mm/madvise: update comment on sys_madvise()

Some new MADV_* advices are not documented in sys_madvise() comment.  So
let's update it.

[akpm@linux-foundation.org: modifications suggested by Michal]
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Chen Gong <gong.chen@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/madvise.c

@@ -639,14 +639,28 @@ madvise_behavior_valid(int behavior)
  *		some pages ahead.
  *  MADV_DONTNEED - the application is finished with the given range,
  *		so the kernel can free resources associated with it.
+ *  MADV_FREE - the application marks pages in the given range as lazy free,
+ *		where actual purges are postponed until memory pressure happens.
  *  MADV_REMOVE - the application wants to free up the given range of
  *		pages and associated backing store.
  *  MADV_DONTFORK - omit this area from child's address space when forking:
  *		typically, to avoid COWing pages pinned by get_user_pages().
  *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
+ *  MADV_HWPOISON - trigger memory error handler as if the given memory range
+ *		were corrupted by unrecoverable hardware memory failure.
+ *  MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
  *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
  *		this area with pages of identical content from other such areas.
  *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
+ *  MADV_HUGEPAGE - the application wants to back the given range by transparent
+ *		huge pages in the future. Existing pages might be coalesced and
+ *		new pages might be allocated as THP.
+ *  MADV_NOHUGEPAGE - mark the given range as not worth being backed by
+ *		transparent huge pages so the existing pages will not be
+ *		coalesced into THP and new pages will not be allocated as THP.
+ *  MADV_DONTDUMP - the application wants to prevent pages in the given range
+ *		from being included in its core dump.
+ *  MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
  *
  * return values:
  *  zero    - success