linux-kernel - Re: [PATCH v3 20/51] PCI: Skip must+optional if there is no optional addon

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Date:	Tue, 18 Aug 2015 15:39:05 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	David Miller <davem@...emloft.net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Wei Yang <weiyang@...ux.vnet.ibm.com>, TJ <linux@....tj>,
	Yijing Wang <wangyijing@...wei.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 20/51] PCI: Skip must+optional if there is no optional addon

On Mon, Aug 17, 2015 at 4:56 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Mon, Jul 27, 2015 at 04:29:38PM -0700, Yinghai Lu wrote:
>> If the bridge does not support hotplug or no child with sriov support
>> we could get out early and don't try must+optional allocation.
>
> You mention non-hotplug bridges and non-SR-IOV devices, but I can't figure
> out how the patch itself relates to those.  How can I connect them?

in setup that does not support hotplug and sriov, then we will not
have optional resources.

>
>> Also in the loop that update res with optional add info, skip resource
>> that add_size is 0.
>>
>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>> ---
>>  drivers/pci/setup-bus.c | 32 +++++++++++++++++++++++++++++---
>>  1 file changed, 29 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
>> index d1f9e19..64ef516 100644
>> --- a/drivers/pci/setup-bus.c
>> +++ b/drivers/pci/setup-bus.c
>> @@ -450,6 +450,24 @@ static bool pci_need_to_release(unsigned long mask, struct resource *res)
>>       return false;   /* should not get here */
>>  }
>>
>> +static bool __has_addon(struct list_head *head,
>> +                     struct list_head *realloc_head)
>
> Why does this have a "__" prefix?

Sorry, will remove that.

>
>> +{
>> +     int add_count = 0;
>> +     struct pci_dev_resource *dev_res, *tmp_res;
>> +
>> +     /* check if we have add really */
>> +     list_for_each_entry(dev_res, head, list) {
>> +             tmp_res = res_to_dev_res(realloc_head, dev_res->res);
>> +             if (!tmp_res || !tmp_res->add_size)
>> +                     continue;
>> +
>> +             add_count++;
>> +     }
>> +
>> +     return add_count != 0;
>> +}
>> +
>>  static bool save_resources(struct list_head *head,
>>                          struct list_head *save_head)
>>  {
>> @@ -481,16 +499,24 @@ static bool __assign_resources_must_add_sorted(struct list_head *head,
>>       struct pci_dev_resource *save_res;
>>       struct pci_dev_resource *dev_res, *tmp_res;
>>       unsigned long fail_type;
>> -     resource_size_t add_align;
>> +     resource_size_t add_align, add_size;
>>       struct resource *res;
>>
>> +     if (!__has_addon(head, realloc_head))
>> +             return false;
>> +
>>       if (!save_resources(head, &save_head))
>>               return false;
>>
>>       /* Update res in head list with add_size in realloc_head list */
>>       list_for_each_entry(dev_res, head, list) {
>>               res = dev_res->res;
>> -             res->end += get_res_add_size(realloc_head, res);
>> +             add_size = get_res_add_size(realloc_head, res);
>> +
>> +             if (!add_size)
>> +                     continue;
>> +
>> +             res->end += add_size;
>>
>>               /*
>>                * There are two kinds of additional resources in the list:
>> @@ -578,7 +604,7 @@ static void __assign_resources_sorted(struct list_head *head,
>>        */
>>
>>       /* Check must+optional add */
>> -     if (realloc_head && !list_empty(realloc_head) &&
>> +     if (realloc_head &&
>
> Why are you dropping the !list_empty() test?

count in __has_addon() will be 0, so we can skip checking here.

>
>>           __assign_resources_must_add_sorted(head, realloc_head))
>>               return;
>>
>> --
>> 1.8.4.5
>>
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