Re: [PATCH] block, nvme: Increase max segments parameter setting value

[Tokunori Ikegami <ikegami.t@gmail.com>]

On 2020/03/24 16:16, Hannes Reinecke wrote:
> On 3/23/20 7:23 PM, Tokunori Ikegami wrote:
>> Currently data length can be specified as UINT_MAX but failed.
>> This is caused by the max segments parameter limit set as USHRT_MAX.
>> To resolve this issue change to increase the value limit range.
>>
>> Signed-off-by: Tokunori Ikegami <ikegami.t@gmail.com>
>> Cc: linux-block@vger.kernel.org
>> Cc: linux-nvme@lists.infradead.org
>> ---
>>   block/blk-settings.c     | 2 +-
>>   drivers/nvme/host/core.c | 2 +-
>>   include/linux/blkdev.h   | 7 ++++---
>>   3 files changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/block/blk-settings.c b/block/blk-settings.c
>> index c8eda2e7b91e..ed40bda573c2 100644
>> --- a/block/blk-settings.c
>> +++ b/block/blk-settings.c
>> @@ -266,7 +266,7 @@ EXPORT_SYMBOL(blk_queue_max_write_zeroes_sectors);
>>    *    Enables a low level driver to set an upper limit on the 
>> number of
>>    *    hw data segments in a request.
>>    **/
>> -void blk_queue_max_segments(struct request_queue *q, unsigned short 
>> max_segments)
>> +void blk_queue_max_segments(struct request_queue *q, unsigned int 
>> max_segments)
>>   {
>>       if (!max_segments) {
>>           max_segments = 1;
>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>> index a4d8c90ee7cc..2b48aab0969e 100644
>> --- a/drivers/nvme/host/core.c
>> +++ b/drivers/nvme/host/core.c
>> @@ -2193,7 +2193,7 @@ static void nvme_set_queue_limits(struct 
>> nvme_ctrl *ctrl,
>>             max_segments = min_not_zero(max_segments, 
>> ctrl->max_segments);
>>           blk_queue_max_hw_sectors(q, ctrl->max_hw_sectors);
>> -        blk_queue_max_segments(q, min_t(u32, max_segments, USHRT_MAX));
>> +        blk_queue_max_segments(q, min_t(u32, max_segments, UINT_MAX));
>>       }
>>       if ((ctrl->quirks & NVME_QUIRK_STRIPE_SIZE) &&
>>           is_power_of_2(ctrl->max_hw_sectors))
>> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
>> index f629d40c645c..4f4224e20c28 100644
>> --- a/include/linux/blkdev.h
>> +++ b/include/linux/blkdev.h
>> @@ -338,8 +338,8 @@ struct queue_limits {
>>       unsigned int        max_write_zeroes_sectors;
>>       unsigned int        discard_granularity;
>>       unsigned int        discard_alignment;
>> +    unsigned int        max_segments;
>>   -    unsigned short        max_segments;
>>       unsigned short        max_integrity_segments;
>>       unsigned short        max_discard_segments;
>>   @@ -1067,7 +1067,8 @@ extern void blk_queue_make_request(struct 
>> request_queue *, make_request_fn *);
>>   extern void blk_queue_bounce_limit(struct request_queue *, u64);
>>   extern void blk_queue_max_hw_sectors(struct request_queue *, 
>> unsigned int);
>>   extern void blk_queue_chunk_sectors(struct request_queue *, 
>> unsigned int);
>> -extern void blk_queue_max_segments(struct request_queue *, unsigned 
>> short);
>> +extern void blk_queue_max_segments(struct request_queue *q,
>> +                   unsigned int max_segments);
>>   extern void blk_queue_max_discard_segments(struct request_queue *,
>>           unsigned short);
>>   extern void blk_queue_max_segment_size(struct request_queue *, 
>> unsigned int);
>> @@ -1276,7 +1277,7 @@ static inline unsigned int 
>> queue_max_hw_sectors(const struct request_queue *q)
>>       return q->limits.max_hw_sectors;
>>   }
>>   -static inline unsigned short queue_max_segments(const struct 
>> request_queue *q)
>> +static inline unsigned int queue_max_segments(const struct 
>> request_queue *q)
>>   {
>>       return q->limits.max_segments;
>>   }
>>
> One would assume that the same reasoning goes for 
> max_integrity_segment, no?

The error case itself can be resolved by the change without the 
max_integrity_segment changes.
Also the value is set to 0 as default and set to 1 by the nvme driver so 
it seems that not necessary to change for this case.

>
> Otherwise looks good.
>
> Reviewed-by: Hannes Reinecke <hare@suse.de>
Thanks for your reviewing.
>
> Cheers,
>
> Hannes

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