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From: Zdenek Kabelac <zdenek.kabelac@gmail.com>
To: LVM general discussion and development <linux-lvm@redhat.com>,
	Pascal <patatetom@gmail.com>
Subject: Re: [linux-lvm] LVM and RO device/partition(s)
Date: Mon, 20 Mar 2023 14:57:49 +0100	[thread overview]
Message-ID: <5b9e31d6-2675-8903-619c-cf33c48f1ba8@gmail.com> (raw)
In-Reply-To: <CAGhAaddYD7Y8ObY6Q3Yprhruzb8s6-q0t+GJUv5oYGLR3LCpRg@mail.gmail.com>

Dne 19. 03. 23 v 11:27 Pascal napsal(a):
> hi,
> 
> the bio_check_ro function of the blk-core.c source file of the Linux kernel 
> refers to LVM :
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/block/blk-core.c?h=v6.2.7#n500 <https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/block/blk-core.c?h=v6.2.7#n500>
> 
> how does LVM currently behave when faced with a device marked as readonly ?
> does it automatically switch itself in readonly mode?
> 
> according to some tests carried out in a virtual machine, it seems that it 
> doesn't and that LVM modifies the disk/partition(s) even though they are all 
> readonly (chmod 444 && blockdev --setro).


Hi

There is no extra logic around RO devices in lvm2.  When lvm2 succeeds opening 
device in write mode, it'll use it for writing.

Also note - when you 'activate' a LV in read-write mode - someone opens such 
LV/device and you later on 'lvchange' such active LV to read-only mode - all 
writers will keep writing to such device.

It's not quite clear which kind of problem you are actually hitting - so maybe 
adding some more descriptive  environment +  logs  might give more info about 
your individual case.

Note: root admin typically can overwrite any 'mild' protections...

Regards

Zdenek

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  reply	other threads:[~2023-03-20 14:00 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-19 10:27 [linux-lvm] LVM and RO device/partition(s) Pascal
2023-03-20 13:57 ` Zdenek Kabelac [this message]
2023-03-20 14:15   ` lacsaP Patatetom
2023-03-20 16:37     ` lacsaP Patatetom
2023-03-22 14:11       ` [linux-lvm] LVM and RO device/partition(s Zdenek Kabelac
2023-03-22 14:50         ` lacsaP Patatetom

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