From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f68.google.com ([74.125.82.68]:38550 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934265AbeEYMtu (ORCPT ); Fri, 25 May 2018 08:49:50 -0400 From: Christian Brauner To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: torvalds@linux-foundation.org, tglx@linutronix.de, kstewart@linuxfoundation.org, gregkh@linuxfoundation.org, pombredanne@nexb.com, linux-api@vger.kernel.org, ebiederm@xmission.com, seth.forshee@canonical.com, viro@zeniv.linux.org.uk, Christian Brauner Subject: [PATCH 6/6 v1 resend] statfs: add ST_PRIVATE Date: Fri, 25 May 2018 14:48:25 +0200 Message-Id: <20180525124825.23875-7-christian@brauner.io> In-Reply-To: <20180525124825.23875-1-christian@brauner.io> References: <20180525124825.23875-1-christian@brauner.io> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Currently userspace can only determine whether a mountpoint is private by parsing /proc//mountinfo. It would be convenient to simply retrieve this property with a statvfs() call. This let's userspace avoid costly parsing, supports cases where /proc is not mounted, and supports usecases where file descriptors to mountpoints are passed between processes that are inspected via fstatvfs(). A mountpoint is considered ST_PRIVATE iff and it is neither ST_SLAVE nor ST_SHARED. Signed-off-by: Christian Brauner --- v0->v1: * non-functional changes: extend commit message --- fs/statfs.c | 2 ++ include/linux/statfs.h | 1 + 2 files changed, 3 insertions(+) diff --git a/fs/statfs.c b/fs/statfs.c index 35ad0402c9a3..899e899ee84c 100644 --- a/fs/statfs.c +++ b/fs/statfs.c @@ -58,6 +58,8 @@ static int calculate_f_flags(struct vfsmount *mnt) if (IS_MNT_SLAVE(real_mount(mnt))) flags |= ST_SLAVE; + else if (!(flags & ST_SHARED)) + flags |= ST_PRIVATE; return flags; } diff --git a/include/linux/statfs.h b/include/linux/statfs.h index 048127effaad..663fa5498a7d 100644 --- a/include/linux/statfs.h +++ b/include/linux/statfs.h @@ -41,6 +41,7 @@ struct kstatfs { #define ST_NODIRATIME (1<<11) /* do not update directory access times */ #define ST_RELATIME (1<<12) /* update atime relative to mtime/ctime */ #define ST_UNBINDABLE (1<<17) /* change to unbindable */ +#define ST_PRIVATE (1<<18) /* change to private */ #define ST_SLAVE (1<<19) /* change to slave */ #define ST_SHARED (1<<20) /* change to shared */ -- 2.17.0