Re: [RHEL7.6 PATCH 22/37] Drivers: hv: vmbus: Fix a rescind issue

On 20-04, Mohammed Gamal wrote:

The current rescind processing code will not correctly handle the case where the host immediately rescinds a channel that has been offerred. In this case, we could be blocked in the open call and since the channel is rescinded, the host will not respond and we could be blocked forever in the vmbus open call.i Fix this problem.

Signed-off-by: K. Y. Srinivasan kys@microsoft.com Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org (cherry picked from commit 7fa32e5ec28b1609abc0b797b58267f725fc3964)

Signed-off-by: Mohammed Gamal mgamal@redhat.com

Just fyi, this patch was already applied by:

http://patchwork.lab.bos.redhat.com/patch/207318/

thus I'll drop it during this patchset integration to rhel tree.

Thanks!

---

drivers/hv/channel.c | 10 ++++++++-- drivers/hv/channel_mgmt.c | 7 ++++--- include/linux/hyperv.h | 1 + 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c index 1c967f5..1d58986 100644 --- a/drivers/hv/channel.c +++ b/drivers/hv/channel.c @@ -659,22 +659,28 @@ void vmbus_close(struct vmbus_channel *channel) */ return; }

• mutex_lock(&vmbus_connection.channel_mutex); /*
  • Close all the sub-channels first and then close the
  • primary channel.
  */ list_for_each_safe(cur, tmp, &channel->sc_list) { cur_channel = list_entry(cur, struct vmbus_channel, sc_list);

• vmbus_close_internal(cur_channel);
  

  if (cur_channel->rescind) {

• 	wait_for_completion(&cur_channel->rescind_event);
  

• 	mutex_lock(&vmbus_connection.channel_mutex);
  

• 	vmbus_close_internal(cur_channel);
  hv_process_channel_removal(
  		   cur_channel->offermsg.child_relid);
  

• } else {
  

• 	mutex_lock(&vmbus_connection.channel_mutex);
  

• 	vmbus_close_internal(cur_channel);
  

  }

• mutex_unlock(&vmbus_connection.channel_mutex);
  

  } /*
  • Now close the primary.
  */
• mutex_lock(&vmbus_connection.channel_mutex); vmbus_close_internal(channel); mutex_unlock(&vmbus_connection.channel_mutex);

} diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index ec5454f..c21020b 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -333,6 +333,7 @@ static struct vmbus_channel *alloc_channel(void) return NULL; spin_lock_init(&channel->lock);

• init_completion(&channel->rescind_event);

INIT_LIST_HEAD(&channel->sc_list); INIT_LIST_HEAD(&channel->percpu_list); @@ -898,6 +899,7 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr) /* * Now wait for offer handling to complete. */

• vmbus_rescind_cleanup(channel); while (READ_ONCE(channel->probe_done) == false) { /*
  • We wait here until any channel offer is currently

@@ -913,7 +915,6 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr) if (channel->device_obj) { if (channel->chn_rescind_callback) { channel->chn_rescind_callback(channel);

• 	vmbus_rescind_cleanup(channel);
  return;
  

  } /*

@@ -922,7 +923,6 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr) */ dev = get_device(&channel->device_obj->device); if (dev) {

• 	vmbus_rescind_cleanup(channel);
  vmbus_device_unregister(channel->device_obj);
  put_device(dev);
  

  }

@@ -936,13 +936,14 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr) * 2. Then close the primary channel. */ mutex_lock(&vmbus_connection.channel_mutex);

• vmbus_rescind_cleanup(channel);
  

  if (channel->state == CHANNEL_OPEN_STATE) { /* * The channel is currently not open; * it is safe for us to cleanup the channel. */ hv_process_channel_removal(rescind->child_relid);

• } else {
  

• 	complete(&channel->rescind_event);
  

  } mutex_unlock(&vmbus_connection.channel_mutex); }

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index 1552a5f..465d5db 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -724,6 +724,7 @@ struct vmbus_channel { u8 monitor_bit; bool rescind; /* got rescind msg */

• struct completion rescind_event;

u32 ringbuffer_gpadlhandle; -- 1.8.3.1