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Date:   Fri, 29 Jan 2021 14:29:31 -0800
From:   Harshad Shirwadkar <harshadshirwadkar@...il.com>
To:     linux-ext4@...r.kernel.org
Cc:     tytso@....edu, Harshad Shirwadkar <harshadshirwadkar@...il.com>
Subject: [PATCH 4/4] ext4: add proc files to monitor new structures

This patch adds a new file "mb_structs" which allows us to see the
largest free order lists and the serialized average fragment tree.

Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@...il.com>
---
 fs/ext4/ext4.h    |  1 +
 fs/ext4/mballoc.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++
 fs/ext4/sysfs.c   |  2 ++
 3 files changed, 82 insertions(+)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index da12a083bf52..835e304e3113 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2809,6 +2809,7 @@ 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_ops;
 extern long ext4_mb_stats;
 extern long ext4_mb_max_to_scan;
 extern int ext4_mb_init(struct super_block *);
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 413259477b03..ec4656903bd4 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2741,6 +2741,85 @@ const struct seq_operations ext4_mb_seq_groups_ops = {
 	.show   = ext4_mb_seq_groups_show,
 };
 
+static void *ext4_mb_seq_structs_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) + ext4_get_groups_count(sb))
+		return NULL;
+	position = *pos + 1;
+	return (void *) ((unsigned long) position);
+}
+
+static void *ext4_mb_seq_structs_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) + ext4_get_groups_count(sb))
+		return NULL;
+	position = *pos + 1;
+	return (void *) ((unsigned long) position);
+}
+
+static int ext4_mb_seq_structs_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 *grpinfo;
+	struct rb_node *n;
+	int i;
+
+	position--;
+
+	if (position >= MB_NUM_ORDERS(sb)) {
+		position -= MB_NUM_ORDERS(sb);
+		if (position == 0)
+			seq_puts(seq, "Group, Avg Fragment Size\n");
+		n = rb_first(&sbi->s_mb_avg_fragment_size_root);
+		for (i = 0; n && i < position; i++)
+			n = rb_next(n);
+		if (!n)
+			return 0;
+		grpinfo = rb_entry(n, struct ext4_group_info, bb_avg_fragment_size_rb);
+		seq_printf(seq, "%d, %d\n",
+			   grpinfo->bb_group,
+			   grpinfo->bb_fragments ? grpinfo->bb_free / grpinfo->bb_fragments : 0);
+		return 0;
+	}
+
+	if (position == 0)
+		seq_puts(seq, "Largest Free Order Lists:\n");
+
+	seq_printf(seq, "[%ld]: ", position);
+	list_for_each_entry(grpinfo, &sbi->s_mb_largest_free_orders[position],
+			    bb_largest_free_order_node)	{
+		seq_printf(seq, "%d ", grpinfo->bb_group);
+	}
+	seq_puts(seq, "\n");
+
+	return 0;
+}
+
+static void ext4_mb_seq_structs_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_ops = {
+	.start  = ext4_mb_seq_structs_start,
+	.next   = ext4_mb_seq_structs_next,
+	.stop   = ext4_mb_seq_structs_stop,
+	.show   = ext4_mb_seq_structs_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 4e27fe6ed3ae..828d58b98310 100644
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -527,6 +527,8 @@ int ext4_register_sysfs(struct super_block *sb)
 					ext4_fc_info_show, sb);
 		proc_create_seq_data("mb_groups", S_IRUGO, sbi->s_proc,
 				&ext4_mb_seq_groups_ops, sb);
+		proc_create_seq_data("mb_structs", 0444, sbi->s_proc,
+				&ext4_mb_seq_structs_ops, sb);
 	}
 	return 0;
 }
-- 
2.30.0.365.g02bc693789-goog

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