Drivers: hv: ring_buffer: wrap around mappings for ring buffers

[cascardo/linux.git] / drivers / hv / ring_buffer.c

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index e3edcae..7e21c2c 100644 (file)
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -27,6 +27,8 @@
 #include <linux/mm.h>
 #include <linux/hyperv.h>
 #include <linux/uio.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
 
 #include "hyperv_vmbus.h"
 
@@ -243,22 +245,46 @@ void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
 
 /* Initialize the ring buffer. */
 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
-                  void *buffer, u32 buflen)
+                      struct page *pages, u32 page_cnt)
 {
-       if (sizeof(struct hv_ring_buffer) != PAGE_SIZE)
-               return -EINVAL;
+       int i;
+       struct page **pages_wraparound;
+
+       BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));
 
        memset(ring_info, 0, sizeof(struct hv_ring_buffer_info));
 
-       ring_info->ring_buffer = (struct hv_ring_buffer *)buffer;
+       /*
+        * First page holds struct hv_ring_buffer, do wraparound mapping for
+        * the rest.
+        */
+       pages_wraparound = kzalloc(sizeof(struct page *) * (page_cnt * 2 - 1),
+                                  GFP_KERNEL);
+       if (!pages_wraparound)
+               return -ENOMEM;
+
+       pages_wraparound[0] = pages;
+       for (i = 0; i < 2 * (page_cnt - 1); i++)
+               pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1];
+
+       ring_info->ring_buffer = (struct hv_ring_buffer *)
+               vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL);
+
+       kfree(pages_wraparound);
+
+
+       if (!ring_info->ring_buffer)
+               return -ENOMEM;
+
        ring_info->ring_buffer->read_index =
                ring_info->ring_buffer->write_index = 0;
 
        /* Set the feature bit for enabling flow control. */
        ring_info->ring_buffer->feature_bits.value = 1;
 
-       ring_info->ring_size = buflen;
-       ring_info->ring_datasize = buflen - sizeof(struct hv_ring_buffer);
+       ring_info->ring_size = page_cnt << PAGE_SHIFT;
+       ring_info->ring_datasize = ring_info->ring_size -
+               sizeof(struct hv_ring_buffer);
 
        spin_lock_init(&ring_info->ring_lock);
 
@@ -268,6 +294,7 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
 /* Cleanup the ring buffer. */
 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
 {
+       vunmap(ring_info->ring_buffer);
 }
 
 /* Write to the ring buffer. */