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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 0378FC54FCB for ; Sat, 25 Apr 2020 17:07:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BEF7720728 for ; Sat, 25 Apr 2020 17:07:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=rath.org header.i=@rath.org header.b="eGgl9IwM"; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b="RY113c8O" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726177AbgDYRHO (ORCPT ); Sat, 25 Apr 2020 13:07:14 -0400 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:60381 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726146AbgDYRHN (ORCPT ); Sat, 25 Apr 2020 13:07:13 -0400 Received: from compute2.internal (compute2.nyi.internal [10.202.2.42]) by mailout.nyi.internal (Postfix) with ESMTP id 2B8385C0172; Sat, 25 Apr 2020 13:07:13 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute2.internal (MEProxy); Sat, 25 Apr 2020 13:07:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rath.org; h=from :to:subject:date:message-id:mime-version:content-type :content-transfer-encoding; s=fm2; bh=+C2VjyQ2cmYFmQIGbS0PPo36mP R3PNjT64EnXqiAICA=; b=eGgl9IwMZh5zq6lvo3Ao7SMrzL20kG8RvjcZ/Bcy8U 7ZoSmdobk8QW7FRVzefYd/KLyH2Hk1jeYHcpEExViJHcF/jnk+5gITxpFBl39Mbe c1tZZaqk+Q8Ys5Eby+utZFrBqbXK1q4orbPlEsvVzOXHbU8sCiuFRV4pGZVAz1jz V2xJfohWHfZXc5ZWzFm6eJzJfETIc94xE0/0qvFPMyYNU2JwKwJ9s07bt8VD9/zu S+Z1c3grdqzPYdp1DQmt7kF5ZAIoRN9p7PSilh/hS96K0Z+J2jm8WV78qtTPefMu Hl7cBia0+eIsFnM/Ka6iZO9d+CSg2B6j+bZVPsa8j6Vg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=content-transfer-encoding:content-type :date:from:message-id:mime-version:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm2; bh=+C2Vjy Q2cmYFmQIGbS0PPo36mPR3PNjT64EnXqiAICA=; b=RY113c8Omdc0T/KoVapopj TqOwNuJ+M7Bt7R8R5e2utKXIW8SZT4L0XUgPjhjFyr+yOvoFaDW8jEyR+ZfgOgKA NMemI8FeirXwMrixWsgHj/r3f6etRmXpn4DMJvNuK40PdjsoZYtEujcm3f1gr1qo x9g+yUiS7DcmN7c4KNCoVxfH/AjWBZ2/pu5zdi5kJn3SB2OC+7hSAGdp2Lnkow2g C8qbB8IgU7lh02r7wTNRo10JBtTW6b7Hy9uOjsjKl9nxOTRtCzH6bD2OiGFRFV3w foMzt56xFWDdvSKb3me9RZSuUGaTzj424iz7UUv3jfTEo9mM40RPqVtfMIRNBJ1g == X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduhedrheeggdekiecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecunecujfgurhephffvufffkfgfgggtgfesthhqtddttd erjeenucfhrhhomheppfhikhholhgruhhsucftrghthhcuoefpihhkohhlrghushesrhgr thhhrdhorhhgqeenucfkphepudekhedrfedrleegrdduleegnecuvehluhhsthgvrhfuih iivgeptdenucfrrghrrghmpehmrghilhhfrhhomheppfhikhholhgruhhssehrrghthhdr ohhrgh X-ME-Proxy: Received: from ebox.rath.org (ebox.rath.org [185.3.94.194]) by mail.messagingengine.com (Postfix) with ESMTPA id 9F4F03065DC2; Sat, 25 Apr 2020 13:07:12 -0400 (EDT) Received: from vostro.rath.org (vostro [192.168.12.4]) by ebox.rath.org (Postfix) with ESMTPS id AEF6F1BF; Sat, 25 Apr 2020 17:07:11 +0000 (UTC) Received: by vostro.rath.org (Postfix, from userid 1000) id 6C908E0096; Sat, 25 Apr 2020 18:06:16 +0100 (BST) From: Nikolaus Rath To: linux-fsdevel@vger.kernel.org, fuse-devel Subject: [fuse] Getting visibility into reads from page cache Mail-Copies-To: never Mail-Followup-To: linux-fsdevel@vger.kernel.org, fuse-devel Date: Sat, 25 Apr 2020 18:06:16 +0100 Message-ID: <87k123h4vr.fsf@vostro.rath.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Hello, For debugging purposes, I would like to get information about read requests for FUSE filesystems that are answered from the page cache (i.e., that never make it to the FUSE userspace daemon). What would be the easiest way to accomplish that? For now I'd be happy with seeing regular reads and knowing when an application uses mmap (so that I know that I might be missing reads). Not having done any real kernel-level work, I would start by looking into using some tracing framework to hook into the relevant kernel function. However, I thought I'd ask here first to make sure that I'm not heading into the completely wrong direction. Best, -Nikolaus --=20 GPG Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F =C2=BBTime flies like an arrow, fruit flies like a Banana.=C2= =AB