[PATCH v3 v3 2/2] ext4: allow clearing mballoc stats through mb_stats

[Baolin Liu <liubaolin12138@163.com>]

From: Baolin Liu <liubaolin@kylinos.cn>

Make /proc/fs/ext4/<dev>/mb_stats writable and clear the runtime
mballoc statistics when 0 is written.
Update the related documentation accordingly.

Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Baolin Liu <liubaolin@kylinos.cn>
---
 Documentation/admin-guide/ext4.rst |  5 ++++
 Documentation/filesystems/proc.rst |  3 +++
 fs/ext4/ext4.h                     |  1 +
 fs/ext4/mballoc.c                  | 29 ++++++++++++++++++++++
 fs/ext4/sysfs.c                    | 40 ++++++++++++++++++++++++++++--
 5 files changed, 76 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/ext4.rst b/Documentation/admin-guide/ext4.rst
index ac0c709ea9e7..fb3887cd5e44 100644
--- a/Documentation/admin-guide/ext4.rst
+++ b/Documentation/admin-guide/ext4.rst
@@ -436,6 +436,11 @@ Files in /proc/fs/ext4/<devname>
   mb_groups
         details of multiblock allocator buddy cache of free blocks
 
+  mb_stats
+        reports runtime statistics from the multiblock allocator
+        (mballoc). Writing 0 to this file clears the current
+        statistics.
+
 /sys entries
 ============
 
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index b0c0d1b45b99..7ce02573a3d9 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -1634,6 +1634,9 @@ directory are shown in Table 1-12, below.
  ==============  ==========================================================
  File            Content
  mb_groups       details of multiblock allocator buddy cache of free blocks
+ mb_stats        reports runtime statistics from the multiblock allocator
+                 (mballoc). Writing 0 to this file clears the current
+                 statistics.
  ==============  ==========================================================
 
 1.9 /proc/consoles
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 293f698b7042..3223e73612ae 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2994,6 +2994,7 @@ 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 1e13ef62cb9d..79ddfa935813 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4723,6 +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 b87d7bdab06a..e90885d470ab 100644
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -52,6 +52,42 @@ typedef enum {
 static const char proc_dirname[] = "fs/ext4";
 static struct proc_dir_entry *ext4_proc_root;
 
+static int ext4_mb_stats_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, ext4_seq_mb_stats_show, pde_data(inode));
+}
+
+static ssize_t ext4_mb_stats_write(struct file *file, const char __user *buf,
+					   size_t count, loff_t *ppos)
+{
+	struct super_block *sb = pde_data(file_inode(file));
+	char kbuf[2];
+
+	if (count == 0 || count > sizeof(kbuf))
+		return -EINVAL;
+
+	if (copy_from_user(kbuf, buf, count))
+		return -EFAULT;
+
+	if (count == 2) {
+		if (kbuf[0] != '0' || kbuf[1] != '\n')
+			return -EINVAL;
+	} else if (kbuf[0] != '0') {
+		return -EINVAL;
+	}
+
+	ext4_mb_stats_clear(EXT4_SB(sb));
+	return count;
+}
+
+static const struct proc_ops ext4_mb_stats_proc_ops = {
+	.proc_open	= ext4_mb_stats_open,
+	.proc_read	= seq_read,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= single_release,
+	.proc_write	= ext4_mb_stats_write,
+};
+
 struct ext4_attr {
 	struct attribute attr;
 	short attr_id;
@@ -630,8 +666,8 @@ 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_single_data("mb_stats", 0444, sbi->s_proc,
-				ext4_seq_mb_stats_show, sb);
+		proc_create_data("mb_stats", 0644, sbi->s_proc,
+				 &ext4_mb_stats_proc_ops, sb);
 		proc_create_seq_data("mb_structs_summary", 0444, sbi->s_proc,
 				&ext4_mb_seq_structs_summary_ops, sb);
 	}
-- 
2.51.0