linux-kernel - Re: [PATCH 11/12] device-dax: Add dis-contiguous resource support

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Date:   Thu, 26 Mar 2020 17:49:42 +0000
From:   Joao Martins <joao.m.martins@...cle.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Linux MM <linux-mm@...ck.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Christoph Hellwig <hch@....de>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 11/12] device-dax: Add dis-contiguous resource support

On 3/25/20 5:48 PM, Dan Williams wrote:
> On Wed, Mar 25, 2020 at 3:35 AM Joao Martins <joao.m.martins@...cle.com> wrote:
>> On 3/24/20 4:12 PM, Joao Martins wrote:
>>> On 3/23/20 11:55 PM, Dan Williams wrote:
>>>>  static ssize_t dev_dax_resize(struct dax_region *dax_region,
>>>>              struct dev_dax *dev_dax, resource_size_t size)
>>>>  {
>>>>      resource_size_t avail = dax_region_avail_size(dax_region), to_alloc;
>>>> -    resource_size_t dev_size = range_len(&dev_dax->range);
>>>> +    resource_size_t dev_size = dev_dax_size(dev_dax);
>>>>      struct resource *region_res = &dax_region->res;
>>>>      struct device *dev = &dev_dax->dev;
>>>> -    const char *name = dev_name(dev);
>>>>      struct resource *res, *first;
>>>> +    resource_size_t alloc = 0;
>>>> +    int rc;
>>>>
>>>>      if (dev->driver)
>>>>              return -EBUSY;
>>>> @@ -684,38 +766,47 @@ static ssize_t dev_dax_resize(struct dax_region *dax_region,
>>>>       * allocating a new resource.
>>>>       */
>>>>      first = region_res->child;
>>>> -    if (!first)
>>>> -            return __alloc_dev_dax_range(dev_dax, dax_region->res.start,
>>>> -                            to_alloc);
>>>
>>> You probably want to retain the condition above?
>>>
>>> Otherwise it removes the ability to create new devices or resizing it , once we
>>> have zero-ed the last one.
>>>
>>
>> A quick unit test that I had stashed here to help explain what I mean:
>>
>>         cd /sys/bus/dax/devices
>>         # dax0.0 is the only dax device in the corresponding dax_region
>>         echo dax0.0 > dax0.0/driver/unbind
>>         echo 0 > dax0.0/size
>>         # Shouldn't fail but returns -ENOSPC despite having
>>         # the full region available
>>         cat $(readlink -f dax0.0/../dax_region/available_size) > dax0.0/size
> 
> Thanks! Will incorporate that test before resending the series.
> 
I'll also add some of these tests (in ndctl.git:tests/daxctl-{devices.sh) as
part of my daxctl counterpart series (except using daxctl equivalent of the above).

	Joao