mm: account reaped page cache on inode cache pruning

Inode cache pruning indirectly reclaims page-cache by invalidating mapping
pages.  Let's account them into reclaim-state to notice this progress in
memory reclaimer.
Signed-off-by: NKonstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/inode.c

@@ -776,6 +776,8 @@ void prune_icache_sb(struct super_block *sb, int nr_to_scan)
 	else
 		__count_vm_events(PGINODESTEAL, reap);
 	spin_unlock(&sb->s_inode_lru_lock);
+	if (current->reclaim_state)
+		current->reclaim_state->reclaimed_slab += reap;
 
 	dispose_list(&freeable);
 }