NVMe write protection support

[Gilles BULOZ]

Hi Christoph,
Our disk manufacturer told me their NVMe does not follow NVMe specification 2.0 but 1.3.
Is there also something in 1.3 to handle the write protection cleanly ?
Currently the only thing I get is a medium error, or an I/O error due to an aborted command leading to problems even when working at 
block device level (using dd) : the device file /dev/nvme0n1 disappears ! So I can't imaging what this would do with a real 
filesystem on top of that.
I'm using kernel 5.18.13 (fedora 36 with updates)
Thanks
Gilles

Le 19/09/2022 à 16:59, Christoph Hellwig a écrit :
> On Tue, Sep 13, 2022 at 07:17:57PM +0200, Gilles BULOZ wrote:
>> But in my case the WP pin when enabled would make the initial state of the
>> namespace at the time of its creation be "Write Protect". Or I could
>> simulate a transition from "No Write Protect" to "Write Protect" but this
>> would be without "Set Features" command.
>> In both cases I would be out of specs.
> I don't think you need that.  Just set bit 0 of the NSATTR field in
> the Identify Namespace stucture to 1 and ignore the Set/Get Features
> parts.  If your pin can be chaned at runtime, make sure that the bit
> is updated based on it and that the Namespace Attribute Changed
> AEN is sent when that happens.
>
>> Also if the implementation is correct in the NVMe, and assuming the kernel
>> already supports this case gracefully, what king of kernel message would I
>> get (in dmesg) in case of a write to a protected device ?
> Opening a block devie that was set to read only before will return
> -EACCES.  If it is set to read-only after it was opened there is no
> special handling and you'll get a good old -EIO.
>
> .