f2fs: show available_nids in f2fs/status

This patch adds an entry in f2fs/status to show # of available nids.
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/debug.c

@@ -97,6 +97,7 @@ static void update_general_status(struct f2fs_sb_info *sbi)
 	si->sits = MAIN_SEGS(sbi);
 	si->dirty_sits = SIT_I(sbi)->dirty_sentries;
 	si->free_nids = NM_I(sbi)->nid_cnt[FREE_NID_LIST];
+	si->avail_nids = NM_I(sbi)->available_nids;
 	si->alloc_nids = NM_I(sbi)->nid_cnt[ALLOC_NID_LIST];
 	si->bg_gc = sbi->bg_gc;
 	si->util_free = (int)(free_user_blocks(sbi) >> sbi->log_blocks_per_seg)
@@ -370,8 +371,8 @@ static int stat_show(struct seq_file *s, void *v)
 			   si->ndirty_imeta);
 		seq_printf(s, "  - NATs: %9d/%9d\n  - SITs: %9d/%9d\n",
 			   si->dirty_nats, si->nats, si->dirty_sits, si->sits);
-		seq_printf(s, "  - free_nids: %9d, alloc_nids: %9d\n",
-			   si->free_nids, si->alloc_nids);
+		seq_printf(s, "  - free_nids: %9d/%9d\n  - alloc_nids: %9d\n",
+			   si->free_nids, si->avail_nids, si->alloc_nids);
 		seq_puts(s, "\nDistribution of User Blocks:");
 		seq_puts(s, " [ valid | invalid | free ]\n");
 		seq_puts(s, "  [");

fs/f2fs/f2fs.h

@@ -2394,7 +2394,8 @@ struct f2fs_stat_info {
 	int ndirty_node, ndirty_dent, ndirty_meta, ndirty_data, ndirty_imeta;
 	int inmem_pages;
 	unsigned int ndirty_dirs, ndirty_files, ndirty_all;
-	int nats, dirty_nats, sits, dirty_sits, free_nids, alloc_nids;
+	int nats, dirty_nats, sits, dirty_sits;
+	int free_nids, avail_nids, alloc_nids;
 	int total_count, utilization;
 	int bg_gc, nr_wb_cp_data, nr_wb_data;
 	int nr_flushing, nr_flushed, nr_discarding, nr_discarded;