From: aaptel@suse.com (Aurélien Aptel)
To: linux-fsdevel@vger.kernel.org
Subject: Duplicate network filesystems
Date: Mon, 11 Feb 2019 18:58:09 +0100 [thread overview]
Message-ID: <87sgwujjgu.fsf@suse.com> (raw)
Hi,
In fs/namespace.c do_add_mount() we do this check:
/* Refuse the same filesystem on the same mount point */
err = -EBUSY;
if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
path->mnt->mnt_root == path->dentry)
goto unlock;
So that mount fails with EBUSY. But for networked filesystems (at least
cifs and nfs) you can do this:
mount //foo /mnt -o A
mount //foo /mnt -o B # different options
Since the SB are different it works, fine.
But mounting a 3rd time with options A succeeds, where from a user POV I
would have expected to fail.
So to recap:
mount //foo /mnt -o A
mount //foo /mnt -o A
# EBUSY => expected behaviour
mount //foo /mnt -o A
mount //foo /mnt -o B
# ok => expected behaviour
mount //foo /mnt -o A
mount //foo /mnt -o B
mount //foo /mnt -o A
# ok => what?
Shouldn't we check the stack of filesystems mounted at the path instead of
just the last one?
Cheers,
--
Aurélien Aptel / SUSE Labs Samba Team
GPG: 1839 CB5F 9F5B FB9B AA97 8C99 03C8 A49B 521B D5D3
SUSE Linux GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
next reply other threads:[~2019-02-11 17:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-11 17:58 Aurélien Aptel [this message]
2019-02-15 3:40 ` Duplicate network filesystems NeilBrown
2019-02-15 10:18 ` Aurélien Aptel
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