mm/util.c: improve kvfree() kerneldoc

Scooped from an email from Matthew.

Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/util.c

@@ -435,11 +435,14 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
 EXPORT_SYMBOL(kvmalloc_node);
 
 /**
- * kvfree - free memory allocated with kvmalloc
- * @addr: pointer returned by kvmalloc
+ * kvfree() - Free memory.
+ * @addr: Pointer to allocated memory.
  *
- * If the memory is allocated from vmalloc area it is freed with vfree().
- * Otherwise kfree() is used.
+ * kvfree frees memory allocated by any of vmalloc(), kmalloc() or kvmalloc().
+ * It is slightly more efficient to use kfree() or vfree() if you are certain
+ * that you know which one to use.
+ *
+ * Context: Any context except NMI.
  */
 void kvfree(const void *addr)
 {