[Devel] [RFC PATCH vz9 v6 47/62] dm-ploop: disable metadata writeback delay

[Alexander Atanasov]

On 20.12.24 16:02, Andrey Zhadchenko wrote:
> Here you are also disabling immediate metadata publish. Then you should 
> also call ploop_attach_end_action() for all requests in 
> ploop_locate_new_cluster_and_attach_pio(). Otherwise there we may have 
> completed write() syscall without metadata changes (they are not delayed 
> now but still executed in-parallel)


I missed to restore that line, yes.
When added back it causes us to "explode" on bat write complete,
i will think how to rearrange but any ideas are welcome.


> 
> On 12/5/24 22:56, Alexander Atanasov wrote:
>> Delayed metadata writeback results in a hang, disable
>> it until it is fixed. Pios end in the waiting list of
>> md and get stuck there never to complete.
>>
>> Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
>> ---
>>   drivers/md/dm-ploop-map.c | 14 +++++++++++---
>>   1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
>> index c88359677ea4..6e4d6f862135 100644
>> --- a/drivers/md/dm-ploop-map.c
>> +++ b/drivers/md/dm-ploop-map.c
>> @@ -817,9 +817,10 @@ static void 
>> ploop_advance_local_after_bat_wb(struct ploop *ploop,
>>       /* holes bit map requires bat_lock */
>>       spin_lock_irqsave(&ploop->bat_lock, flags);
>>       spin_lock(&md->md_lock);
>> +#ifdef PLOOP_DELAYWB
>>       if (piwb->type == PIWB_TYPE_ALLOC)
>>           goto skip_apply;
>> -
>> +#endif
>>       for (; i < last; i++) {
>>           if (piwb->type == PIWB_TYPE_DISCARD) {
>>               ploop_piwb_discard_completed(ploop, success, i + off, 
>> dst_clu[i]);
>> @@ -836,7 +837,9 @@ static void 
>> ploop_advance_local_after_bat_wb(struct ploop *ploop,
>>               ploop_hole_set_bit(i + off, ploop);
>>           }
>>       }
>> +#ifdef PLOOP_DELAYWB
>>   skip_apply:
>> +#endif
>>       WARN_ON_ONCE(!test_bit(MD_WRITEBACK, &md->status));
>>       clear_bit(MD_WRITEBACK, &md->status);
>> @@ -1187,8 +1190,10 @@ static int ploop_alloc_cluster(struct ploop 
>> *ploop, struct ploop_index_wb *piwb,
>>       to = piwb->kmpage;
>>       WRITE_ONCE(to[clu], *dst_clu);
>> +#ifdef PLOOP_DELAYWB
>>       to = piwb->md->kmpage;
>>       WRITE_ONCE(to[clu], *dst_clu);
>> +#endif
>>   out:
>>       return ret;
>>   }
>> @@ -1481,6 +1486,7 @@ static void ploop_submit_cow_index_wb(struct 
>> ploop_cow *cow)
>>       WARN_ON(to[clu]);
>>       WRITE_ONCE(to[clu], cow->dst_clu);
>> +#ifdef PLOOP_DELAYWB
>>       spin_lock_irqsave(&md->md_lock, flags);
>>       to = md->kmpage;
>>       WRITE_ONCE(to[clu], cow->dst_clu);
>> @@ -1488,7 +1494,7 @@ static void ploop_submit_cow_index_wb(struct 
>> ploop_cow *cow)
>>       spin_unlock_irqrestore(&md->md_lock, flags);
>>       ploop_md_up_prio(ploop, md);
>> -
>> +#endif
>>       /* Prevent double clearing of holes_bitmap bit on complete_cow() */
>>       cow->dst_clu = BAT_ENTRY_NONE;
>>       spin_lock_irq(&ploop->deferred_lock);
>> @@ -1918,7 +1924,9 @@ static inline int 
>> ploop_submit_metadata_writeback(struct ploop *ploop, int force
>>        */
>>       llist_for_each_safe(pos, t, ll_wb_batch) {
>>           md = list_entry((struct list_head *)pos, typeof(*md), wb_link);
>> -        if (!llist_empty(&md->wait_llist) || force || 
>> test_bit(MD_HIGHPRIO, &md->status) ||
>> +        /* XXX: fixme delay results in a hang - TBD */
>> +        if (1 || !llist_empty(&md->wait_llist) || force ||
>> +            test_bit(MD_HIGHPRIO, &md->status) ||
>>               time_before(md->dirty_timeout, timeout)) {
>>               /* L1L2 mustn't be redirtyed, when wb in-flight! */
>>               WARN_ON_ONCE(!test_bit(MD_DIRTY, &md->status));

-- 
Regards,
Alexander Atanasov