ext4: Once a day, printk file system error information to dmesg

This allows us to grab any file system error messages by scraping
/var/log/messages.  This will make it easy for us to do error analysis
across the very large number of machines as we deploy ext4 across the
fleet.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4.h

@@ -1166,6 +1166,9 @@ struct ext4_sb_info {
 
 	/* workqueue for dio unwritten */
 	struct workqueue_struct *dio_unwritten_wq;
+
+	/* timer for periodic error stats printing */
+	struct timer_list s_err_report;
 };
 
 static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)

fs/ext4/super.c

@@ -325,6 +325,12 @@ static void __save_error_info(struct super_block *sb, const char *func,
 		es->s_first_error_ino = es->s_last_error_ino;
 		es->s_first_error_block = es->s_last_error_block;
 	}
+	/*
+	 * Start the daily error reporting function if it hasn't been
+	 * started already
+	 */
+	if (!es->s_error_count)
+		mod_timer(&EXT4_SB(sb)->s_err_report, jiffies + 24*60*60*HZ);
 	es->s_error_count = cpu_to_le32(le32_to_cpu(es->s_error_count) + 1);
 }
 
@@ -2480,6 +2486,53 @@ static int ext4_feature_set_ok(struct super_block *sb, int readonly)
 	return 1;
 }
 
+/*
+ * This function is called once a day if we have errors logged
+ * on the file system
+ */
+static void print_daily_error_info(unsigned long arg)
+{
+	struct super_block *sb = (struct super_block *) arg;
+	struct ext4_sb_info *sbi;
+	struct ext4_super_block *es;
+
+	sbi = EXT4_SB(sb);
+	es = sbi->s_es;
+
+	if (es->s_error_count)
+		ext4_msg(sb, KERN_NOTICE, "error count: %u",
+			 le32_to_cpu(es->s_error_count));
+	if (es->s_first_error_time) {
+		printk(KERN_NOTICE "EXT4-fs (%s): initial error at %u: %.*s:%d",
+		       sb->s_id, le32_to_cpu(es->s_first_error_time),
+		       (int) sizeof(es->s_first_error_func),
+		       es->s_first_error_func,
+		       le32_to_cpu(es->s_first_error_line));
+		if (es->s_first_error_ino)
+			printk(": inode %u",
+			       le32_to_cpu(es->s_first_error_ino));
+		if (es->s_first_error_block)
+			printk(": block %llu", (unsigned long long)
+			       le64_to_cpu(es->s_first_error_block));
+		printk("\n");
+	}
+	if (es->s_last_error_time) {
+		printk(KERN_NOTICE "EXT4-fs (%s): last error at %u: %.*s:%d",
+		       sb->s_id, le32_to_cpu(es->s_last_error_time),
+		       (int) sizeof(es->s_last_error_func),
+		       es->s_last_error_func,
+		       le32_to_cpu(es->s_last_error_line));
+		if (es->s_last_error_ino)
+			printk(": inode %u",
+			       le32_to_cpu(es->s_last_error_ino));
+		if (es->s_last_error_block)
+			printk(": block %llu", (unsigned long long)
+			       le64_to_cpu(es->s_last_error_block));
+		printk("\n");
+	}
+	mod_timer(&sbi->s_err_report, jiffies + 24*60*60*HZ);  /* Once a day */
+}
+
 static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 				__releases(kernel_lock)
 				__acquires(kernel_lock)
@@ -3083,6 +3136,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	ext4_msg(sb, KERN_INFO, "mounted filesystem with%s. "
 		"Opts: %s", descr, orig_data);
 
+	init_timer(&sbi->s_err_report);
+	sbi->s_err_report.function = print_daily_error_info;
+	sbi->s_err_report.data = (unsigned long) sb;
+	if (es->s_error_count)
+		mod_timer(&sbi->s_err_report, jiffies + 300*HZ); /* 5 minutes */
+
 	lock_kernel();
 	kfree(orig_data);
 	return 0;