The trace point in svc_xprt_close() reports only some local close
requests. Try to capture more local close requests.
Note that "trace-cmd record -T -e sunrpc:svc_xprt_close" will
neatly capture the identity of the caller requesting the close.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This reverts commit 8e948c365d.
The reverted commit moves a test on a field protected by a mutex outside
of the protection of that mutex, and so is obviously racey.
Depending on how the race goes, si->serv might be NULL when dereferenced
in svc_pool_stats_start(), or svc_pool_stats_stop() might unlock a mutex
that hadn't been locked.
This bug that the commit tried to fix has been addressed by initialising
->mutex earlier.
Fixes: 8e948c365d ("nfsd: fix oops when reading pool_stats before server is started")
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Sourbh reported an oops that is triggerable by trying to read the
pool_stats procfile before nfsd had been started. Move the check for a
NULL serv in svc_pool_stats_start above the mutex acquisition, and fix
the stop routine not to unlock the mutex if there is no serv yet.
Fixes: 7b207ccd98 ("svc: don't hold reference for poolstats, only mutex.")
Reported-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
It is obsolete since sp_lock was discarded in commit 580a25756a
("SUNRPC: discard sp_lock").
Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
svc_find_listener will return the transport instance pointer for the
endpoint accepting connections/peer traffic from the specified transport
class and matching sockaddr.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Add svc_xprt_create_from_sa utility routine and refactor
svc_xprt_create() codebase in order to introduce the capability to
create a svc port from socket address.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
A future patch will remove refcounting on svc_serv as it is of little
use.
It is currently used to keep the svc around while the pool_stats file is
open.
Change this to get the pointer, protected by the mutex, only in
seq_start, and the release the mutex in seq_stop.
This means that if the nfsd server is stopped and restarted while the
pool_stats file it open, then some pool stats info could be from the
first instance and some from the second. This might appear odd, but is
unlikely to be a problem in practice.
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Guillaume says:
> I believe commit 5f7fc5d69f ("SUNRPC: Resupply rq_pages from
> node-local memory") in Linux 6.5+ is incorrect. It passes
> unconditionally rq_pool->sp_id as the NUMA node.
>
> While the comment in the svc_pool declaration in sunrpc/svc.h says
> that sp_id is also the NUMA node id, it might not be the case if
> the svc is created using svc_create_pooled(). svc_created_pooled()
> can use the per-cpu pool mode therefore in this case sp_id would
> be the cpu id.
Fix this by reverting now. At a later point this minor optimization,
and the deceptive labeling of the sp_id field, can be revisited.
Reported-by: Guillaume Morin <guillaume@morinfr.org>
Closes: https://lore.kernel.org/linux-nfs/ZYC9rsno8qYggVt9@bender.morinfr.org/T/#u
Fixes: 5f7fc5d69f ("SUNRPC: Resupply rq_pages from node-local memory")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This removes the need to store and update back-links in the list.
It also remove the need for the _bh version of spin_lock().
Signed-off-by: NeilBrown <neilb@suse.de>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
lwq avoids using back pointers in lists, and uses less locking.
This introduces a new spinlock, but the other one will be removed in a
future patch.
For svc_clean_up_xprts(), we now dequeue the entire queue, walk it to
remove and process the xprts that need cleaning up, then re-enqueue the
remaining queue.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Currently if several items of work become available in quick succession,
that number of threads (if available) will be woken. By the time some
of them wake up another thread that was already cache-warm might have
come along and completed the work. Anecdotal evidence suggests as many
as 15% of wakes find nothing to do once they get to the point of
looking.
This patch changes svc_pool_wake_idle_thread() to wake the first thread
on the queue but NOT remove it. Subsequent calls will wake the same
thread. Once that thread starts it will dequeue itself and after
dequeueing some work to do, it will wake the next thread if there is more
work ready. This results in a more orderly increase in the number of
busy threads.
As a bonus, this allows us to reduce locking around the idle queue.
svc_pool_wake_idle_thread() no longer needs to take a lock (beyond
rcu_read_lock()) as it doesn't manipulate the queue, it just looks at
the first item.
The thread itself can avoid locking by using the new
llist_del_first_this() interface. This will safely remove the thread
itself if it is the head. If it isn't the head, it will do nothing.
If multiple threads call this concurrently only one will succeed. The
others will do nothing, so no corruption can result.
If a thread wakes up and finds that it cannot dequeue itself that means
either
- that it wasn't woken because it was the head of the queue. Maybe the
freezer woke it. In that case it can go back to sleep (after trying
to freeze of course).
- some other thread found there was nothing to do very recently, and
placed itself on the head of the queue in front of this thread.
It must check again after placing itself there, so it can be deemed to
be responsible for any pending work, and this thread can go back to
sleep until woken.
No code ever tests for busy threads any more. Only each thread itself
cares if it is busy. So svc_thread_busy() is no longer needed.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Functions which directly manipulate a 'struct rqst', such as
svc_rqst_alloc() or svc_rqst_release_pages(), can reasonably
have "rqst" in there name.
However functions that act on the running thread, such as
XX_should_sleep() or XX_wait_for_work() should seem more
natural with a "svc_thread_" prefix.
So make those changes.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
With an llist we don't need to take a lock to add a thread to the list,
though we still need a lock to remove it. That will go in the next
patch.
Unlike double-linked lists, a thread cannot reliably remove itself from
the list. Only the first thread can be removed, and that can change
asynchronously. So some care is needed.
We already check if there is pending work to do, so we are unlikely to
add ourselves to the idle list and then want to remove ourselves again.
If we DO find something needs to be done after adding ourselves to the
list, we simply wake up the first thread on the list. If that was us,
we successfully removed ourselves and can continue. If it was some
other thread, they will do the work that needs to be done. We can
safely sleep until woken.
We also remove the test on freezing() from rqst_should_sleep(). Instead
we set TASK_FREEZABLE before scheduling. This makes is safe to
schedule() when a freeze is pending. As we now loop waiting to be
removed from the idle queue, this is a cleaner way to handle freezing.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
We can tell if a pool is congested by checking if the idle list is
empty. We don't need a separate flag.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Rather than searching a list of threads to find an idle one, having a
list of idle threads allows an idle thread to be found immediately.
This adds some spin_lock calls which is not ideal, but as the hold-time
is tiny it is still faster than searching a list. A future patch will
remove them using llist.h. This involves some subtlety and so is left
to a separate patch.
This removes the need for the RQ_BUSY flag. The rqst is "busy"
precisely when it is not on the "idle" list.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
svc threads are currently stopped using kthread_stop(). This requires
identifying a specific thread. However we don't care which thread
stops, just as long as one does.
So instead, set a flag in the svc_pool to say that a thread needs to
die, and have each thread check this flag instead of calling
kthread_should_stop(). The first thread to find and clear this flag
then moves towards exiting.
This removes an explicit dependency on sp_all_threads which will make a
future patch simpler.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Using svc_recv() for (NFSv4.1) back-channel handling means we have just
one mechanism for waking threads.
Also change kthread_freezable_should_stop() in nfs4_callback_svc() to
kthread_should_stop() as used elsewhere.
kthread_freezable_should_stop() effectively adds a try_to_freeze() call,
and svc_recv() already contains that at an appropriate place.
Signed-off-by: NeilBrown <neilb@suse.de>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
svc_get_next_xprt() does a lot more than just get an xprt. It also
decides if it needs to sleep, depending not only on the availability of
xprts but also on the need to exit or handle external work.
So rename it to svc_rqst_wait_for_work() and only do the testing and
waiting. Move all the waiting-related code out of svc_recv() into the
new svc_rqst_wait_for_work().
Move the dequeueing code out of svc_get_next_xprt() into svc_recv().
Previously svc_xprt_dequeue() would be called twice, once before waiting
and possibly once after. Now instead rqst_should_sleep() is called
twice. Once to decide if waiting is needed, and once to check against
after setting the task state do see if we might have missed a wakeup.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
svc_xprt_handle() does lots of things itself, but leaves some to the
caller - svc_recv(). This isn't elegant.
Move that code out of svc_recv() into svc_xprt_handle()
Move the calls to svc_xprt_release() from svc_send() and svc_drop()
(the two possible final steps in svc_process()) and from svc_recv() (in
the case where svc_process() wasn't called) into svc_xprt_handle().
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Based on its name you would think that rqst_should_sleep() would be
read-only, not changing anything. But in fact it will clear
SP_TASK_PENDING if that was set. This is surprising, and it blurs the
line between "check for work to do" and "dequeue work to do".
So change the "test_and_clear" to simple "test" and clear the bit once
the thread has decided to wake up and return to the caller.
With this, it makes sense to *always* set SP_TASK_PENDING when asked,
rather than to set it only if no thread could be woken up.
[ cel: Previously TASK_PENDING indicated there is work waiting but no
idle threads were found to pick up that work. After this patch, it acts
as an XPT_BUSY flag for wake-ups that have no associated xprt. ]
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
svc_xprt_enqueue() can be costly, since it involves selecting and
waking up a process.
More than one enqueue is done per incoming RPC. For example,
svc_data_ready() enqueues, and so does svc_xprt_receive(). Also, if
an RPC message requires more than one call to ->recvfrom() to
receive it fully, each one of those calls does an enqueue.
To get a sense of the average number of transport enqueue operations
needed to process an incoming RPC message, re-use the "packets" pool
stat. Track the number of complete RPC messages processed by each
thread pool.
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Refactor: Extract the loop that finds an idle service thread from
svc_xprt_enqueue() and svc_wake_up(). Both functions do just about
the same thing.
Note that svc_wake_up() currently does not hold the RCU read lock
while waking the target thread. It indeed should hold the lock, just
as svc_xprt_enqueue() does, to ensure the rqstp does not vanish
during the wake-up. This patch adds the RCU lock for svc_wake_up().
Note that shrinking the pool thread count is rare, and calls to
svc_wake_up() are also quite infrequent. In practice, this race is
very unlikely to be hit, so we are not marking the lock fix for
stable backport at this time.
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
The xpt_flags field frequently changes between the time that
svc_xprt_ready() grabs a copy and execution flow arrives at the
tracepoint at the tail of svc_xprt_enqueue(). In fact, there's
usually a sleep/wake-up in there, so those flags are almost
guaranteed to be different.
It would be more useful to record the exact flags that were used to
decide whether the transport is ready, so move the tracepoint.
Moving it means the tracepoint can't pick up the waker's pid. That
can be added to struct svc_rqst if it turns out that is important.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Most svc threads have no interest in a timeout.
nfsd sets it to 1 hour, but this is a wart of no significance.
lockd uses the timeout so that it can call nlmsvc_retry_blocked().
It also sometimes calls svc_wake_up() to ensure this is called.
So change lockd to be consistent and always use svc_wake_up() to trigger
nlmsvc_retry_blocked() - using a timer instead of a timeout to
svc_recv().
And change svc_recv() to not take a timeout arg.
This makes the sp_threads_timedout counter always zero.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
svc_recv() currently returns a 0 on success or one of two errors:
- -EAGAIN means no message was successfully received
- -EINTR means the thread has been told to stop
Previously nfsd would stop as the result of a signal as well as
following kthread_stop(). In that case the difference was useful: EINTR
means stop unconditionally. EAGAIN means stop if kthread_should_stop(),
continue otherwise.
Now threads only exit when kthread_should_stop() so we don't need the
distinction.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
All callers of svc_recv() go on to call svc_process() on success.
Simplify callers by having svc_recv() do that for them.
This loses one call to validate_process_creds() in nfsd. That was
debugging code added 14 years ago. I don't think we need to keep it.
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
The original implementation of nfsd used signals to stop threads during
shutdown.
In Linux 2.3.46pre5 nfsd gained the ability to shutdown threads
internally it if was asked to run "0" threads. After this user-space
transitioned to using "rpc.nfsd 0" to stop nfsd and sending signals to
threads was no longer an important part of the API.
In commit 3ebdbe5203 ("SUNRPC: discard svo_setup and rename
svc_set_num_threads_sync()") (v5.17-rc1~75^2~41) we finally removed the
use of signals for stopping threads, using kthread_stop() instead.
This patch makes the "obvious" next step and removes the ability to
signal nfsd threads - or any svc threads. nfsd stops allowing signals
and we don't check for their delivery any more.
This will allow for some simplification in later patches.
A change worth noting is in nfsd4_ssc_setup_dul(). There was previously
a signal_pending() check which would only succeed when the thread was
being shut down. It should really have tested kthread_should_stop() as
well. Now it just does the latter, not the former.
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Remove a couple of dprintk call sites that are of little value.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Tom Talpey <tom@talpey.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
The preceding block comment before svc_register_xprt_class() is
not related to that function.
While we're here, add proper documenting comments for these two
publicly-visible functions.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Tom Talpey <tom@talpey.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Micro-optimization: Call ktime_get() only when ->xpo_recvfrom() has
given us a full RPC message to process. rq_stime isn't used
otherwise, so this avoids pointless work.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Tom Talpey <tom@talpey.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
svc_init_buffer() is careful to allocate the initial set of server
thread buffer pages from memory on the local NUMA node.
svc_alloc_arg() should also be that careful.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
When enabled, this dprintk() fires for every incoming RPC, which is
an enormous amount of log traffic. These days, after the first few
hundred log messages, the system journald is just going to mute it,
along with all other NFSD debug output.
Let's rely on trace points for this high-traffic information
instead.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Since the ->xprt_ctxt pointer was added to svc_deferred_req, it has not
been sufficient to use kfree() to free a deferred request. We may need
to free the ctxt as well.
As freeing the ctxt is all that ->xpo_release_rqst() does, we repurpose
it to explicit do that even when the ctxt is not stored in an rqst.
So we now have ->xpo_release_ctxt() which is given an xprt and a ctxt,
which may have been taken either from an rqst or from a dreq. The
caller is now responsible for clearing that pointer after the call to
->xpo_release_ctxt.
We also clear dr->xprt_ctxt when the ctxt is moved into a new rqst when
revisiting a deferred request. This ensures there is only one pointer
to the ctxt, so the risk of double freeing in future is reduced. The
new code in svc_xprt_release which releases both the ctxt and any
rq_deferred depends on this.
Fixes: 773f91b2cf ("SUNRPC: Fix NFSD's request deferral on RDMA transports")
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
When an RPC request is deferred, the rq_xprt_ctxt pointer is moved out
of the svc_rqst into the svc_deferred_req.
When the deferred request is revisited, the pointer is copied into
the new svc_rqst - and also remains in the svc_deferred_req.
In the (rare?) case that the request is deferred a second time, the old
svc_deferred_req is reused - it still has all the correct content.
However in that case the rq_xprt_ctxt pointer is NOT cleared so that
when xpo_release_xprt is called, the ctxt is freed (UDP) or possible
added to a free list (RDMA).
When the deferred request is revisited for a second time, it will
reference this ctxt which may be invalid, and the free the object a
second time which is likely to oops.
So change svc_defer() to *always* clear rq_xprt_ctxt, and assert that
the value is now stored in the svc_deferred_req.
Fixes: 773f91b2cf ("SUNRPC: Fix NFSD's request deferral on RDMA transports")
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This patch adds opportunitistic RPC-with-TLS to the Linux in-kernel
NFS server. If the client requests RPC-with-TLS and the user space
handshake agent is running, the server will set up a TLS session.
There are no policy settings yet. For example, the server cannot
yet require the use of RPC-with-TLS to access its data.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This is an eye-catcher for tracepoints that record the XID: it means
svc_rqst() has not received a full RPC Call with an XID yet.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
A single RPC transaction that touches only a couple of pages means
rq_pvec will not be even close to full in svc_xpt_release(). This is
a common case.
Instead, just leave the pages in rq_pvec until it is completely
full. This improves the efficiency of the batch release mechanism
on workloads that involve small RPC messages.
The rq_pvec is also fully emptied just before thread exit.
Reviewed-by: Calum Mackay <calum.mackay@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Clean-up: There doesn't seem to be a reason why this function is
stuck in a header. One thing it prevents is the convenient addition
of tracing. Moving it to a source file also makes the rq_respages
clean-up logic easier to find.
Reviewed-by: Calum Mackay <calum.mackay@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Clean up: All callers of svc_process() ignore its return value, so
svc_process() can safely be converted to return void. Ditto for
svc_send().
The return value of ->xpo_sendto() is now used only as part of a
trace event.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
There's no need for the cost of this extra virtual function call
during every RPC transaction: the RQ_SECURE bit can be set properly
in ->xpo_recvfrom() instead.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Eliminate the use of bus-locked operations in svc_xprt_enqueue(),
which is a hot path. Replace them with per-cpu variables to reduce
cross-CPU memory bus traffic.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Now the entire RPC Call header parsing path is handled via struct
xdr_stream-based decoders.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
The premise that "Once an svc thread is scheduled and executing an
RPC, no other processes will touch svc_rqst::rq_flags" is false.
svc_xprt_enqueue() examines the RQ_BUSY flag in scheduled nfsd
threads when determining which thread to wake up next.
Found via KCSAN.
Fixes: 28df098881 ("SUNRPC: Use RMW bitops in single-threaded hot paths")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Record not only the number of pages requested, but the number of
pages that were actually allocated, to get a measure of progress
(or lack thereof).
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
I noticed CPU pipeline stalls while using perf.
Once an svc thread is scheduled and executing an RPC, no other
processes will touch svc_rqst::rq_flags. Thus bus-locked atomics are
not needed outside the svc thread scheduler.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Clean up: There is one caller. The @cpu argument can be made
implicit now that a get_cpu/put_cpu pair is no longer needed.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
svc_xprt_enqueue() disables preemption via get_cpu() and then asks
for a pool of a specific CPU (current) via svc_pool_for_cpu().
While preemption is disabled, svc_xprt_enqueue() acquires
svc_pool::sp_lock with bottom-halfs disabled, which can sleep on
PREEMPT_RT.
Disabling preemption is not required here. The pool is protected with a
lock so the following list access is safe even cross-CPU. The following
iteration through svc_pool::sp_all_threads is under RCU-readlock and
remaining operations within the loop are atomic and do not rely on
disabled-preemption.
Use raw_smp_processor_id() as the argument for the requested CPU in
svc_pool_for_cpu().
Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Trond Myklebust reports an NFSD crash in svc_rdma_sendto(). Further
investigation shows that the crash occurred while NFSD was handling
a deferred request.
This patch addresses two inter-related issues that prevent request
deferral from working correctly for RPC/RDMA requests:
1. Prevent the crash by ensuring that the original
svc_rqst::rq_xprt_ctxt value is available when the request is
revisited. Otherwise svc_rdma_sendto() does not have a Receive
context available with which to construct its reply.
2. Possibly since before commit 71641d99ce ("svcrdma: Properly
compute .len and .buflen for received RPC Calls"),
svc_rdma_recvfrom() did not include the transport header in the
returned xdr_buf. There should have been no need for svc_defer()
and friends to save and restore that header, as of that commit.
This issue is addressed in a backport-friendly way by simply
having svc_rdma_recvfrom() set rq_xprt_hlen to zero
unconditionally, just as svc_tcp_recvfrom() does. This enables
svc_deferred_recv() to correctly reconstruct an RPC message
received via RPC/RDMA.
Reported-by: Trond Myklebust <trondmy@hammerspace.com>
Link: https://lore.kernel.org/linux-nfs/82662b7190f26fb304eb0ab1bb04279072439d4e.camel@hammerspace.com/
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: <stable@vger.kernel.org>
