[PATCH 2/2] virtio-rng: fixes for device registration/unregistration

From: Sasha Levin
Date: Thu May 15 2014 - 09:22:17 EST


There are several fixes in this patch (mostly because it's hard
splitting them up):

- Revert the name field in struct hwrng back to 'const'. Also, don't
do an extra kmalloc for the name - just wasteful.
- Deal with allocation failures properly.
- Use IDA to allocate device number instead of brute forcing one.

Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
drivers/char/hw_random/virtio-rng.c | 41 ++++++++++++++++++++---------------
include/linux/hw_random.h | 2 +-
2 files changed, 24 insertions(+), 19 deletions(-)

diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index 5b25daa..f3e7150 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -25,6 +25,7 @@
#include <linux/virtio_rng.h>
#include <linux/module.h>

+static DEFINE_IDA(rng_index_ida);

struct virtrng_info {
struct virtio_device *vdev;
@@ -33,6 +34,8 @@ struct virtrng_info {
unsigned int data_avail;
struct completion have_data;
bool busy;
+ char name[25];
+ int index;
};

static void random_recv_done(struct virtqueue *vq)
@@ -92,41 +95,45 @@ static void virtio_cleanup(struct hwrng *rng)

static int probe_common(struct virtio_device *vdev)
{
- int err, i;
+ int err, index;
struct virtrng_info *vi = NULL;

vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
- vi->hwrng.name = kmalloc(40, GFP_KERNEL);
+ if (!vi)
+ return -ENOMEM;
+
+ vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL);
+ if (index < 0) {
+ kfree(vi);
+ return index;
+ }
+ sprintf(vi->name, "virtio_rng.%d", index);
init_completion(&vi->have_data);

- vi->hwrng.read = virtio_read;
- vi->hwrng.cleanup = virtio_cleanup;
- vi->hwrng.priv = (unsigned long)vi;
+ vi->hwrng = (struct hwrng) {
+ .read = virtio_read,
+ .cleanup = virtio_cleanup,
+ .priv = (unsigned long)vi,
+ .name = vi->name,
+ };
vdev->priv = vi;

/* We expect a single virtqueue. */
vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
if (IS_ERR(vi->vq)) {
err = PTR_ERR(vi->vq);
- kfree(vi->hwrng.name);
vi->vq = NULL;
kfree(vi);
- vi = NULL;
+ ida_simple_remove(&rng_index_ida, index);
return err;
}

- i = 0;
- do {
- sprintf(vi->hwrng.name, "virtio_rng.%d", i++);
- err = hwrng_register(&vi->hwrng);
- } while (err == -EEXIST);
-
+ err = hwrng_register(&vi->hwrng);
if (err) {
vdev->config->del_vqs(vdev);
- kfree(vi->hwrng.name);
vi->vq = NULL;
kfree(vi);
- vi = NULL;
+ ida_simple_remove(&rng_index_ida, index);
return err;
}

@@ -140,10 +147,8 @@ static void remove_common(struct virtio_device *vdev)
vi->busy = false;
hwrng_unregister(&vi->hwrng);
vdev->config->del_vqs(vdev);
- kfree(vi->hwrng.name);
- vi->vq = NULL;
+ ida_simple_remove(&rng_index_ida, vi->index);
kfree(vi);
- vi = NULL;
}

static int virtrng_probe(struct virtio_device *vdev)
diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h
index 02d9c87..b4b0eef 100644
--- a/include/linux/hw_random.h
+++ b/include/linux/hw_random.h
@@ -31,7 +31,7 @@
* @priv: Private data, for use by the RNG driver.
*/
struct hwrng {
- char *name;
+ const char *name;
int (*init)(struct hwrng *rng);
void (*cleanup)(struct hwrng *rng);
int (*data_present)(struct hwrng *rng, int wait);
--
1.7.10.4

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