linux-kernel - Re: [Qemu-devel] [PATCH v7 2/6] virtio-pmem: Add virtio pmem driver

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Date:   Wed, 8 May 2019 11:23:32 -0400 (EDT)
From:   Pankaj Gupta <pagupta@...hat.com>
To:     Jakub Staroń <jstaron@...gle.com>
Cc:     linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-acpi@...r.kernel.org,
        qemu-devel@...gnu.org, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, jack@...e.cz, mst@...hat.com,
        jasowang@...hat.com, david@...morbit.com, lcapitulino@...hat.com,
        adilger kernel <adilger.kernel@...ger.ca>, zwisler@...nel.org,
        aarcange@...hat.com, dave jiang <dave.jiang@...el.com>,
        darrick wong <darrick.wong@...cle.com>,
        vishal l verma <vishal.l.verma@...el.com>, david@...hat.com,
        willy@...radead.org, hch@...radead.org, jmoyer@...hat.com,
        nilal@...hat.com, lenb@...nel.org, kilobyte@...band.pl,
        riel@...riel.com, yuval shaia <yuval.shaia@...cle.com>,
        stefanha@...hat.com, pbonzini@...hat.com,
        dan j williams <dan.j.williams@...el.com>, kwolf@...hat.com,
        tytso@....edu, xiaoguangrong eric <xiaoguangrong.eric@...il.com>,
        cohuck@...hat.com, rjw@...ysocki.net, imammedo@...hat.com,
        smbarber@...gle.com
Subject: Re: [Qemu-devel] [PATCH v7 2/6] virtio-pmem: Add virtio pmem driver


> > 
> > > +int virtio_pmem_flush(struct nd_region *nd_region)
> > > +{
> > > +        int err;
> > > +        unsigned long flags;
> > > +        struct scatterlist *sgs[2], sg, ret;
> > > +        struct virtio_device *vdev = nd_region->provider_data;
> > > +        struct virtio_pmem *vpmem = vdev->priv;
> > > +        struct virtio_pmem_request *req;
> > > +
> > > +        might_sleep();
> > > +        req = kmalloc(sizeof(*req), GFP_KERNEL);
> > > +        if (!req)
> > > +                return -ENOMEM;
> > > +
> > > +        req->done = req->wq_buf_avail = false;
> > > +        strcpy(req->name, "FLUSH");
> > > +        init_waitqueue_head(&req->host_acked);
> > > +        init_waitqueue_head(&req->wq_buf);
> > > +        sg_init_one(&sg, req->name, strlen(req->name));
> > > +        sgs[0] = &sg;
> > > +        sg_init_one(&ret, &req->ret, sizeof(req->ret));
> > > +        sgs[1] = &ret;
> > > +
> > > +        spin_lock_irqsave(&vpmem->pmem_lock, flags);
> > > +        err = virtqueue_add_sgs(vpmem->req_vq, sgs, 1, 1, req, GFP_ATOMIC);
> > > +        if (err) {
> > > +                dev_err(&vdev->dev, "failed to send command to virtio pmem device\n");
> > > +
> > > +                list_add_tail(&vpmem->req_list, &req->list);
> > > +                spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> > > +
> > > +                /* When host has read buffer, this completes via host_ack */
> > > +                wait_event(req->wq_buf, req->wq_buf_avail);
> > > +                spin_lock_irqsave(&vpmem->pmem_lock, flags);
> > > +        }
> > 
> > Aren't the arguments in `list_add_tail` swapped? The element we are adding
> 

Yes, arguments for 'list_add_tail' should be swapped.

list_add_tail(&req->list, &vpmem->req_list);


Thank you,
Pankaj