kernel/linux.git/net/rxrpc/peer_object.c, branch v6.12.80

rxrpc, afs: Fix peer hash locking vs RCU callback

2025-02-08T08:58:05+00:00

[ Upstream commit 79d458c13056559d49b5e41fbc4b6890e68cf65b ] In its address list, afs now retains pointers to and refs on one or more rxrpc_peer objects. The address list is freed under RCU and at this time, it puts the refs on those peers. Now, when an rxrpc_peer object runs out of refs, it gets removed from the peer hash table and, for that, rxrpc has to take a spinlock. However, it is now being called from afs's RCU cleanup, which takes place in BH context - but it is just taking an ordinary spinlock. The put may also be called from non-BH context, and so there exists the possibility of deadlock if the BH-based RCU cleanup happens whilst the hash spinlock is held. This led to the attached lockdep complaint. Fix this by changing spinlocks of rxnet->peer_hash_lock back to BH-disabling locks. ================================ WARNING: inconsistent lock state 6.13.0-rc5-build2+ #1223 Tainted: G E -------------------------------- inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage. swapper/1/0 [HC0[0]:SC1[1]:HE1:SE0] takes: ffff88810babe228 (&rxnet->peer_hash_lock){+.?.}-{3:3}, at: rxrpc_put_peer+0xcb/0x180 {SOFTIRQ-ON-W} state was registered at: mark_usage+0x164/0x180 __lock_acquire+0x544/0x990 lock_acquire.part.0+0x103/0x280 _raw_spin_lock+0x2f/0x40 rxrpc_peer_keepalive_worker+0x144/0x440 process_one_work+0x486/0x7c0 process_scheduled_works+0x73/0x90 worker_thread+0x1c8/0x2a0 kthread+0x19b/0x1b0 ret_from_fork+0x24/0x40 ret_from_fork_asm+0x1a/0x30 irq event stamp: 972402 hardirqs last enabled at (972402): [] _raw_spin_unlock_irqrestore+0x2e/0x50 hardirqs last disabled at (972401): [] _raw_spin_lock_irqsave+0x18/0x60 softirqs last enabled at (972300): [] handle_softirqs+0x3ee/0x430 softirqs last disabled at (972313): [] __irq_exit_rcu+0x44/0x110 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&rxnet->peer_hash_lock); lock(&rxnet->peer_hash_lock); *** DEADLOCK *** 1 lock held by swapper/1/0: #0: ffffffff83576be0 (rcu_callback){....}-{0:0}, at: rcu_lock_acquire+0x7/0x30 stack backtrace: CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G E 6.13.0-rc5-build2+ #1223 Tainted: [E]=UNSIGNED_MODULE Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014 Call Trace: dump_stack_lvl+0x57/0x80 print_usage_bug.part.0+0x227/0x240 valid_state+0x53/0x70 mark_lock_irq+0xa5/0x2f0 mark_lock+0xf7/0x170 mark_usage+0xe1/0x180 __lock_acquire+0x544/0x990 lock_acquire.part.0+0x103/0x280 _raw_spin_lock+0x2f/0x40 rxrpc_put_peer+0xcb/0x180 afs_free_addrlist+0x46/0x90 [kafs] rcu_do_batch+0x2d2/0x640 rcu_core+0x2f7/0x350 handle_softirqs+0x1ee/0x430 __irq_exit_rcu+0x44/0x110 irq_exit_rcu+0xa/0x30 sysvec_apic_timer_interrupt+0x7f/0xa0 Fixes: 72904d7b9bfb ("rxrpc, afs: Allow afs to pin rxrpc_peer objects") Signed-off-by: David Howells cc: Marc Dionne cc: Simon Horman cc: linux-afs@lists.infradead.org Link: https://patch.msgid.link/2095618.1737622752@warthog.procyon.org.uk Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

rxrpc, afs: Allow afs to pin rxrpc_peer objects

2023-12-24T15:22:50+00:00

Change rxrpc's API such that: (1) A new function, rxrpc_kernel_lookup_peer(), is provided to look up an rxrpc_peer record for a remote address and a corresponding function, rxrpc_kernel_put_peer(), is provided to dispose of it again. (2) When setting up a call, the rxrpc_peer object used during a call is now passed in rather than being set up by rxrpc_connect_call(). For afs, this meenat passing it to rxrpc_kernel_begin_call() rather than the full address (the service ID then has to be passed in as a separate parameter). (3) A new function, rxrpc_kernel_remote_addr(), is added so that afs can get a pointer to the transport address for display purposed, and another, rxrpc_kernel_remote_srx(), to gain a pointer to the full rxrpc address. (4) The function to retrieve the RTT from a call, rxrpc_kernel_get_srtt(), is then altered to take a peer. This now returns the RTT or -1 if there are insufficient samples. (5) Rename rxrpc_kernel_get_peer() to rxrpc_kernel_call_get_peer(). (6) Provide a new function, rxrpc_kernel_get_peer(), to get a ref on a peer the caller already has. This allows the afs filesystem to pin the rxrpc_peer records that it is using, allowing faster lookups and pointer comparisons rather than comparing sockaddr_rxrpc contents. It also makes it easier to get hold of the RTT. The following changes are made to afs: (1) The addr_list struct's addrs[] elements now hold a peer struct pointer and a service ID rather than a sockaddr_rxrpc. (2) When displaying the transport address, rxrpc_kernel_remote_addr() is used. (3) The port arg is removed from afs_alloc_addrlist() since it's always overridden. (4) afs_merge_fs_addr4() and afs_merge_fs_addr6() do peer lookup and may now return an error that must be handled. (5) afs_find_server() now takes a peer pointer to specify the address. (6) afs_find_server(), afs_compare_fs_alists() and afs_merge_fs_addr[46]{} now do peer pointer comparison rather than address comparison. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org

rxrpc: Stash the network namespace pointer in rxrpc_local

2023-01-06T09:43:31+00:00

Stash the network namespace pointer in the rxrpc_local struct in addition to a pointer to the rxrpc-specific net namespace info. Use this to remove some places where the socket is passed as a parameter. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org

rxrpc: Fix switched parameters in peer tracing

2022-12-19T09:51:31+00:00

Fix the switched parameters on rxrpc_alloc_peer() and rxrpc_get_peer(). The ref argument and the why argument got mixed. Fixes: 47c810a79844 ("rxrpc: trace: Don't use __builtin_return_address for rxrpc_peer tracing") Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: David S. Miller

rxrpc: Fix locking issues in rxrpc_put_peer_locked()

2022-12-19T09:51:31+00:00

Now that rxrpc_put_local() may call kthread_stop(), it can't be called under spinlock as it might sleep. This can cause a problem in the peer keepalive code in rxrpc as it tries to avoid dropping the peer_hash_lock from the point it needs to re-add peer->keepalive_link to going round the loop again in rxrpc_peer_keepalive_dispatch(). Fix this by just dropping the lock when we don't need it and accepting that we'll have to take it again. This code is only called about every 20s for each peer, so not very often. This allows rxrpc_put_peer_unlocked() to be removed also. If triggered, this bug produces an oops like the following, as reproduced by a syzbot reproducer for a different oops[1]: BUG: sleeping function called from invalid context at kernel/sched/completion.c:101 ... RCU nest depth: 0, expected: 0 3 locks held by kworker/u9:0/50: #0: ffff88810e74a138 ((wq_completion)krxrpcd){+.+.}-{0:0}, at: process_one_work+0x294/0x636 #1: ffff8881013a7e20 ((work_completion)(&rxnet->peer_keepalive_work)){+.+.}-{0:0}, at: process_one_work+0x294/0x636 #2: ffff88817d366390 (&rxnet->peer_hash_lock){+.+.}-{2:2}, at: rxrpc_peer_keepalive_dispatch+0x2bd/0x35f ... Call Trace: dump_stack_lvl+0x4c/0x5f __might_resched+0x2cf/0x2f2 __wait_for_common+0x87/0x1e8 kthread_stop+0x14d/0x255 rxrpc_peer_keepalive_dispatch+0x333/0x35f rxrpc_peer_keepalive_worker+0x2e9/0x449 process_one_work+0x3c1/0x636 worker_thread+0x25f/0x359 kthread+0x1a6/0x1b5 ret_from_fork+0x1f/0x30 Fixes: a275da62e8c1 ("rxrpc: Create a per-local endpoint receive queue and I/O thread") Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Link: https://lore.kernel.org/r/0000000000002b4a9f05ef2b616f@google.com/ [1] Signed-off-by: David S. Miller

rxrpc: Remove the _bh annotation from all the spinlocks

2022-12-01T13:36:42+00:00

None of the spinlocks in rxrpc need a _bh annotation now as the RCU callback routines no longer take spinlocks and the bulk of the packet wrangling code is now run in the I/O thread, not softirq context. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org

rxrpc: trace: Don't use __builtin_return_address for rxrpc_peer tracing

2022-12-01T13:36:38+00:00

In rxrpc tracing, use enums to generate lists of points of interest rather than __builtin_return_address() for the rxrpc_peer tracepoint Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org

rxrpc: trace: Don't use __builtin_return_address for rxrpc_local tracing

2022-12-01T13:36:38+00:00

In rxrpc tracing, use enums to generate lists of points of interest rather than __builtin_return_address() for the rxrpc_local tracepoint Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org

rxrpc: Remove the [_k]net() debugging macros

2022-12-01T13:36:38+00:00

Remove the _net() and knet() debugging macros in favour of tracepoints. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org

rxrpc: Fix congestion management

2022-11-08T16:42:28+00:00

rxrpc has a problem in its congestion management in that it saves the congestion window size (cwnd) from one call to another, but if this is 0 at the time is saved, then the next call may not actually manage to ever transmit anything. To this end: (1) Don't save cwnd between calls, but rather reset back down to the initial cwnd and re-enter slow-start if data transmission is idle for more than an RTT. (2) Preserve ssthresh instead, as that is a handy estimate of pipe capacity. Knowing roughly when to stop slow start and enter congestion avoidance can reduce the tendency to overshoot and drop larger amounts of packets when probing. In future, cwind growth also needs to be constrained when the window isn't being filled due to being application limited. Reported-by: Simon Wilkinson cc: Marc Dionne cc: linux-afs@lists.infradead.org