From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:42596 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230322AbhBFDME (ORCPT ); Fri, 5 Feb 2021 22:12:04 -0500 Date: Fri, 5 Feb 2021 16:05:51 -0800 From: Andrew Morton Subject: Re: [PATCH] tmpfs: Disallow CONFIG_TMPFS_INODE64 on s390 Message-Id: <20210205160551.cf57c4293ba5ccb8eb648c11@linux-foundation.org> In-Reply-To: <20210205230620.518245-1-seth.forshee@canonical.com> References: <20210205230620.518245-1-seth.forshee@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit List-ID: To: Seth Forshee Cc: Hugh Dickins , Chris Down , Amir Goldstein , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , linux-mm@kvack.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org On Fri, 5 Feb 2021 17:06:20 -0600 Seth Forshee wrote: > This feature requires ino_t be 64-bits, which is true for every > 64-bit architecture but s390, so prevent this option from being > selected there. > The previous patch nicely described the end-user impact of the bug. This is especially important when requesting a -stable backport. Here's what I ended up with: From: Seth Forshee Subject: tmpfs: disallow CONFIG_TMPFS_INODE64 on s390 Currently there is an assumption in tmpfs that 64-bit architectures also have a 64-bit ino_t. This is not true on s390 which has a 32-bit ino_t. With CONFIG_TMPFS_INODE64=y tmpfs mounts will get 64-bit inode numbers and display "inode64" in the mount options, but passing the "inode64" mount option will fail. This leads to the following behavior: # mkdir mnt # mount -t tmpfs nodev mnt # mount -o remount,rw mnt mount: /home/ubuntu/mnt: mount point not mounted or bad option. As mount sees "inode64" in the mount options and thus passes it in the options for the remount. So prevent CONFIG_TMPFS_INODE64 from being selected on s390. Link: https://lkml.kernel.org/r/20210205230620.518245-1-seth.forshee@canonical.com Fixes: ea3271f7196c ("tmpfs: support 64-bit inums per-sb") Signed-off-by: Seth Forshee Cc: Chris Down Cc: Hugh Dickins Cc: Amir Goldstein Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Christian Borntraeger Cc: [5.9+] Signed-off-by: Andrew Morton --- fs/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/fs/Kconfig~tmpfs-disallow-config_tmpfs_inode64-on-s390 +++ a/fs/Kconfig @@ -203,7 +203,7 @@ config TMPFS_XATTR config TMPFS_INODE64 bool "Use 64-bit ino_t by default in tmpfs" - depends on TMPFS && 64BIT + depends on TMPFS && 64BIT && !S390 default n help tmpfs has historically used only inode numbers as wide as an unsigned _