[PATCH v1] ext4: add mb_stats_clear for mballoc statistics

[Baolin Liu]

From: Baolin Liu <liubaolin@xxxxxxxxxx>

Add a write-only mb_stats_clear sysfs knob to reset ext4 mballoc
runtime statistics.This makes it easier to inspect allocator
activity for a specific workload instead of using counters
accumulated since mount.

Signed-off-by: Baolin Liu <liubaolin@xxxxxxxxxx>
---
 fs/ext4/ext4.h    |  1 +
 fs/ext4/mballoc.c | 31 +++++++++++++++++++++++++++++++
 fs/ext4/sysfs.c   | 24 ++++++++++++++++++++++++
 3 files changed, 56 insertions(+)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 7617e2d454ea..3a32e1a515dd 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2995,6 +2995,7 @@ int ext4_fc_record_regions(struct super_block *sb, int ino,
 extern const struct seq_operations ext4_mb_seq_groups_ops;
 extern const struct seq_operations ext4_mb_seq_structs_summary_ops;
 extern int ext4_seq_mb_stats_show(struct seq_file *seq, void *offset);
+extern void ext4_mb_stats_clear(struct ext4_sb_info *sbi);
 extern int ext4_mb_init(struct super_block *);
 extern void ext4_mb_release(struct super_block *);
 extern ext4_fsblk_t ext4_mb_new_blocks(handle_t *,
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index bb58eafb87bc..382c91586b26 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3219,6 +3219,8 @@ int ext4_seq_mb_stats_show(struct seq_file *seq, void *offset)
 	}
 	seq_printf(seq, "\treqs: %u\n", atomic_read(&sbi->s_bal_reqs));
 	seq_printf(seq, "\tsuccess: %u\n", atomic_read(&sbi->s_bal_success));
+	seq_printf(seq, "\tblocks_allocated: %u\n",
+		   atomic_read(&sbi->s_bal_allocated));
 
 	seq_printf(seq, "\tgroups_scanned: %u\n",
 		   atomic_read(&sbi->s_bal_groups_scanned));
@@ -4721,6 +4723,35 @@ static void ext4_mb_collect_stats(struct ext4_allocation_context *ac)
 		trace_ext4_mballoc_prealloc(ac);
 }
 
+void ext4_mb_stats_clear(struct ext4_sb_info *sbi)
+{
+	int i;
+
+	atomic_set(&sbi->s_bal_reqs, 0);
+	atomic_set(&sbi->s_bal_success, 0);
+	atomic_set(&sbi->s_bal_allocated, 0);
+	atomic_set(&sbi->s_bal_groups_scanned, 0);
+
+	for (i = 0; i < EXT4_MB_NUM_CRS; i++) {
+		atomic64_set(&sbi->s_bal_cX_hits[i], 0);
+		atomic64_set(&sbi->s_bal_cX_groups_considered[i], 0);
+		atomic_set(&sbi->s_bal_cX_ex_scanned[i], 0);
+		atomic64_set(&sbi->s_bal_cX_failed[i], 0);
+	}
+
+	atomic_set(&sbi->s_bal_ex_scanned, 0);
+	atomic_set(&sbi->s_bal_goals, 0);
+	atomic_set(&sbi->s_bal_stream_goals, 0);
+	atomic_set(&sbi->s_bal_len_goals, 0);
+	atomic_set(&sbi->s_bal_2orders, 0);
+	atomic_set(&sbi->s_bal_breaks, 0);
+	atomic_set(&sbi->s_mb_lost_chunks, 0);
+	atomic_set(&sbi->s_mb_buddies_generated, 0);
+	atomic64_set(&sbi->s_mb_generation_time, 0);
+	atomic_set(&sbi->s_mb_preallocated, 0);
+	atomic_set(&sbi->s_mb_discarded, 0);
+}
+
 /*
  * Called on failure; free up any blocks from the inode PA for this
  * context.  We don't need this for MB_GROUP_PA because we only change
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
index 923b375e017f..a5bd88a99f22 100644
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -41,6 +41,7 @@ typedef enum {
 	attr_pointer_atomic,
 	attr_journal_task,
 	attr_err_report_sec,
+	attr_mb_stats_clear,
 } attr_id_t;
 
 typedef enum {
@@ -161,6 +162,25 @@ static ssize_t err_report_sec_store(struct ext4_sb_info *sbi,
 	return count;
 }
 
+static ssize_t mb_stats_clear_store(struct ext4_sb_info *sbi,
+				    const char *buf, size_t count)
+{
+	int val;
+	int ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	ret = kstrtoint(skip_spaces(buf), 0, &val);
+	if (ret)
+		return ret;
+	if (val != 1)
+		return -EINVAL;
+
+	ext4_mb_stats_clear(sbi);
+	return count;
+}
+
 static ssize_t journal_task_show(struct ext4_sb_info *sbi, char *buf)
 {
 	if (!sbi->s_journal)
@@ -251,6 +271,7 @@ EXT4_ATTR_OFFSET(mb_best_avail_max_trim_order, 0644, mb_order,
 EXT4_ATTR_OFFSET(err_report_sec, 0644, err_report_sec, ext4_sb_info, s_err_report_sec);
 EXT4_RW_ATTR_SBI_UI(inode_goal, s_inode_goal);
 EXT4_RW_ATTR_SBI_UI(mb_stats, s_mb_stats);
+EXT4_ATTR(mb_stats_clear, 0200, mb_stats_clear);
 EXT4_RW_ATTR_SBI_UI(mb_max_to_scan, s_mb_max_to_scan);
 EXT4_RW_ATTR_SBI_UI(mb_min_to_scan, s_mb_min_to_scan);
 EXT4_RW_ATTR_SBI_UI(mb_order2_req, s_mb_order2_reqs);
@@ -301,6 +322,7 @@ static struct attribute *ext4_attrs[] = {
 	ATTR_LIST(inode_readahead_blks),
 	ATTR_LIST(inode_goal),
 	ATTR_LIST(mb_stats),
+	ATTR_LIST(mb_stats_clear),
 	ATTR_LIST(mb_max_to_scan),
 	ATTR_LIST(mb_min_to_scan),
 	ATTR_LIST(mb_order2_req),
@@ -561,6 +583,8 @@ static ssize_t ext4_attr_store(struct kobject *kobj,
 		return trigger_test_error(sbi, buf, len);
 	case attr_err_report_sec:
 		return err_report_sec_store(sbi, buf, len);
+	case attr_mb_stats_clear:
+		return mb_stats_clear_store(sbi, buf, len);
 	default:
 		return ext4_generic_attr_store(a, sbi, buf, len);
 	}
-- 
2.51.0