dmaengine: idxd: fix cdev setup and free device lifetime issues

The char device setup and cleanup has device lifetime issues regarding when
parts are initialized and cleaned up. The initialization of struct device is
done incorrectly. device_initialize() needs to be called on the 'struct
device' and then additional changes can be added. The ->release() function
needs to be setup via device_type before dev_set_name() to allow proper
cleanup. The change re-parents the cdev under the wq->conf_dev to get
natural reference inheritance. No known dependency on the old device path exists.

Reported-by: Jason Gunthorpe <jgg@nvidia.com>
Fixes: 42d279f913 ("dmaengine: idxd: add char driver to expose submission portal to userland")
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/161852987721.2203940.1478218825576630810.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/idxd/cdev.c

@@ -39,15 +39,15 @@ struct idxd_user_context {
 	struct iommu_sva *sva;
 };
 
-enum idxd_cdev_cleanup {
-	CDEV_NORMAL = 0,
-	CDEV_FAILED,
-};
-
 static void idxd_cdev_dev_release(struct device *dev)
 {
-	dev_dbg(dev, "releasing cdev device\n");
-	kfree(dev);
+	struct idxd_cdev *idxd_cdev = container_of(dev, struct idxd_cdev, dev);
+	struct idxd_cdev_context *cdev_ctx;
+	struct idxd_wq *wq = idxd_cdev->wq;
+
+	cdev_ctx = &ictx[wq->idxd->type];
+	ida_simple_remove(&cdev_ctx->minor_ida, idxd_cdev->minor);
+	kfree(idxd_cdev);
 }
 
 static struct device_type idxd_cdev_device_type = {
@@ -62,14 +62,11 @@ static inline struct idxd_cdev *inode_idxd_cdev(struct inode *inode)
 	return container_of(cdev, struct idxd_cdev, cdev);
 }
 
-static inline struct idxd_wq *idxd_cdev_wq(struct idxd_cdev *idxd_cdev)
-{
-	return container_of(idxd_cdev, struct idxd_wq, idxd_cdev);
-}
-
 static inline struct idxd_wq *inode_wq(struct inode *inode)
 {
-	return idxd_cdev_wq(inode_idxd_cdev(inode));
+	struct idxd_cdev *idxd_cdev = inode_idxd_cdev(inode);
+
+	return idxd_cdev->wq;
 }
 
 static int idxd_cdev_open(struct inode *inode, struct file *filp)
@@ -220,11 +217,10 @@ static __poll_t idxd_cdev_poll(struct file *filp,
 	struct idxd_user_context *ctx = filp->private_data;
 	struct idxd_wq *wq = ctx->wq;
 	struct idxd_device *idxd = wq->idxd;
-	struct idxd_cdev *idxd_cdev = &wq->idxd_cdev;
 	unsigned long flags;
 	__poll_t out = 0;
 
-	poll_wait(filp, &idxd_cdev->err_queue, wait);
+	poll_wait(filp, &wq->err_queue, wait);
 	spin_lock_irqsave(&idxd->dev_lock, flags);
 	if (idxd->sw_err.valid)
 		out = EPOLLIN | EPOLLRDNORM;
@@ -246,98 +242,67 @@ int idxd_cdev_get_major(struct idxd_device *idxd)
 	return MAJOR(ictx[idxd->type].devt);
 }
 
-static int idxd_wq_cdev_dev_setup(struct idxd_wq *wq)
+int idxd_wq_add_cdev(struct idxd_wq *wq)
 {
 	struct idxd_device *idxd = wq->idxd;
-	struct idxd_cdev *idxd_cdev = &wq->idxd_cdev;
-	struct idxd_cdev_context *cdev_ctx;
+	struct idxd_cdev *idxd_cdev;
+	struct cdev *cdev;
 	struct device *dev;
-	int minor, rc;
+	struct idxd_cdev_context *cdev_ctx;
+	int rc, minor;
 
-	idxd_cdev->dev = kzalloc(sizeof(*idxd_cdev->dev), GFP_KERNEL);
-	if (!idxd_cdev->dev)
+	idxd_cdev = kzalloc(sizeof(*idxd_cdev), GFP_KERNEL);
+	if (!idxd_cdev)
 		return -ENOMEM;
 
-	dev = idxd_cdev->dev;
-	dev->parent = &idxd->pdev->dev;
-	dev_set_name(dev, "%s/wq%u.%u", idxd_get_dev_name(idxd),
-		     idxd->id, wq->id);
-	dev->bus = idxd_get_bus_type(idxd);
-
+	idxd_cdev->wq = wq;
+	cdev = &idxd_cdev->cdev;
+	dev = &idxd_cdev->dev;
 	cdev_ctx = &ictx[wq->idxd->type];
 	minor = ida_simple_get(&cdev_ctx->minor_ida, 0, MINORMASK, GFP_KERNEL);
 	if (minor < 0) {
-		rc = minor;
-		kfree(dev);
-		goto ida_err;
-	}
-
-	dev->devt = MKDEV(MAJOR(cdev_ctx->devt), minor);
-	dev->type = &idxd_cdev_device_type;
-	rc = device_register(dev);
-	if (rc < 0) {
-		dev_err(&idxd->pdev->dev, "device register failed\n");
-		goto dev_reg_err;
+		kfree(idxd_cdev);
+		return minor;
 	}
 	idxd_cdev->minor = minor;
 
-	return 0;
+	device_initialize(dev);
+	dev->parent = &wq->conf_dev;
+	dev->bus = idxd_get_bus_type(idxd);
+	dev->type = &idxd_cdev_device_type;
+	dev->devt = MKDEV(MAJOR(cdev_ctx->devt), minor);
 
- dev_reg_err:
-	ida_simple_remove(&cdev_ctx->minor_ida, MINOR(dev->devt));
-	put_device(dev);
- ida_err:
-	idxd_cdev->dev = NULL;
-	return rc;
-}
-
-static void idxd_wq_cdev_cleanup(struct idxd_wq *wq,
-				 enum idxd_cdev_cleanup cdev_state)
-{
-	struct idxd_cdev *idxd_cdev = &wq->idxd_cdev;
-	struct idxd_cdev_context *cdev_ctx;
-
-	cdev_ctx = &ictx[wq->idxd->type];
-	if (cdev_state == CDEV_NORMAL)
-		cdev_del(&idxd_cdev->cdev);
-	device_unregister(idxd_cdev->dev);
-	/*
-	 * The device_type->release() will be called on the device and free
-	 * the allocated struct device. We can just forget it.
-	 */
-	ida_simple_remove(&cdev_ctx->minor_ida, idxd_cdev->minor);
-	idxd_cdev->dev = NULL;
-	idxd_cdev->minor = -1;
-}
-
-int idxd_wq_add_cdev(struct idxd_wq *wq)
-{
-	struct idxd_cdev *idxd_cdev = &wq->idxd_cdev;
-	struct cdev *cdev = &idxd_cdev->cdev;
-	struct device *dev;
-	int rc;
-
-	rc = idxd_wq_cdev_dev_setup(wq);
+	rc = dev_set_name(dev, "%s/wq%u.%u", idxd_get_dev_name(idxd),
+			  idxd->id, wq->id);
 	if (rc < 0)
-		return rc;
+		goto err;
 
-	dev = idxd_cdev->dev;
+	wq->idxd_cdev = idxd_cdev;
 	cdev_init(cdev, &idxd_cdev_fops);
-	cdev_set_parent(cdev, &dev->kobj);
-	rc = cdev_add(cdev, dev->devt, 1);
+	rc = cdev_device_add(cdev, dev);
 	if (rc) {
 		dev_dbg(&wq->idxd->pdev->dev, "cdev_add failed: %d\n", rc);
-		idxd_wq_cdev_cleanup(wq, CDEV_FAILED);
-		return rc;
+		goto err;
 	}
 
-	init_waitqueue_head(&idxd_cdev->err_queue);
 	return 0;
+
+ err:
+	put_device(dev);
+	wq->idxd_cdev = NULL;
+	return rc;
 }
 
 void idxd_wq_del_cdev(struct idxd_wq *wq)
 {
-	idxd_wq_cdev_cleanup(wq, CDEV_NORMAL);
+	struct idxd_cdev *idxd_cdev;
+	struct idxd_cdev_context *cdev_ctx;
+
+	cdev_ctx = &ictx[wq->idxd->type];
+	idxd_cdev = wq->idxd_cdev;
+	wq->idxd_cdev = NULL;
+	cdev_device_del(&idxd_cdev->cdev, &idxd_cdev->dev);
+	put_device(&idxd_cdev->dev);
 }
 
 int idxd_cdev_register(void)

drivers/dma/idxd/idxd.h

@@ -80,10 +80,10 @@ enum idxd_wq_type {
 };
 
 struct idxd_cdev {
+	struct idxd_wq *wq;
 	struct cdev cdev;
-	struct device *dev;
+	struct device dev;
 	int minor;
-	struct wait_queue_head err_queue;
 };
 
 #define IDXD_ALLOCATED_BATCH_SIZE	128U
@@ -109,7 +109,8 @@ struct idxd_dma_chan {
 struct idxd_wq {
 	void __iomem *portal;
 	struct device conf_dev;
-	struct idxd_cdev idxd_cdev;
+	struct idxd_cdev *idxd_cdev;
+	struct wait_queue_head err_queue;
 	struct idxd_device *idxd;
 	int id;
 	enum idxd_wq_type type;

drivers/dma/idxd/init.c

@@ -176,7 +176,7 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
 		}
 
 		mutex_init(&wq->wq_lock);
-		wq->idxd_cdev.minor = -1;
+		init_waitqueue_head(&wq->err_queue);
 		wq->max_xfer_bytes = idxd->max_xfer_bytes;
 		wq->max_batch_size = idxd->max_batch_size;
 		wq->wqcfg = kzalloc_node(idxd->wqcfg_size, GFP_KERNEL, dev_to_node(dev));

drivers/dma/idxd/irq.c

@@ -133,7 +133,7 @@ static int process_misc_interrupts(struct idxd_device *idxd, u32 cause)
 			struct idxd_wq *wq = idxd->wqs[id];
 
 			if (wq->type == IDXD_WQT_USER)
-				wake_up_interruptible(&wq->idxd_cdev.err_queue);
+				wake_up_interruptible(&wq->err_queue);
 		} else {
 			int i;
 
@@ -141,7 +141,7 @@ static int process_misc_interrupts(struct idxd_device *idxd, u32 cause)
 				struct idxd_wq *wq = idxd->wqs[i];
 
 				if (wq->type == IDXD_WQT_USER)
-					wake_up_interruptible(&wq->idxd_cdev.err_queue);
+					wake_up_interruptible(&wq->err_queue);
 			}
 		}
 

drivers/dma/idxd/sysfs.c

@@ -1169,8 +1169,16 @@ static ssize_t wq_cdev_minor_show(struct device *dev,
 				  struct device_attribute *attr, char *buf)
 {
 	struct idxd_wq *wq = container_of(dev, struct idxd_wq, conf_dev);
+	int minor = -1;
 
-	return sprintf(buf, "%d\n", wq->idxd_cdev.minor);
+	mutex_lock(&wq->wq_lock);
+	if (wq->idxd_cdev)
+		minor = wq->idxd_cdev->minor;
+	mutex_unlock(&wq->wq_lock);
+
+	if (minor == -1)
+		return -ENXIO;
+	return sysfs_emit(buf, "%d\n", minor);
 }
 
 static struct device_attribute dev_attr_wq_cdev_minor =