Re: [md PATCH 02/36] md/bad-block-log: add sysfs interface for accessing bad-block-log.

[Namhyung Kim <namhyung@gmail.com>]

NeilBrown <neilb@suse.de> writes:

> This can show the log (providing it fits in one page) and
> allows bad blocks to be 'acknowledged' meaning that they
> have safely been recorded in metadata.
>
> Clearing bad blocks is not allowed via sysfs (except for
> code testing).  A bad block can only be cleared when
> a write to the block succeeds.
>
> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
>
>  drivers/md/md.c |  127 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 127 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 220fadb..9324635 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -2712,6 +2712,35 @@ static ssize_t recovery_start_store(mdk_rdev_t *rdev, const char *buf, size_t le
>  static struct rdev_sysfs_entry rdev_recovery_start =
>  __ATTR(recovery_start, S_IRUGO|S_IWUSR, recovery_start_show, recovery_start_store);
>  
> +
> +static ssize_t
> +badblocks_show(struct badblocks *bb, char *page, int unack);
> +static ssize_t
> +badblocks_store(struct badblocks *bb, const char *page, size_t len, int unack);
> +
> +static ssize_t bb_show(mdk_rdev_t *rdev, char *page)
> +{
> +	return badblocks_show(&rdev->badblocks, page, 0);
> +}
> +static ssize_t bb_store(mdk_rdev_t *rdev, const char *page, size_t len)
> +{
> +	return badblocks_store(&rdev->badblocks, page, len, 0);
> +}
> +static struct rdev_sysfs_entry rdev_bad_blocks =
> +__ATTR(bad_blocks, S_IRUGO|S_IWUSR, bb_show, bb_store);
> +
> +
> +static ssize_t ubb_show(mdk_rdev_t *rdev, char *page)
> +{
> +	return badblocks_show(&rdev->badblocks, page, 1);
> +}
> +static ssize_t ubb_store(mdk_rdev_t *rdev, const char *page, size_t len)
> +{
> +	return badblocks_store(&rdev->badblocks, page, len, 1);
> +}
> +static struct rdev_sysfs_entry rdev_unack_bad_blocks =
> +__ATTR(unacknowledged_bad_blocks, S_IRUGO|S_IWUSR, ubb_show, ubb_store);
> +
>  static struct attribute *rdev_default_attrs[] = {
>  	&rdev_state.attr,
>  	&rdev_errors.attr,
> @@ -2719,6 +2748,8 @@ static struct attribute *rdev_default_attrs[] = {
>  	&rdev_offset.attr,
>  	&rdev_size.attr,
>  	&rdev_recovery_start.attr,
> +	&rdev_bad_blocks.attr,
> +	&rdev_unack_bad_blocks.attr,
>  	NULL,
>  };
>  static ssize_t
> @@ -7775,6 +7806,102 @@ void md_ack_all_badblocks(struct badblocks *bb)
>  }
>  EXPORT_SYMBOL_GPL(md_ack_all_badblocks);
>  
> +/* sysfs access to bad-blocks list.
> + * We present two files.
> + * 'bad-blocks' lists sector numbers and lengths of ranges that
> + *    are recorded as bad.  The list is truncated to fit within
> + *    the one-page limit of sysfs.
> + *    Writing "sector length" to this file adds an acknowledged
> + *    bad block list.
> + * 'unacknowledged-bad-blocks' lists bad blocks that have not yet
> + *    been acknowledged.  Writing to this file adds bad blocks
> + *    without acknowledging them.  This is largely for testing.
> + *
> + */
> +
> +static ssize_t
> +badblocks_show(struct badblocks *bb, char *page, int unack)
> +{
> +	size_t len = 0;
> +	int i;
> +	u64 *p;
> +	int havelock = 0;
> +
> +	if (bb->shift < 0)
> +		return 0;
> +
> +	rcu_read_lock();
> +	p = rcu_dereference(bb->active_page);
> +	if (!p) {
> +		spin_lock_irq(&bb->lock);
> +		p = bb->page;
> +		havelock = 1;
> +	}
> +
> +	i = 0;
> +
> +	while (len < PAGE_SIZE && i < bb->count) {
> +		sector_t s = BB_OFFSET(p[i]);
> +		unsigned int length = BB_LEN(p[i]);
> +		int ack = BB_ACK(p[i]);
> +		i++;
> +
> +		if (unack && ack)
> +			continue;
> +
> +		len += snprintf(page+len, PAGE_SIZE-len, "%llu %u\n",
> +				(unsigned long long)s << bb->shift,
> +				length << bb->shift);
> +	}
> +
> +	if (havelock)
> +		spin_unlock_irq(&bb->lock);
> +	rcu_read_unlock();
> +
> +	return len;
> +}
> +
> +#define DO_DEBUG 1
> +
> +static ssize_t
> +badblocks_store(struct badblocks *bb, const char *page, size_t len, int unack)
> +{
> +	unsigned long long sector;
> +	int length;
> +	char newline;
> +#ifdef DO_DEBUG
> +	/* Allow clearing via sysfs *only* for testing/debugging.
> +	 * Normally only a successful write may clear a badblock
> +	 */
> +	int clear = 0;
> +	if (page[0] == '-') {
> +		clear = 1;
> +		page++;
> +	}
> +#endif /* DO_DEBUG */
> +
> +	switch (sscanf(page, "%llu %d%c", &sector, &length, &newline)) {

What if user provides negative 'length' here? Should we check that case?


> +	case 3:
> +		if (newline != '\n')
> +			return -EINVAL;
> +	case 2:
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +#ifdef DO_DEBUG
> +	if (clear) {
> +		md_clear_badblocks(bb, sector, length);
> +		return len;
> +	}
> +#endif /* DO_DEBUG */
> +	if (md_set_badblocks(bb, sector, length, !unack))
> +		return len;
> +	else
> +		return -ENOSPC;
> +}
> +
>  static int md_notify_reboot(struct notifier_block *this,
>  			    unsigned long code, void *x)
>  {
>
>
> --
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