On Fri, Apr 10, 2015 at 04:53:04PM +0800, Wei Yang wrote:
> Each VF will get a reference to its PF, while it is not returned back in
> all cases and leave a removed PF's pci_dev un-released.
>
> As commit ac205b7b ("PCI: make sriov work with hotplug remove") indicates,
> when removing devices on a bus, we do it in the reverse order. This means
> we would remove VFs first, then PFs. After doing so, VF's removal is done
> with pci_stop_and_remove_bus_device() instead of virtfn_remove().
> virtfn_remove() returns the reference of its PF, while
> pci_stop_and_remove_bus_device() doesn't.
Please use conventional citation style (12-char SHA1).
ac205b7bb72f appeared in v3.4. Did that commit cause a regression?
Should this patch be marked for stable?
"After doing so, VF removal is done with pci_stop_and_remove_device() ..."
After doing what? After removing the VFs and PFs? After commit
ac205b7bb72f?
Prior to your patch, the VF reference was released in virtfn_remove(),
which is only called via pci_disable_sriov(). This typically happens in
a driver .remove() method. The reference is *not* released if we call
pci_stop_and_remove_bus_device(VF) directly, as we would via the
remove_store() (sysfs "remove" file) or hot unplug paths, e.g.,
pciehp_unconfigure_device().
After your patch, the VF reference is released in pci_destroy_dev(). This
is called from pci_disable_sriov(), so it happens in that path as before.
But pci_destroy_dev() is called from pci_stop_and_remove_bus_device(), so
the reference is now released for all the paths that use
pci_stop_and_remove_bus_device().
What about the other things done in virtfn_remove(), e.g., the sysfs link
removal? Your patch fixes a reference count leak, but don't we still have
a sysfs link leak?
It would be useful to mention a way to cause the leak. I suspect writing
to a VF's sysfs "remove" file is the easiest.
> This patches moves the return of PF's reference to pci_destroy_dev() to
> make sure the PF's pci_dev is released in any case.
>
> Signed-off-by: Wei Yang <weiyang@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/pci/iov.c | 1 -
> drivers/pci/remove.c | 5 +++++
> 2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 4b3a4ea..9b04bde 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -167,7 +167,6 @@ static void virtfn_remove(struct pci_dev *dev, int id, int reset)
>
> /* balance pci_get_domain_bus_and_slot() */
> pci_dev_put(virtfn);
> - pci_dev_put(dev);
> }
>
> static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
> diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
> index 8bd76c9..836ddf6 100644
> --- a/drivers/pci/remove.c
> +++ b/drivers/pci/remove.c
> @@ -41,6 +41,11 @@ static void pci_destroy_dev(struct pci_dev *dev)
> list_del(&dev->bus_list);
> up_write(&pci_bus_sem);
>
> +#ifdef CONFIG_PCI_IOV
> + if (dev->is_virtfn)
> + pci_dev_put(dev->physfn);
> +#endif
> +
> pci_free_resources(dev);
> put_device(&dev->dev);
> }
> --
> 1.7.9.5
>
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