Re: kernel 4.1-rc7 deadlock
by Josh Boyer
On Mon, Jun 15, 2015 at 5:58 AM, Morten Stevens
<mstevens(a)fedoraproject.org> wrote:
> Hi Josh,
>
> Could you please add this patch to the 4.1-rc8 kernel for rawhide?
>
> https://lkml.org/lkml/2015/6/14/169
Done. I'd been watching that thread as well.
As an aside, it is better to send such requests to the Fedora kernel
list (CC'd now.) That way everyone sees it and it doesn't get lost in
someone's inbox.
josh
> mm: shmem_zero_setup skip security check and lockdep conflict with XFS
>
> It appears that, at some point last year, XFS made directory handling
> changes which bring it into lockdep conflict with shmem_zero_setup():
> it is surprising that mmap() can clone an inode while holding mmap_sem,
> but that has been so for many years.
>
> Since those few lockdep traces that I've seen all implicated selinux,
> I'm hoping that we can use the __shmem_file_setup(,,,S_PRIVATE) which
> v3.13's commit c7277090927a ("security: shmem: implement kernel private
> shmem inodes") introduced to avoid LSM checks on kernel-internal inodes:
> the mmap("/dev/zero") cloned inode is indeed a kernel-internal detail.
>
> This also covers the !CONFIG_SHMEM use of ramfs to support /dev/zero
> (and MAP_SHARED|MAP_ANONYMOUS). I thought there were also drivers
> which cloned inode in mmap(), but if so, I cannot locate them now.
> Reported-and-tested-by: Prarit Bhargava <prarit(a)redhat.com>
> Reported-by: Daniel Wagner <wagi(a)monom.org>
> Reported-by: Morten Stevens <mstevens(a)fedoraproject.org>
> Signed-off-by: Hugh Dickins <hughd(a)google.com>
> ---
> mm/shmem.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
> --- 4.1-rc7/mm/shmem.c 2015-04-26 19:16:31.352191298 -0700
> +++ linux/mm/shmem.c 2015-06-14 09:26:49.461120166 -0700
> @@ -3401,7 +3401,13 @@ int shmem_zero_setup(struct vm_area_stru
> struct file *file;
> loff_t size = vma->vm_end - vma->vm_start;
>
> - file = shmem_file_setup("dev/zero", size, vma->vm_flags);
> + /*
> + * Cloning a new file under mmap_sem leads to a lock ordering
> conflict
> + * between XFS directory reading and selinux: since this file is
> only
> + * accessible to the user through its mapping, use S_PRIVATE flag to
> + * bypass file security, in the same way as
> shmem_kernel_file_setup().
> + */
> + file = __shmem_file_setup("dev/zero", size, vma->vm_flags,
> S_PRIVATE);
> if (IS_ERR(file))
> return PTR_ERR(file);
>
>
> Thank you,
>
> Best regards,
>
> Morten
8 years, 3 months
fedora 14 kernel performance with ip forwarding workload
by Jesse Brandeburg
The other day I was running the stock fedora kernel on my ip
forwarding setup, to see what the performance was, and the performance
wasn't very good.
system is S5520HC dual socket 2.93GHz Xeon 5570 (Nehalem) with 3 quad
port 82580 adapters (12 ports). Traffic is bidirectional 64 byte
packets being forwarded and received on each port, basically port to
port routing. I am only using 12 flows currently.
The driver is igb, and I am using an affinity script that lines up
each pair of ports that are forwarding traffic into optimal
configurations for cache locality. I am also disabling
remote_node_defrag_ratio to stop cross node traffic.
With the fedora default kernel from F14 it appears that
CONFIG_NETFILTER=y means that I cannot unload all of netfilter even if
I stop iptables service.
perf showed netfilter being prominent, and removing it gives me much
higher throughput. Is there a reason CONFIG_NETFILTER=y ? Isn't it a
good thing to be able to disable netfilter if you want to?
Jesse
8 years, 4 months
