On Thu, Oct 26, 2023 at 10:49:28AM +0800, Lu Baolu wrote:
> +static ssize_t hwpt_fault_fops_write(struct file *filep,
> + const char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + size_t response_size = sizeof(struct iommu_hwpt_page_response);
> + struct hw_pgtable_fault *fault = filep->private_data;
> + struct iommu_hwpt_page_response response;
> + struct iommufd_hw_pagetable *hwpt;
> + struct iopf_group *iter, *group;
> + struct iommufd_device *idev;
> + size_t done = 0;
> + int rc = 0;
> +
> + if (*ppos || count % response_size)
> + return -ESPIPE;
> +
> + mutex_lock(&fault->mutex);
> + while (!list_empty(&fault->response) && count > done) {
> + rc = copy_from_user(&response, buf + done, response_size);
> + if (rc)
> + break;
> +
> + /* Get the device that this response targets at. */
> + idev = container_of(iommufd_get_object(fault->ictx,
> + response.dev_id,
> + IOMMUFD_OBJ_DEVICE),
> + struct iommufd_device, obj);
> + if (IS_ERR(idev)) {
> + rc = PTR_ERR(idev);
> + break;
> + }
See here it might be better to have a per-fd list of outstanding
faults per-fd and then the cookie would just index that list, then you
get everything in one shot instead of having to do a xarray looking
and then a linear list search
> +static const struct file_operations hwpt_fault_fops = {
> + .owner = THIS_MODULE,
> + .read = hwpt_fault_fops_read,
> + .write = hwpt_fault_fops_write,
> +};
nonseekable_open() behavior should be integrated into this
> +static int hw_pagetable_get_fault_fd(struct hw_pgtable_fault *fault)
> +{
> + struct file *filep;
> + int fdno;
> +
> + fdno = get_unused_fd_flags(O_CLOEXEC);
> + if (fdno < 0)
> + return fdno;
> +
> + filep = anon_inode_getfile("[iommufd-pgfault]", &hwpt_fault_fops,
> + fault, O_RDWR);
> + if (IS_ERR(filep)) {
> + put_unused_fd(fdno);
> + return PTR_ERR(filep);
> + }
> +
> + fd_install(fdno, filep);
> + fault->fault_file = filep;
> + fault->fault_fd = fdno;
fd_install must be the very last thing before returning success from a
system call because we cannot undo it.
There are other failure paths before here and the final return
Jason
