[PATCH 4.17 079/324] nbd: Add the nbd NBD_DISCONNECT_ON_CLOSE config flag.

Greg Kroah-Hartman
2018-08-23T08:43:16Z

From: Doron Roberts-Kedes <doronrk@fb.com>

[ Upstream commit 08ba91ee6e2c1c08d3f0648f978cbb5dbf3491d8 ]

If NBD_DISCONNECT_ON_CLOSE is set on a device, then the driver will
issue a disconnect from nbd_release if the device has no remaining
bdev->bd_openers.

Fix ret val so reconfigure with only setting the flag succeeds.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Doron Roberts-Kedes <doronrk@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/block/nbd.c | 40 +++++++++++++++++++++++++++++++++-------
include/uapi/linux/nbd.h | 3 +++
2 files changed, 36 insertions(+), 7 deletions(-)

--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -76,6 +76,7 @@ struct link_dead_args {
#define NBD_HAS_CONFIG_REF 4
#define NBD_BOUND 5
#define NBD_DESTROY_ON_DISCONNECT 6
+#define NBD_DISCONNECT_ON_CLOSE 7

struct nbd_config {
u32 flags;
@@ -138,6 +139,7 @@ static void nbd_config_put(struct nbd_de
static void nbd_connect_reply(struct genl_info *info, int index);
static int nbd_genl_status(struct sk_buff *skb, struct genl_info *info);
static void nbd_dead_link_work(struct work_struct *work);
+static void nbd_disconnect_and_put(struct nbd_device *nbd);

static inline struct device *nbd_to_dev(struct nbd_device *nbd)
{
@@ -1291,6 +1293,12 @@ out:
static void nbd_release(struct gendisk *disk, fmode_t mode)
{
struct nbd_device *nbd = disk->private_data;
+ struct block_device *bdev = bdget_disk(disk, 0);
+
+ if (test_bit(NBD_DISCONNECT_ON_CLOSE, &nbd->config->runtime_flags) &&
+ bdev->bd_openers == 0)
+ nbd_disconnect_and_put(nbd);
+
nbd_config_put(nbd);
nbd_put(nbd);
}
@@ -1690,6 +1698,10 @@ again:
&config->runtime_flags);
put_dev = true;
}
+ if (flags & NBD_CFLAG_DISCONNECT_ON_CLOSE) {
+ set_bit(NBD_DISCONNECT_ON_CLOSE,
+ &config->runtime_flags);
+ }
}

if (info->attrs[NBD_ATTR_SOCKETS]) {
@@ -1734,6 +1746,16 @@ out:
return ret;
}

+static void nbd_disconnect_and_put(struct nbd_device *nbd)
+{
+ 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);
+}
+
static int nbd_genl_disconnect(struct sk_buff *skb, struct genl_info *info)
{
struct nbd_device *nbd;
@@ -1766,12 +1788,7 @@ static int nbd_genl_disconnect(struct sk
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_disconnect_and_put(nbd);
nbd_config_put(nbd);
nbd_put(nbd);
return 0;
@@ -1782,7 +1799,7 @@ static int nbd_genl_reconfigure(struct s
struct nbd_device *nbd = NULL;
struct nbd_config *config;
int index;
- int ret = -EINVAL;
+ int ret = 0;
bool put_dev = false;

if (!netlink_capable(skb, CAP_SYS_ADMIN))
@@ -1822,6 +1839,7 @@ static int nbd_genl_reconfigure(struct s
!nbd->task_recv) {
dev_err(nbd_to_dev(nbd),
"not configured, cannot reconfigure\n");
+ ret = -EINVAL;
goto out;
}

@@ -1846,6 +1864,14 @@ static int nbd_genl_reconfigure(struct s
&config->runtime_flags))
refcount_inc(&nbd->refs);
}
+
+ if (flags & NBD_CFLAG_DISCONNECT_ON_CLOSE) {
+ set_bit(NBD_DISCONNECT_ON_CLOSE,
+ &config->runtime_flags);
+ } else {
+ clear_bit(NBD_DISCONNECT_ON_CLOSE,
+ &config->runtime_flags);
+ }
}

if (info->attrs[NBD_ATTR_SOCKETS]) {
--- a/include/uapi/linux/nbd.h
+++ b/include/uapi/linux/nbd.h
@@ -53,6 +53,9 @@ enum {
/* These are client behavior specific flags. */
#define NBD_CFLAG_DESTROY_ON_DISCONNECT (1 << 0) /* delete the nbd device on
disconnect. */
+#define NBD_CFLAG_DISCONNECT_ON_CLOSE (1 << 1) /* disconnect the nbd device on
+ * close by last opener.
+ */

/* userspace doesn't need the nbd_device structure */