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>

2 files changed, 62 insertions, 0 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 6b96125e7255..5d3d768d9503 100644
--- a/fs/ext4/ext4.h
+++ b/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)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index a94d3f56898f..ed00c14d7081 100644
--- a/fs/ext4/super.c
+++ b/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 @@ no_journal:
         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;