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nbd: add device refcounting
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In order to support deleting the device on disconnect we need to
refcount the actual nbd_device struct.  So add the refcounting framework
and change how we free the normal devices at rmmod time so we can catch
reference leaks.

Signed-off-by: Josef Bacik <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
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@josefbacik @axboe
josefbacik authored and axboe committed Apr 17, 2017
1 parent 47d902b commit c6a4759
Showing 1 changed file with 86 additions and 18 deletions.
104 changes: 86 additions & 18 deletions drivers/block/nbd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -99,10 +99,12 @@ struct nbd_device {

int index;
refcount_t config_refs;
refcount_t refs;
struct nbd_config *config;
struct mutex config_lock;
struct gendisk *disk;

struct list_head list;
struct task_struct *task_recv;
struct task_struct *task_setup;
};
Expand Down Expand Up @@ -165,6 +167,28 @@ static struct device_attribute pid_attr = {
.show = pid_show,
};

static void nbd_dev_remove(struct nbd_device *nbd)
{
struct gendisk *disk = nbd->disk;
if (disk) {
del_gendisk(disk);
blk_cleanup_queue(disk->queue);
blk_mq_free_tag_set(&nbd->tag_set);
put_disk(disk);
}
kfree(nbd);
}

static void nbd_put(struct nbd_device *nbd)
{
if (refcount_dec_and_mutex_lock(&nbd->refs,
&nbd_index_mutex)) {
idr_remove(&nbd_index_idr, nbd->index);
mutex_unlock(&nbd_index_mutex);
nbd_dev_remove(nbd);
}
}

static int nbd_disconnected(struct nbd_config *config)
{
return test_bit(NBD_DISCONNECTED, &config->runtime_flags) ||
Expand Down Expand Up @@ -1005,6 +1029,7 @@ static void nbd_config_put(struct nbd_device *nbd)
}
nbd_reset(nbd);
mutex_unlock(&nbd->config_lock);
nbd_put(nbd);
module_put(THIS_MODULE);
}
}
Expand Down Expand Up @@ -1199,6 +1224,10 @@ static int nbd_open(struct block_device *bdev, fmode_t mode)
ret = -ENXIO;
goto out;
}
if (!refcount_inc_not_zero(&nbd->refs)) {
ret = -ENXIO;
goto out;
}
if (!refcount_inc_not_zero(&nbd->config_refs)) {
struct nbd_config *config;

Expand All @@ -1214,6 +1243,7 @@ static int nbd_open(struct block_device *bdev, fmode_t mode)
goto out;
}
refcount_set(&nbd->config_refs, 1);
refcount_inc(&nbd->refs);
mutex_unlock(&nbd->config_lock);
}
out:
Expand All @@ -1225,6 +1255,7 @@ static void nbd_release(struct gendisk *disk, fmode_t mode)
{
struct nbd_device *nbd = disk->private_data;
nbd_config_put(nbd);
nbd_put(nbd);
}

static const struct block_device_operations nbd_fops =
Expand Down Expand Up @@ -1378,18 +1409,6 @@ static const struct blk_mq_ops nbd_mq_ops = {
.timeout = nbd_xmit_timeout,
};

static void nbd_dev_remove(struct nbd_device *nbd)
{
struct gendisk *disk = nbd->disk;
if (disk) {
del_gendisk(disk);
blk_cleanup_queue(disk->queue);
blk_mq_free_tag_set(&nbd->tag_set);
put_disk(disk);
}
kfree(nbd);
}

static int nbd_dev_add(int index)
{
struct nbd_device *nbd;
Expand Down Expand Up @@ -1452,6 +1471,8 @@ static int nbd_dev_add(int index)

mutex_init(&nbd->config_lock);
refcount_set(&nbd->config_refs, 0);
refcount_set(&nbd->refs, 1);
INIT_LIST_HEAD(&nbd->list);
disk->major = NBD_MAJOR;
disk->first_minor = index << part_shift;
disk->fops = &nbd_fops;
Expand Down Expand Up @@ -1549,28 +1570,40 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
} else {
nbd = idr_find(&nbd_index_idr, index);
}
mutex_unlock(&nbd_index_mutex);
if (!nbd) {
printk(KERN_ERR "nbd: couldn't find device at index %d\n",
index);
mutex_unlock(&nbd_index_mutex);
return -EINVAL;
}
if (!refcount_inc_not_zero(&nbd->refs)) {
mutex_unlock(&nbd_index_mutex);
if (index == -1)
goto again;
printk(KERN_ERR "nbd: device at index %d is going down\n",
index);
return -EINVAL;
}
mutex_unlock(&nbd_index_mutex);

mutex_lock(&nbd->config_lock);
if (refcount_read(&nbd->config_refs)) {
mutex_unlock(&nbd->config_lock);
nbd_put(nbd);
if (index == -1)
goto again;
printk(KERN_ERR "nbd: nbd%d already in use\n", index);
return -EBUSY;
}
if (WARN_ON(nbd->config)) {
mutex_unlock(&nbd->config_lock);
nbd_put(nbd);
return -EINVAL;
}
config = nbd->config = nbd_alloc_config();
if (!nbd->config) {
mutex_unlock(&nbd->config_lock);
nbd_put(nbd);
printk(KERN_ERR "nbd: couldn't allocate config\n");
return -ENOMEM;
}
Expand Down Expand Up @@ -1655,21 +1688,31 @@ static int nbd_genl_disconnect(struct sk_buff *skb, struct genl_info *info)
index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
mutex_lock(&nbd_index_mutex);
nbd = idr_find(&nbd_index_idr, index);
mutex_unlock(&nbd_index_mutex);
if (!nbd) {
mutex_unlock(&nbd_index_mutex);
printk(KERN_ERR "nbd: couldn't find device at index %d\n",
index);
return -EINVAL;
}
if (!refcount_inc_not_zero(&nbd->config_refs))
if (!refcount_inc_not_zero(&nbd->refs)) {
mutex_unlock(&nbd_index_mutex);
printk(KERN_ERR "nbd: device at index %d is going down\n",
index);
return -EINVAL;
}
mutex_unlock(&nbd_index_mutex);
if (!refcount_inc_not_zero(&nbd->config_refs)) {
nbd_put(nbd);
return 0;
}
mutex_lock(&nbd->config_lock);
nbd_disconnect(nbd);
mutex_unlock(&nbd->config_lock);
if (test_and_clear_bit(NBD_HAS_CONFIG_REF,
&nbd->config->runtime_flags))
nbd_config_put(nbd);
nbd_config_put(nbd);
nbd_put(nbd);
return 0;
}

Expand All @@ -1690,16 +1733,24 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
mutex_lock(&nbd_index_mutex);
nbd = idr_find(&nbd_index_idr, index);
mutex_unlock(&nbd_index_mutex);
if (!nbd) {
mutex_unlock(&nbd_index_mutex);
printk(KERN_ERR "nbd: couldn't find a device at index %d\n",
index);
return -EINVAL;
}
if (!refcount_inc_not_zero(&nbd->refs)) {
mutex_unlock(&nbd_index_mutex);
printk(KERN_ERR "nbd: device at index %d is going down\n",
index);
return -EINVAL;
}
mutex_unlock(&nbd_index_mutex);

if (!refcount_inc_not_zero(&nbd->config_refs)) {
dev_err(nbd_to_dev(nbd),
"not configured, cannot reconfigure\n");
nbd_put(nbd);
return -EINVAL;
}

Expand Down Expand Up @@ -1758,6 +1809,7 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
out:
mutex_unlock(&nbd->config_lock);
nbd_config_put(nbd);
nbd_put(nbd);
return ret;
}

Expand Down Expand Up @@ -2003,16 +2055,32 @@ static int __init nbd_init(void)

static int nbd_exit_cb(int id, void *ptr, void *data)
{
struct list_head *list = (struct list_head *)data;
struct nbd_device *nbd = ptr;
nbd_dev_remove(nbd);

refcount_inc(&nbd->refs);
list_add_tail(&nbd->list, list);
return 0;
}

static void __exit nbd_cleanup(void)
{
struct nbd_device *nbd;
LIST_HEAD(del_list);

nbd_dbg_close();

idr_for_each(&nbd_index_idr, &nbd_exit_cb, NULL);
mutex_lock(&nbd_index_mutex);
idr_for_each(&nbd_index_idr, &nbd_exit_cb, &del_list);
mutex_unlock(&nbd_index_mutex);

list_for_each_entry(nbd, &del_list, list) {
if (refcount_read(&nbd->refs) != 2)
printk(KERN_ERR "nbd: possibly leaking a device\n");
nbd_put(nbd);
nbd_put(nbd);
}

idr_destroy(&nbd_index_idr);
genl_unregister_family(&nbd_genl_family);
destroy_workqueue(recv_workqueue);
Expand Down

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