linux-stable.git/include/linux/sunrpc, branch linux-3.19.y

sunrpc: make debugfs file creation failure non-fatal

2015-04-19T08:10:16+00:00

commit f9c72d10d6fbf949558cd088389a42213ed7b12d upstream.

We currently have a problem that SELinux policy is being enforced when
creating debugfs files. If a debugfs file is created as a side effect of
doing some syscall, then that creation can fail if the SELinux policy
for that process prevents it.

This seems wrong. We don't do that for files under /proc, for instance,
so Bruce has proposed a patch to fix that.

While discussing that patch however, Greg K.H. stated:

    "No kernel code should care / fail if a debugfs function fails, so
     please fix up the sunrpc code first."

This patch converts all of the sunrpc debugfs setup code to be void
return functins, and the callers to not look for errors from those
functions.

This should allow rpc_clnt and rpc_xprt creation to work, even if the
kernel fails to create debugfs files for some reason.

Symptoms were failing krb5 mounts on systems using gss-proxy and
selinux.

Fixes: 388f0c776781 "sunrpc: add a debugfs rpc_xprt directory..."
Signed-off-by: Jeff Layton 
Acked-by: Greg Kroah-Hartman 
Signed-off-by: J. Bruce Fields 
Signed-off-by: Greg Kroah-Hartman

SUNRPC: NULL utsname dereference on NFS umount during namespace cleanup

2015-03-06T22:57:31+00:00

commit 03a9a42a1a7e5b3e7919ddfacc1d1cc81882a955 upstream.

Fix an Oopsable condition when nsm_mon_unmon is called as part of the
namespace cleanup, which now apparently happens after the utsname
has been freed.

Link: http://lkml.kernel.org/r/20150125220604.090121ae@neptune.home
Reported-by: Bruno Prémont 
Signed-off-by: Trond Myklebust 
Signed-off-by: Greg Kroah-Hartman

sunrpc: convert to lockless lookup of queued server threads

2014-12-09T16:22:22+00:00

Testing has shown that the pool->sp_lock can be a bottleneck on a busy
server. Every time data is received on a socket, the server must take
that lock in order to dequeue a thread from the sp_threads list.

Address this problem by eliminating the sp_threads list (which contains
threads that are currently idle) and replacing it with a RQ_BUSY flag in
svc_rqst. This allows us to walk the sp_all_threads list under the
rcu_read_lock and find a suitable thread for the xprt by doing a
test_and_set_bit.

Note that we do still have a potential atomicity problem however with
this approach.  We don't want svc_xprt_do_enqueue to set the
rqst->rq_xprt pointer unless a test_and_set_bit of RQ_BUSY returned
zero (which indicates that the thread was idle). But, by the time we
check that, the bit could be flipped by a waking thread.

To address this, we acquire a new per-rqst spinlock (rq_lock) and take
that before doing the test_and_set_bit. If that returns false, then we
can set rq_xprt and drop the spinlock. Then, when the thread wakes up,
it must set the bit under the same spinlock and can trust that if it was
already set then the rq_xprt is also properly set.

With this scheme, the case where we have an idle thread no longer needs
to take the highly contended pool->sp_lock at all, and that removes the
bottleneck.

That still leaves one issue: What of the case where we walk the whole
sp_all_threads list and don't find an idle thread? Because the search is
lockess, it's possible for the queueing to race with a thread that is
going to sleep. To address that, we queue the xprt and then search again.

If we find an idle thread at that point, we can't attach the xprt to it
directly since that might race with a different thread waking up and
finding it.  All we can do is wake the idle thread back up and let it
attempt to find the now-queued xprt.

Signed-off-by: Jeff Layton 
Tested-by: Chris Worley 
Signed-off-by: J. Bruce Fields

sunrpc: fix potential races in pool_stats collection

2014-12-09T16:22:22+00:00

In a later patch, we'll be removing some spinlocking around the socket
and thread queueing code in order to fix some contention problems. At
that point, the stats counters will no longer be protected by the
sp_lock.

Change the counters to atomic_long_t fields, except for the
"sockets_queued" counter which will still be manipulated under a
spinlock.

Signed-off-by: Jeff Layton 
Tested-by: Chris Worley 
Signed-off-by: J. Bruce Fields

sunrpc: add a rcu_head to svc_rqst and use kfree_rcu to free it

2014-12-09T16:22:22+00:00

...also make the manipulation of sp_all_threads list use RCU-friendly
functions.

Signed-off-by: Jeff Layton 
Tested-by: Chris Worley 
Signed-off-by: J. Bruce Fields

sunrpc: convert sp_task_pending flag to use atomic bitops

2014-12-09T16:22:21+00:00

In a later patch, we'll want to be able to handle this flag without
holding the sp_lock. Change this field to an unsigned long flags
field, and declare a new flag in it that can be managed with atomic
bitops.

Signed-off-by: Jeff Layton 
Signed-off-by: J. Bruce Fields

sunrpc: move rq_cachetype field to better optimize space

2014-12-09T16:22:21+00:00

There are a couple of holes in the svc_rqst field on x86_64. Move the
rq_cachetype to a different location to eliminate both of them.

Signed-off-by: Jeff Layton 
Signed-off-by: J. Bruce Fields

sunrpc: move rq_splice_ok flag into rq_flags

2014-12-09T16:22:21+00:00

Signed-off-by: Jeff Layton 
Signed-off-by: J. Bruce Fields

sunrpc: move rq_dropme flag into rq_flags

2014-12-09T16:22:20+00:00

Signed-off-by: Jeff Layton 
Signed-off-by: J. Bruce Fields

sunrpc: move rq_usedeferral flag to rq_flags

2014-12-09T16:22:20+00:00

Signed-off-by: Jeff Layton 
Signed-off-by: J. Bruce Fields