[PATCH v5 02/29] iommufd: Introduce iommufd_object_alloc_ucmd helper

[Nicolin Chen <nicolinc@nvidia.com>]

An object allocator needs to call either iommufd_object_finalize() upon a
success or iommufd_object_abort_and_destroy() upon an error code.

To reduce duplication, store a new_obj in the struct iommufd_ucmd and call
iommufd_object_finalize/iommufd_object_abort_and_destroy() accordingly in
the main function.

This will also ease a driver-allocated object so that a driver can simply
return with an error code to trigger an iommufd_object_abort_and_destroy()
instead of doing an abort itself.

Similar to iommufd_object_alloc() and __iommufd_object_alloc(), add a pair
of helpers: __iommufd_object_alloc_ucmd() and iommufd_object_alloc_ucmd().

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 drivers/iommu/iommufd/iommufd_private.h |  1 +
 include/linux/iommufd.h                 | 23 +++++++++++++++++++++++
 drivers/iommu/iommufd/driver.c          | 18 ++++++++++++++++++
 drivers/iommu/iommufd/main.c            |  7 +++++++
 4 files changed, 49 insertions(+)

diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 10899e2cd34a..16767c231580 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -135,6 +135,7 @@ struct iommufd_ucmd {
 	void __user *ubuffer;
 	u32 user_size;
 	void *cmd;
+	struct iommufd_object *new_obj;
 };
 
 int iommufd_vfio_ioctl(struct iommufd_ctx *ictx, unsigned int cmd,
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 498c9a768506..47f38034f5e7 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -22,6 +22,7 @@ struct iommu_user_data_array;
 struct iommufd_access;
 struct iommufd_ctx;
 struct iommufd_device;
+struct iommufd_ucmd;
 struct iommufd_viommu_ops;
 struct page;
 
@@ -51,6 +52,18 @@ struct iommufd_object {
 	unsigned int id;
 };
 
+#define __iommufd_object_alloc_ucmd(ucmd, ptr, type, obj)                      \
+	container_of(_iommufd_object_alloc_ucmd(                               \
+			     ucmd,                                             \
+			     sizeof(*(ptr)) + BUILD_BUG_ON_ZERO(               \
+						      offsetof(typeof(*(ptr)), \
+							       obj) != 0),     \
+			     type),                                            \
+		     typeof(*(ptr)), obj)
+
+#define iommufd_object_alloc_ucmd(ucmd, ptr, type) \
+	__iommufd_object_alloc_ucmd(ucmd, ptr, type, obj)
+
 struct iommufd_device *iommufd_device_bind(struct iommufd_ctx *ictx,
 					   struct device *dev, u32 *id);
 void iommufd_device_unbind(struct iommufd_device *idev);
@@ -193,6 +206,9 @@ static inline int iommufd_vfio_compat_set_no_iommu(struct iommufd_ctx *ictx)
 struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
 					     size_t size,
 					     enum iommufd_object_type type);
+struct iommufd_object *
+_iommufd_object_alloc_ucmd(struct iommufd_ucmd *ucmd, size_t size,
+			   enum iommufd_object_type type);
 struct device *iommufd_viommu_find_dev(struct iommufd_viommu *viommu,
 				       unsigned long vdev_id);
 int iommufd_viommu_get_vdev_id(struct iommufd_viommu *viommu,
@@ -208,6 +224,13 @@ _iommufd_object_alloc(struct iommufd_ctx *ictx, size_t size,
 	return ERR_PTR(-EOPNOTSUPP);
 }
 
+static inline struct iommufd_object *
+_iommufd_object_alloc_ucmd(struct iommufd_ucmd *ucmd, size_t size,
+			   enum iommufd_object_type type)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
 static inline struct device *
 iommufd_viommu_find_dev(struct iommufd_viommu *viommu, unsigned long vdev_id)
 {
diff --git a/drivers/iommu/iommufd/driver.c b/drivers/iommu/iommufd/driver.c
index 922cd1fe7ec2..28dec9e09720 100644
--- a/drivers/iommu/iommufd/driver.c
+++ b/drivers/iommu/iommufd/driver.c
@@ -36,6 +36,24 @@ struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
 }
 EXPORT_SYMBOL_NS_GPL(_iommufd_object_alloc, "IOMMUFD");
 
+struct iommufd_object *_iommufd_object_alloc_ucmd(struct iommufd_ucmd *ucmd,
+						  size_t size,
+						  enum iommufd_object_type type)
+{
+	struct iommufd_object *new_obj;
+
+	if (ucmd->new_obj)
+		return ERR_PTR(-EBUSY);
+
+	new_obj = _iommufd_object_alloc(ucmd->ictx, size, type);
+	if (IS_ERR(new_obj))
+		return new_obj;
+
+	ucmd->new_obj = new_obj;
+	return new_obj;
+}
+EXPORT_SYMBOL_NS_GPL(_iommufd_object_alloc_ucmd, "IOMMUFD");
+
 /* Caller should xa_lock(&viommu->vdevs) to protect the return value */
 struct device *iommufd_viommu_find_dev(struct iommufd_viommu *viommu,
 				       unsigned long vdev_id)
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 347c56ef44d8..c6d0b446e632 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -416,6 +416,13 @@ static long iommufd_fops_ioctl(struct file *filp, unsigned int cmd,
 	if (ret)
 		return ret;
 	ret = op->execute(&ucmd);
+
+	if (ucmd.new_obj) {
+		if (ret)
+			iommufd_object_abort_and_destroy(ictx, ucmd.new_obj);
+		else
+			iommufd_object_finalize(ictx, ucmd.new_obj);
+	}
 	return ret;
 }
 
-- 
2.43.0