linux-kernel - Re: [PATCH v1 3/7] nvmet: implement namespace identify descriptor list

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Date:   Thu, 1 Jun 2017 08:42:33 +0200
From:   Christoph Hellwig <hch@....de>
To:     Johannes Thumshirn <jthumshirn@...e.de>
Cc:     Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
        Keith Busch <keith.busch@...el.com>,
        Hannes Reinecke <hare@...e.de>,
        Max Gurtovoy <maxg@...lanox.com>,
        Linux NVMe Mailinglist <linux-nvme@...ts.infradead.org>,
        Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 3/7] nvmet: implement namespace identify descriptor
        list

On Wed, May 31, 2017 at 03:32:13PM +0200, Johannes Thumshirn wrote:
> A NVMe Identify NS command with a CNS value of '3' is expecting a list
> of Namespace Identification Descriptor structures to be returned to
> the host for the namespace requested in the namespace identify
> command.
> 
> This Namespace Identification Descriptor structure consists of the
> type of the namespace identifier, the length of the identifier and the
> actual identifier.
> 
> Valid types are EUI-64, NGUID and UUID which we have saved in our
> nvme_ns structure if they have been configured via configfs. If no
> value has been assigened to one of these we return an "invalid opcode"
> back to the host to maintain backward compatibiliy with older
> implementations without Namespace Identify Descriptor list support.
> 
> Signed-off-by: Johannes Thumshirn <jthumshirn@...e.de>
> ---
>  drivers/nvme/target/admin-cmd.c | 63 +++++++++++++++++++++++++++++++++++++++++
>  include/linux/nvme.h            | 18 ++++++++++++

Can you split all the new structures in nvme.h into a separate patch
at the beginning of the series?

> +	static const int buf_size = SZ_4K;

Please add a NVME_IDENTIFY_DATA_SIZE define to nvme.h (and I'd slighty
prefer to define it to 4096 instead of the odd SZ_4K).  And also replace
all the places where we use a magic 4096 for the identify payload with
it.

> +	nid_list = kzalloc(buf_size, GFP_KERNEL);
> +	if (!nid_list) {
> +		status = NVME_SC_INTERNAL;
> +		goto out_put_ns;
> +	}
> +
> +	p = nid_list;

No need for the dynamic allocation.  Just do a straight nvmet_copy_to_sgl
from the stack for each element.

> +
> +	if (memchr_inv(&ns->uuid, 0, sizeof(ns->uuid))) {
> +		ns_nid = (struct nvme_ns_nid *)p;
> +		ns_nid->nidt = NVME_NIDT_UUID;
> +		ns_nid->nidl = NVME_NIDT_UUID_LEN;
> +		memcpy(&ns_nid->nid, &ns->uuid, sizeof(ns->uuid));
> +		pos += sizeof(struct nvme_ns_nid) + sizeof(ns->uuid);
> +		if (pos > buf_size) {
> +			status = NVME_SC_INVALID_OPCODE | NVME_SC_DNR;
> +			goto out_free_nid_list;
> +		}
> +		p += pos;
> +	}

E.g. something like

	struct nvme_ns_identifier_hdr nih;

	...

		memset(&nih, 0, sizeof(nih));
		nih.nidt = NVME_NIDT_UUID;
		nih.nidl = NVME_NIDT_UUID_LEN;
		status = nvmet_copy_to_sgl(req, off, &nih, sizeof(nih));
		if (status)
			goto out_put_ns;
		off += sizeof(nih);

		status = nvmet_copy_to_sgl(req, off, &ns->uuid,
				sizeof(ns->uuid));
		if (status)
			goto out_put_ns;
		off += sizeof(ns->uuid);