[PATCH v7 8/8] dmaengine: idxd: fix cdev setup and free device lifetime issues

Dave Jiang
2021-03-22T23:32:43Z

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: 42d279f9137a ("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>
---
drivers/dma/idxd/cdev.c | 131 +++++++++++++++++-----------------------------
drivers/dma/idxd/idxd.h | 7 +-
drivers/dma/idxd/init.c | 2 -
drivers/dma/idxd/irq.c | 4 +
drivers/dma/idxd/sysfs.c | 8 ++-
5 files changed, 63 insertions(+), 89 deletions(-)

diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
index 0db9b82ed8cf..b4ff97f93f13 100644
--- a/drivers/dma/idxd/cdev.c
+++ b/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 +242,69 @@ 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;
-
- 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;
+ 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);

- 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];
+ mutex_lock(&wq->wq_lock);
+ idxd_cdev = wq->idxd_cdev;
+ wq->idxd_cdev = NULL;
+ mutex_unlock(&wq->wq_lock);
+ cdev_device_del(&idxd_cdev->cdev, &idxd_cdev->dev);
+ put_device(&idxd_cdev->dev);
}

int idxd_cdev_register(void)
diff --git a/drivers/dma/idxd/idxd.h b/drivers/dma/idxd/idxd.h
index 35bb616f04d5..acb70c3b7e36 100644
--- a/drivers/dma/idxd/idxd.h
+++ b/drivers/dma/idxd/idxd.h
@@ -79,10 +79,10 @@ 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
@@ -108,7 +108,8 @@ 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;
diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index 72b859c33937..7847daa51d4c 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -273,7 +273,7 @@ static int idxd_setup_internals(struct idxd_device *idxd)
wq->id = i;
wq->idxd = 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));
diff --git a/drivers/dma/idxd/irq.c b/drivers/dma/idxd/irq.c
index 7b0181532f77..fc0781e3f36d 100644
--- a/drivers/dma/idxd/irq.c
+++ b/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);
}
}

diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
index 03079ff54889..8a08988ea9d1 100644
--- a/drivers/dma/idxd/sysfs.c
+++ b/drivers/dma/idxd/sysfs.c
@@ -1174,8 +1174,14 @@ 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);
+
+ return sprintf(buf, "%d\n", minor);
}

static struct device_attribute dev_attr_wq_cdev_minor =