fb: defio nopage

Convert fb defio from nopage to fault.
Switch from OOM to SIGBUS if the resource is not available.

Signed-off-by: Nick Piggin <[e-mail]>
Cc: "Antonino A. Daplas" <[e-mail]>
Cc: Paul Mundt <[e-mail]>
Cc: Jaya Kumar <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/fb/deferred_io.txt

···
 works:
 
 - userspace app like Xfbdev mmaps framebuffer
-- deferred IO and driver sets up nopage and page_mkwrite handlers
+- deferred IO and driver sets up fault and page_mkwrite handlers
 - userspace app tries to write to mmaped vaddress
-- we get pagefault and reach nopage handler
-- nopage handler finds and returns physical page
+- we get pagefault and reach fault handler
+- fault handler finds and returns physical page
 - we get page_mkwrite where we add this page to a list
 - schedule a workqueue task to be run after a delay
 - app continues writing to that page with no additional cost. this is

drivers/video/fb_defio.c

···
 #include <linux/pagemap.h>
 
 /* this is to find and return the vmalloc-ed fb pages */
-static struct page* fb_deferred_io_nopage(struct vm_area_struct *vma,
-					unsigned long vaddr, int *type)
+static int fb_deferred_io_fault(struct vm_area_struct *vma,
+				struct vm_fault *vmf)
 {
 	unsigned long offset;
 	struct page *page;
···
 	/* info->screen_base is in System RAM */
 	void *screen_base = (void __force *) info->screen_base;
 
-	offset = (vaddr - vma->vm_start) + (vma->vm_pgoff << PAGE_SHIFT);
+	offset = vmf->pgoff << PAGE_SHIFT;
 	if (offset >= info->fix.smem_len)
-		return NOPAGE_SIGBUS;
+		return VM_FAULT_SIGBUS;
 
 	page = vmalloc_to_page(screen_base + offset);
 	if (!page)
-		return NOPAGE_OOM;
+		return VM_FAULT_SIGBUS;
 
 	get_page(page);
-	if (type)
-		*type = VM_FAULT_MINOR;
-	return page;
+	vmf->page = page;
+	return 0;
 }
 
 int fb_deferred_io_fsync(struct file *file, struct dentry *dentry, int datasync)
···
 }
 
 static struct vm_operations_struct fb_deferred_io_vm_ops = {
-	.nopage   	= fb_deferred_io_nopage,
+	.fault		= fb_deferred_io_fault,
 	.page_mkwrite	= fb_deferred_io_mkwrite,
 };