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From: Christoph Hellwig <hch@lst.de>
To: Max Gurtovoy <maxg@mellanox.com>
Cc: axboe@kernel.dk, jsmart2021@gmail.com, sagi@grimberg.me,
	martin.petersen@oracle.com, shlomin@mellanox.com,
	linux-rdma@vger.kernel.org, israelr@mellanox.com,
	vladimirk@mellanox.com, linux-nvme@lists.infradead.org,
	idanb@mellanox.com, jgg@mellanox.com, oren@mellanox.com,
	kbusch@kernel.org, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 08/17] nvme-rdma: add metadata/T10-PI support
Date: Fri, 24 Apr 2020 09:09:30 +0200	[thread overview]
Message-ID: <20200424070930.GC24059@lst.de> (raw)
In-Reply-To: <688ec4ba-78e8-0ba3-9ee9-3c19b3e7b0c6@mellanox.com>

On Thu, Apr 23, 2020 at 12:22:27PM +0300, Max Gurtovoy wrote:
>>> diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
>>> index e38f8f7..23cc77e 100644
>>> --- a/drivers/nvme/host/rdma.c
>>> +++ b/drivers/nvme/host/rdma.c
>>> @@ -67,6 +67,9 @@ struct nvme_rdma_request {
>>>   	struct ib_cqe		reg_cqe;
>>>   	struct nvme_rdma_queue  *queue;
>>>   	struct nvme_rdma_sgl	data_sgl;
>>> +	/* Metadata (T10-PI) support */
>>> +	struct nvme_rdma_sgl	*md_sgl;
>>> +	bool			use_md;
>> Do we need a use_md flag vs just using md_sgl as a boolean and/or
>> using blk_integrity_rq?
>
> md_sgl will be used if we'll get a blk request with blk_integrity (memory 
> domain).
>
> use_md will be responsible for wire domain.
>
> so instead of this bool we can check in any place (after prev commit 
> changes):
>
> "
>
> if (queue->pi_support && nvme_ns_has_pi(ns))
>                 req->use_md = c.common.opcode == nvme_cmd_write ||
>                               c.common.opcode == nvme_cmd_read;
>
> "
>
> And this is less readable IMO.

It would obviously have to go into a little helper, but I really hate
adding lots of little fields caching easily derived information.  There
are a few exception, for example if we really need to not touch too
many cache lines.  Do you have a git tree with your current code?  That
might be a little easier to follow than the various patches, maybe
I can think of something better.

>>> +	if (blk_integrity_rq(rq)) {
>>> +		memset(req->md_sgl, 0, sizeof(struct nvme_rdma_sgl));
>> Why do we need this memset?
>
> just good practice we took from drivers/scsi/scsi_lib.c.
>
> It's not a must and I can remove it if needed and test it.

I think (and please double check) that we initialize all three fields
anyway, so the memset should not be needed.

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WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Max Gurtovoy <maxg@mellanox.com>
Cc: Christoph Hellwig <hch@lst.de>,
	linux-nvme@lists.infradead.org, kbusch@kernel.org,
	sagi@grimberg.me, martin.petersen@oracle.com,
	jsmart2021@gmail.com, linux-rdma@vger.kernel.org,
	idanb@mellanox.com, axboe@kernel.dk, vladimirk@mellanox.com,
	oren@mellanox.com, shlomin@mellanox.com, israelr@mellanox.com,
	jgg@mellanox.com
Subject: Re: [PATCH 08/17] nvme-rdma: add metadata/T10-PI support
Date: Fri, 24 Apr 2020 09:09:30 +0200	[thread overview]
Message-ID: <20200424070930.GC24059@lst.de> (raw)
In-Reply-To: <688ec4ba-78e8-0ba3-9ee9-3c19b3e7b0c6@mellanox.com>

On Thu, Apr 23, 2020 at 12:22:27PM +0300, Max Gurtovoy wrote:
>>> diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
>>> index e38f8f7..23cc77e 100644
>>> --- a/drivers/nvme/host/rdma.c
>>> +++ b/drivers/nvme/host/rdma.c
>>> @@ -67,6 +67,9 @@ struct nvme_rdma_request {
>>>   	struct ib_cqe		reg_cqe;
>>>   	struct nvme_rdma_queue  *queue;
>>>   	struct nvme_rdma_sgl	data_sgl;
>>> +	/* Metadata (T10-PI) support */
>>> +	struct nvme_rdma_sgl	*md_sgl;
>>> +	bool			use_md;
>> Do we need a use_md flag vs just using md_sgl as a boolean and/or
>> using blk_integrity_rq?
>
> md_sgl will be used if we'll get a blk request with blk_integrity (memory 
> domain).
>
> use_md will be responsible for wire domain.
>
> so instead of this bool we can check in any place (after prev commit 
> changes):
>
> "
>
> if (queue->pi_support && nvme_ns_has_pi(ns))
>                 req->use_md = c.common.opcode == nvme_cmd_write ||
>                               c.common.opcode == nvme_cmd_read;
>
> "
>
> And this is less readable IMO.

It would obviously have to go into a little helper, but I really hate
adding lots of little fields caching easily derived information.  There
are a few exception, for example if we really need to not touch too
many cache lines.  Do you have a git tree with your current code?  That
might be a little easier to follow than the various patches, maybe
I can think of something better.

>>> +	if (blk_integrity_rq(rq)) {
>>> +		memset(req->md_sgl, 0, sizeof(struct nvme_rdma_sgl));
>> Why do we need this memset?
>
> just good practice we took from drivers/scsi/scsi_lib.c.
>
> It's not a must and I can remove it if needed and test it.

I think (and please double check) that we initialize all three fields
anyway, so the memset should not be needed.

  reply	other threads:[~2020-04-24  7:09 UTC|newest]

Thread overview: 118+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-27 17:15 [PATCH 00/17 V5] nvme-rdma/nvmet-rdma: Add metadata/T10-PI support Max Gurtovoy
2020-03-27 17:15 ` Max Gurtovoy
2020-03-27 17:15 ` [PATCH 1/1] nvme-cli/fabrics: Add pi_enable param to connect cmd Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-03-27 17:15 ` [PATCH 01/17] nvme: introduce namespace features flag Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 11:59   ` Christoph Hellwig
2020-04-21 11:59     ` Christoph Hellwig
2020-04-21 15:53     ` James Smart
2020-04-21 15:53       ` James Smart
2020-04-21 18:11       ` Christoph Hellwig
2020-04-21 18:11         ` Christoph Hellwig
2020-03-27 17:15 ` [PATCH 02/17] nvme: Add has_md field to the nvme_req structure Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 11:59   ` Christoph Hellwig
2020-04-21 11:59     ` Christoph Hellwig
2020-03-27 17:15 ` [PATCH 03/17] nvme: Enforce extended LBA format for fabrics metadata Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 12:08   ` Christoph Hellwig
2020-04-21 12:08     ` Christoph Hellwig
2020-03-27 17:15 ` [PATCH 04/17] nvme: introduce max_integrity_segments ctrl attribute Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 12:09   ` Christoph Hellwig
2020-04-21 12:09     ` Christoph Hellwig
2020-03-27 17:15 ` [PATCH 05/17] nvme-fabrics: Allow user enabling metadata/T10-PI support Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 12:12   ` Christoph Hellwig
2020-04-21 12:12     ` Christoph Hellwig
2020-04-21 15:17   ` Christoph Hellwig
2020-04-21 15:17     ` Christoph Hellwig
2020-04-22 22:07     ` Max Gurtovoy
2020-04-22 22:07       ` Max Gurtovoy
2020-04-22 22:24       ` James Smart
2020-04-22 22:24         ` James Smart
2020-04-22 22:39         ` Max Gurtovoy
2020-04-22 22:39           ` Max Gurtovoy
2020-04-23  5:54           ` Christoph Hellwig
2020-04-23  5:54             ` Christoph Hellwig
2020-04-23  7:30             ` Max Gurtovoy
2020-04-23  7:30               ` Max Gurtovoy
2020-04-24  7:06               ` Christoph Hellwig
2020-04-24  7:06                 ` Christoph Hellwig
2020-04-26  9:48                 ` Max Gurtovoy
2020-04-26  9:48                   ` Max Gurtovoy
2020-04-27  6:04                   ` Christoph Hellwig
2020-04-27  6:04                     ` Christoph Hellwig
2020-04-27 13:52                     ` Max Gurtovoy
2020-04-27 13:52                       ` Max Gurtovoy
2020-04-27 13:54                       ` Christoph Hellwig
2020-04-27 13:54                         ` Christoph Hellwig
2020-04-28  9:18                         ` Max Gurtovoy
2020-04-28  9:18                           ` Max Gurtovoy
2020-04-23  5:53       ` Christoph Hellwig
2020-04-23  5:53         ` Christoph Hellwig
2020-03-27 17:15 ` [PATCH 06/17] nvme: introduce NVME_INLINE_MD_SG_CNT Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 12:12   ` Christoph Hellwig
2020-04-21 12:12     ` Christoph Hellwig
2020-03-27 17:15 ` [PATCH 07/17] nvme-rdma: Introduce nvme_rdma_sgl structure Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 12:13   ` Christoph Hellwig
2020-04-21 12:13     ` Christoph Hellwig
2020-03-27 17:15 ` [PATCH 08/17] nvme-rdma: add metadata/T10-PI support Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 12:20   ` Christoph Hellwig
2020-04-21 12:20     ` Christoph Hellwig
2020-04-23  9:22     ` Max Gurtovoy
2020-04-23  9:22       ` Max Gurtovoy
2020-04-24  7:09       ` Christoph Hellwig [this message]
2020-04-24  7:09         ` Christoph Hellwig
2020-04-26 10:04         ` Max Gurtovoy
2020-04-26 10:04           ` Max Gurtovoy
2020-03-27 17:15 ` [PATCH 09/17] nvmet: prepare metadata request Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 15:21   ` Christoph Hellwig
2020-04-21 15:21     ` Christoph Hellwig
2020-03-27 17:15 ` [PATCH 10/17] nvmet: add metadata characteristics for a namespace Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 15:23   ` Christoph Hellwig
2020-04-21 15:23     ` Christoph Hellwig
2020-03-27 17:15 ` [PATCH 11/17] nvmet: Rename nvmet_rw_len to nvmet_rw_data_len Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-03-27 17:15 ` [PATCH 12/17] nvmet: Rename nvmet_check_data_len to nvmet_check_transfer_len Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-03-27 17:15 ` [PATCH 13/17] nvme: Add Metadata Capabilities enumerations Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 15:24   ` Christoph Hellwig
2020-04-21 15:24     ` Christoph Hellwig
2020-04-23 12:09     ` Max Gurtovoy
2020-04-23 12:09       ` Max Gurtovoy
2020-04-24  7:12       ` Christoph Hellwig
2020-04-24  7:12         ` Christoph Hellwig
2020-03-27 17:15 ` [PATCH 14/17] nvmet: Add metadata/T10-PI support Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 15:30   ` Christoph Hellwig
2020-04-21 15:30     ` Christoph Hellwig
2020-04-23 12:39     ` Max Gurtovoy
2020-04-23 12:39       ` Max Gurtovoy
2020-04-24  7:14       ` Christoph Hellwig
2020-04-24  7:14         ` Christoph Hellwig
2020-04-26 10:50         ` Max Gurtovoy
2020-04-26 10:50           ` Max Gurtovoy
2020-04-27  6:06           ` Christoph Hellwig
2020-04-27  6:06             ` Christoph Hellwig
2020-03-27 17:15 ` [PATCH 15/17] nvmet: Add metadata support for block devices Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 15:33   ` Christoph Hellwig
2020-04-21 15:33     ` Christoph Hellwig
2020-04-23 17:25     ` Max Gurtovoy
2020-04-23 17:25       ` Max Gurtovoy
2020-04-24  7:54       ` Christoph Hellwig
2020-04-24  7:54         ` Christoph Hellwig
2020-03-27 17:15 ` [PATCH 16/17] RDMA/rw: Expose maximal page list for a device per 1 MR Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-03-27 17:15 ` [PATCH 17/17] nvmet-rdma: Add metadata/T10-PI support Max Gurtovoy
2020-03-27 17:15   ` Max Gurtovoy
2020-04-21 15:37   ` Christoph Hellwig
2020-04-21 15:37     ` Christoph Hellwig

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