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[PATCH] md/md-linear: Enable atomic writes

John Garry posted 1 patch 4 weeks, 1 day ago
[PATCH] md/md-linear: Enable atomic writes
Posted by John Garry 4 weeks, 1 day ago 
All the infrastructure has already been plumbed to support this for
stacked devices, so just enable the request_queue limits features flag.

A note about chunk sectors for linear arrays:
While it is possible to set a chunk sectors param for building a linear
array, this is for specifying the granularity at which data sectors from
the device are used. It is not the same as a stripe size, like for RAID0. 

As such, it is not appropriate to set chunk_sectors request queue limit to
the same value, as chunk_sectors request limit is a boundary for which
requests cannot straddle.

However, request_queue limit max_hw_sectors is set to chunk sectors, which
almost has the same effect as setting chunk_sectors limit.

Signed-off-by: John Garry <john.g.garry@oracle.com>

diff --git a/drivers/md/md-linear.c b/drivers/md/md-linear.c
index 5d9b081153757..30ac29b990c9b 100644
--- a/drivers/md/md-linear.c
+++ b/drivers/md/md-linear.c
@@ -74,6 +74,7 @@ static int linear_set_limits(struct mddev *mddev)
 	lim.max_hw_sectors = mddev->chunk_sectors;
 	lim.max_write_zeroes_sectors = mddev->chunk_sectors;
 	lim.io_min = mddev->chunk_sectors << 9;
+	lim.features |= BLK_FEAT_ATOMIC_WRITES;
 	err = mddev_stack_rdev_limits(mddev, &lim, MDDEV_STACK_INTEGRITY);
 	if (err)
 		return err;
-- 
2.43.5
Re: [PATCH] md/md-linear: Enable atomic writes
Posted by Yu Kuai 3 weeks, 6 days ago 
在 2025/09/04 0:10, John Garry 写道:
> All the infrastructure has already been plumbed to support this for
> stacked devices, so just enable the request_queue limits features flag.
> 
> A note about chunk sectors for linear arrays:
> While it is possible to set a chunk sectors param for building a linear
> array, this is for specifying the granularity at which data sectors from
> the device are used. It is not the same as a stripe size, like for RAID0.
> 
> As such, it is not appropriate to set chunk_sectors request queue limit to
> the same value, as chunk_sectors request limit is a boundary for which
> requests cannot straddle.
> 
> However, request_queue limit max_hw_sectors is set to chunk sectors, which
> almost has the same effect as setting chunk_sectors limit.
> 
> Signed-off-by: John Garry <john.g.garry@oracle.com>
> 
> diff --git a/drivers/md/md-linear.c b/drivers/md/md-linear.c
> index 5d9b081153757..30ac29b990c9b 100644
> --- a/drivers/md/md-linear.c
> +++ b/drivers/md/md-linear.c
> @@ -74,6 +74,7 @@ static int linear_set_limits(struct mddev *mddev)
>   	lim.max_hw_sectors = mddev->chunk_sectors;
>   	lim.max_write_zeroes_sectors = mddev->chunk_sectors;
>   	lim.io_min = mddev->chunk_sectors << 9;
> +	lim.features |= BLK_FEAT_ATOMIC_WRITES;
>   	err = mddev_stack_rdev_limits(mddev, &lim, MDDEV_STACK_INTEGRITY);
>   	if (err)
>   		return err;
> 

LGRM
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Re: [PATCH] md/md-linear: Enable atomic writes
Posted by John Garry 1 week, 2 days ago 
On 05/09/2025 10:02, Yu Kuai wrote:
> 在 2025/09/04 0:10, John Garry 写道:
>> All the infrastructure has already been plumbed to support this for
>> stacked devices, so just enable the request_queue limits features flag.
>>
>> A note about chunk sectors for linear arrays:
>> While it is possible to set a chunk sectors param for building a linear
>> array, this is for specifying the granularity at which data sectors from
>> the device are used. It is not the same as a stripe size, like for RAID0.
>>
>> As such, it is not appropriate to set chunk_sectors request queue 
>> limit to
>> the same value, as chunk_sectors request limit is a boundary for which
>> requests cannot straddle.
>>
>> However, request_queue limit max_hw_sectors is set to chunk sectors, 
>> which
>> almost has the same effect as setting chunk_sectors limit.
>>
>> Signed-off-by: John Garry <john.g.garry@oracle.com>
>>
>> diff --git a/drivers/md/md-linear.c b/drivers/md/md-linear.c
>> index 5d9b081153757..30ac29b990c9b 100644
>> --- a/drivers/md/md-linear.c
>> +++ b/drivers/md/md-linear.c
>> @@ -74,6 +74,7 @@ static int linear_set_limits(struct mddev *mddev)
>>       lim.max_hw_sectors = mddev->chunk_sectors;
>>       lim.max_write_zeroes_sectors = mddev->chunk_sectors;
>>       lim.io_min = mddev->chunk_sectors << 9;
>> +    lim.features |= BLK_FEAT_ATOMIC_WRITES;
>>       err = mddev_stack_rdev_limits(mddev, &lim, MDDEV_STACK_INTEGRITY);
>>       if (err)
>>           return err;
>>
> 
> LGRM
> Reviewed-by: Yu Kuai <yukuai3@huawei.com>
> 

thanks

Could I have this picked up now? Maybe it was missed.
Re: [PATCH] md/md-linear: Enable atomic writes
Posted by Yu Kuai 1 week, 2 days ago 
Hi,

在 2025/09/23 16:21, John Garry 写道:
> On 05/09/2025 10:02, Yu Kuai wrote:
>> 在 2025/09/04 0:10, John Garry 写道:
>>> All the infrastructure has already been plumbed to support this for
>>> stacked devices, so just enable the request_queue limits features flag.
>>>
>>> A note about chunk sectors for linear arrays:
>>> While it is possible to set a chunk sectors param for building a linear
>>> array, this is for specifying the granularity at which data sectors from
>>> the device are used. It is not the same as a stripe size, like for 
>>> RAID0.
>>>
>>> As such, it is not appropriate to set chunk_sectors request queue 
>>> limit to
>>> the same value, as chunk_sectors request limit is a boundary for which
>>> requests cannot straddle.
>>>
>>> However, request_queue limit max_hw_sectors is set to chunk sectors, 
>>> which
>>> almost has the same effect as setting chunk_sectors limit.
>>>
>>> Signed-off-by: John Garry <john.g.garry@oracle.com>
>>>
>>> diff --git a/drivers/md/md-linear.c b/drivers/md/md-linear.c
>>> index 5d9b081153757..30ac29b990c9b 100644
>>> --- a/drivers/md/md-linear.c
>>> +++ b/drivers/md/md-linear.c
>>> @@ -74,6 +74,7 @@ static int linear_set_limits(struct mddev *mddev)
>>>       lim.max_hw_sectors = mddev->chunk_sectors;
>>>       lim.max_write_zeroes_sectors = mddev->chunk_sectors;
>>>       lim.io_min = mddev->chunk_sectors << 9;
>>> +    lim.features |= BLK_FEAT_ATOMIC_WRITES;
>>>       err = mddev_stack_rdev_limits(mddev, &lim, MDDEV_STACK_INTEGRITY);
>>>       if (err)
>>>           return err;
>>>
>>
>> LGRM
>> Reviewed-by: Yu Kuai <yukuai3@huawei.com>
>>
> 
> thanks
> 
> Could I have this picked up now? Maybe it was missed.
> 
Already picked last weekend, sorry that I forgot to reply.

https://git.kernel.org/pub/scm/linux/kernel/git/mdraid/linux.git/commit/?h=md-6.18&id=b481e72d24feac15017b579232370aa4b33d4129

Thanks,
Kuai
> .
>

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