[PATCH v2 5/5] ext4: add proc files to monitor new structures

[Harshad Shirwadkar <harshadshirwadkar@gmail.com>]

This patch adds a new file "mb_structs_summary" which allows us to see the
summary of the new allocator structures added in this series.

Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
---
 fs/ext4/ext4.h    |  1 +
 fs/ext4/mballoc.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++
 fs/ext4/sysfs.c   |  2 ++
 3 files changed, 87 insertions(+)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 0601c997c87f..39830c07c27e 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2817,6 +2817,7 @@ int __init ext4_fc_init_dentry_cache(void);
 
 /* mballoc.c */
 extern const struct seq_operations ext4_mb_seq_groups_ops;
+extern const struct seq_operations ext4_mb_seq_structs_summary_ops;
 extern long ext4_mb_stats;
 extern long ext4_mb_max_to_scan;
 extern int ext4_seq_mb_stats_show(struct seq_file *seq, void *offset);
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 63562f5f42f1..d9cb74787a47 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2864,6 +2864,90 @@ int ext4_seq_mb_stats_show(struct seq_file *seq, void *offset)
 	return 0;
 }
 
+static void *ext4_mb_seq_structs_summary_start(struct seq_file *seq, loff_t *pos)
+{
+	struct super_block *sb = PDE_DATA(file_inode(seq->file));
+	unsigned long position;
+
+	read_lock(&EXT4_SB(sb)->s_mb_rb_lock);
+
+	if (*pos < 0 || *pos >= MB_NUM_ORDERS(sb) + 1)
+		return NULL;
+	position = *pos + 1;
+	return (void *) ((unsigned long) position);
+}
+
+static void *ext4_mb_seq_structs_summary_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct super_block *sb = PDE_DATA(file_inode(seq->file));
+	unsigned long position;
+
+	++*pos;
+	if (*pos < 0 || *pos >= MB_NUM_ORDERS(sb) + 1)
+		return NULL;
+	position = *pos + 1;
+	return (void *) ((unsigned long) position);
+}
+
+static int ext4_mb_seq_structs_summary_show(struct seq_file *seq, void *v)
+{
+	struct super_block *sb = PDE_DATA(file_inode(seq->file));
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	unsigned long position = ((unsigned long) v);
+	struct ext4_group_info *grp;
+	struct rb_node *n;
+	int count, min, max;
+
+	position--;
+
+	if (position >= MB_NUM_ORDERS(sb)) {
+		seq_puts(seq, "Tree\n");
+		n = rb_first(&sbi->s_mb_avg_fragment_size_root);
+		if (!n) {
+			seq_puts(seq, "<Empty>\n");
+			return 0;
+		}
+		grp = rb_entry(n, struct ext4_group_info, bb_avg_fragment_size_rb);
+		min = grp->bb_fragments ? grp->bb_free / grp->bb_fragments : 0;
+		count = 1;
+		while (rb_next(n)) {
+			count++;
+			n = rb_next(n);
+		}
+		grp = rb_entry(n, struct ext4_group_info, bb_avg_fragment_size_rb);
+		max = grp->bb_fragments ? grp->bb_free / grp->bb_fragments : 0;
+
+		seq_printf(seq, "Min: %d, Max: %d, Num Nodes: %d\n",
+			   min, max, count);
+		return 0;
+	}
+
+	if (position == 0)
+		seq_puts(seq, "Largest Free Order Lists:\n");
+
+	seq_printf(seq, "Order %ld list: ", position);
+	count = 0;
+	list_for_each_entry(grp, &sbi->s_mb_largest_free_orders[position],
+			    bb_largest_free_order_node)
+		count++;
+	seq_printf(seq, "%d Groups\n", count);
+	return 0;
+}
+
+static void ext4_mb_seq_structs_summary_stop(struct seq_file *seq, void *v)
+{
+	struct super_block *sb = PDE_DATA(file_inode(seq->file));
+
+	read_unlock(&EXT4_SB(sb)->s_mb_rb_lock);
+}
+
+const struct seq_operations ext4_mb_seq_structs_summary_ops = {
+	.start  = ext4_mb_seq_structs_summary_start,
+	.next   = ext4_mb_seq_structs_summary_next,
+	.stop   = ext4_mb_seq_structs_summary_stop,
+	.show   = ext4_mb_seq_structs_summary_show,
+};
+
 static struct kmem_cache *get_groupinfo_cache(int blocksize_bits)
 {
 	int cache_index = blocksize_bits - EXT4_MIN_BLOCK_LOG_SIZE;
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
index 752d1c261e2a..b78bc6b57bce 100644
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -529,6 +529,8 @@ int ext4_register_sysfs(struct super_block *sb)
 				&ext4_mb_seq_groups_ops, sb);
 		proc_create_single_data("mb_stats", 0444, sbi->s_proc,
 				ext4_seq_mb_stats_show, sb);
+		proc_create_seq_data("mb_structs_summary", 0444, sbi->s_proc,
+				&ext4_mb_seq_structs_summary_ops, sb);
 	}
 	return 0;
 }
-- 
2.30.0.478.g8a0d178c01-goog