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    SubjectRe: [PATCH -v3 40/47] PCI: Add pci bus removal through /sys/.../pci_bus/.../remove
    Hi Yinghai,
    I found many other drivers assume that a pci bus won't disappear if
    the corresponding PCI bridge device still exists. The sysfs interface proposed
    here breaks that assumption and may cause many access-after-free issues.
    So what's the purpose of this interface? Should we remove this interface or
    enhance other drivers to avoid invalid memory access issues?
    Thanks!
    Gerry

    On 03/19/2012 01:46 PM, Yinghai Lu wrote:
    > it supports both pci root bus and pci bus under pci bridge.
    >
    > -v2: Change to three returns way in dev_bus_remove_store.
    >
    > Signed-off-by: Yinghai Lu <yinghai@kernel.org>
    > Cc: Randy Dunlap <rdunlap@xenotime.net>
    > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    > Cc: linux-doc@vger.kernel.org
    > ---
    > Documentation/ABI/testing/sysfs-bus-pci | 8 ++++++++
    > drivers/pci/pci-sysfs.c | 30 ++++++++++++++++++++++++++++++
    > 2 files changed, 38 insertions(+), 0 deletions(-)
    >
    > diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
    > index 95f0f37..22392de 100644
    > --- a/Documentation/ABI/testing/sysfs-bus-pci
    > +++ b/Documentation/ABI/testing/sysfs-bus-pci
    > @@ -92,6 +92,14 @@ Description:
    > hot-remove the PCI device and any of its children.
    > Depends on CONFIG_HOTPLUG.
    >
    > +What: /sys/bus/pci/devices/.../pci_bus/.../remove
    > +Date: March 2012
    > +Contact: Linux PCI developers <linux-pci@vger.kernel.org>
    > +Description:
    > + Writing a non-zero value to this attribute will
    > + hot-remove the PCI bus and any of its children.
    > + Depends on CONFIG_HOTPLUG.
    > +
    > What: /sys/bus/pci/devices/.../pci_bus/.../rescan
    > Date: May 2011
    > Contact: Linux PCI developers <linux-pci@vger.kernel.org>
    > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
    > index d33a1bc..afba77b 100644
    > --- a/drivers/pci/pci-sysfs.c
    > +++ b/drivers/pci/pci-sysfs.c
    > @@ -391,6 +391,35 @@ remove_store(struct device *dev, struct device_attribute *dummy,
    > return count;
    > }
    >
    > +static void bus_remove_callback(struct device *dev)
    > +{
    > + struct pci_bus *bus = to_pci_bus(dev);
    > +
    > + mutex_lock(&pci_remove_rescan_mutex);
    > + pci_stop_and_remove_bus(bus);
    > + mutex_unlock(&pci_remove_rescan_mutex);
    > +}
    > +static ssize_t
    > +dev_bus_remove_store(struct device *dev, struct device_attribute *attr,
    > + const char *buf, size_t count)
    > +{
    > + int err;
    > + unsigned long val;
    > +
    > + if (kstrtoul(buf, 0, &val) < 0)
    > + return -EINVAL;
    > +
    > + if (!val)
    > + return count;
    > +
    > + err = device_schedule_callback(dev, bus_remove_callback);
    > +
    > + if (err)
    > + return err;
    > +
    > + return count;
    > +}
    > +
    > static void bus_rescan_callback(struct device *dev)
    > {
    > struct pci_bus *bus = to_pci_bus(dev);
    > @@ -450,6 +479,7 @@ struct device_attribute pci_dev_attrs[] = {
    > struct device_attribute pcibus_dev_attrs[] = {
    > #ifdef CONFIG_HOTPLUG
    > __ATTR(rescan, (S_IWUSR|S_IWGRP), NULL, dev_bus_rescan_store),
    > + __ATTR(remove, (S_IWUSR|S_IWGRP), NULL, dev_bus_remove_store),
    > #endif
    > __ATTR(cpuaffinity, S_IRUGO, pci_bus_show_cpumaskaffinity, NULL),
    > __ATTR(cpulistaffinity, S_IRUGO, pci_bus_show_cpulistaffinity, NULL),



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