linux.git/net/sunrpc, branch v3.19-rc2

sunrpc/cache: convert to use string_escape_str()

2014-12-09T16:30:20+00:00

There is nice kernel helper to escape a given strings by provided rules. Let's
use it instead of custom approach.

Signed-off-by: Andy Shevchenko 
[bfields@redhat.com: fix length calculation]
Signed-off-by: J. Bruce Fields

sunrpc: only call test_bit once in svc_xprt_received

2014-12-09T16:29:14+00:00

...move the WARN_ON_ONCE inside the following if block since they use
the same condition.

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

sunrpc: add some tracepoints around enqueue and dequeue of svc_xprt

2014-12-09T16:29:14+00:00

These were useful when I was tracking down a race condition between
svc_xprt_do_enqueue and svc_get_next_xprt.

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

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: require svc_create callers to pass in meaningful shutdown routine

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

Currently all svc_create callers pass in NULL for the shutdown parm,
which then gets fixed up to be svc_rpcb_cleanup if the service uses
rpcbind.

Simplify this by instead having the the only caller that requires it
(lockd) pass in svc_rpcb_cleanup and get rid of the special casing.

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

sunrpc: have svc_wake_up only deal with pool 0

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

The way that svc_wake_up works is a bit inefficient. It walks all of the
available pools for a service and either wakes up a task in each one or
sets the SP_TASK_PENDING flag in each one.

When svc_wake_up is called, there is no need to wake up more than one
thread to do this work. In practice, only lockd currently uses this
function and it's single threaded anyway. Thus, this just boils down to
doing a wake up of a thread in pool 0 or setting a single flag.

Eliminate the for loop in this function and change it to just operate on
pool 0. Also update the comments that sit above it and get rid of some
code that has been commented out for years now.

Signed-off-by: Jeff Layton 
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_splice_ok flag into rq_flags

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

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