[PATCH] Allow NULL pointers in percpu_free

The patch (as824b) makes percpu_free() ignore NULL arguments, as one would
expect for a deallocation routine.  (Note that free_percpu is #defined as
percpu_free in include/linux/percpu.h.) A few callers are updated to remove
now-unneeded tests for NULL.  A few other callers already seem to assume
that passing a NULL pointer to percpu_free() is okay!

The patch also removes an unnecessary NULL check in percpu_depopulate().

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/block/blktrace.c b/block/blktrace.c
index 74e02c0..d3679dd 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -394,8 +394,7 @@
 	if (bt) {
 		if (bt->dropped_file)
 			debugfs_remove(bt->dropped_file);
-		if (bt->sequence)
-			free_percpu(bt->sequence);
+		free_percpu(bt->sequence);
 		if (bt->rchan)
 			relay_close(bt->rchan);
 		kfree(bt);