Sometimes the kernel doesn't take full advantage of system memory
bandwidth, leading to a single CPU spending excessive time in
initialization paths where the data scales with memory size.
Multithreading naturally addresses this problem.
Extend padata, a framework that handles many parallel yet singlethreaded
jobs, to also handle multithreaded jobs by adding support for splitting up
the work evenly, specifying a minimum amount of work that's appropriate
for one helper thread to do, load balancing between helpers, and
coordinating them.
This is inspired by work from Pavel Tatashin and Steve Sistare.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Josh Triplett <josh@joshtriplett.org>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Robert Elliott <elliott@hpe.com>
Cc: Shile Zhang <shile.zhang@linux.alibaba.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Link: http://lkml.kernel.org/r/20200527173608.2885243-5-daniel.m.jordan@oracle.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
padata allocates per-CPU, per-instance work structs for parallel jobs. A
do_parallel call assigns a job to a sequence number and hashes the number
to a CPU, where the job will eventually run using the corresponding work.
This approach fit with how padata used to bind a job to each CPU
round-robin, makes less sense after commit bfde23ce20 ("padata: unbind
parallel jobs from specific CPUs") because a work isn't bound to a
particular CPU anymore, and isn't needed at all for multithreaded jobs
because they don't have sequence numbers.
Replace the per-CPU works with a preallocated pool, which allows sharing
them between existing padata users and the upcoming multithreaded user.
The pool will also facilitate setting NUMA-aware concurrency limits with
later users.
The pool is sized according to the number of possible CPUs. With this
limit, MAX_OBJ_NUM no longer makes sense, so remove it.
If the global pool is exhausted, a parallel job is run in the current task
instead to throttle a system trying to do too much in parallel.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Josh Triplett <josh@joshtriplett.org>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Robert Elliott <elliott@hpe.com>
Cc: Shile Zhang <shile.zhang@linux.alibaba.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Link: http://lkml.kernel.org/r/20200527173608.2885243-4-daniel.m.jordan@oracle.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
padata will soon initialize the system's struct pages in parallel, so it
needs to be ready by page_alloc_init_late().
The error return from padata_driver_init() triggers an initcall warning,
so add a warning to padata_init() to avoid silent failure.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Josh Triplett <josh@joshtriplett.org>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Robert Elliott <elliott@hpe.com>
Cc: Shile Zhang <shile.zhang@linux.alibaba.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Link: http://lkml.kernel.org/r/20200527173608.2885243-3-daniel.m.jordan@oracle.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "padata: parallelize deferred page init", v3.
Deferred struct page init is a bottleneck in kernel boot--the biggest for
us and probably others. Optimizing it maximizes availability for
large-memory systems and allows spinning up short-lived VMs as needed
without having to leave them running. It also benefits bare metal
machines hosting VMs that are sensitive to downtime. In projects such as
VMM Fast Restart[1], where guest state is preserved across kexec reboot,
it helps prevent application and network timeouts in the guests.
So, multithread deferred init to take full advantage of system memory
bandwidth.
Extend padata, a framework that handles many parallel singlethreaded jobs,
to handle multithreaded jobs as well by adding support for splitting up
the work evenly, specifying a minimum amount of work that's appropriate
for one helper thread to do, load balancing between helpers, and
coordinating them. More documentation in patches 4 and 8.
This series is the first step in a project to address other memory
proportional bottlenecks in the kernel such as pmem struct page init, vfio
page pinning, hugetlb fallocate, and munmap. Deferred page init doesn't
require concurrency limits, resource control, or priority adjustments like
these other users will because it happens during boot when the system is
otherwise idle and waiting for page init to finish.
This has been run on a variety of x86 systems and speeds up kernel boot by
4% to 49%, saving up to 1.6 out of 4 seconds. Patch 6 has more numbers.
This patch (of 8):
padata_driver_exit() is unnecessary because padata isn't built as a module
and doesn't exit.
padata's init routine will soon allocate memory, so getting rid of the
exit function now avoids pointless code to free it.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Josh Triplett <josh@joshtriplett.org>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Robert Elliott <elliott@hpe.com>
Cc: Shile Zhang <shile.zhang@linux.alibaba.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Link: http://lkml.kernel.org/r/20200527173608.2885243-1-daniel.m.jordan@oracle.com
Link: http://lkml.kernel.org/r/20200527173608.2885243-2-daniel.m.jordan@oracle.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Removing the pcrypt module triggers this:
general protection fault, probably for non-canonical
address 0xdead000000000122
CPU: 5 PID: 264 Comm: modprobe Not tainted 5.6.0+ #2
Hardware name: QEMU Standard PC
RIP: 0010:__cpuhp_state_remove_instance+0xcc/0x120
Call Trace:
padata_sysfs_release+0x74/0xce
kobject_put+0x81/0xd0
padata_free+0x12/0x20
pcrypt_exit+0x43/0x8ee [pcrypt]
padata instances wrongly use the same hlist node for the online and dead
states, so __padata_free()'s second cpuhp remove call chokes on the node
that the first poisoned.
cpuhp multi-instance callbacks only walk forward in cpuhp_step->list and
the same node is linked in both the online and dead lists, so the list
corruption that results from padata_alloc() adding the node to a second
list without removing it from the first doesn't cause problems as long
as no instances are freed.
Avoid the issue by giving each state its own node.
Fixes: 894c9ef978 ("padata: validate cpumask without removed CPU during offline")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Simplify the error handling in pcrypt_create_aead() by taking advantage
of crypto_grab_aead() now handling an ERR_PTR() name and by taking
advantage of crypto_drop_aead() now accepting (as a no-op) a spawn that
hasn't been grabbed yet.
This required also making padata_free_shell() accept a NULL argument.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
According to Geert's report[0],
kernel/padata.c: warning: 'err' may be used uninitialized in this
function [-Wuninitialized]: => 539:2
Warning is seen only with older compilers on certain archs. The
runtime effect is potentially returning garbage down the stack when
padata's cpumasks are modified before any pcrypt requests have run.
Simplest fix is to initialize err to the success value.
[0] http://lkml.kernel.org/r/20200210135506.11536-1-geert@linux-m68k.org
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Fixes: bbefa1dd6a ("crypto: pcrypt - Avoid deadlock by using per-instance padata queues")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Remove references to unused functions, standardize language, update to
reflect new functionality, migrate to rst format, and fix all kernel-doc
warnings.
Fixes: 815613da6a ("kernel/padata.c: removed unused code")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
reorder_objects is unused since the rework of padata's flushing, so
remove it.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Since commit 63d3578892 ("crypto: pcrypt - remove padata cpumask
notifier") this feature is unused, so get rid of it.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
lockdep complains when padata's paths to update cpumasks via CPU hotplug
and sysfs are both taken:
# echo 0 > /sys/devices/system/cpu/cpu1/online
# echo ff > /sys/kernel/pcrypt/pencrypt/parallel_cpumask
======================================================
WARNING: possible circular locking dependency detected
5.4.0-rc8-padata-cpuhp-v3+ #1 Not tainted
------------------------------------------------------
bash/205 is trying to acquire lock:
ffffffff8286bcd0 (cpu_hotplug_lock.rw_sem){++++}, at: padata_set_cpumask+0x2b/0x120
but task is already holding lock:
ffff8880001abfa0 (&pinst->lock){+.+.}, at: padata_set_cpumask+0x26/0x120
which lock already depends on the new lock.
padata doesn't take cpu_hotplug_lock and pinst->lock in a consistent
order. Which should be first? CPU hotplug calls into padata with
cpu_hotplug_lock already held, so it should have priority.
Fixes: 6751fb3c0e ("padata: Use get_online_cpus/put_online_cpus")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Configuring an instance's parallel mask without any online CPUs...
echo 2 > /sys/kernel/pcrypt/pencrypt/parallel_cpumask
echo 0 > /sys/devices/system/cpu/cpu1/online
...makes tcrypt mode=215 crash like this:
divide error: 0000 [#1] SMP PTI
CPU: 4 PID: 283 Comm: modprobe Not tainted 5.4.0-rc8-padata-doc-v2+ #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20191013_105130-anatol 04/01/2014
RIP: 0010:padata_do_parallel+0x114/0x300
Call Trace:
pcrypt_aead_encrypt+0xc0/0xd0 [pcrypt]
crypto_aead_encrypt+0x1f/0x30
do_mult_aead_op+0x4e/0xdf [tcrypt]
test_mb_aead_speed.constprop.0.cold+0x226/0x564 [tcrypt]
do_test+0x28c2/0x4d49 [tcrypt]
tcrypt_mod_init+0x55/0x1000 [tcrypt]
...
cpumask_weight() in padata_cpu_hash() returns 0 because the mask has no
CPUs. The problem is __padata_remove_cpu() checks for valid masks too
early and so doesn't mark the instance PADATA_INVALID as expected, which
would have made padata_do_parallel() return error before doing the
division.
Fix by introducing a second padata CPU hotplug state before
CPUHP_BRINGUP_CPU so that __padata_remove_cpu() sees the online mask
without @cpu. No need for the second argument to padata_replace() since
@cpu is now already missing from the online mask.
Fixes: 33e5445068 ("padata: Handle empty padata cpumasks")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
If the pcrypt template is used multiple times in an algorithm, then a
deadlock occurs because all pcrypt instances share the same
padata_instance, which completes requests in the order submitted. That
is, the inner pcrypt request waits for the outer pcrypt request while
the outer request is already waiting for the inner.
This patch fixes this by allocating a set of queues for each pcrypt
instance instead of using two global queues. In order to maintain
the existing user-space interface, the pinst structure remains global
so any sysfs modifications will apply to every pcrypt instance.
Note that when an update occurs we have to allocate memory for
every pcrypt instance. Should one of the allocations fail we
will abort the update without rolling back changes already made.
The new per-instance data structure is called padata_shell and is
essentially a wrapper around parallel_data.
Reproducer:
#include <linux/if_alg.h>
#include <sys/socket.h>
#include <unistd.h>
int main()
{
struct sockaddr_alg addr = {
.salg_type = "aead",
.salg_name = "pcrypt(pcrypt(rfc4106-gcm-aesni))"
};
int algfd, reqfd;
char buf[32] = { 0 };
algfd = socket(AF_ALG, SOCK_SEQPACKET, 0);
bind(algfd, (void *)&addr, sizeof(addr));
setsockopt(algfd, SOL_ALG, ALG_SET_KEY, buf, 20);
reqfd = accept(algfd, 0, 0);
write(reqfd, buf, 32);
read(reqfd, buf, 16);
}
Reported-by: syzbot+56c7151cad94eec37c521f0e47d2eee53f9361c4@syzkaller.appspotmail.com
Fixes: 5068c7a883 ("crypto: pcrypt - Add pcrypt crypto parallelization wrapper")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The function padata_remove_cpu was supposed to have been removed
along with padata_add_cpu but somehow it remained behind. Let's
kill it now as it doesn't even have a prototype anymore.
Fixes: 815613da6a ("kernel/padata.c: removed unused code")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The function padata_flush_queues is fundamentally broken because
it cannot force padata users to complete the request that is
underway. IOW padata has to passively wait for the completion
of any outstanding work.
As it stands flushing is used in two places. Its use in padata_stop
is simply unnecessary because nothing depends on the queues to
be flushed afterwards.
The other use in padata_replace is more substantial as we depend
on it to free the old pd structure. This patch instead uses the
pd->refcnt to dynamically free the pd structure once all requests
are complete.
Fixes: 2b73b07ab8 ("padata: Flush the padata queues actively")
Cc: <stable@vger.kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
With the removal of the ENODATA case from padata_get_next, the cpu_index
field is no longer useful, so it can go away.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Padata binds the parallel part of a job to a single CPU and round-robins
over all CPUs in the system for each successive job. Though the serial
parts rely on per-CPU queues for correct ordering, they're not necessary
for parallel work, and it improves performance to run the job locally on
NUMA machines and let the scheduler pick the CPU within a node on a busy
system.
So, make the parallel workqueue unbound.
Update the parallel workqueue's cpumask when the instance's parallel
cpumask changes.
Now that parallel jobs no longer run on max_active=1 workqueues, two or
more parallel works that hash to the same CPU may run simultaneously,
finish out of order, and so be serialized out of order. Prevent this by
keeping the works sorted on the reorder list by sequence number and
checking that in the reordering logic.
padata_get_next becomes padata_find_next so it can be reused for the end
of padata_reorder, where it's used to avoid uselessly queueing work when
the next job by sequence number isn't finished yet but a later job that
hashed to the same CPU has.
The ENODATA case in padata_find_next no longer makes sense because
parallel jobs aren't bound to specific CPUs. The EINPROGRESS case takes
care of the scenario where a parallel job is potentially running on the
same CPU as padata_find_next, and with only one error code left, just
use NULL instead.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
padata currently uses one per-CPU workqueue per instance for all work.
Prepare for running parallel jobs on an unbound workqueue by introducing
dedicated workqueues for parallel and serial work.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
With pcrypt's cpumask no longer used, take the CPU hotplug lock inside
padata_alloc_possible.
Useful later in the series for avoiding nested acquisition of the CPU
hotplug lock in padata when padata_alloc_possible is allocating an
unbound workqueue.
Without this patch, this nested acquisition would happen later in the
series:
pcrypt_init_padata
get_online_cpus
alloc_padata_possible
alloc_padata
alloc_workqueue(WQ_UNBOUND) // later in the series
alloc_and_link_pwqs
apply_wqattrs_lock
get_online_cpus // recursive rwsem acquisition
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
padata_do_parallel currently returns -EINVAL if the callback CPU isn't
in the callback cpumask.
pcrypt tries to prevent this situation by keeping its own callback
cpumask in sync with padata's and checks that the callback CPU it passes
to padata is valid. Make padata handle this instead.
padata_do_parallel now takes a pointer to the callback CPU and updates
it for the caller if an alternate CPU is used. Overall behavior in
terms of which callback CPUs are chosen stays the same.
Prepares for removal of the padata cpumask notifier in pcrypt, which
will fix a lockdep complaint about nested acquisition of the CPU hotplug
lock later in the series.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Move workqueue allocation inside of padata to prepare for further
changes to how padata uses workqueues.
Guarantees the workqueue is created with max_active=1, which padata
relies on to work correctly. No functional change.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: linux-crypto@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Exercising CPU hotplug on a 5.2 kernel with recent padata fixes from
cryptodev-2.6.git in an 8-CPU kvm guest...
# modprobe tcrypt alg="pcrypt(rfc4106(gcm(aes)))" type=3
# echo 0 > /sys/devices/system/cpu/cpu1/online
# echo c > /sys/kernel/pcrypt/pencrypt/parallel_cpumask
# modprobe tcrypt mode=215
...caused the following crash:
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 2 PID: 134 Comm: kworker/2:2 Not tainted 5.2.0-padata-base+ #7
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-<snip>
Workqueue: pencrypt padata_parallel_worker
RIP: 0010:padata_reorder+0xcb/0x180
...
Call Trace:
padata_do_serial+0x57/0x60
pcrypt_aead_enc+0x3a/0x50 [pcrypt]
padata_parallel_worker+0x9b/0xe0
process_one_work+0x1b5/0x3f0
worker_thread+0x4a/0x3c0
...
In padata_alloc_pd, pd->cpu is set using the user-supplied cpumask
instead of the effective cpumask, and in this case cpumask_first picked
an offline CPU.
The offline CPU's reorder->list.next is NULL in padata_reorder because
the list wasn't initialized in padata_init_pqueues, which only operates
on CPUs in the effective mask.
Fix by using the effective mask in padata_alloc_pd.
Fixes: 6fc4dbcf02 ("padata: Replace delayed timer with immediate workqueue in padata_reorder")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
With the removal of the padata timer, padata_do_serial no longer
needs special CPU handling, so remove it.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The function padata_reorder will use a timer when it cannot progress
while completed jobs are outstanding (pd->reorder_objects > 0). This
is suboptimal as if we do end up using the timer then it would have
introduced a gratuitous delay of one second.
In fact we can easily distinguish between whether completed jobs
are outstanding and whether we can make progress. All we have to
do is look at the next pqueue list.
This patch does that by replacing pd->processed with pd->cpu so
that the next pqueue is more accessible.
A work queue is used instead of the original try_again to avoid
hogging the CPU.
Note that we don't bother removing the work queue in
padata_flush_queues because the whole premise is broken. You
cannot flush async crypto requests so it makes no sense to even
try. A subsequent patch will fix it by replacing it with a ref
counting scheme.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Testing padata with the tcrypt module on a 5.2 kernel...
# modprobe tcrypt alg="pcrypt(rfc4106(gcm(aes)))" type=3
# modprobe tcrypt mode=211 sec=1
...produces this splat:
INFO: task modprobe:10075 blocked for more than 120 seconds.
Not tainted 5.2.0-base+ #16
modprobe D 0 10075 10064 0x80004080
Call Trace:
? __schedule+0x4dd/0x610
? ring_buffer_unlock_commit+0x23/0x100
schedule+0x6c/0x90
schedule_timeout+0x3b/0x320
? trace_buffer_unlock_commit_regs+0x4f/0x1f0
wait_for_common+0x160/0x1a0
? wake_up_q+0x80/0x80
{ crypto_wait_req } # entries in braces added by hand
{ do_one_aead_op }
{ test_aead_jiffies }
test_aead_speed.constprop.17+0x681/0xf30 [tcrypt]
do_test+0x4053/0x6a2b [tcrypt]
? 0xffffffffa00f4000
tcrypt_mod_init+0x50/0x1000 [tcrypt]
...
The second modprobe command never finishes because in padata_reorder,
CPU0's load of reorder_objects is executed before the unlocking store in
spin_unlock_bh(pd->lock), causing CPU0 to miss CPU1's increment:
CPU0 CPU1
padata_reorder padata_do_serial
LOAD reorder_objects // 0
INC reorder_objects // 1
padata_reorder
TRYLOCK pd->lock // failed
UNLOCK pd->lock
CPU0 deletes the timer before returning from padata_reorder and since no
other job is submitted to padata, modprobe waits indefinitely.
Add a pair of full barriers to guarantee proper ordering:
CPU0 CPU1
padata_reorder padata_do_serial
UNLOCK pd->lock
smp_mb()
LOAD reorder_objects
INC reorder_objects
smp_mb__after_atomic()
padata_reorder
TRYLOCK pd->lock
smp_mb__after_atomic is needed so the read part of the trylock operation
comes after the INC, as Andrea points out. Thanks also to Andrea for
help with writing a litmus test.
Fixes: 16295bec63 ("padata: Generic parallelization/serialization interface")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: <stable@vger.kernel.org>
Cc: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-arch@vger.kernel.org
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The kobj_type default_attrs field is being replaced by the
default_groups field. Replace padata_attr_type's default_attrs field
with default_groups and use the ATTRIBUTE_GROUPS macro to create
padata_default_groups.
This patch was tested by loading the pcrypt module and verifying that
the sysfs files for the attributes in the default groups were created.
Signed-off-by: Kimberly Brown <kimbrownkd@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Trivial fix to clean up an indentation issue
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Add SPDX license identifier according to the type of license text found
in the file.
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Signed-off-by: Cheah Kok Cheong <thrust73@gmail.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
If the algorithm we're parallelizing is asynchronous we might change
CPUs between padata_do_parallel() and padata_do_serial(). However, we
don't expect this to happen as we need to enqueue the padata object into
the per-cpu reorder queue we took it from, i.e. the same-cpu's parallel
queue.
Ensure we're not switching CPUs for a given padata object by tracking
the CPU within the padata object. If the serial callback gets called on
the wrong CPU, defer invoking padata_reorder() via a kernel worker on
the CPU we're expected to run on.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The reorder timer function runs on the CPU where the timer interrupt was
handled which is not necessarily one of the CPUs of the 'pcpu' CPU mask
set.
Ensure the padata_reorder() callback runs on the correct CPU, which is
one in the 'pcpu' CPU mask set and, preferrably, the next expected one.
Do so by comparing the current CPU with the expected target CPU. If they
match, call padata_reorder() right away. If they differ, schedule a work
item on the target CPU that does the padata_reorder() call for us.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The parallel queue per-cpu data structure gets initialized only for CPUs
in the 'pcpu' CPU mask set. This is not sufficient as the reorder timer
may run on a different CPU and might wrongly decide it's the target CPU
for the next reorder item as per-cpu memory gets memset(0) and we might
be waiting for the first CPU in cpumask.pcpu, i.e. cpu_index 0.
Make the '__this_cpu_read(pd->pqueue->cpu_index) == next_queue->cpu_index'
compare in padata_get_next() fail in this case by initializing the
cpu_index member of all per-cpu parallel queues. Use -1 for unused ones.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
pcrypt_init_padata()
cpus_read_lock()
padata_alloc_possible()
padata_alloc()
cpus_read_lock()
The nested call to cpus_read_lock() works with the current implementation,
but prevents the conversion to a percpu rwsem.
The other caller of padata_alloc_possible() is pcrypt_init_padata() which
calls from a cpus_read_lock() protected region as well.
Remove the cpus_read_lock() call in padata_alloc() and document the
calling convention.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-crypto@vger.kernel.org
Link: http://lkml.kernel.org/r/20170524081547.571278910@linutronix.de
No users outside of padata.c
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-crypto@vger.kernel.org
Link: http://lkml.kernel.org/r/20170524081547.491457256@linutronix.de
Per Dan's static checker warning, the code that returns NULL was removed
in 2010, so this patch updates the comments and fixes the code
assumptions.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The author meant to free the variable that was just allocated, instead
of the one that failed to be allocated, but made a simple typo. This
patch rectifies that.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: stable@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Under extremely heavy uses of padata, crashes occur, and with list
debugging turned on, this happens instead:
[87487.298728] WARNING: CPU: 1 PID: 882 at lib/list_debug.c:33
__list_add+0xae/0x130
[87487.301868] list_add corruption. prev->next should be next
(ffffb17abfc043d0), but was ffff8dba70872c80. (prev=ffff8dba70872b00).
[87487.339011] [<ffffffff9a53d075>] dump_stack+0x68/0xa3
[87487.342198] [<ffffffff99e119a1>] ? console_unlock+0x281/0x6d0
[87487.345364] [<ffffffff99d6b91f>] __warn+0xff/0x140
[87487.348513] [<ffffffff99d6b9aa>] warn_slowpath_fmt+0x4a/0x50
[87487.351659] [<ffffffff9a58b5de>] __list_add+0xae/0x130
[87487.354772] [<ffffffff9add5094>] ? _raw_spin_lock+0x64/0x70
[87487.357915] [<ffffffff99eefd66>] padata_reorder+0x1e6/0x420
[87487.361084] [<ffffffff99ef0055>] padata_do_serial+0xa5/0x120
padata_reorder calls list_add_tail with the list to which its adding
locked, which seems correct:
spin_lock(&squeue->serial.lock);
list_add_tail(&padata->list, &squeue->serial.list);
spin_unlock(&squeue->serial.lock);
This therefore leaves only place where such inconsistency could occur:
if padata->list is added at the same time on two different threads.
This pdata pointer comes from the function call to
padata_get_next(pd), which has in it the following block:
next_queue = per_cpu_ptr(pd->pqueue, cpu);
padata = NULL;
reorder = &next_queue->reorder;
if (!list_empty(&reorder->list)) {
padata = list_entry(reorder->list.next,
struct padata_priv, list);
spin_lock(&reorder->lock);
list_del_init(&padata->list);
atomic_dec(&pd->reorder_objects);
spin_unlock(&reorder->lock);
pd->processed++;
goto out;
}
out:
return padata;
I strongly suspect that the problem here is that two threads can race
on reorder list. Even though the deletion is locked, call to
list_entry is not locked, which means it's feasible that two threads
pick up the same padata object and subsequently call list_add_tail on
them at the same time. The fix is thus be hoist that lock outside of
that block.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Remove the unused but set variable pinst in padata_parallel_worker to
fix the following warning when building with 'W=1':
kernel/padata.c: In function ‘padata_parallel_worker’:
kernel/padata.c:68:26: warning: variable ‘pinst’ set but not used [-Wunused-but-set-variable]
Also remove the now unused variable pd which is only used to set pinst.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Install the callbacks via the state machine. CPU-hotplug multinstance support
is used with the nocalls() version. Maybe parts of padata_alloc() could be
moved into the online callback so that we could invoke ->startup callback for
instance and drop get_online_cpus().
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-crypto@vger.kernel.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160906170457.32393-14-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
A recent cleanup removed some exported functions that were not used
anywhere, which in turn exposed the fact that some other functions in
the same file are only used in some configurations.
We now get a warning about them when CONFIG_HOTPLUG_CPU is disabled:
kernel/padata.c:670:12: error: '__padata_remove_cpu' defined but not used [-Werror=unused-function]
static int __padata_remove_cpu(struct padata_instance *pinst, int cpu)
^~~~~~~~~~~~~~~~~~~
kernel/padata.c:650:12: error: '__padata_add_cpu' defined but not used [-Werror=unused-function]
static int __padata_add_cpu(struct padata_instance *pinst, int cpu)
This rearranges the code so the __padata_remove_cpu/__padata_add_cpu
functions are within the #ifdef that protects the code that calls them.
[akpm@linux-foundation.org: coding-style fixes]
Fixes: 4ba6d78c671e ("kernel/padata.c: removed unused code")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Richard Cochran <rcochran@linutronix.de>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
By accident I stumbled across code that has never been used. This
driver has EXPORT_SYMBOL functions, and the only user of the code is
pcrypt.c, but this only uses a subset of the exported symbols.
According to 'git log -G', the functions, padata_set_cpumasks,
padata_add_cpu, and padata_remove_cpu have never been used since they
were first introduced. This patch removes the unused code.
On one 64 bit build, with CRYPTO_PCRYPT built in, the text is more than
4k smaller.
kbuild_hp> size $KBUILD_OUTPUT/vmlinux
text data bss dec hex filename
10566658 4678360 1122304 16367322 f9beda vmlinux
10561984 4678360 1122304 16362648 f9ac98 vmlinux
On another config, 32 bit, the saving is about 0.5k bytes.
kbuild_hp-x86> size $KBUILD_OUTPUT/vmlinux
6012005 2409513 2785280 11206798 ab008e vmlinux
6011491 2409513 2785280 11206284 aafe8c vmlinux
Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
printk and friends can now format bitmaps using '%*pb[l]'. cpumask
and nodemask also provide cpumask_pr_args() and nodemask_pr_args()
respectively which can be used to generate the two printf arguments
necessary to format the specified cpu/nodemask.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A kernel with enabled lockdep complains about the wrong usage of
rcu_dereference() under a rcu_read_lock_bh() protected region.
===============================
[ INFO: suspicious RCU usage. ]
3.13.0-rc1+ #126 Not tainted
-------------------------------
linux/kernel/padata.c:115 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 1
1 lock held by cryptomgr_test/153:
#0: (rcu_read_lock_bh){.+....}, at: [<ffffffff8115c235>] padata_do_parallel+0x5/0x270
Fix that by using rcu_dereference_bh() instead.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Using a spinlock to atomically increase a counter sounds wrong -- we've
atomic_t for this!
Also move 'seq_nr' to a different cache line than 'lock' to reduce cache
line trashing. This has the nice side effect of decreasing the size of
struct parallel_data from 192 to 128 bytes for a x86-64 build, e.g.
occupying only two instead of three cache lines.
Those changes results in a 5% performance increase on an IPsec test run
using pcrypt.
Btw. the seq_lock spinlock was never explicitly initialized -- one more
reason to get rid of it.
Signed-off-by: Mathias Krause <mathias.krause@secunet.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
padata_cpu_callback() takes pinst->lock, to avoid taking
an uninitialized lock, register the notifier after it's
initialization.
Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Share code between CPU_ONLINE and CPU_DOWN_FAILED, same to
CPU_DOWN_PREPARE and CPU_UP_CANCELED.
It will fix 2 bugs:
"not check the return value of __padata_remove_cpu() and __padata_add_cpu()".
"need add 'break' between CPU_UP_CANCELED and CPU_DOWN_FAILED".
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
We don't remove the cpu that went offline from our cpumasks
on cpu hotplug. This got lost somewhere along the line, so
restore it. This fixes a hang of the padata instance on cpu
hotplug.
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
We use the active cpumask to determine the superset of cpus
to use for parallelization. However, the active cpumask is
for internal usage of the scheduler and therefore not the
appropriate cpumask for these purposes. So use the online
cpumask instead.
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Add a reference to the padata api documentation at Documentation/padata.txt
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Daniel Jordan