[Nbd] [PATCH] nbd: ref count the socks array
In preparation for allowing seamless reconnects we need a way to make
sure that we don't free the socks array out from underneath ourselves.
So a socks_ref counter in order to keep track of who is using the socks
array, and only free it and change num_connections once our reference
reduces to zero.
We also need to make sure that somebody calling SET_SOCK isn't coming in
before we're done with our socks array, so add a waitqueue to wait on
previous users of the socks array before initiating a new socks array.
Signed-off-by: Josef Bacik <jbacik@...2204...>
---
drivers/block/nbd.c | 126 +++++++++++++++++++++++++++++++++++++---------------
1 file changed, 91 insertions(+), 35 deletions(-)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 1914ba2..3dc2f1d 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -54,19 +54,24 @@ struct nbd_sock {
#define NBD_TIMEDOUT 0
#define NBD_DISCONNECT_REQUESTED 1
#define NBD_DISCONNECTED 2
-#define NBD_RUNNING 3
+#define NBD_HAS_SOCKS_REF 3
struct nbd_device {
u32 flags;
unsigned long runtime_flags;
+
+ struct mutex socks_lock;
struct nbd_sock **socks;
+ atomic_t socks_ref;
+ wait_queue_head_t socks_wq;
+ int num_connections;
+
int magic;
struct blk_mq_tag_set tag_set;
struct mutex config_lock;
struct gendisk *disk;
- int num_connections;
atomic_t recv_threads;
wait_queue_head_t recv_wq;
loff_t blksize;
@@ -102,7 +107,6 @@ static int part_shift;
static int nbd_dev_dbg_init(struct nbd_device *nbd);
static void nbd_dev_dbg_close(struct nbd_device *nbd);
-
static inline struct device *nbd_to_dev(struct nbd_device *nbd)
{
return disk_to_dev(nbd->disk);
@@ -125,6 +129,27 @@ static const char *nbdcmd_to_ascii(int cmd)
return "invalid";
}
+static int nbd_socks_get_unless_zero(struct nbd_device *nbd)
+{
+ return atomic_add_unless(&nbd->socks_ref, 1, 0);
+}
+
+static void nbd_socks_put(struct nbd_device *nbd)
+{
+ if (atomic_dec_and_test(&nbd->socks_ref)) {
+ mutex_lock(&nbd->socks_lock);
+ if (nbd->num_connections) {
+ int i;
+ for (i = 0; i < nbd->num_connections; i++)
+ kfree(nbd->socks[i]);
+ kfree(nbd->socks);
+ nbd->num_connections = 0;
+ nbd->socks = NULL;
+ }
+ mutex_unlock(&nbd->socks_lock);
+ }
+}
+
static int nbd_size_clear(struct nbd_device *nbd, struct block_device *bdev)
{
bdev->bd_inode->i_size = 0;
@@ -190,6 +215,7 @@ static void sock_shutdown(struct nbd_device *nbd)
mutex_lock(&nsock->tx_lock);
kernel_sock_shutdown(nsock->sock, SHUT_RDWR);
mutex_unlock(&nsock->tx_lock);
+ nsock->dead = true;
}
dev_warn(disk_to_dev(nbd->disk), "shutting down sockets\n");
}
@@ -200,6 +226,9 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);
struct nbd_device *nbd = cmd->nbd;
+ if (!nbd_socks_get_unless_zero(nbd))
+ return BLK_EH_HANDLED;
+
if (nbd->num_connections > 1) {
dev_err_ratelimited(nbd_to_dev(nbd),
"Connection timed out, retrying\n");
@@ -219,6 +248,7 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
}
mutex_unlock(&nbd->config_lock);
blk_mq_requeue_request(req, true);
+ nbd_socks_put(nbd);
return BLK_EH_RESET_TIMER;
}
mutex_unlock(&nbd->config_lock);
@@ -228,10 +258,9 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
}
set_bit(NBD_TIMEDOUT, &nbd->runtime_flags);
req->errors++;
-
- mutex_lock(&nbd->config_lock);
sock_shutdown(nbd);
- mutex_unlock(&nbd->config_lock);
+ nbd_socks_put(nbd);
+
return BLK_EH_HANDLED;
}
@@ -523,6 +552,7 @@ static void recv_work(struct work_struct *work)
nbd_end_request(cmd);
}
+ nbd_socks_put(nbd);
atomic_dec(&nbd->recv_threads);
wake_up(&nbd->recv_wq);
}
@@ -598,9 +628,16 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
struct nbd_sock *nsock;
int ret;
+ if (!nbd_socks_get_unless_zero(nbd)) {
+ dev_err_ratelimited(disk_to_dev(nbd->disk),
+ "Socks array is empty\n");
+ return -EINVAL;
+ }
+
if (index >= nbd->num_connections) {
dev_err_ratelimited(disk_to_dev(nbd->disk),
"Attempted send on invalid socket\n");
+ nbd_socks_put(nbd);
return -EINVAL;
}
req->errors = 0;
@@ -608,8 +645,10 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
nsock = nbd->socks[index];
if (nsock->dead) {
index = find_fallback(nbd, index);
- if (index < 0)
+ if (index < 0) {
+ nbd_socks_put(nbd);
return -EIO;
+ }
nsock = nbd->socks[index];
}
@@ -627,7 +666,7 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
goto again;
}
mutex_unlock(&nsock->tx_lock);
-
+ nbd_socks_put(nbd);
return ret;
}
@@ -656,6 +695,25 @@ static int nbd_queue_rq(struct blk_mq_hw_ctx *hctx,
return BLK_MQ_RQ_QUEUE_OK;
}
+static int nbd_wait_for_socks(struct nbd_device *nbd)
+{
+ int ret;
+
+ if (!atomic_read(&nbd->socks_ref))
+ return 0;
+
+ do {
+ mutex_unlock(&nbd->socks_lock);
+ mutex_unlock(&nbd->config_lock);
+ ret = wait_event_interruptible(nbd->socks_wq,
+ atomic_read(&nbd->socks_ref) == 0);
+ mutex_lock(&nbd->config_lock);
+ mutex_lock(&nbd->socks_lock);
+ } while (!ret && atomic_read(&nbd->socks_ref));
+
+ return ret;
+}
+
static int nbd_add_socket(struct nbd_device *nbd, struct block_device *bdev,
unsigned long arg)
{
@@ -668,21 +726,30 @@ static int nbd_add_socket(struct nbd_device *nbd, struct block_device *bdev,
if (!sock)
return err;
- if (!nbd->task_setup)
+ err = -EINVAL;
+ mutex_lock(&nbd->socks_lock);
+ if (!nbd->task_setup) {
nbd->task_setup = current;
+ if (nbd_wait_for_socks(nbd))
+ goto out;
+ atomic_inc(&nbd->socks_ref);
+ set_bit(NBD_HAS_SOCKS_REF, &nbd->runtime_flags);
+ }
+
if (nbd->task_setup != current) {
dev_err(disk_to_dev(nbd->disk),
"Device being setup by another task");
- return -EINVAL;
+ goto out;
}
+ err = -ENOMEM;
socks = krealloc(nbd->socks, (nbd->num_connections + 1) *
sizeof(struct nbd_sock *), GFP_KERNEL);
if (!socks)
- return -ENOMEM;
+ goto out;
nsock = kzalloc(sizeof(struct nbd_sock), GFP_KERNEL);
if (!nsock)
- return -ENOMEM;
+ goto out;
nbd->socks = socks;
@@ -694,7 +761,10 @@ static int nbd_add_socket(struct nbd_device *nbd, struct block_device *bdev,
if (max_part)
bdev->bd_invalidated = 1;
- return 0;
+ err = 0;
+out:
+ mutex_unlock(&nbd->socks_lock);
+ return err;
}
/* Reset all properties of an NBD device */
@@ -750,20 +820,17 @@ static void send_disconnects(struct nbd_device *nbd)
static int nbd_disconnect(struct nbd_device *nbd, struct block_device *bdev)
{
dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n");
- if (!nbd->socks)
+ if (!nbd_socks_get_unless_zero(nbd))
return -EINVAL;
mutex_unlock(&nbd->config_lock);
fsync_bdev(bdev);
mutex_lock(&nbd->config_lock);
- /* Check again after getting mutex back. */
- if (!nbd->socks)
- return -EINVAL;
-
if (!test_and_set_bit(NBD_DISCONNECT_REQUESTED,
&nbd->runtime_flags))
send_disconnects(nbd);
+ nbd_socks_put(nbd);
return 0;
}
@@ -773,22 +840,9 @@ static int nbd_clear_sock(struct nbd_device *nbd, struct block_device *bdev)
nbd_clear_que(nbd);
kill_bdev(bdev);
nbd_bdev_reset(bdev);
- /*
- * We want to give the run thread a chance to wait for everybody
- * to clean up and then do it's own cleanup.
- */
- if (!test_bit(NBD_RUNNING, &nbd->runtime_flags) &&
- nbd->num_connections) {
- int i;
-
- for (i = 0; i < nbd->num_connections; i++)
- kfree(nbd->socks[i]);
- kfree(nbd->socks);
- nbd->socks = NULL;
- nbd->num_connections = 0;
- }
nbd->task_setup = NULL;
-
+ if (test_and_clear_bit(NBD_HAS_SOCKS_REF, &nbd->runtime_flags))
+ nbd_socks_put(nbd);
return 0;
}
@@ -809,7 +863,6 @@ static int nbd_start_device(struct nbd_device *nbd, struct block_device *bdev)
goto out_err;
}
- set_bit(NBD_RUNNING, &nbd->runtime_flags);
blk_mq_update_nr_hw_queues(&nbd->tag_set, nbd->num_connections);
args = kcalloc(num_connections, sizeof(*args), GFP_KERNEL);
if (!args) {
@@ -833,6 +886,7 @@ static int nbd_start_device(struct nbd_device *nbd, struct block_device *bdev)
for (i = 0; i < num_connections; i++) {
sk_set_memalloc(nbd->socks[i]->sock->sk);
atomic_inc(&nbd->recv_threads);
+ atomic_inc(&nbd->socks_ref);
INIT_WORK(&args[i].work, recv_work);
args[i].nbd = nbd;
args[i].index = i;
@@ -849,7 +903,6 @@ static int nbd_start_device(struct nbd_device *nbd, struct block_device *bdev)
mutex_lock(&nbd->config_lock);
nbd->task_recv = NULL;
out_err:
- clear_bit(NBD_RUNNING, &nbd->runtime_flags);
nbd_clear_sock(nbd, bdev);
/* user requested, ignore socket errors */
@@ -1149,12 +1202,15 @@ static int nbd_dev_add(int index)
nbd->magic = NBD_MAGIC;
mutex_init(&nbd->config_lock);
+ mutex_init(&nbd->socks_lock);
+ atomic_set(&nbd->socks_ref, 0);
disk->major = NBD_MAJOR;
disk->first_minor = index << part_shift;
disk->fops = &nbd_fops;
disk->private_data = nbd;
sprintf(disk->disk_name, "nbd%d", index);
init_waitqueue_head(&nbd->recv_wq);
+ init_waitqueue_head(&nbd->socks_wq);
nbd_reset(nbd);
add_disk(disk);
return index;
--
2.7.4
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