kernel/linux.git/fs/nfs/callback.c, branch v6.19.11

NFSv4.1: protect destroying and nullifying bc_serv structure

2025-11-23T20:30:12+00:00

When we are shutting down the client, we free the callback server structure and then at a later pointer we free the transport used by the client. Yet, it's possible that after the callback server is freed, the transport receives a backchannel request at which point we can dereferene freed memory. Instead, do the freeing the bc server and nullying bc_serv under the lock. Signed-off-by: Olga Kornievskaia Signed-off-by: Trond Myklebust

NFSv4.1: pass transport for callback shutdown

2025-11-23T20:30:12+00:00

When we are setting up the 4.1 callback server, we pass in the appropriate rpc_xprt transport pointer with which to associate the callback server structure. Similarly, pass in the rpc_xprt pointer for when we are shutting down the callback. This will be used to make sure that we free the server structure and then clear the rpc_xprt's bc_server pointer in a safe manner. Signed-off-by: Olga Kornievskaia Signed-off-by: Trond Myklebust

SUNRPC: Move the svc_rpcb_cleanup() call sites

2025-09-23T17:28:19+00:00

Clean up: because svc_rpcb_cleanup() and svc_xprt_destroy_all() are always invoked in pairs, we can deduplicate code by moving the svc_rpcb_cleanup() call sites into svc_xprt_destroy_all(). Signed-off-by: Chuck Lever Tested-by: Olga Kornievskaia Signed-off-by: Anna Schumaker

NFS: Remove rpcbind cleanup for NFSv4.0 callback

2025-09-23T17:28:19+00:00

The NFS client's NFSv4.0 callback listeners are created with SVC_SOCK_ANONYMOUS, therefore svc_setup_socket() does not register them with the client's rpcbind service. And, note that nfs_callback_down_net() does not call svc_rpcb_cleanup() at all when shutting down the callback server. Even if svc_setup_socket() were to attempt to register or unregister these sockets, the callback service has vs_hidden set, which shunts the rpcbind upcalls. The svc_rpcb_cleanup() error flow was introduced by commit c946556b8749 ("NFS: move per-net callback thread initialization to nfs_callback_up_net()"). It doesn't appear in the code that was relocated by that commit. Therefore, there is no need to call svc_rpcb_cleanup() when listener creation fails during callback server start-up. Signed-off-by: Chuck Lever Signed-off-by: Anna Schumaker

nfsd: don't use sv_nrthreads in connection limiting calculations.

2025-01-06T14:37:36+00:00

The heuristic for limiting the number of incoming connections to nfsd currently uses sv_nrthreads - allowing more connections if more threads were configured. A future patch will allow number of threads to grow dynamically so that there will be no need to configure sv_nrthreads. So we need a different solution for limiting connections. It isn't clear what problem is solved by limiting connections (as mentioned in a code comment) but the most likely problem is a connection storm - many connections that are not doing productive work. These will be closed after about 6 minutes already but it might help to slow down a storm. This patch adds a per-connection flag XPT_PEER_VALID which indicates that the peer has presented a filehandle for which it has some sort of access. i.e the peer is known to be trusted in some way. We now only count connections which have NOT been determined to be valid. There should be relative few of these at any given time. If the number of non-validated peer exceed a limit - currently 64 - we close the oldest non-validated peer to avoid having too many of these useless connections. Note that this patch significantly changes the meaning of the various configuration parameters for "max connections". The next patch will remove all of these. Signed-off-by: NeilBrown Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

sunrpc: allow svc threads to fail initialisation cleanly

2024-09-20T23:31:03+00:00

If an svc thread needs to perform some initialisation that might fail, it has no good way to handle the failure. Before the thread can exit it must call svc_exit_thread(), but that requires the service mutex to be held. The thread cannot simply take the mutex as that could deadlock if there is a concurrent attempt to shut down all threads (which is unlikely, but not impossible). nfsd currently call svc_exit_thread() unprotected in the unlikely event that unshare_fs_struct() fails. We can clean this up by introducing svc_thread_init_status() by which an svc thread can report whether initialisation has succeeded. If it has, it continues normally into the action loop. If it has not, svc_thread_init_status() immediately aborts the thread. svc_start_kthread() waits for either of these to happen, and calls svc_exit_thread() (under the mutex) if the thread aborted. Signed-off-by: NeilBrown Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

nfsd: stop setting ->pg_stats for unused stats

2024-03-01T14:12:08+00:00

A lot of places are setting a blank svc_stats in ->pg_stats and never utilizing these stats. Remove all of these extra structs as we're not reporting these stats anywhere. Signed-off-by: Josef Bacik Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

SUNRPC: discard sv_refcnt, and svc_get/svc_put

2024-01-07T22:54:33+00:00

sv_refcnt is no longer useful. lockd and nfs-cb only ever have the svc active when there are a non-zero number of threads, so sv_refcnt mirrors sv_nrthreads. nfsd also keeps the svc active between when a socket is added and when the first thread is started, but we don't really need a refcount for that. We can simply not destroy the svc while there are any permanent sockets attached. So remove sv_refcnt and the get/put functions. Instead of a final call to svc_put(), call svc_destroy() instead. This is changed to also store NULL in the passed-in pointer to make it easier to avoid use-after-free situations. Signed-off-by: NeilBrown Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever

SUNRPC: change how svc threads are asked to exit.

2023-10-16T16:44:04+00:00

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 Signed-off-by: Chuck Lever

SUNRPC: integrate back-channel processing with svc_recv()

2023-10-16T16:44:03+00:00

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 Cc: Trond Myklebust Cc: Anna Schumaker Signed-off-by: Chuck Lever