Re: [PATCH] dm-raid1: keep writing after leg failure

[Heinz Mauelshagen <heinzm@redhat.com>]

Acked-by: Heinz Mauelshagen <heinzm@redhat.com>

On 05/13/2015 08:04 AM, Lidong Zhong wrote:
> Currently if there is a leg failure, the bio will be put into the hold
> list until userspace replace/remove the leg. Here we are trying to make
> dm-raid1 ignore the failure and keep the following bios going on.
> This is because there maybe a temporary path failure in clvmd
> which leads to cluster raid1 remove/replace the fake device failure. And
> it takes a long time to do the full sync if we readd the device back.
>
> This patch merges the former five small patches to implement this
> feature. The userspace should pass "keep_log" into kernel to make this feature to
> take effect when creating dm-raid1, same as "handle_errors".
>
> Signed-off-by: Lidong Zhong <lzhong@suse.com>
> Tested-by: Liuhua Wang <lwang@suse.com>
> ---
>   drivers/md/dm-raid1.c | 62 ++++++++++++++++++++++++++++++++++++++++-----------
>   1 file changed, 49 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
> index 089d627..3de48d1 100644
> --- a/drivers/md/dm-raid1.c
> +++ b/drivers/md/dm-raid1.c
> @@ -24,7 +24,9 @@
>   #define MAX_RECOVERY 1	/* Maximum number of regions recovered in parallel. */
>   
>   #define DM_RAID1_HANDLE_ERRORS 0x01
> +#define DM_RAID1_KEEP_LOG      0x02
>   #define errors_handled(p)	((p)->features & DM_RAID1_HANDLE_ERRORS)
> +#define keep_log(p)	        ((p)->features & DM_RAID1_KEEP_LOG)
>   
>   static DECLARE_WAIT_QUEUE_HEAD(_kmirrord_recovery_stopped);
>   
> @@ -229,7 +231,7 @@ static void fail_mirror(struct mirror *m, enum dm_raid1_error error_type)
>   	if (m != get_default_mirror(ms))
>   		goto out;
>   
> -	if (!ms->in_sync) {
> +	if (!ms->in_sync && !keep_log(ms)) {
>   		/*
>   		 * Better to issue requests to same failing device
>   		 * than to risk returning corrupt data.
> @@ -370,6 +372,17 @@ static int recover(struct mirror_set *ms, struct dm_region *reg)
>   	return r;
>   }
>   
> +static void reset_ms_flags(struct mirror_set *ms)
> +{
> +	unsigned int m;
> +
> +	ms->leg_failure = 0;
> +	for (m = 0; m < ms->nr_mirrors; m++) {
> +		atomic_set(&(ms->mirror[m].error_count), 0);
> +		ms->mirror[m].error_type = 0;
> +	}
> +}
> +
>   static void do_recovery(struct mirror_set *ms)
>   {
>   	struct dm_region *reg;
> @@ -398,6 +411,7 @@ static void do_recovery(struct mirror_set *ms)
>   		/* the sync is complete */
>   		dm_table_event(ms->ti->table);
>   		ms->in_sync = 1;
> +		reset_ms_flags(ms);
>   	}
>   }
>   
> @@ -759,7 +773,7 @@ static void do_writes(struct mirror_set *ms, struct bio_list *writes)
>   		dm_rh_delay(ms->rh, bio);
>   
>   	while ((bio = bio_list_pop(&nosync))) {
> -		if (unlikely(ms->leg_failure) && errors_handled(ms)) {
> +		if (unlikely(ms->leg_failure) && errors_handled(ms) && !keep_log(ms)) {
>   			spin_lock_irq(&ms->lock);
>   			bio_list_add(&ms->failures, bio);
>   			spin_unlock_irq(&ms->lock);
> @@ -809,9 +823,21 @@ static void do_failures(struct mirror_set *ms, struct bio_list *failures)
>   		 * be wrong if the failed leg returned after reboot and
>   		 * got replicated back to the good legs.)
>   		 */
> -		if (!get_valid_mirror(ms))
> +
> +		/*
> +		 * We return EIO when there's no valid mirror legs
> +		 * -or-
> +		 * the log device is failed if keep_log is set
> +		 */
> +		if (unlikely(!get_valid_mirror(ms) || (keep_log(ms) && ms->log_failure)))
>   			bio_endio(bio, -EIO);
> -		else if (errors_handled(ms))
> +		/*
> +		 * After the userspace get noticed that the leg has failed,
> +		 * we just pretend that the bio has suceeded since the region
> +		 * has already been marked nosync. It's OK do the recovery after
> +		 * the device comes back
> +		 */
> +		else if (errors_handled(ms) && !keep_log(ms))
>   			hold_bio(ms, bio);
>   		else
>   			bio_endio(bio, 0);
> @@ -987,6 +1013,7 @@ static int parse_features(struct mirror_set *ms, unsigned argc, char **argv,
>   	unsigned num_features;
>   	struct dm_target *ti = ms->ti;
>   	char dummy;
> +	int i;
>   
>   	*args_used = 0;
>   
> @@ -1007,14 +1034,20 @@ static int parse_features(struct mirror_set *ms, unsigned argc, char **argv,
>   		return -EINVAL;
>   	}
>   
> -	if (!strcmp("handle_errors", argv[0]))
> -		ms->features |= DM_RAID1_HANDLE_ERRORS;
> -	else {
> -		ti->error = "Unrecognised feature requested";
> -		return -EINVAL;
> -	}
> +	for (i = 0; i < num_features; i++) {
> +		if (!strcmp("handle_errors", argv[0]))
> +			ms->features |= DM_RAID1_HANDLE_ERRORS;
> +		else if (!strcmp("keep_log", argv[0]))
> +			ms->features |= DM_RAID1_KEEP_LOG;
> +		else {
> +			ti->error = "Unrecognised feature requested";
> +			return -EINVAL;
> +		}
>   
> -	(*args_used)++;
> +		argc--;
> +		argv++;
> +		(*args_used)++;
> +	}
>   
>   	return 0;
>   }
> @@ -1029,7 +1062,7 @@ static int parse_features(struct mirror_set *ms, unsigned argc, char **argv,
>    * log_type is "core" or "disk"
>    * #log_params is between 1 and 3
>    *
> - * If present, features must be "handle_errors".
> + * If present, features must be "handle_errors" and/or "keep_log".
>    */
>   static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
>   {
> @@ -1394,8 +1427,11 @@ static void mirror_status(struct dm_target *ti, status_type_t type,
>   			DMEMIT(" %s %llu", ms->mirror[m].dev->name,
>   			       (unsigned long long)ms->mirror[m].offset);
>   
> -		if (ms->features & DM_RAID1_HANDLE_ERRORS)
> +		if (errors_handled(ms) && keep_log(ms))
> +			DMEMIT(" 2 handle_errors keep_log");
> +		else if (errors_handled(ms))
>   			DMEMIT(" 1 handle_errors");
> +
>   	}
>   }
>