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=-14.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 33BCBC43387 for ; Thu, 3 Jan 2019 20:25:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F14CF2184B for ; Thu, 3 Jan 2019 20:25:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ZBElct8B" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727809AbfACUZk (ORCPT ); Thu, 3 Jan 2019 15:25:40 -0500 Received: from mail-lj1-f193.google.com ([209.85.208.193]:34601 "EHLO mail-lj1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726864AbfACUZj (ORCPT ); Thu, 3 Jan 2019 15:25:39 -0500 Received: by mail-lj1-f193.google.com with SMTP id u89-v6so30816452lje.1 for ; Thu, 03 Jan 2019 12:25:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6zp4ONwVhSrOAGCBr8XdvNaVeQ4j2NYgbK7Hle4PIX0=; b=ZBElct8B16fincxcBvQZr6euiXN33OklGsc95g9GYeS5YmEddEd+wgSCTvXp6Yu9kK 33YkxzNiqG6zHTHRv0pqq3oqip1BiCDlMAz8lHS51W5Uz5doK+6Teu32QGVp53U3NE2g FYV+6N5WLP8SFAa/NMa2BdgxkXx6C5abVHkWhCaoVafT7SIC0kHSVDAVPeElu1+kct+D Ov0f1xeJAqVn5WvWPC8qb40EsapngCymXURHi5V5hHA4WFJS1HOpTj9PWDohSP7uHEdE bAdbrshk74UREcePcjEEQgIjBBFp75RHCW4W4nZe9ijY+KOGLAcRCfAGzpV9Ra181L+5 wkYg== 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=6zp4ONwVhSrOAGCBr8XdvNaVeQ4j2NYgbK7Hle4PIX0=; b=FoC5DzADW6G4z8Mut4qxza88QMFkSmqdiAt+J7sMBKA0gXMCSF1u4ZFz91K3zKqCNE nkQHsGg52IugBZF4B1gWxiIbSpFitevr4hOM+6GNpBvVOTkLkOZ5s3NVj6A99aj2Rcku IRC/1EQKdN0sbIo5QBr3JLBcM8ZXmWOlyNle2W00D6Tv0BiwCLQqelhcRlE/XZH+IF8g Awmy+s+5YFZ3icQjkBf9Xs4JD7g757wjZCfh7rhlCmvBh+Md6zbk821R8DfxMvm4A/sc lvLGaKQalmu3eI+Yck82iqH4As+YxKOUVmPmsRWBeR2N7jlomU0zm59vruUBIDO/Ff5l L/Jw== X-Gm-Message-State: AJcUukfpJ9rYPB1429lCDaLHpHqY1f0+aQ/TSOi2x4OqUGoodpfDXb03 oSz0DhrDH1pavCr0nYUQPVxkdZZW4Q2vxIlneYhiAw== X-Google-Smtp-Source: ALg8bN4/45dtUfoDrp3s9zkzpMtPL8k43Rr+MbVRtlk2MXNSiDV02vHnjL98qdm2F6YdjtRA0eIbIDGXRy6O1ApkbzY= X-Received: by 2002:a2e:29d7:: with SMTP id p84-v6mr27200151ljp.12.1546547135540; Thu, 03 Jan 2019 12:25:35 -0800 (PST) MIME-Version: 1.0 References: <20181223143550.10672-1-christian@brauner.io> <20181223143550.10672-2-christian@brauner.io> In-Reply-To: <20181223143550.10672-2-christian@brauner.io> From: Todd Kjos Date: Thu, 3 Jan 2019 12:25:24 -0800 Message-ID: Subject: Re: [PATCH v1 2/2] binderfs: reserve devices for initial mount To: Christian Brauner Cc: Greg Kroah-Hartman , Todd Kjos , "open list:ANDROID DRIVERS" , LKML , =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= , Martijn Coenen , joel@joelfernandes.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Dec 23, 2018 at 6:36 AM Christian Brauner wrote: > > The binderfs instance in the initial ipc namespace will always have a > reserve of 4 binder devices unless explicitly capped by specifying a lower > value via the "max" mount option. > This ensures when binder devices are removed (on accident or on purpose) > they can always be recreated without risking that all minor numbers have > already been used up. > > Cc: Todd Kjos > Cc: Greg Kroah-Hartman > Signed-off-by: Christian Brauner > --- > v1: > - patch introduced > v0: > - patch not present > --- > drivers/android/binderfs.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c > index 873adda064ac..aa635c7ea727 100644 > --- a/drivers/android/binderfs.c > +++ b/drivers/android/binderfs.c > @@ -40,6 +40,8 @@ > #define INODE_OFFSET 3 > #define INTSTRLEN 21 > #define BINDERFS_MAX_MINOR (1U << MINORBITS) > +/* Ensure that the initial ipc namespace always has a devices available. */ > +#define BINDERFS_MAX_MINOR_CAPPED (BINDERFS_MAX_MINOR - 4) Why do you ever need more minors per instance than the number of devices listed in CONFIG_ANDROID_BINDER_DEVICES? > > static struct vfsmount *binderfs_mnt; > > @@ -129,11 +131,14 @@ static int binderfs_binder_device_create(struct inode *ref_inode, > struct inode *inode = NULL; > struct super_block *sb = ref_inode->i_sb; > struct binderfs_info *info = sb->s_fs_info; > + bool use_reserve = (info->ipc_ns == &init_ipc_ns); > > /* Reserve new minor number for the new device. */ > mutex_lock(&binderfs_minors_mutex); > if (++info->device_count <= info->mount_opts.max) > - minor = ida_alloc_max(&binderfs_minors, BINDERFS_MAX_MINOR, > + minor = ida_alloc_max(&binderfs_minors, > + use_reserve ? BINDERFS_MAX_MINOR : > + BINDERFS_MAX_MINOR_CAPPED, > GFP_KERNEL); > else > minor = -ENOSPC; > -- > 2.19.1 >