scsi: storvsc: Reduce default ring buffer size to 128 Kbytes

[thirdparty/kernel/stable.git] / drivers / scsi / storvsc_drv.c

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 84380bae20f1ec350d5209931cdca018351199f1..8472de1007fffca12f41823e3ed8e45dac1ee06d 100644 (file)
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -385,7 +385,7 @@ enum storvsc_request_type {
  * This is the end of Protocol specific defines.
  */
 
-static int storvsc_ringbuffer_size = (256 * PAGE_SIZE);
+static int storvsc_ringbuffer_size = (128 * 1024);
 static u32 max_outstanding_req_per_channel;
 
 static int storvsc_vcpus_per_sub_channel = 4;
@@ -668,13 +668,22 @@ static void  handle_multichannel_storage(struct hv_device *device, int max_chns)
 {
        struct device *dev = &device->device;
        struct storvsc_device *stor_device;
-       int num_cpus = num_online_cpus();
        int num_sc;
        struct storvsc_cmd_request *request;
        struct vstor_packet *vstor_packet;
        int ret, t;
 
-       num_sc = ((max_chns > num_cpus) ? num_cpus : max_chns);
+       /*
+        * If the number of CPUs is artificially restricted, such as
+        * with maxcpus=1 on the kernel boot line, Hyper-V could offer
+        * sub-channels >= the number of CPUs. These sub-channels
+        * should not be created. The primary channel is already created
+        * and assigned to one CPU, so check against # CPUs - 1.
+        */
+       num_sc = min((int)(num_online_cpus() - 1), max_chns);
+       if (!num_sc)
+               return;
+
        stor_device = get_out_stor_device(device);
        if (!stor_device)
                return;