fb: fsync() method for deferred I/O flush.

There are cases when we do not want to wait on the delay for automatically
updating the "real" framebuffer, this implements a simple ->fsync() hook
for explicitly flushing the deferred I/O work.  The ->page_mkwrite()
handler will rearm the work queue normally.

(akpm: nuke unneeded ifdefs, forward-delcare struct dentry)
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>
Cc: Jaya Kumar <jayakumar.lkml@gmail.com>
Acked-by: NAntonino Daplas <adaplas@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/video/fb_defio.c

@@ -47,6 +47,18 @@ static struct page* fb_deferred_io_nopage(struct vm_area_struct *vma,
 	return page;
 }
 
+int fb_deferred_io_fsync(struct file *file, struct dentry *dentry, int datasync)
+{
+	struct fb_info *info = file->private_data;
+
+	/* Kill off the delayed work */
+	cancel_rearming_delayed_work(&info->deferred_work);
+
+	/* Run it immediately */
+	return schedule_delayed_work(&info->deferred_work, 0);
+}
+EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);
+
 /* vm_ops->page_mkwrite handler */
 static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
 				  struct page *page)

drivers/video/fbmem.c

@@ -1266,6 +1266,9 @@ static const struct file_operations fb_fops = {
 #ifdef HAVE_ARCH_FB_UNMAPPED_AREA
 	.get_unmapped_area = get_fb_unmapped_area,
 #endif
+#ifdef CONFIG_FB_DEFERRED_IO
+	.fsync =	fb_deferred_io_fsync,
+#endif
 };
 
 struct class *fb_class;

include/linux/fb.h

@@ -4,6 +4,8 @@
 #include <asm/types.h>
 #include <linux/i2c.h>
 
+struct dentry;
+
 /* Definitions of frame buffers						*/
 
 #define FB_MAJOR		29
@@ -927,11 +929,11 @@ static inline void __fb_pad_aligned_buffer(u8 *dst, u32 d_pitch,
 	}
 }
 
-#ifdef CONFIG_FB_DEFERRED_IO
 /* drivers/video/fb_defio.c */
 extern void fb_deferred_io_init(struct fb_info *info);
 extern void fb_deferred_io_cleanup(struct fb_info *info);
-#endif
+extern int fb_deferred_io_fsync(struct file *file, struct dentry *dentry,
+				int datasync);
 
 /* drivers/video/fbsysfs.c */
 extern struct fb_info *framebuffer_alloc(size_t size, struct device *dev);