kernel/linux.git/net/rxrpc/peer_object.c, branch v6.19.11

rxrpc: Fix irq-disabled in local_bh_enable()

2025-07-17T14:50:48+00:00

The rxrpc_assess_MTU_size() function calls down into the IP layer to find out the MTU size for a route. When accepting an incoming call, this is called from rxrpc_new_incoming_call() which holds interrupts disabled across the code that calls down to it. Unfortunately, the IP layer uses local_bh_enable() which, config dependent, throws a warning if IRQs are enabled: WARNING: CPU: 1 PID: 5544 at kernel/softirq.c:387 __local_bh_enable_ip+0x43/0xd0 ... RIP: 0010:__local_bh_enable_ip+0x43/0xd0 ... Call Trace: rt_cache_route+0x7e/0xa0 rt_set_nexthop.isra.0+0x3b3/0x3f0 __mkroute_output+0x43a/0x460 ip_route_output_key_hash+0xf7/0x140 ip_route_output_flow+0x1b/0x90 rxrpc_assess_MTU_size.isra.0+0x2a0/0x590 rxrpc_new_incoming_peer+0x46/0x120 rxrpc_alloc_incoming_call+0x1b1/0x400 rxrpc_new_incoming_call+0x1da/0x5e0 rxrpc_input_packet+0x827/0x900 rxrpc_io_thread+0x403/0xb60 kthread+0x2f7/0x310 ret_from_fork+0x2a/0x230 ret_from_fork_asm+0x1a/0x30 ... hardirqs last enabled at (23): _raw_spin_unlock_irq+0x24/0x50 hardirqs last disabled at (24): _raw_read_lock_irq+0x17/0x70 softirqs last enabled at (0): copy_process+0xc61/0x2730 softirqs last disabled at (25): rt_add_uncached_list+0x3c/0x90 Fix this by moving the call to rxrpc_assess_MTU_size() out of rxrpc_init_peer() and further up the stack where it can be done without interrupts disabled. It shouldn't be a problem for rxrpc_new_incoming_call() to do it after the locks are dropped as pmtud is going to be performed by the I/O thread - and we're in the I/O thread at this point. Fixes: a2ea9a907260 ("rxrpc: Use irq-disabling spinlocks between app and I/O thread") Signed-off-by: David Howells Reviewed-by: Jeffrey Altman cc: Marc Dionne cc: Junvyyang, Tencent Zhuque Lab cc: LePremierHomme cc: Simon Horman cc: linux-afs@lists.infradead.org Link: https://patch.msgid.link/20250717074350.3767366-2-dhowells@redhat.com Signed-off-by: Jakub Kicinski

rxrpc: kdoc: Update function descriptions and add link from rxrpc.rst

2025-04-15T00:36:40+00:00

Update the kerneldoc function descriptions to add "Return:" sections for AF_RXRPC exported functions that have return values to stop the kdoc builder from throwing warnings. Also add links from the rxrpc.rst API doc to add a function API reference at the end. (Note that the API doc really needs updating, but that's beyond this patchset). Signed-off-by: David Howells cc: Marc Dionne cc: Simon Horman cc: linux-afs@lists.infradead.org Link: https://patch.msgid.link/20250411095303.2316168-2-dhowells@redhat.com Signed-off-by: Jakub Kicinski

afs: Use the per-peer app data provided by rxrpc

2025-03-10T09:47:15+00:00

Make use of the per-peer application data that rxrpc now allows the application to store on the rxrpc_peer struct to hold a back pointer to the afs_server record that peer represents an endpoint for. Then, when a call comes in to the AFS cache manager, this can be used to map it to the correct server record rather than having to use a UUID-to-server mapping table and having to do an additional lookup. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20250224234154.2014840-14-dhowells@redhat.com/ # v1 Link: https://lore.kernel.org/r/20250310094206.801057-10-dhowells@redhat.com/ # v4

rxrpc: Allow the app to store private data on peer structs

2025-03-10T09:47:15+00:00

Provide a way for the application (e.g. the afs filesystem) to store private data on the rxrpc_peer structs for later retrieval via the call object. This will allow afs to store a pointer to the afs_server object on the rxrpc_peer struct, thereby obviating the need for afs to keep lookup tables by which it can associate an incoming call with server that transmitted it. Signed-off-by: David Howells cc: Marc Dionne cc: Jakub Kicinski cc: "David S. Miller" cc: Eric Dumazet cc: Paolo Abeni cc: Simon Horman cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org cc: netdev@vger.kernel.org Link: https://lore.kernel.org/r/20250224234154.2014840-13-dhowells@redhat.com/ # v1 Link: https://lore.kernel.org/r/20250310094206.801057-9-dhowells@redhat.com/ # v4

rxrpc: Fix locking issues with the peer record hash

2025-02-21T23:06:29+00:00

rxrpc_new_incoming_peer() can't use spin_lock_bh() whilst its caller has interrupts disabled. WARNING: CPU: 0 PID: 1550 at kernel/softirq.c:369 __local_bh_enable_ip+0x46/0xd0 ... Call Trace: rxrpc_alloc_incoming_call+0x1b0/0x400 rxrpc_new_incoming_call+0x1dd/0x5e0 rxrpc_input_packet+0x84a/0x920 rxrpc_io_thread+0x40d/0xb40 kthread+0x2ec/0x300 ret_from_fork+0x24/0x40 ret_from_fork_asm+0x1a/0x30 irq event stamp: 1811 hardirqs last enabled at (1809): _raw_spin_unlock_irq+0x24/0x50 hardirqs last disabled at (1810): _raw_read_lock_irq+0x17/0x70 softirqs last enabled at (1182): handle_softirqs+0x3ee/0x430 softirqs last disabled at (1811): rxrpc_new_incoming_peer+0x56/0x120 Fix this by using a plain spin_lock() instead. IRQs are held, so softirqs can't happen. Fixes: a2ea9a907260 ("rxrpc: Use irq-disabling spinlocks between app and I/O thread") Signed-off-by: David Howells cc: Marc Dionne cc: Simon Horman cc: linux-afs@lists.infradead.org Link: https://patch.msgid.link/20250218192250.296870-4-dhowells@redhat.com Signed-off-by: Jakub Kicinski

rxrpc: peer->mtu_lock is redundant

2025-02-21T23:06:29+00:00

The peer->mtu_lock is only used to lock around writes to peer->max_data - and nothing else; further, all such writes take place in the I/O thread and the lock is only ever write-locked and never read-locked. In a couple of places, the write_seqcount_begin() is wrapped in preempt_disable/enable(), but not in all places. This can cause lockdep to complain: WARNING: CPU: 0 PID: 1549 at include/linux/seqlock.h:221 rxrpc_input_ack_trailer+0x305/0x430 ... RIP: 0010:rxrpc_input_ack_trailer+0x305/0x430 Fix this by just getting rid of the lock. Fixes: eeaedc5449d9 ("rxrpc: Implement path-MTU probing using padded PING ACKs (RFC8899)") Signed-off-by: David Howells cc: Marc Dionne cc: Simon Horman cc: linux-afs@lists.infradead.org Link: https://patch.msgid.link/20250218192250.296870-3-dhowells@redhat.com Signed-off-by: Jakub Kicinski

rxrpc, afs: Fix peer hash locking vs RCU callback

2025-01-27T22:46:18+00:00

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

rxrpc: Manage RTT per-call rather than per-peer

2024-12-09T21:48:32+00:00

Manage the determination of RTT on a per-call (ie. per-RPC op) basis rather than on a per-peer basis, averaging across all calls going to that peer. The problem is that the RTT measurements from the initial packets on a call may be off because the server may do some setting up (such as getting a lock on a file) before accepting the rest of the data in the RPC and, further, the RTT may be affected by server-side file operations, for instance if a large amount of data is being written or read. Note: When handling the FS.StoreData-type RPCs, for example, the server uses the userStatus field in the header of ACK packets as supplementary flow control to aid in managing this. AF_RXRPC does not yet support this, but it should be added. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Jakub Kicinski

rxrpc: Use irq-disabling spinlocks between app and I/O thread

2024-12-09T21:48:31+00:00

Where a spinlock is used by both the application thread and the I/O thread, use irq-disabling locking so that an interrupt taken on the app thread doesn't also slow down the I/O thread. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Jakub Kicinski

rxrpc: Implement path-MTU probing using padded PING ACKs (RFC8899)

2024-12-09T21:48:25+00:00

Implement path-MTU probing (along the lines of RFC8899) by padding some of the PING ACKs we send. PING ACKs get their own individual responses quite apart from the acking of data (though, as ACKs, they fulfil that role also). The probing concentrates on packet sizes that correspond how many subpackets can be stuffed inside a jumbo packet as jumbo DATA packets are just aggregations of individual DATA packets and can be split easily for retransmission purposes. If we want to perform probing, we advertise this by setting the maximum number of jumbo subpackets to 0 in the ack trailer when we send an ACK and see if the peer is also advertising the service. This is interpreted by non-supporting Rx stacks as an indication that jumbo packets aren't supported. The MTU sizes advertised in the ACK trailer AF_RXRPC transmits are pegged at a maximum of 1444 unless pmtud is supported by both sides. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Link: https://patch.msgid.link/20241204074710.990092-10-dhowells@redhat.com Signed-off-by: Jakub Kicinski