md: change bitmap_unplug and others to void functions

bitmap_unplug only ever returns 0, so it may as well be void.  Two callers try
to print a message if it returns non-zero, but that message is already printed
by bitmap_file_kick.

write_page returns an error which is not consistently checked.  It always
causes BITMAP_WRITE_ERROR to be set on an error, and that can more
conveniently be checked.

When the return of write_page is checked, an error causes bitmap_file_kick to
be called - so move that call into write_page - and protect against recursive
calls into bitmap_file_kick.

bitmap_update_sb returns an error that is never checked.

So make these 'void' and be consistent about checking the bit.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 36c05ba..65ddc88 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1640,7 +1640,6 @@
 
 static void md_update_sb(mddev_t * mddev, int force_change)
 {
-	int err;
 	struct list_head *tmp;
 	mdk_rdev_t *rdev;
 	int sync_req;
@@ -1727,7 +1726,7 @@
 		"md: updating %s RAID superblock on device (in sync %d)\n",
 		mdname(mddev),mddev->in_sync);
 
-	err = bitmap_update_sb(mddev->bitmap);
+	bitmap_update_sb(mddev->bitmap);
 	ITERATE_RDEV(mddev,rdev,tmp) {
 		char b[BDEVNAME_SIZE];
 		dprintk(KERN_INFO "md: ");