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: Paul Mundt <lethal@linux-sh.org>
Cc: Jaya Kumar <jayakumar.lkml@gmail.com>
Acked-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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;