Re: [PATCH] ext4: add sysfs entry showing whether the fs contains errors

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Tue, May 06, 2014 at 03:19:17PM +0200, Lukas Czerner wrote:
> Currently there is no easy way to tell that the mounted file system
> contains errors other than checking for log messages, or reading the
> information directly from superblock.
> 
> This patch adds new sysfs entry "contains_errors" for each ext4 file
> system so user can simply check
> 
> cat /sys/fs/ext4/sda/contains_errors

Minor complaint: "contains" makes me think that cat'ing that file will return
either 0 or 1, not a string of error text.  Perhaps we could shorten it to
/sys/fs/ext4/sda/errors ?

Otherwise looks good to me.

--D
> 
> If the file system is not marked as containing errors then the file is
> empty. Otherwise it would print the same information that could be found
> in the log. For example:
> 
> error count: 1
> EXT4-fs (sda): initial error at 1399305407: trigger_test_error:2630
> EXT4-fs (sda): last error at 1399305407: trigger_test_error:2630
> 
> Signed-off-by: Lukas Czerner <lczerner@redhat.com>
> ---
>  fs/ext4/super.c | 100 ++++++++++++++++++++++++++++++++++++++------------------
>  1 file changed, 68 insertions(+), 32 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 6f9e6fa..61dc3d6 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -2502,6 +2502,59 @@ static ssize_t lifetime_write_kbytes_show(struct ext4_attr *a,
>  			  EXT4_SB(sb)->s_sectors_written_start) >> 1)));
>  }
>  
> +static ssize_t get_fs_errors(struct ext4_sb_info *sbi, char *buf, ssize_t size)
> +{
> +	struct super_block *sb = sbi->s_buddy_cache->i_sb;
> +	struct ext4_super_block *es = sbi->s_es;
> +	int len = 0;
> +
> +	if (es->s_error_count)
> +		len = snprintf(buf + len, size - len,
> +			       "error count: %u\n",
> +			       le32_to_cpu(es->s_error_count));
> +	if (es->s_first_error_time) {
> +		len += snprintf(buf + len, size - len,
> +				"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)
> +			len += snprintf(buf + len, size - len,
> +					": inode %u",
> +					le32_to_cpu(es->s_first_error_ino));
> +		if (es->s_first_error_block)
> +			len += snprintf(buf + len, size - len,
> +					": block %llu", (unsigned long long)
> +					le64_to_cpu(es->s_first_error_block));
> +		len += snprintf(buf + len, size - len, "\n");
> +	}
> +	if (es->s_last_error_time) {
> +		len += snprintf(buf + len, size - len,
> +				"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)
> +			len += snprintf(buf + len, size - len,
> +					": inode %u",
> +					le32_to_cpu(es->s_last_error_ino));
> +		if (es->s_last_error_block)
> +			len += snprintf(buf + len, size - len,
> +					": block %llu", (unsigned long long)
> +					le64_to_cpu(es->s_last_error_block));
> +		len += snprintf(buf + len, size - len, "\n");
> +	}
> +	return len;
> +}
> +
> +static ssize_t contains_errors_show(struct ext4_attr *a,
> +				    struct ext4_sb_info *sbi, char *buf)
> +{
> +	return get_fs_errors(sbi, buf, PAGE_SIZE);
> +}
> +
>  static ssize_t inode_readahead_blks_store(struct ext4_attr *a,
>  					  struct ext4_sb_info *sbi,
>  					  const char *buf, size_t count)
> @@ -2617,6 +2670,7 @@ static struct ext4_attr ext4_attr_##_name = {			\
>  EXT4_RO_ATTR(delayed_allocation_blocks);
>  EXT4_RO_ATTR(session_write_kbytes);
>  EXT4_RO_ATTR(lifetime_write_kbytes);
> +EXT4_RO_ATTR(contains_errors);
>  EXT4_RW_ATTR(reserved_clusters);
>  EXT4_ATTR_OFFSET(inode_readahead_blks, 0644, sbi_ui_show,
>  		 inode_readahead_blks_store, s_inode_readahead_blks);
> @@ -2659,6 +2713,7 @@ static struct attribute *ext4_attrs[] = {
>  	ATTR_LIST(warning_ratelimit_burst),
>  	ATTR_LIST(msg_ratelimit_interval_ms),
>  	ATTR_LIST(msg_ratelimit_burst),
> +	ATTR_LIST(contains_errors),
>  	NULL,
>  };
>  
> @@ -2792,42 +2847,23 @@ 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;
> +	ssize_t size;
> +	char *buf = NULL;
>  
>  	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");
> +	buf = kmalloc(255, GFP_NOFS);
> +	if (!buf) {
> +		ext4_msg(sb, KERN_NOTICE, "File system contains errors, "
> +					  "running e2fsck is recommended");
> +		return;
>  	}
> +
> +	size = get_fs_errors(sbi, buf, 255);
> +	if (size)
> +		ext4_msg(sb, KERN_NOTICE, "%s", buf);
> +	kfree(buf);
> +
>  	mod_timer(&sbi->s_err_report, jiffies + 24*60*60*HZ);  /* Once a day */
>  }
>  
> -- 
> 1.8.3.1
> 
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