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

[Lidong Zhong]

>>> On 4/8/2015 at 08:27 PM, in message <55251EBC.3060101 at redhat.com>, Heinz
Mauelshagen <heinzm at redhat.com> wrote: 
> Lidong, 
>  
> please see the patch series of 3 in response with $Subject. 
>  

Hi Heinz,
Thanks for your correction.

Regards,
Lidong

> Heinz 
>  
> On 04/03/2015 05:51 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. 
> > --- 
> >   drivers/md/dm-raid1.c | 30 ++++++++++++++++++++++++++---- 
> >   1 file changed, 26 insertions(+), 4 deletions(-) 
> > 
> > diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c 
> > index 9584443..e237c42 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); 
> >    
> > @@ -750,7 +752,7 @@ 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); 
> > @@ -800,9 +802,19 @@ 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 the log device is failed if keep_log is set 
> > +		 */ 
> > +		if (!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); 
> > @@ -1005,8 +1017,15 @@ static int parse_features(struct mirror_set *ms,  
> unsigned argc, char **argv, 
> >   		return -EINVAL; 
> >   	} 
> >    
> > +	argc--; 
> > +	argv++; 
> >   	(*args_used)++; 
> >    
> > +	if (!strcmp("keep_log", argv[0])) { 
> > +		ms->features |= DM_RAID1_KEEP_LOG; 
> > +		(*args_used)++; 
> > +	} 
> > + 
> >   	return 0; 
> >   } 
> >    
> > @@ -1382,8 +1401,11 @@ 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"); 
> > + 
> >   	} 
> >   } 
> >    
>  
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