staging: vc04_services: add vchiq_pagelist_info structure

The current dma_map_sg based implementation for bulk messages
computes many offsets into a single allocation multiple times in
both the create and free code paths. This is inefficient,
error prone and in fact still has a few lingering issues
with arm64.

This change replaces a small portion of that inplementation with
new code that uses a new struct vchiq_pagelist_info to store the
needed information rather then complex offset calculations.

This improved implementation should be more efficient and easier
to understand and maintain.

Tests Run(Both Pass):
vchiq_test -p 1
vchiq_test -f 10

Signed-off-by: Michael Zoran <[e-mail]>
Reviewed-by: Eric Anholt <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c

···
    VCHIQ_ARM_STATE_T arm_state;
 } VCHIQ_2835_ARM_STATE_T;
 
+struct vchiq_pagelist_info {
+	PAGELIST_T *pagelist;
+	size_t pagelist_buffer_size;
+	dma_addr_t dma_addr;
+	enum dma_data_direction dma_dir;
+	unsigned int num_pages;
+	unsigned int pages_need_release;
+	struct page **pages;
+	struct scatterlist *scatterlist;
+	unsigned int scatterlist_mapped;
+};
+
 static void __iomem *g_regs;
 static unsigned int g_cache_line_size = sizeof(CACHE_LINE_SIZE);
 static unsigned int g_fragments_size;
···
 static irqreturn_t
 vchiq_doorbell_irq(int irq, void *dev_id);
 
-static int
+static struct vchiq_pagelist_info *
 create_pagelist(char __user *buf, size_t count, unsigned short type,
-		struct task_struct *task, PAGELIST_T **ppagelist,
-		dma_addr_t *dma_addr);
+		struct task_struct *task);
 
 static void
-free_pagelist(dma_addr_t dma_addr, PAGELIST_T *pagelist, int actual);
+free_pagelist(struct vchiq_pagelist_info *pagelistinfo,
+	      int actual);
 
 int vchiq_platform_init(struct platform_device *pdev, VCHIQ_STATE_T *state)
 {
···
 vchiq_prepare_bulk_data(VCHIQ_BULK_T *bulk, VCHI_MEM_HANDLE_T memhandle,
 	void *offset, int size, int dir)
 {
-	PAGELIST_T *pagelist;
-	int ret;
-	dma_addr_t dma_addr;
+	struct vchiq_pagelist_info *pagelistinfo;
 
 	WARN_ON(memhandle != VCHI_MEM_HANDLE_INVALID);
 
-	ret = create_pagelist((char __user *)offset, size,
-			(dir == VCHIQ_BULK_RECEIVE)
-			? PAGELIST_READ
-			: PAGELIST_WRITE,
-			current,
-			&pagelist,
-			&dma_addr);
+	pagelistinfo = create_pagelist((char __user *)offset, size,
+				       (dir == VCHIQ_BULK_RECEIVE)
+				       ? PAGELIST_READ
+				       : PAGELIST_WRITE,
+				       current);
 
-	if (ret != 0)
+	if (!pagelistinfo)
 		return VCHIQ_ERROR;
 
 	bulk->handle = memhandle;
-	bulk->data = (void *)(unsigned long)dma_addr;
+	bulk->data = (void *)(unsigned long)pagelistinfo->dma_addr;
 
-	/* Store the pagelist address in remote_data, which isn't used by the
-	   slave. */
-	bulk->remote_data = pagelist;
+	/*
+	 * Store the pagelistinfo address in remote_data,
+	 * which isn't used by the slave.
+	 */
+	bulk->remote_data = pagelistinfo;
 
 	return VCHIQ_SUCCESS;
 }
···
 vchiq_complete_bulk(VCHIQ_BULK_T *bulk)
 {
 	if (bulk && bulk->remote_data && bulk->actual)
-		free_pagelist((dma_addr_t)(unsigned long)bulk->data,
-			      (PAGELIST_T *)bulk->remote_data, bulk->actual);
+		free_pagelist((struct vchiq_pagelist_info *)bulk->remote_data,
+			      bulk->actual);
 }
 
 void
···
 	return ret;
 }
 
+static void
+cleaup_pagelistinfo(struct vchiq_pagelist_info *pagelistinfo)
+{
+	if (pagelistinfo->scatterlist_mapped) {
+		dma_unmap_sg(g_dev, pagelistinfo->scatterlist,
+			     pagelistinfo->num_pages, pagelistinfo->dma_dir);
+	}
+
+	if (pagelistinfo->pages_need_release) {
+		unsigned int i;
+
+		for (i = 0; i < pagelistinfo->num_pages; i++)
+			put_page(pagelistinfo->pages[i]);
+	}
+
+	dma_free_coherent(g_dev, pagelistinfo->pagelist_buffer_size,
+			  pagelistinfo->pagelist, pagelistinfo->dma_addr);
+}
+
 /* There is a potential problem with partial cache lines (pages?)
 ** at the ends of the block when reading. If the CPU accessed anything in
 ** the same line (page?) then it may have pulled old data into the cache,
···
 ** cached area.
 */
 
-static int
+static struct vchiq_pagelist_info *
 create_pagelist(char __user *buf, size_t count, unsigned short type,
-		struct task_struct *task, PAGELIST_T **ppagelist,
-		dma_addr_t *dma_addr)
+		struct task_struct *task)
 {
 	PAGELIST_T *pagelist;
+	struct vchiq_pagelist_info *pagelistinfo;
 	struct page **pages;
 	u32 *addrs;
 	unsigned int num_pages, offset, i, k;
 	int actual_pages;
-        unsigned long *need_release;
 	size_t pagelist_size;
 	struct scatterlist *scatterlist, *sg;
 	int dma_buffers;
-	int dir;
+	dma_addr_t dma_addr;
 
 	offset = ((unsigned int)(unsigned long)buf & (PAGE_SIZE - 1));
 	num_pages = (count + offset + PAGE_SIZE - 1) / PAGE_SIZE;
 
 	pagelist_size = sizeof(PAGELIST_T) +
-			(num_pages * sizeof(unsigned long)) +
-			sizeof(unsigned long) +
+			(num_pages * sizeof(u32)) +
 			(num_pages * sizeof(pages[0]) +
-			(num_pages * sizeof(struct scatterlist)));
-
-	*ppagelist = NULL;
-
-	dir = (type == PAGELIST_WRITE) ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
+			(num_pages * sizeof(struct scatterlist))) +
+			sizeof(struct vchiq_pagelist_info);
 
 	/* Allocate enough storage to hold the page pointers and the page
 	** list
 	*/
 	pagelist = dma_zalloc_coherent(g_dev,
 				       pagelist_size,
-				       dma_addr,
+				       &dma_addr,
 				       GFP_KERNEL);
 
 	vchiq_log_trace(vchiq_arm_log_level, "create_pagelist - %pK",
 			pagelist);
 	if (!pagelist)
-		return -ENOMEM;
+		return NULL;
 
-	addrs = pagelist->addrs;
-        need_release = (unsigned long *)(addrs + num_pages);
-	pages = (struct page **)(addrs + num_pages + 1);
-	scatterlist = (struct scatterlist *)(pages + num_pages);
+	addrs		= pagelist->addrs;
+	pages		= (struct page **)(addrs + num_pages);
+	scatterlist	= (struct scatterlist *)(pages + num_pages);
+	pagelistinfo	= (struct vchiq_pagelist_info *)
+			  (scatterlist + num_pages);
+
+	pagelist->length = count;
+	pagelist->type = type;
+	pagelist->offset = offset;
+
+	/* Populate the fields of the pagelistinfo structure */
+	pagelistinfo->pagelist = pagelist;
+	pagelistinfo->pagelist_buffer_size = pagelist_size;
+	pagelistinfo->dma_addr = dma_addr;
+	pagelistinfo->dma_dir =  (type == PAGELIST_WRITE) ?
+				  DMA_TO_DEVICE : DMA_FROM_DEVICE;
+	pagelistinfo->num_pages = num_pages;
+	pagelistinfo->pages_need_release = 0;
+	pagelistinfo->pages = pages;
+	pagelistinfo->scatterlist = scatterlist;
+	pagelistinfo->scatterlist_mapped = 0;
 
 	if (is_vmalloc_addr(buf)) {
 		unsigned long length = count;
···
 			length -= bytes;
 			off = 0;
 		}
-		*need_release = 0; /* do not try and release vmalloc pages */
+		/* do not try and release vmalloc pages */
 	} else {
 		down_read(&task->mm->mmap_sem);
 		actual_pages = get_user_pages(
···
 				actual_pages--;
 				put_page(pages[actual_pages]);
 			}
-			dma_free_coherent(g_dev, pagelist_size,
-					  pagelist, *dma_addr);
-			if (actual_pages == 0)
-				actual_pages = -ENOMEM;
-			return actual_pages;
+			cleaup_pagelistinfo(pagelistinfo);
+			return NULL;
 		}
-		*need_release = 1; /* release user pages */
+		 /* release user pages */
+		pagelistinfo->pages_need_release = 1;
 	}
-
-	pagelist->length = count;
-	pagelist->type = type;
-	pagelist->offset = offset;
 
 	/*
 	 * Initialize the scatterlist so that the magic cookie
···
 	dma_buffers = dma_map_sg(g_dev,
 				 scatterlist,
 				 num_pages,
-				 dir);
+				 pagelistinfo->dma_dir);
 
 	if (dma_buffers == 0) {
-		dma_free_coherent(g_dev, pagelist_size,
-				  pagelist, *dma_addr);
-
-		return -EINTR;
+		cleaup_pagelistinfo(pagelistinfo);
+		return NULL;
 	}
+
+	pagelistinfo->scatterlist_mapped = 1;
 
 	/* Combine adjacent blocks for performance */
 	k = 0;
···
 		char *fragments;
 
 		if (down_interruptible(&g_free_fragments_sema) != 0) {
-			dma_unmap_sg(g_dev, scatterlist, num_pages,
-				     DMA_BIDIRECTIONAL);
-			dma_free_coherent(g_dev, pagelist_size,
-					  pagelist, *dma_addr);
-			return -EINTR;
+			cleaup_pagelistinfo(pagelistinfo);
+			return NULL;
 		}
 
 		WARN_ON(g_free_fragments == NULL);
···
 			(fragments - g_fragments_base) / g_fragments_size;
 	}
 
-	*ppagelist = pagelist;
-
-	return 0;
+	return pagelistinfo;
 }
 
 static void
-free_pagelist(dma_addr_t dma_addr, PAGELIST_T *pagelist, int actual)
+free_pagelist(struct vchiq_pagelist_info *pagelistinfo,
+	      int actual)
 {
-        unsigned long *need_release;
-	struct page **pages;
-	unsigned int num_pages, i;
-	size_t pagelist_size;
-	struct scatterlist *scatterlist;
-	int dir;
+	unsigned int i;
+	PAGELIST_T *pagelist   = pagelistinfo->pagelist;
+	struct page **pages    = pagelistinfo->pages;
+	unsigned int num_pages = pagelistinfo->num_pages;
 
 	vchiq_log_trace(vchiq_arm_log_level, "free_pagelist - %pK, %d",
-			pagelist, actual);
+			pagelistinfo->pagelist, actual);
 
-	dir = (pagelist->type == PAGELIST_WRITE) ? DMA_TO_DEVICE :
-						   DMA_FROM_DEVICE;
-
-	num_pages =
-		(pagelist->length + pagelist->offset + PAGE_SIZE - 1) /
-		PAGE_SIZE;
-
-	pagelist_size = sizeof(PAGELIST_T) +
-			(num_pages * sizeof(unsigned long)) +
-			sizeof(unsigned long) +
-			(num_pages * sizeof(pages[0]) +
-			(num_pages * sizeof(struct scatterlist)));
-
-        need_release = (unsigned long *)(pagelist->addrs + num_pages);
-	pages = (struct page **)(pagelist->addrs + num_pages + 1);
-	scatterlist = (struct scatterlist *)(pages + num_pages);
-
-	dma_unmap_sg(g_dev, scatterlist, num_pages, dir);
+	/*
+	 * NOTE: dma_unmap_sg must be called before the
+	 * cpu can touch any of the data/pages.
+	 */
+	dma_unmap_sg(g_dev, pagelistinfo->scatterlist,
+		     pagelistinfo->num_pages, pagelistinfo->dma_dir);
+	pagelistinfo->scatterlist_mapped = 0;
 
 	/* Deal with any partial cache lines (fragments) */
 	if (pagelist->type >= PAGELIST_READ_WITH_FRAGMENTS) {
···
 		up(&g_free_fragments_sema);
 	}
 
-	if (*need_release) {
-		unsigned int length = pagelist->length;
-		unsigned int offset = pagelist->offset;
-
-		for (i = 0; i < num_pages; i++) {
-			struct page *pg = pages[i];
-
-			if (pagelist->type != PAGELIST_WRITE) {
-				unsigned int bytes = PAGE_SIZE - offset;
-
-				if (bytes > length)
-					bytes = length;
-
-				length -= bytes;
-				offset = 0;
-				set_page_dirty(pg);
-			}
-			put_page(pg);
-		}
+	/* Need to mark all the pages dirty. */
+	if (pagelist->type != PAGELIST_WRITE &&
+	    pagelistinfo->pages_need_release) {
+		for (i = 0; i < num_pages; i++)
+			set_page_dirty(pages[i]);
 	}
 
-	dma_free_coherent(g_dev, pagelist_size,
-			  pagelist, dma_addr);
+	cleaup_pagelistinfo(pagelistinfo);
 }