[PATCH] ext4: notify sysfs on errors_count value change

[Jonathan Davies <jonathan.davies@nutanix.com>]

After s_error_count is incremented, signal the change in the
corresponding sysfs attribute via sysfs_notify. This allows userspace to
poll() on changes to /sys/fs/ext4/*/errors_count.

Signed-off-by: Jonathan Davies <jonathan.davies@nutanix.com>
---
 fs/ext4/ext4.h  | 1 +
 fs/ext4/super.c | 1 +
 fs/ext4/sysfs.c | 7 +++++++
 3 files changed, 9 insertions(+)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 37002663..f313f5be 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -3614,6 +3614,7 @@ extern const struct inode_operations ext4_symlink_inode_operations;
 extern const struct inode_operations ext4_fast_symlink_inode_operations;
 
 /* sysfs.c */
+extern void ext4_notify_error_sysfs(struct super_block *sb);
 extern int ext4_register_sysfs(struct super_block *sb);
 extern void ext4_unregister_sysfs(struct super_block *sb);
 extern int __init ext4_init_sysfs(void);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index d29f6aa..2525239 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5579,6 +5579,7 @@ static void ext4_update_super(struct super_block *sb)
 		if (!es->s_error_count)
 			mod_timer(&sbi->s_err_report, jiffies + 24*60*60*HZ);
 		le32_add_cpu(&es->s_error_count, sbi->s_add_error_count);
+		ext4_notify_error_sysfs(sb);
 		sbi->s_add_error_count = 0;
 	}
 	spin_unlock(&sbi->s_error_lock);
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
index 55fcab6..254b7fc 100644
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -506,6 +506,13 @@ static struct kobj_type ext4_feat_ktype = {
 	.release	= (void (*)(struct kobject *))kfree,
 };
 
+void ext4_notify_error_sysfs(struct super_block *sb)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+
+	sysfs_notify(&sbi->s_kobj, NULL, "errors_count");
+}
+
 static struct kobject *ext4_root;
 
 static struct kobject *ext4_feat;
-- 
2.9.3