Re: [PATCH 01/11] powerpc/powernv/ioda: Fix ref count for devices with their own PE

[Andrew Donnellan <ajd@linux.ibm.com>]

On 9/9/19 5:45 pm, Frederic Barrat wrote:
> Taking a reference on the pci_dev structure was required with initial
> commit 184cd4a3b962 ("powerpc/powernv: PCI support for p7IOC under
> OPAL v2"), where we were storing the pci_dev in the pci_dn structure.
> 
> However, the pci_dev was later removed from the pci_dn structure, but
> the reference was kept. See commit 902bdc57451c ("powerpc/powernv/idoa:
> Remove unnecessary pcidev from pci_dn").
> 
> The pnv_ioda_pe structure life cycle is the same as the pci_dev
> structure, the PE is freed when the device is released. So we don't
> need a reference for the pci_dev stored in the PE, otherwise the
> pci_dev will never be released. Which is not really a surprise as the
> comment (removed here as no longer needed) was stating as much.
> 
> Fixes: 902bdc57451c ("powerpc/powernv/idoa: Remove unnecessary pcidev from pci_dn")
> Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
> ---
>   arch/powerpc/platforms/powernv/pci-ioda.c | 11 +----------
>   1 file changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index d8080558d020..92767f006f20 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -1062,14 +1062,6 @@ static struct pnv_ioda_pe *pnv_ioda_setup_dev_PE(struct pci_dev *dev)
>   		return NULL;
>   	}
>   
> -	/* NOTE: We get only one ref to the pci_dev for the pdn, not for the
> -	 * pointer in the PE data structure, both should be destroyed at the
> -	 * same time. However, this needs to be looked at more closely again
> -	 * once we actually start removing things (Hotplug, SR-IOV, ...)
> -	 *
> -	 * At some point we want to remove the PDN completely anyways
> -	 */
> -	pci_dev_get(dev);
>   	pdn->pe_number = pe->pe_number;
>   	pe->flags = PNV_IODA_PE_DEV;
>   	pe->pdev = dev;
> @@ -1084,7 +1076,6 @@ static struct pnv_ioda_pe *pnv_ioda_setup_dev_PE(struct pci_dev *dev)
>   		pnv_ioda_free_pe(pe);
>   		pdn->pe_number = IODA_INVALID_PE;
>   		pe->pdev = NULL;
> -		pci_dev_put(dev);
>   		return NULL;
>   	}
>   
> @@ -1228,7 +1219,7 @@ static struct pnv_ioda_pe *pnv_ioda_setup_npu_PE(struct pci_dev *npu_pdev)
>   			 */
>   			dev_info(&npu_pdev->dev,
>   				"Associating to existing PE %x\n", pe_num);
> -			pci_dev_get(npu_pdev);
> +			pci_dev_get(npu_pdev); // still needed after 902bdc57451c ?

Did you mean to leave that comment in?

>   			npu_pdn = pci_get_pdn(npu_pdev);
>   			rid = npu_pdev->bus->number << 8 | npu_pdn->devfn;
>   			npu_pdn->pe_number = pe_num;
> 

-- 
Andrew Donnellan              OzLabs, ADL Canberra
ajd@linux.ibm.com             IBM Australia Limited