Use blk_mq_unique_tag() to generate requestIDs for StorVSC, avoiding
all issues with allocating enough entries in the VMbus requestor.

Suggested-by: Michael Kelley <mikel...@microsoft.com>
Signed-off-by: Andrea Parri (Microsoft) <parri.and...@gmail.com>
---
 drivers/hv/channel.c              | 14 +++---
 drivers/hv/ring_buffer.c          | 12 ++---
 drivers/net/hyperv/netvsc.c       |  8 ++--
 drivers/net/hyperv/rndis_filter.c |  2 +
 drivers/scsi/storvsc_drv.c        | 73 ++++++++++++++++++++++++++-----
 include/linux/hyperv.h            | 13 +++++-
 6 files changed, 92 insertions(+), 30 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index db30be8f9ccea..f78e02ace51e8 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -1121,15 +1121,14 @@ EXPORT_SYMBOL_GPL(vmbus_recvpacket_raw);
  * vmbus_next_request_id - Returns a new request id. It is also
  * the index at which the guest memory address is stored.
  * Uses a spin lock to avoid race conditions.
- * @rqstor: Pointer to the requestor struct
+ * @channel: Pointer to the VMbus channel struct
  * @rqst_add: Guest memory address to be stored in the array
  */
-u64 vmbus_next_request_id(struct vmbus_requestor *rqstor, u64 rqst_addr)
+u64 vmbus_next_request_id(struct vmbus_channel *channel, u64 rqst_addr)
 {
+       struct vmbus_requestor *rqstor = &channel->requestor;
        unsigned long flags;
        u64 current_id;
-       const struct vmbus_channel *channel =
-               container_of(rqstor, const struct vmbus_channel, requestor);
 
        /* Check rqstor has been initialized */
        if (!channel->rqstor_size)
@@ -1163,16 +1162,15 @@ EXPORT_SYMBOL_GPL(vmbus_next_request_id);
 /*
  * vmbus_request_addr - Returns the memory address stored at @trans_id
  * in @rqstor. Uses a spin lock to avoid race conditions.
- * @rqstor: Pointer to the requestor struct
+ * @channel: Pointer to the VMbus channel struct
  * @trans_id: Request id sent back from Hyper-V. Becomes the requestor's
  * next request id.
  */
-u64 vmbus_request_addr(struct vmbus_requestor *rqstor, u64 trans_id)
+u64 vmbus_request_addr(struct vmbus_channel *channel, u64 trans_id)
 {
+       struct vmbus_requestor *rqstor = &channel->requestor;
        unsigned long flags;
        u64 req_addr;
-       const struct vmbus_channel *channel =
-               container_of(rqstor, const struct vmbus_channel, requestor);
 
        /* Check rqstor has been initialized */
        if (!channel->rqstor_size)
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index ecd82ebfd5bc4..46d8e038e4ee1 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -310,10 +310,12 @@ int hv_ringbuffer_write(struct vmbus_channel *channel,
         */
 
        if (desc->flags == VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED) {
-               rqst_id = vmbus_next_request_id(&channel->requestor, requestid);
-               if (rqst_id == VMBUS_RQST_ERROR) {
-                       spin_unlock_irqrestore(&outring_info->ring_lock, flags);
-                       return -EAGAIN;
+               if (channel->next_request_id_callback != NULL) {
+                       rqst_id = channel->next_request_id_callback(channel, 
requestid);
+                       if (rqst_id == VMBUS_RQST_ERROR) {
+                               
spin_unlock_irqrestore(&outring_info->ring_lock, flags);
+                               return -EAGAIN;
+                       }
                }
        }
        desc = hv_get_ring_buffer(outring_info) + old_write;
@@ -341,7 +343,7 @@ int hv_ringbuffer_write(struct vmbus_channel *channel,
        if (channel->rescind) {
                if (rqst_id != VMBUS_NO_RQSTOR) {
                        /* Reclaim request ID to avoid leak of IDs */
-                       vmbus_request_addr(&channel->requestor, rqst_id);
+                       channel->request_addr_callback(channel, rqst_id);
                }
                return -ENODEV;
        }
diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index c64cc7639c39c..1a221ce2d6fdc 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -730,7 +730,7 @@ static void netvsc_send_tx_complete(struct net_device *ndev,
        int queue_sends;
        u64 cmd_rqst;
 
-       cmd_rqst = vmbus_request_addr(&channel->requestor, (u64)desc->trans_id);
+       cmd_rqst = channel->request_addr_callback(channel, (u64)desc->trans_id);
        if (cmd_rqst == VMBUS_RQST_ERROR) {
                netdev_err(ndev, "Incorrect transaction id\n");
                return;
@@ -790,8 +790,8 @@ static void netvsc_send_completion(struct net_device *ndev,
 
        /* First check if this is a VMBUS completion without data payload */
        if (!msglen) {
-               cmd_rqst = vmbus_request_addr(&incoming_channel->requestor,
-                                             (u64)desc->trans_id);
+               cmd_rqst = 
incoming_channel->request_addr_callback(incoming_channel,
+                                                                  
(u64)desc->trans_id);
                if (cmd_rqst == VMBUS_RQST_ERROR) {
                        netdev_err(ndev, "Invalid transaction id\n");
                        return;
@@ -1602,6 +1602,8 @@ struct netvsc_device *netvsc_device_add(struct hv_device 
*device,
                       netvsc_poll, NAPI_POLL_WEIGHT);
 
        /* Open the channel */
+       device->channel->next_request_id_callback = vmbus_next_request_id;
+       device->channel->request_addr_callback = vmbus_request_addr;
        device->channel->rqstor_size = netvsc_rqstor_size(netvsc_ring_bytes);
        ret = vmbus_open(device->channel, netvsc_ring_bytes,
                         netvsc_ring_bytes,  NULL, 0,
diff --git a/drivers/net/hyperv/rndis_filter.c 
b/drivers/net/hyperv/rndis_filter.c
index 123cc9d25f5ed..ebf34bf3f9075 100644
--- a/drivers/net/hyperv/rndis_filter.c
+++ b/drivers/net/hyperv/rndis_filter.c
@@ -1259,6 +1259,8 @@ static void netvsc_sc_open(struct vmbus_channel *new_sc)
        /* Set the channel before opening.*/
        nvchan->channel = new_sc;
 
+       new_sc->next_request_id_callback = vmbus_next_request_id;
+       new_sc->request_addr_callback = vmbus_request_addr;
        new_sc->rqstor_size = netvsc_rqstor_size(netvsc_ring_bytes);
        ret = vmbus_open(new_sc, netvsc_ring_bytes,
                         netvsc_ring_bytes, NULL, 0,
diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 6bc5453cea8a7..1c05fabc06b04 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -684,6 +684,62 @@ static void storvsc_change_target_cpu(struct vmbus_channel 
*channel, u32 old,
        spin_unlock_irqrestore(&stor_device->lock, flags);
 }
 
+u64 storvsc_next_request_id(struct vmbus_channel *channel, u64 rqst_addr)
+{
+       struct storvsc_cmd_request *request =
+               (struct storvsc_cmd_request *)(unsigned long)rqst_addr;
+       struct storvsc_device *stor_device;
+       struct hv_device *device;
+
+       device = (channel->primary_channel != NULL) ?
+               channel->primary_channel->device_obj : channel->device_obj;
+       if (device == NULL)
+               return VMBUS_RQST_ERROR;
+
+       stor_device = get_out_stor_device(device);
+       if (stor_device == NULL)
+               return VMBUS_RQST_ERROR;
+
+       if (request == &stor_device->init_request)
+               return VMBUS_RQST_INIT;
+       if (request == &stor_device->reset_request)
+               return VMBUS_RQST_RESET;
+
+       return blk_mq_unique_tag(request->cmd->request);
+}
+
+u64 storvsc_request_addr(struct vmbus_channel *channel, u64 rqst_id)
+{
+       struct storvsc_cmd_request *request;
+       struct storvsc_device *stor_device;
+       struct hv_device *device;
+       struct Scsi_Host *shost;
+       struct scsi_cmnd *scmnd;
+
+       device = (channel->primary_channel != NULL) ?
+               channel->primary_channel->device_obj : channel->device_obj;
+       if (device == NULL)
+               return VMBUS_RQST_ERROR;
+
+       stor_device = get_out_stor_device(device);
+       if (stor_device == NULL)
+               return VMBUS_RQST_ERROR;
+
+       if (rqst_id == VMBUS_RQST_INIT)
+               return (unsigned long)&stor_device->init_request;
+       if (rqst_id == VMBUS_RQST_RESET)
+               return (unsigned long)&stor_device->reset_request;
+
+       shost = stor_device->host;
+
+       scmnd = scsi_host_find_tag(shost, rqst_id);
+       if (scmnd == NULL)
+               return VMBUS_RQST_ERROR;
+
+       request = (struct storvsc_cmd_request *)(unsigned 
long)scsi_cmd_priv(scmnd);
+       return (unsigned long)request;
+}
+
 static void handle_sc_creation(struct vmbus_channel *new_sc)
 {
        struct hv_device *device = new_sc->primary_channel->device_obj;
@@ -698,11 +754,8 @@ static void handle_sc_creation(struct vmbus_channel 
*new_sc)
 
        memset(&props, 0, sizeof(struct vmstorage_channel_properties));
 
-       /*
-        * The size of vmbus_requestor is an upper bound on the number of 
requests
-        * that can be in-progress at any one time across all channels.
-        */
-       new_sc->rqstor_size = scsi_driver.can_queue;
+       new_sc->next_request_id_callback = storvsc_next_request_id;
+       new_sc->request_addr_callback = storvsc_request_addr;
 
        ret = vmbus_open(new_sc,
                         storvsc_ringbuffer_size,
@@ -1255,8 +1308,7 @@ static void storvsc_on_channel_callback(void *context)
                struct storvsc_cmd_request *request;
                u64 cmd_rqst;
 
-               cmd_rqst = vmbus_request_addr(&channel->requestor,
-                                             desc->trans_id);
+               cmd_rqst = channel->request_addr_callback(channel, 
desc->trans_id);
                if (cmd_rqst == VMBUS_RQST_ERROR) {
                        dev_err(&device->device,
                                "Incorrect transaction id\n");
@@ -1290,11 +1342,8 @@ static int storvsc_connect_to_vsp(struct hv_device 
*device, u32 ring_size,
 
        memset(&props, 0, sizeof(struct vmstorage_channel_properties));
 
-       /*
-        * The size of vmbus_requestor is an upper bound on the number of 
requests
-        * that can be in-progress at any one time across all channels.
-        */
-       device->channel->rqstor_size = scsi_driver.can_queue;
+       device->channel->next_request_id_callback = storvsc_next_request_id;
+       device->channel->request_addr_callback = storvsc_request_addr;
 
        ret = vmbus_open(device->channel,
                         ring_size,
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 2c18c8e768efe..5692ffa60e022 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -779,7 +779,11 @@ struct vmbus_requestor {
 
 #define VMBUS_NO_RQSTOR U64_MAX
 #define VMBUS_RQST_ERROR (U64_MAX - 1)
+/* NetVSC-specific */
 #define VMBUS_RQST_ID_NO_RESPONSE (U64_MAX - 2)
+/* StorVSC-specific */
+#define VMBUS_RQST_INIT (U64_MAX - 2)
+#define VMBUS_RQST_RESET (U64_MAX - 3)
 
 struct vmbus_device {
        u16  dev_type;
@@ -1007,13 +1011,18 @@ struct vmbus_channel {
        u32 fuzz_testing_interrupt_delay;
        u32 fuzz_testing_message_delay;
 
+       /* callback to generate a request ID from a request address */
+       u64 (*next_request_id_callback)(struct vmbus_channel *channel, u64 
rqst_addr);
+       /* callback to retrieve a request address from a request ID */
+       u64 (*request_addr_callback)(struct vmbus_channel *channel, u64 
rqst_id);
+
        /* request/transaction ids for VMBus */
        struct vmbus_requestor requestor;
        u32 rqstor_size;
 };
 
-u64 vmbus_next_request_id(struct vmbus_requestor *rqstor, u64 rqst_addr);
-u64 vmbus_request_addr(struct vmbus_requestor *rqstor, u64 trans_id);
+u64 vmbus_next_request_id(struct vmbus_channel *channel, u64 rqst_addr);
+u64 vmbus_request_addr(struct vmbus_channel *channel, u64 trans_id);
 
 static inline bool is_hvsock_channel(const struct vmbus_channel *c)
 {
-- 
2.25.1

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