkmTtvofDcvgjl16avtrdFAUVJuW+UdELM0wnf6b3BVEwpCwIf1OQUrVF8AJ0h05 5syA== X-Gm-Message-State: AOAM530Ke5ecJbGkWqUguuuTN4kOSuBSe2sLY8xOVZFOPrJrB4fxdsyX +Y1TDReuStLdwpLuqslHCtEyJoI/afqhXvFhp2lEzw== X-Google-Smtp-Source: ABdhPJxB/evMZ5+0ZnmBx4YzSXoXDzPSNs9Cjc++wXkfuUDJKvalsR0eiNz5UMmlIUDOEP5Cy96B5iGq/jW2A8IePJ4= X-Received: by 2002:a50:fb10:: with SMTP id d16mr1638111edq.134.1596613429317; Wed, 05 Aug 2020 00:43:49 -0700 (PDT) MIME-Version: 1.0 References: <158454378820.2863966.10496767254293183123.stgit@warthog.procyon.org.uk> <158454391302.2863966.1884682840541676280.stgit@warthog.procyon.org.uk> <1293241.1595501326@warthog.procyon.org.uk> <43c061d26ddef2aa3ca1ac726da7db9ab461e7be.camel@themaw.net> In-Reply-To: From: Miklos Szeredi Date: Wed, 5 Aug 2020 09:43:38 +0200 Message-ID: Subject: Re: [PATCH 13/17] watch_queue: Implement mount topology and attribute change notifications [ver #5] To: Ian Kent Cc: David Howells , Linus Torvalds , Al Viro , Casey Schaufler , Stephen Smalley , Nicolas Dichtel , Christian Brauner , andres@anarazel.de, Jeff Layton , dray@redhat.com, Karel Zak , keyrings@vger.kernel.org, Linux API , linux-fsdevel@vger.kernel.org, LSM , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Wed, Aug 5, 2020 at 3:54 AM Ian Kent wrote: > > > > It's way more useful to have these in the notification than > > > obtainable > > > via fsinfo() IMHO. > > > > What is it useful for? > > Only to verify that you have seen all the notifications. > > If you have to grab that info with a separate call then the count > isn't necessarily consistent because other notifications can occur > while you grab it. No, no no. The watch queue will signal an overflow, without any additional overhead for the normal case. If you think of this as a protocol stack, then the overflow detection happens on the transport layer, instead of the application layer. The application layer is responsible for restoring state in case of a transport layer error, but detection of that error is not the responsibility of the application layer. Thanks, Miklos