> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Friday, July 14, 2023 10:21 PM
>
> On Mon, Jul 10, 2023 at 07:59:22PM -0700, Yi Liu wrote:
> > It's common to get a reference to the iommufd context from a given file
> > descriptor. So adds an API for it. Existing users of this API are compiled
> > only when IOMMUFD is enabled, so no need to have a stub for the IOMMUFD
> > disabled case.
> >
> > Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
> > ---
> > drivers/iommu/iommufd/main.c | 23 +++++++++++++++++++++++
> > include/linux/iommufd.h | 1 +
> > 2 files changed, 24 insertions(+)
> >
> > diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
> > index 32ce7befc8dd..e99a338d4fdf 100644
> > --- a/drivers/iommu/iommufd/main.c
> > +++ b/drivers/iommu/iommufd/main.c
> > @@ -377,6 +377,29 @@ struct iommufd_ctx *iommufd_ctx_from_file(struct file *file)
> > }
> > EXPORT_SYMBOL_NS_GPL(iommufd_ctx_from_file, IOMMUFD);
> >
> > +/**
> > + * iommufd_ctx_from_fd - Acquires a reference to the iommufd context
> > + * @fd: File descriptor to obtain the reference from
> > + *
> > + * Returns a pointer to the iommufd_ctx, otherwise ERR_PTR. On success
> > + * the caller is responsible to call iommufd_ctx_put().
> > + */
> > +struct iommufd_ctx *iommufd_ctx_from_fd(int fd)
> > +{
> > + struct iommufd_ctx *iommufd;
> > + struct fd f;
> > +
> > + f = fdget(fd);
> > + if (!f.file)
> > + return ERR_PTR(-EBADF);
> > +
> > + iommufd = iommufd_ctx_from_file(f.file);
> > +
> > + fdput(f);
> > + return iommufd;
> > +}
> > +EXPORT_SYMBOL_NS_GPL(iommufd_ctx_from_fd, IOMMUFD);
>
> This is a little wonky since iommufd_ctx_from_file() also obtains a
> reference
Yes. that's why need fdput() always.
> Just needs to be like this:
>
> struct iommufd_ctx *iommufd_ctx_from_fd(int fd)
> {
> struct file *file;
>
> file = fget(fd);
> if (!file)
> return ERR_PTR(-EBADF);
>
> if (file->f_op != &iommufd_fops) {
> fput(file);
> return ERR_PTR(-EBADFD);
> }
> /* fget is the same as iommufd_ctx_get() */
> return file->private_data;
> }
> EXPORT_SYMBOL_NS_GPL(iommufd_ctx_from_fd, IOMMUFD);
This one looks ok to me. Thanks.
Regards,
Yi Liu
