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Message-ID: <CACGkMEsNTtD9nc7dRi9LH4jwh37kXQgM2WjbJfoz-MsHFe750Q@mail.gmail.com>
Date: Wed, 17 Sep 2025 16:36:42 +0800
From: Jason Wang <jasowang@...hat.com>
To: Eugenio Pérez <eperezma@...hat.com>
Cc: "Michael S . Tsirkin" <mst@...hat.com>, Stefano Garzarella <sgarzare@...hat.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, linux-kernel@...r.kernel.org,
Maxime Coquelin <mcoqueli@...hat.com>, Yongji Xie <xieyongji@...edance.com>,
Cindy Lu <lulu@...hat.com>, Laurent Vivier <lvivier@...hat.com>, virtualization@...ts.linux.dev
Subject: Re: [PATCH v2 2/7] vduse: make domain_lock an rwlock
On Tue, Sep 16, 2025 at 9:08 PM Eugenio Pérez <eperezma@...hat.com> wrote:
>
> It will be used in a few more scenarios read-only so make it more
> scalable.
>
> Suggested-by: Xie Yongji <xieyongji@...edance.com>
> Signed-off-by: Eugenio Pérez <eperezma@...hat.com>
Acked-by: Jason Wang <jasowang@...hat.com>
Thanks
> ---
> v2: New in v2
> ---
> drivers/vdpa/vdpa_user/vduse_dev.c | 41 +++++++++++++++---------------
> 1 file changed, 21 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index e7bced0b5542..2b6a8958ffe0 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -14,6 +14,7 @@
> #include <linux/cdev.h>
> #include <linux/device.h>
> #include <linux/eventfd.h>
> +#include <linux/rwlock.h>
> #include <linux/slab.h>
> #include <linux/wait.h>
> #include <linux/dma-map-ops.h>
> @@ -117,7 +118,7 @@ struct vduse_dev {
> struct vduse_umem *umem;
> struct mutex mem_lock;
> unsigned int bounce_size;
> - struct mutex domain_lock;
> + rwlock_t domain_lock;
> };
>
> struct vduse_dev_msg {
> @@ -1176,9 +1177,9 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> if (entry.start > entry.last)
> break;
>
> - mutex_lock(&dev->domain_lock);
> + read_lock(&dev->domain_lock);
> if (!dev->domain) {
> - mutex_unlock(&dev->domain_lock);
> + read_unlock(&dev->domain_lock);
> break;
> }
> spin_lock(&dev->domain->iotlb_lock);
> @@ -1193,7 +1194,7 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> entry.perm = map->perm;
> }
> spin_unlock(&dev->domain->iotlb_lock);
> - mutex_unlock(&dev->domain_lock);
> + read_unlock(&dev->domain_lock);
> ret = -EINVAL;
> if (!f)
> break;
> @@ -1346,10 +1347,10 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> sizeof(umem.reserved)))
> break;
>
> - mutex_lock(&dev->domain_lock);
> + write_lock(&dev->domain_lock);
> ret = vduse_dev_reg_umem(dev, umem.iova,
> umem.uaddr, umem.size);
> - mutex_unlock(&dev->domain_lock);
> + write_unlock(&dev->domain_lock);
> break;
> }
> case VDUSE_IOTLB_DEREG_UMEM: {
> @@ -1363,10 +1364,10 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> if (!is_mem_zero((const char *)umem.reserved,
> sizeof(umem.reserved)))
> break;
> - mutex_lock(&dev->domain_lock);
> + write_lock(&dev->domain_lock);
> ret = vduse_dev_dereg_umem(dev, umem.iova,
> umem.size);
> - mutex_unlock(&dev->domain_lock);
> + write_unlock(&dev->domain_lock);
> break;
> }
> case VDUSE_IOTLB_GET_INFO: {
> @@ -1385,9 +1386,9 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> sizeof(info.reserved)))
> break;
>
> - mutex_lock(&dev->domain_lock);
> + read_lock(&dev->domain_lock);
> if (!dev->domain) {
> - mutex_unlock(&dev->domain_lock);
> + read_unlock(&dev->domain_lock);
> break;
> }
> spin_lock(&dev->domain->iotlb_lock);
> @@ -1402,7 +1403,7 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> info.capability |= VDUSE_IOVA_CAP_UMEM;
> }
> spin_unlock(&dev->domain->iotlb_lock);
> - mutex_unlock(&dev->domain_lock);
> + read_unlock(&dev->domain_lock);
> if (!map)
> break;
>
> @@ -1425,10 +1426,10 @@ static int vduse_dev_release(struct inode *inode, struct file *file)
> {
> struct vduse_dev *dev = file->private_data;
>
> - mutex_lock(&dev->domain_lock);
> + write_lock(&dev->domain_lock);
> if (dev->domain)
> vduse_dev_dereg_umem(dev, 0, dev->domain->bounce_size);
> - mutex_unlock(&dev->domain_lock);
> + write_unlock(&dev->domain_lock);
> spin_lock(&dev->msg_lock);
> /* Make sure the inflight messages can processed after reconncection */
> list_splice_init(&dev->recv_list, &dev->send_list);
> @@ -1647,7 +1648,7 @@ static struct vduse_dev *vduse_dev_create(void)
>
> mutex_init(&dev->lock);
> mutex_init(&dev->mem_lock);
> - mutex_init(&dev->domain_lock);
> + rwlock_init(&dev->domain_lock);
> spin_lock_init(&dev->msg_lock);
> INIT_LIST_HEAD(&dev->send_list);
> INIT_LIST_HEAD(&dev->recv_list);
> @@ -1805,7 +1806,7 @@ static ssize_t bounce_size_store(struct device *device,
> int ret;
>
> ret = -EPERM;
> - mutex_lock(&dev->domain_lock);
> + write_lock(&dev->domain_lock);
> if (dev->domain)
> goto unlock;
>
> @@ -1821,7 +1822,7 @@ static ssize_t bounce_size_store(struct device *device,
> dev->bounce_size = bounce_size & PAGE_MASK;
> ret = count;
> unlock:
> - mutex_unlock(&dev->domain_lock);
> + write_unlock(&dev->domain_lock);
> return ret;
> }
>
> @@ -2045,11 +2046,11 @@ static int vdpa_dev_add(struct vdpa_mgmt_dev *mdev, const char *name,
> if (ret)
> return ret;
>
> - mutex_lock(&dev->domain_lock);
> + write_lock(&dev->domain_lock);
> if (!dev->domain)
> dev->domain = vduse_domain_create(VDUSE_IOVA_SIZE - 1,
> dev->bounce_size);
> - mutex_unlock(&dev->domain_lock);
> + write_unlock(&dev->domain_lock);
> if (!dev->domain) {
> put_device(&dev->vdev->vdpa.dev);
> return -ENOMEM;
> @@ -2059,10 +2060,10 @@ static int vdpa_dev_add(struct vdpa_mgmt_dev *mdev, const char *name,
> ret = _vdpa_register_device(&dev->vdev->vdpa, dev->vq_num);
> if (ret) {
> put_device(&dev->vdev->vdpa.dev);
> - mutex_lock(&dev->domain_lock);
> + write_lock(&dev->domain_lock);
> vduse_domain_destroy(dev->domain);
> dev->domain = NULL;
> - mutex_unlock(&dev->domain_lock);
> + write_unlock(&dev->domain_lock);
> return ret;
> }
>
> --
> 2.51.0
>
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