linux-kernel - Re: [PATCH] pblk: fix max

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Date:   Thu, 7 Mar 2019 08:59:45 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Matias Bjørling <mb@...htnvm.io>,
        Javier González <javier@...igon.com>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pblk: fix max_io calculation

On 3/7/19 8:57 AM, Matias Bjørling wrote:
> On 3/7/19 1:18 PM, Javier González wrote:
>> When calculating the maximun I/O size allowed into the buffer, consider
>> the write size (ws_opt) used by the write thread in order to cover the
>> case in which, due to flushes, the mem and subm pointers are disaligned
>> by (ws_opt - 1). This case currently translates into a stall when
>> an I/O of the largest possible size is submitted.
>>
>> Fixes: f9f9d1ae2c66 ("lightnvm: pblk: prevent stall due to wb threshold")
>>
>> Signed-off-by: Javier González <javier@...igon.com>
>> ---
>>
>> Matias: Can you apply this as a fix to 5.1. This is a case I missed when fixing
>> the wb threshold, which is also scheduled for 5.1
>>
>> Thanks,
>> Javier
>>
>>   drivers/lightnvm/pblk-rl.c | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/lightnvm/pblk-rl.c b/drivers/lightnvm/pblk-rl.c
>> index b014957dde0b..a5f8bc2defbc 100644
>> --- a/drivers/lightnvm/pblk-rl.c
>> +++ b/drivers/lightnvm/pblk-rl.c
>> @@ -233,10 +233,15 @@ void pblk_rl_init(struct pblk_rl *rl, int budget, int threshold)
>>   	/* To start with, all buffer is available to user I/O writers */
>>   	rl->rb_budget = budget;
>>   	rl->rb_user_max = budget;
>> -	rl->rb_max_io = threshold ? (budget - threshold) : (budget - 1);
>>   	rl->rb_gc_max = 0;
>>   	rl->rb_state = PBLK_RL_HIGH;
>>   
>> +	/* Maximize I/O size and ansure that back threshold is respected */
>> +	if (threshold)
>> +		rl->rb_max_io = budget - pblk->min_write_pgs_data - threshold;
>> +	else
>> +		rl->rb_max_io = budget - pblk->min_write_pgs_data - 1;
>> +
>>   	atomic_set(&rl->rb_user_cnt, 0);
>>   	atomic_set(&rl->rb_gc_cnt, 0);
>>   	atomic_set(&rl->rb_space, -1);
>>
> 
> Hi Jens,
> 
> If possible, could you please pick this one up for 5.1? It fixes a 
> previous patch that was introduced in 5.1 that should fix a stall, but 
> didn't quite catch it.

Applied

-- 
Jens Axboe