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=-12.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 D3ABCC07E95 for ; Wed, 7 Jul 2021 21:06:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B501861C77 for ; Wed, 7 Jul 2021 21:06:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232521AbhGGVJb (ORCPT ); Wed, 7 Jul 2021 17:09:31 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:47039 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230500AbhGGVJa (ORCPT ); Wed, 7 Jul 2021 17:09:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1625692009; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=+7m/eIRlnZBYcjDw1k2mlaQoBa6NNsCMDSwIdGed5BM=; b=Rso6/edC2GhT0wlGQ/FQft0gTRyeU8rj6MUFhEinOXyIJuMOwtmKmHiBs6o5NaR5vf77/D BsjVfu1LsVRr9JYMgBJpPwdkLUHB6i7uHaP9B7MpyYopYVpycnPWirV/9hLV6MNSUvEQa3 mGRd+dapSvitF4ks1oG0vwRPYJCK6CY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-202-l2kfGnpAOr-A8Ox8VlWyDQ-1; Wed, 07 Jul 2021 17:06:48 -0400 X-MC-Unique: l2kfGnpAOr-A8Ox8VlWyDQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0DE6D100C610; Wed, 7 Jul 2021 21:06:47 +0000 (UTC) Received: from horse.redhat.com (ovpn-115-221.rdu2.redhat.com [10.10.115.221]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8AC3560C05; Wed, 7 Jul 2021 21:06:36 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 23F3522054F; Wed, 7 Jul 2021 17:06:36 -0400 (EDT) Date: Wed, 7 Jul 2021 17:06:36 -0400 From: Vivek Goyal To: Christoph Hellwig Cc: Stefan Hajnoczi , viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, virtio-fs@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [Virtio-fs] [PATCH 3/2] fs: simplify get_filesystem_list / get_all_fs_names Message-ID: <20210707210636.GC244500@redhat.com> References: <20210621062657.3641879-1-hch@lst.de> <20210622081217.GA2975@lst.de> <20210629205048.GE5231@redhat.com> <20210630053601.GA29241@lst.de> <20210707210404.GB244500@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210707210404.GB244500@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Jul 07, 2021 at 05:04:04PM -0400, Vivek Goyal wrote: > On Wed, Jun 30, 2021 at 07:36:01AM +0200, Christoph Hellwig wrote: > > On Tue, Jun 29, 2021 at 04:50:48PM -0400, Vivek Goyal wrote: > > > May be we should modify mount_block_root() code so that it does not > > > require that extra "\0". Possibly zero initialize page and that should > > > make sure list_bdev_fs_names() does not have to worry about it. > > > > > > It is possible that a page gets full from the list of filesystems, and > > > last byte on page is terminating null. In that case just zeroing page > > > will not help. We can keep track of some sort of end pointer and make > > > sure we are not searching beyond that for valid filesystem types. > > > > > > end = page + PAGE_SIZE - 1; > > > > > > mount_block_root() > > > { > > > for (p = fs_names; p < end && *p; p += strlen(p)+1) { > > > } > > > } > > > > Maybe. To honest I'd prefer to not even touch this unrelated code given > > how full of landmines it is :) > > Hi Christoph, > > How about following patch. This applies on top of your patches. I noticed > that Al had suggested to return number of filesystems from helper > functions. I just did that and used that to iterate in the loop. > > I tested it with a virtual block device (root=/dev/vda1) and it works. > I also filled page with garbage after allocation to make sure natually > occurring null is not there in the middle of page to terminate string. > > If you like it, can you please incorporate it in your patches. I noticed this will break with "root_fs_names=". Sorry, will have to fix split_fs_names() as well. Will do. Vivek > > Thanks > Vivek > > --- > fs/filesystems.c | 5 ++++- > include/linux/fs.h | 2 +- > init/do_mounts.c | 7 ++++--- > 3 files changed, 9 insertions(+), 5 deletions(-) > > Index: redhat-linux/fs/filesystems.c > =================================================================== > --- redhat-linux.orig/fs/filesystems.c 2021-07-07 16:12:08.890562576 -0400 > +++ redhat-linux/fs/filesystems.c 2021-07-07 16:27:51.197620063 -0400 > @@ -209,10 +209,11 @@ SYSCALL_DEFINE3(sysfs, int, option, unsi > } > #endif > > -void __init list_bdev_fs_names(char *buf, size_t size) > +int __init list_bdev_fs_names(char *buf, size_t size) > { > struct file_system_type *p; > size_t len; > + int count = 0; > > read_lock(&file_systems_lock); > for (p = file_systems; p; p = p->next) { > @@ -226,8 +227,10 @@ void __init list_bdev_fs_names(char *buf > memcpy(buf, p->name, len); > buf += len; > size -= len; > + count++; > } > read_unlock(&file_systems_lock); > + return count; > } > > #ifdef CONFIG_PROC_FS > Index: redhat-linux/include/linux/fs.h > =================================================================== > --- redhat-linux.orig/include/linux/fs.h 2021-07-07 15:36:43.224418935 -0400 > +++ redhat-linux/include/linux/fs.h 2021-07-07 16:12:18.232949807 -0400 > @@ -3622,7 +3622,7 @@ int proc_nr_dentry(struct ctl_table *tab > void *buffer, size_t *lenp, loff_t *ppos); > int proc_nr_inodes(struct ctl_table *table, int write, > void *buffer, size_t *lenp, loff_t *ppos); > -void __init list_bdev_fs_names(char *buf, size_t size); > +int __init list_bdev_fs_names(char *buf, size_t size); > > #define __FMODE_EXEC ((__force int) FMODE_EXEC) > #define __FMODE_NONOTIFY ((__force int) FMODE_NONOTIFY) > Index: redhat-linux/init/do_mounts.c > =================================================================== > --- redhat-linux.orig/init/do_mounts.c 2021-07-07 16:12:08.890562576 -0400 > +++ redhat-linux/init/do_mounts.c 2021-07-07 16:23:32.308889444 -0400 > @@ -391,15 +391,16 @@ void __init mount_block_root(char *name, > char *fs_names = page_address(page); > char *p; > char b[BDEVNAME_SIZE]; > + int num_fs, i; > > scnprintf(b, BDEVNAME_SIZE, "unknown-block(%u,%u)", > MAJOR(ROOT_DEV), MINOR(ROOT_DEV)); > if (root_fs_names) > split_fs_names(fs_names, root_fs_names); > else > - list_bdev_fs_names(fs_names, PAGE_SIZE); > + num_fs = list_bdev_fs_names(fs_names, PAGE_SIZE); > retry: > - for (p = fs_names; *p; p += strlen(p)+1) { > + for (p = fs_names, i = 0; i < num_fs; p += strlen(p)+1, i++) { > int err = do_mount_root(name, p, flags, root_mount_data); > switch (err) { > case 0: > @@ -432,7 +433,7 @@ retry: > printk("List of all partitions:\n"); > printk_all_partitions(); > printk("No filesystem could mount root, tried: "); > - for (p = fs_names; *p; p += strlen(p)+1) > + for (p = fs_names, i = 0; i < num_fs; p += strlen(p)+1, i++) > printk(" %s", p); > printk("\n"); > panic("VFS: Unable to mount root fs on %s", b); > >