mm: remove unevictable_pgs_mlockfreed

Simply remove UNEVICTABLE_MLOCKFREED and unevictable_pgs_mlockfreed line
from /proc/vmstat: Johannes and Mel point out that it was very unlikely to
have been used by any tool, and of course we can restore it easily enough
if that turns out to be wrong.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ying Han <yinghan@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/vm_event_item.h

@@ -52,7 +52,6 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 		UNEVICTABLE_PGMUNLOCKED,
 		UNEVICTABLE_PGCLEARED,	/* on COW, page truncate */
 		UNEVICTABLE_PGSTRANDED,	/* unable to isolate on unlock */
-		UNEVICTABLE_MLOCKFREED,	/* no longer useful: always zero */
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 		THP_FAULT_ALLOC,
 		THP_FAULT_FALLBACK,

mm/vmstat.c

@@ -794,7 +794,6 @@ const char * const vmstat_text[] = {
 	"unevictable_pgs_munlocked",
 	"unevictable_pgs_cleared",
 	"unevictable_pgs_stranded",
-	"unevictable_pgs_mlockfreed",	/* no longer useful: always zero */
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	"thp_fault_alloc",