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From: David Hildenbrand <david@redhat.com>
To: Pankaj Gupta <pagupta@redhat.com>
Cc: linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-acpi@vger.kernel.org,
	qemu-devel@nongnu.org, linux-ext4@vger.kernel.org,
	linux-xfs@vger.kernel.org,
	dan j williams <dan.j.williams@intel.com>,
	zwisler@kernel.org, vishal l verma <vishal.l.verma@intel.com>,
	dave jiang <dave.jiang@intel.com>,
	mst@redhat.com, jasowang@redhat.com, willy@infradead.org,
	rjw@rjwysocki.net, hch@infradead.org, lenb@kernel.org,
	jack@suse.cz, tytso@mit.edu,
	adilger kernel <adilger.kernel@dilger.ca>,
	darrick wong <darrick.wong@oracle.com>,
	lcapitulino@redhat.com, kwolf@redhat.com, imammedo@redhat.com,
	jmoyer@redhat.com, nilal@redhat.com, riel@surriel.com,
	stefanha@redhat.com, aarcange@redhat.com, david@fromorbit.com,
	cohuck@redhat.com,
	xiaoguangrong eric <xiaoguangrong.eric@gmail.com>,
	pbonzini@redhat.com, kilobyte@angband.pl,
	yuval shaia <yuval.shaia@oracle.com>,
	jstaron@google.com
Subject: Re: [PATCH v8 2/6] virtio-pmem: Add virtio pmem driver
Date: Tue, 14 May 2019 11:34:05 +0200	[thread overview]
Message-ID: <86298c2c-cc7c-5b97-0f11-335d7da8c450@redhat.com> (raw)
In-Reply-To: <752392764.28554139.1557826022323.JavaMail.zimbra@redhat.com>

>>
>>> +	}
>>> +
>>> +	/* When host has read buffer, this completes via host_ack */
>>
>> "A host repsonse results in "host_ack" getting called" ... ?
>>
>>> +	wait_event(req->host_acked, req->done);
>>> +	err = req->ret;
>>> +ret:
>>> +	kfree(req);
>>> +	return err;
>>> +};
>>> +
>>> +/* The asynchronous flush callback function */
>>> +int async_pmem_flush(struct nd_region *nd_region, struct bio *bio)
>>> +{
>>> +	int rc = 0;
>>> +
>>> +	/* Create child bio for asynchronous flush and chain with
>>> +	 * parent bio. Otherwise directly call nd_region flush.
>>> +	 */
>>> +	if (bio && bio->bi_iter.bi_sector != -1) {
>>> +		struct bio *child = bio_alloc(GFP_ATOMIC, 0);
>>> +
>>> +		if (!child)
>>> +			return -ENOMEM;
>>> +		bio_copy_dev(child, bio);
>>> +		child->bi_opf = REQ_PREFLUSH;
>>> +		child->bi_iter.bi_sector = -1;
>>> +		bio_chain(child, bio);
>>> +		submit_bio(child);
>>
>> return 0;
>>
>> Then, drop the "else" case and "int rc" and do directly
>>
>> if (virtio_pmem_flush(nd_region))
>> 	return -EIO;
> 
> and another 'return 0' here :)
> 
> I don't like return from multiple places instead I prefer
> single exit point from function.

Makes this function more complicated than necessary. I agree when there
are locks involved.

>  
>>
>>> +
>>> +	return 0;
>>> +};
>>> +
>>> +static int virtio_pmem_probe(struct virtio_device *vdev)
>>> +{
>>> +	int err = 0;
>>> +	struct resource res;
>>> +	struct virtio_pmem *vpmem;
>>> +	struct nd_region_desc ndr_desc = {};
>>> +	int nid = dev_to_node(&vdev->dev);
>>> +	struct nd_region *nd_region;
>>
>> Nit: use reverse Christmas tree layout :)
> 
> Done.
> 
>>
>>> +
>>> +	if (!vdev->config->get) {
>>> +		dev_err(&vdev->dev, "%s failure: config access disabled\n",
>>> +			__func__);
>>> +		return -EINVAL;
>>> +	}
>>> +
>>> +	vpmem = devm_kzalloc(&vdev->dev, sizeof(*vpmem), GFP_KERNEL);
>>> +	if (!vpmem) {
>>> +		err = -ENOMEM;
>>> +		goto out_err;
>>> +	}
>>> +
>>> +	vpmem->vdev = vdev;
>>> +	vdev->priv = vpmem;
>>> +	err = init_vq(vpmem);
>>> +	if (err)
>>> +		goto out_err;
>>> +
>>> +	virtio_cread(vpmem->vdev, struct virtio_pmem_config,
>>> +			start, &vpmem->start);
>>> +	virtio_cread(vpmem->vdev, struct virtio_pmem_config,
>>> +			size, &vpmem->size);
>>> +
>>> +	res.start = vpmem->start;
>>> +	res.end   = vpmem->start + vpmem->size-1;
>>> +	vpmem->nd_desc.provider_name = "virtio-pmem";
>>> +	vpmem->nd_desc.module = THIS_MODULE;
>>> +
>>> +	vpmem->nvdimm_bus = nvdimm_bus_register(&vdev->dev,
>>> +						&vpmem->nd_desc);
>>> +	if (!vpmem->nvdimm_bus)
>>> +		goto out_vq;
>>> +
>>> +	dev_set_drvdata(&vdev->dev, vpmem->nvdimm_bus);
>>> +
>>> +	ndr_desc.res = &res;
>>> +	ndr_desc.numa_node = nid;
>>> +	ndr_desc.flush = async_pmem_flush;
>>> +	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
>>> +	set_bit(ND_REGION_ASYNC, &ndr_desc.flags);
>>> +	nd_region = nvdimm_pmem_region_create(vpmem->nvdimm_bus, &ndr_desc);
>>> +
>>
>> I'd drop this empty line.
> 
> hmm.
> 

The common pattern after allocating something, immediately check for it
in the next line (like you do throughout this patch ;) )

...
>> You are not freeing "vdev->priv".
> 
> vdev->priv is vpmem which is allocated using devm API.

I'm confused. Looking at drivers/virtio/virtio_balloon.c:

static void virtballoon_remove(struct virtio_device *vdev)
{
	struct virtio_balloon *vb = vdev->priv;

	...

	kfree(vb);
}

I think you should do the same here, vdev->priv is allocated in
virtio_pmem_probe.

But maybe I am missing something important here :)

>>
>>> +	nvdimm_bus_unregister(nvdimm_bus);
>>> +	vdev->config->del_vqs(vdev);
>>> +	vdev->config->reset(vdev);
>>> +}
>>> +

-- 

Thanks,

David / dhildenb

  reply	other threads:[~2019-05-14  9:34 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-10 15:51 [PATCH v8 0/6] " Pankaj Gupta
2019-05-10 15:51 ` [PATCH v8 1/6] libnvdimm: nd_region flush callback support Pankaj Gupta
2019-05-10 15:51 ` [PATCH v8 2/6] virtio-pmem: Add virtio pmem driver Pankaj Gupta
2019-05-12 16:51   ` Michael S. Tsirkin
2019-05-13  4:43     ` [Qemu-devel] " Pankaj Gupta
2019-05-14  8:19   ` David Hildenbrand
2019-05-14  9:27     ` Pankaj Gupta
2019-05-14  9:34       ` David Hildenbrand [this message]
2019-05-14  9:47         ` Pankaj Gupta
2019-05-14  9:57           ` David Hildenbrand
2019-05-14 10:02             ` Pankaj Gupta
2019-05-10 15:51 ` [PATCH v8 3/6] libnvdimm: add dax_dev sync flag Pankaj Gupta
2019-05-10 20:14   ` Dan Williams
2019-05-11  0:45     ` Pankaj Gupta
2019-05-11  0:59       ` Dan Williams
2019-05-11  1:23         ` [Qemu-devel] " Pankaj Gupta
2019-05-13 17:32           ` Pankaj Gupta
2019-05-13 17:52             ` Dan Williams
2019-05-14  5:27               ` Pankaj Gupta
2019-05-10 15:52 ` [PATCH v8 4/6] dax: check synchronous mapping is supported Pankaj Gupta
2019-05-10 15:52 ` [PATCH v8 5/6] ext4: disable map_sync for async flush Pankaj Gupta
2019-05-10 15:52 ` [PATCH v8 6/6] xfs: " Pankaj Gupta
2019-05-10 16:30 ` [PATCH v8 0/6] virtio pmem driver Michael S. Tsirkin
2019-05-10 20:15 ` Dan Williams
2019-05-10 23:33   ` Pankaj Gupta
2019-05-12 16:52     ` Michael S. Tsirkin

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