Re: [RFC PATCH v2 1/4] jbd2: make jdb2_debug module parameter per device

[harshad shirwadkar]

Hey hi! I don't see my previous comments being handled here or am I
missing something? It'd be really handy to have the device name
printed in jbd2 logs.

On Sat, Jan 23, 2021 at 4:01 AM Chunguang Xu <brookxu.cn@xxxxxxxxx> wrote:
>
> From: Chunguang Xu <brookxu@xxxxxxxxxxx>
>
> On a multi-disk machine, because jbd2's debugging switch is global,this
> confuses the logs of multiple disks. It is not easy to distinguish the
> logs of each disk and the amount of generated logs is very large. Maybe
> a separate debugging switch for each disk would be better, so that we
> can easily distinguish the logs of a certain disk.
>
> Signed-off-by: Chunguang Xu <brookxu@xxxxxxxxxxx>
> Reviewed-by: Harshad Shirwadkar <harshadshirwadkar@xxxxxxxxx>
> ---
>  fs/jbd2/journal.c     | 55 ++++++++++++++++++++++++++++++++++++++++---
>  fs/jbd2/transaction.c |  2 +-
>  include/linux/jbd2.h  |  7 ++++++
>  3 files changed, 60 insertions(+), 4 deletions(-)
>
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index 2dc944442802..1f32b854ea28 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -101,13 +101,13 @@ EXPORT_SYMBOL(jbd2_inode_cache);
>  static int jbd2_journal_create_slab(size_t slab_size);
>
>  #ifdef CONFIG_JBD2_DEBUG
> -void __jbd2_debug(int level, const char *file, const char *func,
> +void jbd2_log(int level, journal_t *j, const char *file, const char *func,
>                   unsigned int line, const char *fmt, ...)
>  {
>         struct va_format vaf;
>         va_list args;
>
> -       if (level > jbd2_journal_enable_debug)
> +       if (!j || (level > jbd2_journal_enable_debug && level > j->j_debug_level))
>                 return;
>         va_start(args, fmt);
>         vaf.fmt = fmt;
> @@ -115,7 +115,7 @@ void __jbd2_debug(int level, const char *file, const char *func,
>         printk(KERN_DEBUG "%s: (%s, %u): %pV", file, func, line, &vaf);
>         va_end(args);
>  }
> -EXPORT_SYMBOL(__jbd2_debug);
> +EXPORT_SYMBOL(jbd2_log);
>  #endif
>
>  /* Checksumming functions */
> @@ -1257,6 +1257,48 @@ static int jbd2_seq_info_release(struct inode *inode, struct file *file)
>         return seq_release(inode, file);
>  }
>
> +#ifdef CONFIG_JBD2_DEBUG
> +static int jbd2_proc_debug_show(struct seq_file *m, void *v)
> +{
> +       journal_t *j = m->private;
> +
> +       seq_printf(m, "%d\n", j->j_debug_level);
> +       return 0;
> +}
> +
> +static int jbd2_proc_debug_open(struct inode *inode, struct file *file)
> +{
> +       journal_t *journal = PDE_DATA(inode);
> +
> +       return single_open(file, jbd2_proc_debug_show, journal);
> +}
> +
> +static ssize_t jbd2_proc_debug_write(struct file *file,
> +               const char __user *buffer, size_t count, loff_t *ppos)
> +{
> +       struct seq_file *seq = file->private_data;
> +       journal_t *j = seq->private;
> +       char c;
> +
> +       if (get_user(c, buffer))
> +               return -EFAULT;
> +
> +       if (c < '0' || c > '5')
> +               return -EINVAL;
> +
> +       j->j_debug_level = c - '0';
> +       return count;
> +}
> +
> +static const struct proc_ops jbd2_debug_proc_ops = {
> +       .proc_open      = jbd2_proc_debug_open,
> +       .proc_read      = seq_read,
> +       .proc_write     = jbd2_proc_debug_write,
> +       .proc_release   = single_release,
> +       .proc_lseek     = seq_lseek,
> +};
> +#endif
> +
>  static const struct proc_ops jbd2_info_proc_ops = {
>         .proc_open      = jbd2_seq_info_open,
>         .proc_read      = seq_read,
> @@ -1272,12 +1314,19 @@ static void jbd2_stats_proc_init(journal_t *journal)
>         if (journal->j_proc_entry) {
>                 proc_create_data("info", S_IRUGO, journal->j_proc_entry,
>                                  &jbd2_info_proc_ops, journal);
> +#ifdef CONFIG_JBD2_DEBUG
> +               proc_create_data("jbd2_debug", S_IRUGO, journal->j_proc_entry,
> +                                &jbd2_debug_proc_ops, journal);
> +#endif
>         }
>  }
>
>  static void jbd2_stats_proc_exit(journal_t *journal)
>  {
>         remove_proc_entry("info", journal->j_proc_entry);
> +#ifdef CONFIG_JBD2_DEBUG
> +       remove_proc_entry("jbd2_debug", journal->j_proc_entry);
> +#endif
>         remove_proc_entry(journal->j_devname, proc_jbd2_stats);
>  }
>
> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
> index 9396666b7314..71787e826788 100644
> --- a/fs/jbd2/transaction.c
> +++ b/fs/jbd2/transaction.c
> @@ -150,7 +150,7 @@ static inline void update_t_max_wait(transaction_t *transaction,
>                                      unsigned long ts)
>  {
>  #ifdef CONFIG_JBD2_DEBUG
> -       if (jbd2_journal_enable_debug &&
> +       if ((jbd2_journal_enable_debug || transaction->t_journal->j_debug_level) &&
>             time_after(transaction->t_start, ts)) {
>                 ts = jbd2_time_diff(ts, transaction->t_start);
>                 spin_lock(&transaction->t_handle_lock);
> diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> index 99d3cd051ac3..600a2ea8324a 100644
> --- a/include/linux/jbd2.h
> +++ b/include/linux/jbd2.h
> @@ -1211,6 +1211,13 @@ struct journal_s
>          */
>         struct transaction_stats_s j_stats;
>
> +#ifdef CONFIG_JBD2_DEBUG
> +       /**
> +        * @j_debug_level: debugging level for jbd2.
> +        */
> +       unsigned int j_debug_level;
> +#endif
> +
>         /**
>          * @j_failed_commit: Failed journal commit ID.
>          */
> --
> 2.30.0
>