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/include/linux/raid/bitmap.h b/include/linux/raid/bitmap.h
index dd5a05d..75e17a0 100644
--- a/include/linux/raid/bitmap.h
+++ b/include/linux/raid/bitmap.h
@@ -262,7 +262,7 @@
 
 char *file_path(struct file *file, char *buf, int count);
 void bitmap_print_sb(struct bitmap *bitmap);
-int bitmap_update_sb(struct bitmap *bitmap);
+void bitmap_update_sb(struct bitmap *bitmap);
 
 int  bitmap_setallbits(struct bitmap *bitmap);
 void bitmap_write_all(struct bitmap *bitmap);
@@ -278,8 +278,8 @@
 void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int aborted);
 void bitmap_close_sync(struct bitmap *bitmap);
 
-int bitmap_unplug(struct bitmap *bitmap);
-int bitmap_daemon_work(struct bitmap *bitmap);
+void bitmap_unplug(struct bitmap *bitmap);
+void bitmap_daemon_work(struct bitmap *bitmap);
 #endif
 
 #endif