This patchset is to avoid an unexpected situation when an interface's
namespace is being changed.
When interface's namespace is being changed, dev_change_net_namespace()
is called. This removes and re-allocates many resources that include
sysfs files. The "/net/class/net/<interface name>" is one of them.
If the sysfs creation routine(device_rename()) found duplicate sysfs
file name, it warns about it and fails. But unfortunately, at that point,
dev_change_net_namespace() doesn't return fail because rollback cost
is too high.
So, the interface can't have a sysfs file.
The approach of this patchset is to find the duplicate sysfs file as
fast as possible. If it found that, dev_change_net_namespace() returns
fail immediately with zero rollback cost.
1. The first patch is to add class_find_and_get_file_ns() helper function.
That function will be used for checking the existence of duplicate
sysfs file.
2. The second patch is to add netdev_class_has_file_ns().
That function is to check whether duplicate sysfs file in
the "/sys/class/net*" using class_find_and_get_file_ns().
3. The last patch is to avoid an unexpected situation.
a) If duplicate sysfs is existing, it fails as fast as possible in
the dev_change_net_namespace()
b) Acquire rtnl_lock() in both bond_create_sysfs() and bond_destroy_sysfs()
to avoid race condition.
c) Do not remove "/sys/class/net/bonding_masters" sysfs file by
bond_destroy_sysfs() if the file wasn't created by bond_create_sysfs().
Test commands#1:
ip netns add nst
ip link add bonding_masters type dummy
modprobe bonding
ip link set bonding_masters netns nst
Test commands#2:
ip link add bonding_masters type dummy
ls /sys/class/net
modprobe bonding
modprobe -rv bonding
ls /sys/class/net
After removing the bonding module, we can see the "bonding_masters"
interface's sysfs will be removed.
This is an unexpected situation.
Taehee Yoo (3):
class: add class_find_and_get_file_ns() helper function
net: core: add netdev_class_has_file_ns() helper function
net: core: avoid warning in dev_change_net_namespace()
drivers/base/class.c | 12 ++++++++++++
drivers/net/bonding/bond_sysfs.c | 13 ++++++++++++-
include/linux/device/class.h | 4 +++-
include/linux/netdevice.h | 2 +-
include/net/bonding.h | 1 +
net/core/dev.c | 4 ++++
net/core/net-sysfs.c | 13 +++++++++++++
7 files changed, 46 insertions(+), 3 deletions(-)
--
2.17.1
On Tue, Mar 24, 2020 at 12:30:41PM +0000, Taehee Yoo wrote:
> This patchset is to avoid an unexpected situation when an interface's
> namespace is being changed.
>
> When interface's namespace is being changed, dev_change_net_namespace()
> is called. This removes and re-allocates many resources that include
> sysfs files. The "/net/class/net/<interface name>" is one of them.
> If the sysfs creation routine(device_rename()) found duplicate sysfs
> file name, it warns about it and fails. But unfortunately, at that point,
> dev_change_net_namespace() doesn't return fail because rollback cost
> is too high.
> So, the interface can't have a sysfs file.
>
> The approach of this patchset is to find the duplicate sysfs file as
> fast as possible. If it found that, dev_change_net_namespace() returns
> fail immediately with zero rollback cost.
>
> 1. The first patch is to add class_find_and_get_file_ns() helper function.
> That function will be used for checking the existence of duplicate
> sysfs file.
> 2. The second patch is to add netdev_class_has_file_ns().
> That function is to check whether duplicate sysfs file in
> the "/sys/class/net*" using class_find_and_get_file_ns().
> 3. The last patch is to avoid an unexpected situation.
> a) If duplicate sysfs is existing, it fails as fast as possible in
> the dev_change_net_namespace()
> b) Acquire rtnl_lock() in both bond_create_sysfs() and bond_destroy_sysfs()
> to avoid race condition.
> c) Do not remove "/sys/class/net/bonding_masters" sysfs file by
> bond_destroy_sysfs() if the file wasn't created by bond_create_sysfs().
>
> Test commands#1:
> ip netns add nst
> ip link add bonding_masters type dummy
> modprobe bonding
> ip link set bonding_masters netns nst
>
> Test commands#2:
> ip link add bonding_masters type dummy
> ls /sys/class/net
> modprobe bonding
> modprobe -rv bonding
> ls /sys/class/net
>
> After removing the bonding module, we can see the "bonding_masters"
> interface's sysfs will be removed.
> This is an unexpected situation.
>
> Taehee Yoo (3):
> class: add class_find_and_get_file_ns() helper function
> net: core: add netdev_class_has_file_ns() helper function
> net: core: avoid warning in dev_change_net_namespace()
>
> drivers/base/class.c | 12 ++++++++++++
> drivers/net/bonding/bond_sysfs.c | 13 ++++++++++++-
> include/linux/device/class.h | 4 +++-
> include/linux/netdevice.h | 2 +-
> include/net/bonding.h | 1 +
> net/core/dev.c | 4 ++++
> net/core/net-sysfs.c | 13 +++++++++++++
> 7 files changed, 46 insertions(+), 3 deletions(-)
I don't seem to see patch 1/3 anywhere...
On Tue, 24 Mar 2020 at 22:28, Greg KH <[email protected]> wrote:
>
Hi Greg!
> On Tue, Mar 24, 2020 at 12:30:41PM +0000, Taehee Yoo wrote:
> > This patchset is to avoid an unexpected situation when an interface's
> > namespace is being changed.
> >
> > When interface's namespace is being changed, dev_change_net_namespace()
> > is called. This removes and re-allocates many resources that include
> > sysfs files. The "/net/class/net/<interface name>" is one of them.
> > If the sysfs creation routine(device_rename()) found duplicate sysfs
> > file name, it warns about it and fails. But unfortunately, at that point,
> > dev_change_net_namespace() doesn't return fail because rollback cost
> > is too high.
> > So, the interface can't have a sysfs file.
> >
> > The approach of this patchset is to find the duplicate sysfs file as
> > fast as possible. If it found that, dev_change_net_namespace() returns
> > fail immediately with zero rollback cost.
> >
> > 1. The first patch is to add class_find_and_get_file_ns() helper function.
> > That function will be used for checking the existence of duplicate
> > sysfs file.
> > 2. The second patch is to add netdev_class_has_file_ns().
> > That function is to check whether duplicate sysfs file in
> > the "/sys/class/net*" using class_find_and_get_file_ns().
> > 3. The last patch is to avoid an unexpected situation.
> > a) If duplicate sysfs is existing, it fails as fast as possible in
> > the dev_change_net_namespace()
> > b) Acquire rtnl_lock() in both bond_create_sysfs() and bond_destroy_sysfs()
> > to avoid race condition.
> > c) Do not remove "/sys/class/net/bonding_masters" sysfs file by
> > bond_destroy_sysfs() if the file wasn't created by bond_create_sysfs().
> >
> > Test commands#1:
> > ip netns add nst
> > ip link add bonding_masters type dummy
> > modprobe bonding
> > ip link set bonding_masters netns nst
> >
> > Test commands#2:
> > ip link add bonding_masters type dummy
> > ls /sys/class/net
> > modprobe bonding
> > modprobe -rv bonding
> > ls /sys/class/net
> >
> > After removing the bonding module, we can see the "bonding_masters"
> > interface's sysfs will be removed.
> > This is an unexpected situation.
> >
> > Taehee Yoo (3):
> > class: add class_find_and_get_file_ns() helper function
> > net: core: add netdev_class_has_file_ns() helper function
> > net: core: avoid warning in dev_change_net_namespace()
> >
> > drivers/base/class.c | 12 ++++++++++++
> > drivers/net/bonding/bond_sysfs.c | 13 ++++++++++++-
> > include/linux/device/class.h | 4 +++-
> > include/linux/netdevice.h | 2 +-
> > include/net/bonding.h | 1 +
> > net/core/dev.c | 4 ++++
> > net/core/net-sysfs.c | 13 +++++++++++++
> > 7 files changed, 46 insertions(+), 3 deletions(-)
>
> I don't seem to see patch 1/3 anywhere...
>
I don't know why the first patch was lost.
Below is the lkml link.
https://lkml.org/lkml/2020/3/24/576
I will resend the first patch.
Thank you!
Taehee Yoo