NetBSD Problem Report #60024

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Date: Sat, 21 Feb 2026 10:08:07 +0000 (UTC)
From: imuwoto@gmail.com
Reply-To: imuwoto@gmail.com
To: gnats-bugs@NetBSD.org
Subject: zfs mount overrides zfs properties like "readonly"
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X-From4GNATS: "imuwoto@gmail.com via gnats" <gnats-admin@NetBSD.org>

>Number:         60024
>Category:       kern
>Synopsis:       zfs mount overrides zfs properties like "readonly"
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          needs-pullups
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Feb 21 10:10:00 +0000 2026
>Closed-Date:    
>Last-Modified:  Tue Mar 17 00:28:12 +0000 2026
>Originator:     YAMAMOTO Takashi
>Release:        NetBSD 10.1
>Organization:
>Environment:
amd64
>Description:
see the following example, where readonly=on property is
somehow disabled by a re-mount.

uma# zfs set readonly=on y/tmp
uma# zfs get readonly y/tmp
NAME   PROPERTY  VALUE   SOURCE
y/tmp  readonly  on      local
uma# zfs umount y/tmp
uma# zfs get readonly y/tmp
NAME   PROPERTY  VALUE   SOURCE
y/tmp  readonly  on      local
uma# zfs mount y/tmp      
uma# zfs get readonly y/tmp
NAME   PROPERTY  VALUE   SOURCE
y/tmp  readonly  off     temporary
uma# 
>How-To-Repeat:

>Fix:
i'm testing this: https://github.com/yamt/netbsd-src/commit/1ba3ad1c41aa1a43de794d27ffaeb817ad58a3c1

>Release-Note:

>Audit-Trail:
From: "YAMAMOTO Takashi" <yamt@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/60024 CVS commit: src/external/cddl/osnet/sys/kern
Date: Sun, 1 Mar 2026 13:52:29 +0000

 Module Name:	src
 Committed By:	yamt
 Date:		Sun Mar  1 13:52:29 UTC 2026

 Modified Files:
 	src/external/cddl/osnet/sys/kern: vfs.c

 Log Message:
 solaris vfs_optionisset: treat 0 as unspecified

 this allows users to leave it default.

 before this change, when a user runs "zfs mount -a",
 it was processed as "mount them read-write, overriding readonly property".
 i don't think it's what the user usually intends.

 looking at the illumos code, it seems that mount options there are
 basically tri-state. that is, "ro", "rw", and unspecified.
 as NetBSD only has a single bit, MNT_RDONLY or !MNT_RDONLY, this commit
 maps !MNT_RDONLY to unspecified, which i believe more often matches
 the user's intention. it also seems like what illumos does for the legacy
 MS_RDONLY bit if i read their code correctly. that is, if MS_RDONLY is set,
 it sets MNTOPT_RO. on the other hand, a lack of MS_RDONLY doesn't imply
 MNTOPT_RW.

 references:
 "Temporary Mount Point Properties" section of zfs(8)

 PR/60024
 https://gnats.netbsd.org/60024


 To generate a diff of this commit:
 cvs rdiff -u -r1.9 -r1.10 src/external/cddl/osnet/sys/kern/vfs.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: open->needs-pullups
State-Changed-By: yamt@NetBSD.org
State-Changed-When: Tue, 17 Mar 2026 00:28:12 +0000
State-Changed-Why:
pullup-11.
i haven't investigated earlier branches.


>Unformatted:

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