staging: comedi: comedi_buf: factor out common code to free the async buffer

The function comedi_buf_alloc() uses two loops to free the async buffer's
buf_page_list. The first one is used at the beginning to deallocate the
current buffer. The second is used to cleanup if the new buffer allocation
fails.

Factor out the common code to a new function.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedi_buf.c

@@ -22,6 +22,43 @@
 #include "comedidev.h"
 #include "comedi_internal.h"
 
+static void __comedi_buf_free(struct comedi_device *dev,
+			      struct comedi_subdevice *s,
+			      unsigned n_pages)
+{
+	struct comedi_async *async = s->async;
+	struct comedi_buf_page *buf;
+	unsigned i;
+
+	if (async->prealloc_buf) {
+		vunmap(async->prealloc_buf);
+		async->prealloc_buf = NULL;
+		async->prealloc_bufsz = 0;
+	}
+
+	if (!async->buf_page_list)
+		return;
+
+	for (i = 0; i < n_pages; ++i) {
+		buf = &async->buf_page_list[i];
+		if (buf->virt_addr) {
+			clear_bit(PG_reserved,
+				  &(virt_to_page(buf->virt_addr)->flags));
+			if (s->async_dma_dir != DMA_NONE) {
+				dma_free_coherent(dev->hw_dev,
+						  PAGE_SIZE,
+						  buf->virt_addr,
+						  buf->dma_addr);
+			} else {
+				free_page((unsigned long)buf->virt_addr);
+			}
+		}
+	}
+	vfree(async->buf_page_list);
+	async->buf_page_list = NULL;
+	async->n_buf_pages = 0;
+}
+
 int comedi_buf_alloc(struct comedi_device *dev, struct comedi_subdevice *s,
 		     unsigned long new_size)
 {
@@ -34,39 +71,9 @@ int comedi_buf_alloc(struct comedi_device *dev, struct comedi_subdevice *s,
 	if (async->prealloc_buf && async->prealloc_bufsz == new_size)
 		return 0;
 
-	/*  deallocate old buffer */
-	if (async->prealloc_buf) {
-		vunmap(async->prealloc_buf);
-		async->prealloc_buf = NULL;
-		async->prealloc_bufsz = 0;
-	}
-	if (async->buf_page_list) {
-		unsigned i;
-		for (i = 0; i < async->n_buf_pages; ++i) {
-			if (async->buf_page_list[i].virt_addr) {
-				clear_bit(PG_reserved,
-					&(virt_to_page(async->buf_page_list[i].
-							virt_addr)->flags));
-				if (s->async_dma_dir != DMA_NONE) {
-					dma_free_coherent(dev->hw_dev,
-							  PAGE_SIZE,
-							  async->
-							  buf_page_list
-							  [i].virt_addr,
-							  async->
-							  buf_page_list
-							  [i].dma_addr);
-				} else {
-					free_page((unsigned long)
-						  async->buf_page_list[i].
-						  virt_addr);
-				}
-			}
-		}
-		vfree(async->buf_page_list);
-		async->buf_page_list = NULL;
-		async->n_buf_pages = 0;
-	}
+	/* deallocate old buffer */
+	__comedi_buf_free(dev, s, async->n_buf_pages);
+
 	/*  allocate new buffer */
 	if (new_size) {
 		unsigned i = 0;
@@ -114,36 +121,9 @@ int comedi_buf_alloc(struct comedi_device *dev, struct comedi_subdevice *s,
 		}
 		vfree(pages);
 
-		if (async->prealloc_buf == NULL) {
-			/* Some allocation failed above. */
-			if (async->buf_page_list) {
-				for (i = 0; i < n_pages; i++) {
-					if (async->buf_page_list[i].virt_addr ==
-					    NULL) {
-						break;
-					}
-					clear_bit(PG_reserved,
-						&(virt_to_page(async->
-							buf_page_list[i].
-							virt_addr)->flags));
-					if (s->async_dma_dir != DMA_NONE) {
-						dma_free_coherent(dev->hw_dev,
-								  PAGE_SIZE,
-								  async->
-								  buf_page_list
-								  [i].virt_addr,
-								  async->
-								  buf_page_list
-								  [i].dma_addr);
-					} else {
-						free_page((unsigned long)
-							  async->buf_page_list
-							  [i].virt_addr);
-					}
-				}
-				vfree(async->buf_page_list);
-				async->buf_page_list = NULL;
-			}
+		if (!async->prealloc_buf) {
+			/* Some allocation failed above */
+			__comedi_buf_free(dev, s, n_pages);
 			return -ENOMEM;
 		}
 		async->n_buf_pages = n_pages;