Re: [PATCH] IB/mad: Use ID allocator routines to allocate agent number

[Leon Romanovsky <leon@kernel.org>]

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On Tue, May 29, 2018 at 11:54:59AM +0300, Leon Romanovsky wrote:
> On Tue, May 29, 2018 at 09:38:08AM +0200, Hans Westgaard Ry wrote:
> > The agent TID is a 64 bit value split in two dwords.  The least
> > significant dword is the TID running counter. The most significant
> > dword is the agent number. In the CX-3 shared port model, the mlx4
> > driver uses the most significant byte of the agent number to store the
> > slave number, making agent numbers greater and equal to 2^24 (3 bytes)
> > unusable.  The current codebase uses a variable which is incremented
> > atomically for each new agent number giving too large agent numbers
> > over time.  The IDA set of functions are used instead of the simple
> > counter approach. This allows re-use of agent numbers. A sysctl
> > variable is also introduced, to control the max agent number.
>
> Why don't you simply limit this number per-driver? By default, any
> variable is allowed and mlx4_ib will set something else.
>
> What is the advantage of having sysctl?

Anyway, it doesn't pass smoke test.

[  126.428407] RPC: Unregistered rdma transport module.
[  126.428513] RPC: Unregistered rdma backchannel transport module.
[  194.664081] IPv6: ADDRCONF(NETDEV_UP): ib0: link is not ready
[  209.068702] BUG: unable to handle kernel NULL pointer dereference at 0000000000000070
[  209.068858] PGD 80000000341cf067 P4D 80000000341cf067 PUD 34188067 PMD 0
[  209.068941] Oops: 0002 [#1] SMP PTI
[  209.069006] Modules linked in: netconsole nfsv3 nfs fscache
mlx4_ib(-) mlx4_en mlx4_core devlink ib_ipoib rdma_ucm ib_ucm ib_uverbs
ib_umad rdma_cm ib_cm iw_cm ib_core dm_mirror dm_region_hash dm_log
dm_mod nfsd pcspkr i2c_piix4 auth_rpcgss nfs_acl lockd grace sunrpc
ip_tables ata_generic cirrus drm_kms_helper pata_acpi syscopyarea
sysfillrect sysimgblt fb_sys_fops ttm drm e1000 virtio_console i2c_core
serio_raw ata_piix floppy [last unloaded: mlxfw]
[  209.069312] CPU: 4 PID: 11048 Comm: modprobe Not tainted 4.17.0-rc7-2018-05-29_11-04-56_Hans_Westgaard_Ry__hans_westga #1
[  209.069413] Hardware name: Red Hat KVM, BIOS Bochs 01/01/2011
[  209.069486] RIP: 0010:_raw_spin_lock_irqsave+0x1e/0x40
[  209.069536] RSP: 0018:ffffc90000b4fd70 EFLAGS: 00010046
[  209.069591] RAX: 0000000000000000 RBX: 0000000000000246 RCX: ffffea0004d7ed00
[  209.069653] RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000070
[  209.069717] RBP: 0000000000000000 R08: ffff88013446fc00 R09: 000000018010000f
[  209.069778] R10: 0000000000000001 R11: ffff88013446fc00 R12: 0000000000000070
[  209.069849] R13: 0000000000000202 R14: 0000000000000000 R15: 0000000000000000
[  209.069915] FS:  00007fc34caf7740(0000) GS:ffff88013fd00000(0000) knlGS:0000000000000000
[  209.069987] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  209.070043] CR2: 0000000000000070 CR3: 000000008853e000 CR4: 00000000000006e0
[  209.070128] Call Trace:
[  209.070189]  ib_unregister_mad_agent+0x2d/0x540 [ib_core]
[  209.070260]  ? __slab_free+0x9a/0x2d0
[  209.070332]  ib_agent_port_close+0xad/0xf0 [ib_core]
[  209.070396]  ib_mad_remove_device+0x59/0xb0 [ib_core]
[  209.070466]  ib_unregister_device+0xd4/0x180 [ib_core]
[  209.070537]  mlx4_ib_remove+0x67/0x1f0 [mlx4_ib]
[  209.070594]  mlx4_remove_device+0x93/0xa0 [mlx4_core]
[  209.070648]  mlx4_unregister_interface+0x37/0x90 [mlx4_core]
[  209.070705]  mlx4_ib_cleanup+0xc/0x4db [mlx4_ib]
[  209.072113]  __x64_sys_delete_module+0x15b/0x260
[  209.073567]  ? exit_to_usermode_loop+0x7f/0x95
[  209.074945]  do_syscall_64+0x48/0x100
[  209.076448]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  209.077799] RIP: 0033:0x7fc34bfe36b7
[  209.079122] RSP: 002b:00007ffc8ffa98b8 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
[  209.080500] RAX: ffffffffffffffda RBX: 00000000013455c0 RCX: 00007fc34bfe36b7
[  209.081875] RDX: 0000000000000000 RSI: 0000000000000800 RDI: 0000000001345628
[  209.083265] RBP: 0000000000000000 R08: 00007fc34c2a8060 R09: 00007fc34c053a40
[  209.084655] R10: 00007ffc8ffa9640 R11: 0000000000000206 R12: 0000000000000000
[  209.086028] R13: 0000000000000001 R14: 0000000001345628 R15: 0000000000000000
[  209.087416] Code: 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00
00 53 9c 58 0f 1f 44 00 00 48 89 c3 fa 66 0f 1f 44 00 00 31 c0 ba 01 00
00 00 <f0> 0f b1 17 85 c0 75 05 48 89 d8 5b c3 89 c6 e8 1e c9 81 ff eb
[  209.090262] RIP: _raw_spin_lock_irqsave+0x1e/0x40 RSP: ffffc90000b4fd70
[  209.091720] CR2: 0000000000000070
[  209.093137] ---[ end trace 7b8a6faa27868861 ]---
[  209.094546] Kernel panic - not syncing: Fatal exception
[  209.096910] Kernel Offset: disabled
[  209.098291] ---[ end Kernel panic - not syncing: Fatal exception ]---

Thanks

>
> Thanks



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