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From:   David Howells <dhowells@redhat.com>
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To:     Miklos Szeredi <miklos@szeredi.hu>
Cc:     dhowells@redhat.com, Karel Zak <kzak@redhat.com>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>, dray@redhat.com,
        Miklos Szeredi <mszeredi@redhat.com>,
        Steven Whitehouse <swhiteho@redhat.com>,
        Jeff Layton <jlayton@redhat.com>, Ian Kent <raven@themaw.net>,
        andres@anarazel.de, keyrings@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Lennart Poettering <lennart@poettering.net>,
        Aleksa Sarai <cyphar@cyphar.com>
Subject: Re: Upcoming: Notifications, FS notifications and fsinfo()
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Date:   Thu, 02 Apr 2020 16:42:45 +0100
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Miklos Szeredi <miklos@szeredi.hu> wrote:

> > ext4_show_mount(), for example, doesn't lock against "mount -o remount=
", so
> > the configuration can be changing whilst it's being rendered to text.
> =

> Does s_umount nest inside namespace_sem?  I really don't see the
> relation of those locks.

If I understand aright what Al has told me, it's a bad idea to do any bloc=
king
operation inside of namespace_sem apart from kmalloc(GFP_KERNEL).

David