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Subject[PATCH] drbd: standardize kthread/workqueue thread naming to include drbd minor number
Date
From: Eric Wheeler <git@linux.ewheeler.net>

For DRBD resources with long names that start with the same prefix,
it was difficult to find all process pids for that minor since names
are truncated to the task_struct's comm field (16 bytes).

This patch names all processes associated with a DRBD device as drbdN_*
where N is the DRBD minor in the same ways that the drbdN_submit workqueue
is named. Userspace tools can then lookup the name=>minor=>pid mapping
and for all pids and use tools like chrt, ioprio, nice, add pids to
cgroups, or for other useful purpose.

Signed-off-by: Eric Wheeler <drbd@linux.ewheeler.net>
---
drivers/block/drbd/drbd_main.c | 31 +++++++++++++++++++++++++++++--
drivers/block/drbd/drbd_receiver.c | 19 +++++++++++++++++--
2 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 8cb3791..c5444b3 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -330,7 +330,21 @@ static int drbd_thread_setup(void *arg)
unsigned long flags;
int retval;

- snprintf(current->comm, sizeof(current->comm), "drbd_%c_%s",
+ int i, minor = -1;
+ struct drbd_device *device;
+
+ idr_for_each_entry(&resource->devices, device, i) {
+ if (minor >= 0 && minor != device->minor)
+ pr_err("drbd: %s(%s): minor is different. was %d is now %d\n",
+ __func__,
+ resource->name,
+ minor, device->minor);
+
+ minor = device->minor;
+ }
+
+ snprintf(current->comm, sizeof(current->comm), "drbd%d_%c_%s",
+ minor,
thi->name[0],
resource->name);

@@ -389,6 +403,8 @@ int drbd_thread_start(struct drbd_thread *thi)
{
struct drbd_resource *resource = thi->resource;
struct task_struct *nt;
+ struct drbd_device *device;
+ int i, minor = -1;
unsigned long flags;

/* is used from state engine doing drbd_thread_stop_nowait,
@@ -417,8 +433,19 @@ int drbd_thread_start(struct drbd_thread *thi)
spin_unlock_irqrestore(&thi->t_lock, flags);
flush_signals(current); /* otherw. may get -ERESTARTNOINTR */

+ idr_for_each_entry(&resource->devices, device, i) {
+ if (minor >= 0 && minor != device->minor)
+ pr_err("drbd: drbd_thread_start(%s, %s): minor is different. was %d is now %d\n",
+ thi->name,
+ thi->resource->name,
+ minor, device->minor);
+
+ minor = device->minor;
+ }
+
nt = kthread_create(drbd_thread_setup, (void *) thi,
- "drbd_%c_%s", thi->name[0], thi->resource->name);
+ "drbd%d_%c_%s",
+ minor, thi->name[0], thi->resource->name);

if (IS_ERR(nt)) {
drbd_err(resource, "Couldn't start thread\n");
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 796eaf3..62a902f 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -934,7 +934,7 @@ static int conn_connect(struct drbd_connection *connection)
struct drbd_socket sock, msock;
struct drbd_peer_device *peer_device;
struct net_conf *nc;
- int vnr, timeout, h;
+ int vnr, timeout, h, i, minor = -1;
bool discard_my_data, ok;
enum drbd_state_rv rv;
struct accept_wait_data ad = {
@@ -1132,10 +1132,25 @@ static int conn_connect(struct drbd_connection *connection)
}

drbd_thread_start(&connection->ack_receiver);
+
+ if (connection->resource) {
+ struct drbd_device *device;
+
+ idr_for_each_entry(&connection->resource->devices, device, i) {
+ if (minor >= 0 && minor != device->minor)
+ pr_err("drbd: conn_connect(%s): minor is different. was %d is now %d\n",
+ connection->resource->name,
+ minor, device->minor);
+
+ minor = device->minor;
+ }
+ }
/* opencoded create_singlethread_workqueue(),
* to be able to use format string arguments */
connection->ack_sender =
- alloc_ordered_workqueue("drbd_as_%s", WQ_MEM_RECLAIM, connection->resource->name);
+ alloc_ordered_workqueue("drbd%d_as_%s",
+ WQ_MEM_RECLAIM, minor, connection->resource->name);
+
if (!connection->ack_sender) {
drbd_err(connection, "Failed to create workqueue ack_sender\n");
return 0;
--
1.8.3.1
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