lib/ref_tracker: improve printing stats

In case the library is tracking busy subsystem, simply
printing stack for every active reference will spam log
with long, hard to read, redundant stack traces. To improve
readabilty following changes have been made:
- reports are printed per stack_handle - log is more compact,
- added display name for ref_tracker_dir - it will differentiate
multiple subsystems,
- stack trace is printed indented, in the same printk call,
- info about dropped references is printed as well.

Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

lib: add tests for reference tracker

This module uses reference tracker, forcing two issues.

1) Double free of a tracker

2) leak of two trackers, one being allocated from softirq context.

"modprobe test_ref_tracker" would emit the following traces.
(Use scripts/decode_stacktrace.sh if necessary)

[ 171.648681] reference already released.
[ 171.653213] allocated in:
[ 171.656523] alloctest_ref_tracker_alloc2+0x1c/0x20 [test_ref_tracker]
[ 171.656526] init_module+0x86/0x1000 [test_ref_tracker]
[ 171.656528] do_one_initcall+0x9c/0x220
[ 171.656532] do_init_module+0x60/0x240
[ 171.656536] load_module+0x32b5/0x3610
[ 171.656538] __do_sys_init_module+0x148/0x1a0
[ 171.656540] __x64_sys_init_module+0x1d/0x20
[ 171.656542] do_syscall_64+0x4a/0xb0
[ 171.656546] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 171.656549] freed in:
[ 171.659520] alloctest_ref_tracker_free+0x13/0x20 [test_ref_tracker]
[ 171.659522] init_module+0xec/0x1000 [test_ref_tracker]
[ 171.659523] do_one_initcall+0x9c/0x220
[ 171.659525] do_init_module+0x60/0x240
[ 171.659527] load_module+0x32b5/0x3610
[ 171.659529] __do_sys_init_module+0x148/0x1a0
[ 171.659532] __x64_sys_init_module+0x1d/0x20
[ 171.659534] do_syscall_64+0x4a/0xb0
[ 171.659536] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 171.659575] ------------[ cut here ]------------
[ 171.659576] WARNING: CPU: 5 PID: 13016 at lib/ref_tracker.c:112 ref_tracker_free+0x224/0x270
[ 171.659581] Modules linked in: test_ref_tracker(+)
[ 171.659591] CPU: 5 PID: 13016 Comm: modprobe Tainted: G S 5.16.0-smp-DEV #290
[ 171.659595] RIP: 0010:ref_tracker_free+0x224/0x270
[ 171.659599] Code: 5e 41 5f 5d c3 48 c7 c7 04 9c 74 a6 31 c0 e8 62 ee 67 00 83 7b 14 00 75 1a 83 7b 18 00 75 30 4c 89 ff 4c 89 f6 e8 9c 00 69 00 <0f> 0b bb ea ff ff ff eb ae 48 c7 c7 3a 0a 77 a6 31 c0 e8 34 ee 67
[ 171.659601] RSP: 0018:ffff89058ba0bbd0 EFLAGS: 00010286
[ 171.659603] RAX: 0000000000000029 RBX: ffff890586b19780 RCX: 08895bff57c7d100
[ 171.659604] RDX: c0000000ffff7fff RSI: 0000000000000282 RDI: ffffffffc0407000
[ 171.659606] RBP: ffff89058ba0bc88 R08: 0000000000000000 R09: ffffffffa6f342e0
[ 171.659607] R10: 00000000ffff7fff R11: 0000000000000000 R12: 000000008f000000
[ 171.659608] R13: 0000000000000014 R14: 0000000000000282 R15: ffffffffc0407000
[ 171.659609] FS: 00007f97ea29d740(0000) GS:ffff8923ff940000(0000) knlGS:0000000000000000
[ 171.659611] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 171.659613] CR2: 00007f97ea299000 CR3: 0000000186b4a004 CR4: 00000000001706e0
[ 171.659614] Call Trace:
[ 171.659615] <TASK>
[ 171.659631] ? alloctest_ref_tracker_free+0x13/0x20 [test_ref_tracker]
[ 171.659633] ? init_module+0x105/0x1000 [test_ref_tracker]
[ 171.659636] ? do_one_initcall+0x9c/0x220
[ 171.659638] ? do_init_module+0x60/0x240
[ 171.659641] ? load_module+0x32b5/0x3610
[ 171.659644] ? __do_sys_init_module+0x148/0x1a0
[ 171.659646] ? __x64_sys_init_module+0x1d/0x20
[ 171.659649] ? do_syscall_64+0x4a/0xb0
[ 171.659652] ? entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 171.659656] ? 0xffffffffc040a000
[ 171.659658] alloctest_ref_tracker_free+0x13/0x20 [test_ref_tracker]
[ 171.659660] init_module+0x105/0x1000 [test_ref_tracker]
[ 171.659663] do_one_initcall+0x9c/0x220
[ 171.659666] do_init_module+0x60/0x240
[ 171.659669] load_module+0x32b5/0x3610
[ 171.659672] __do_sys_init_module+0x148/0x1a0
[ 171.659676] __x64_sys_init_module+0x1d/0x20
[ 171.659678] do_syscall_64+0x4a/0xb0
[ 171.659694] ? exc_page_fault+0x6e/0x140
[ 171.659696] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 171.659698] RIP: 0033:0x7f97ea3dbe7a
[ 171.659700] Code: 48 8b 0d 61 8d 06 00 f7 d8 64 89 01 48 83 c8 ff c3 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 49 89 ca b8 af 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 2e 8d 06 00 f7 d8 64 89 01 48
[ 171.659701] RSP: 002b:00007ffea67ce608 EFLAGS: 00000246 ORIG_RAX: 00000000000000af
[ 171.659703] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f97ea3dbe7a
[ 171.659704] RDX: 00000000013a0ba0 RSI: 0000000000002808 RDI: 00007f97ea299000
[ 171.659705] RBP: 00007ffea67ce670 R08: 0000000000000003 R09: 0000000000000000
[ 171.659706] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000013a1048
[ 171.659707] R13: 00000000013a0ba0 R14: 0000000001399930 R15: 00000000013a1030
[ 171.659709] </TASK>
[ 171.659710] ---[ end trace f5dbd6afa41e60a9 ]---
[ 171.659712] leaked reference.
[ 171.663393] alloctest_ref_tracker_alloc0+0x1c/0x20 [test_ref_tracker]
[ 171.663395] test_ref_tracker_timer_func+0x9/0x20 [test_ref_tracker]
[ 171.663397] call_timer_fn+0x31/0x140
[ 171.663401] expire_timers+0x46/0x110
[ 171.663403] __run_timers+0x16f/0x1b0
[ 171.663404] run_timer_softirq+0x1d/0x40
[ 171.663406] __do_softirq+0x148/0x2d3
[ 171.663408] leaked reference.
[ 171.667101] alloctest_ref_tracker_alloc1+0x1c/0x20 [test_ref_tracker]
[ 171.667103] init_module+0x81/0x1000 [test_ref_tracker]
[ 171.667104] do_one_initcall+0x9c/0x220
[ 171.667106] do_init_module+0x60/0x240
[ 171.667108] load_module+0x32b5/0x3610
[ 171.667111] __do_sys_init_module+0x148/0x1a0
[ 171.667113] __x64_sys_init_module+0x1d/0x20
[ 171.667115] do_syscall_64+0x4a/0xb0
[ 171.667117] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 171.667131] ------------[ cut here ]------------
[ 171.667132] WARNING: CPU: 5 PID: 13016 at lib/ref_tracker.c:30 ref_tracker_dir_exit+0x104/0x130
[ 171.667136] Modules linked in: test_ref_tracker(+)
[ 171.667144] CPU: 5 PID: 13016 Comm: modprobe Tainted: G S W 5.16.0-smp-DEV #290
[ 171.667147] RIP: 0010:ref_tracker_dir_exit+0x104/0x130
[ 171.667150] Code: 01 00 00 00 00 ad de 48 89 03 4c 89 63 08 48 89 df e8 20 a0 d5 ff 4c 89 f3 4d 39 ee 75 a8 4c 89 ff 48 8b 75 d0 e8 7c 05 69 00 <0f> 0b eb 0c 4c 89 ff 48 8b 75 d0 e8 6c 05 69 00 41 8b 47 08 83 f8
[ 171.667151] RSP: 0018:ffff89058ba0bc68 EFLAGS: 00010286
[ 171.667154] RAX: 08895bff57c7d100 RBX: ffffffffc0407010 RCX: 000000000000003b
[ 171.667156] RDX: 000000000000003c RSI: 0000000000000282 RDI: ffffffffc0407000
[ 171.667157] RBP: ffff89058ba0bc98 R08: 0000000000000000 R09: ffffffffa6f342e0
[ 171.667159] R10: 00000000ffff7fff R11: 0000000000000000 R12: dead000000000122
[ 171.667160] R13: ffffffffc0407010 R14: ffffffffc0407010 R15: ffffffffc0407000
[ 171.667162] FS: 00007f97ea29d740(0000) GS:ffff8923ff940000(0000) knlGS:0000000000000000
[ 171.667164] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 171.667166] CR2: 00007f97ea299000 CR3: 0000000186b4a004 CR4: 00000000001706e0
[ 171.667169] Call Trace:
[ 171.667170] <TASK>
[ 171.667171] ? 0xffffffffc040a000
[ 171.667173] init_module+0x126/0x1000 [test_ref_tracker]
[ 171.667175] do_one_initcall+0x9c/0x220
[ 171.667179] do_init_module+0x60/0x240
[ 171.667182] load_module+0x32b5/0x3610
[ 171.667186] __do_sys_init_module+0x148/0x1a0
[ 171.667189] __x64_sys_init_module+0x1d/0x20
[ 171.667192] do_syscall_64+0x4a/0xb0
[ 171.667194] ? exc_page_fault+0x6e/0x140
[ 171.667196] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 171.667199] RIP: 0033:0x7f97ea3dbe7a
[ 171.667200] Code: 48 8b 0d 61 8d 06 00 f7 d8 64 89 01 48 83 c8 ff c3 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 49 89 ca b8 af 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 2e 8d 06 00 f7 d8 64 89 01 48
[ 171.667201] RSP: 002b:00007ffea67ce608 EFLAGS: 00000246 ORIG_RAX: 00000000000000af
[ 171.667203] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f97ea3dbe7a
[ 171.667204] RDX: 00000000013a0ba0 RSI: 0000000000002808 RDI: 00007f97ea299000
[ 171.667205] RBP: 00007ffea67ce670 R08: 0000000000000003 R09: 0000000000000000
[ 171.667206] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000013a1048
[ 171.667207] R13: 00000000013a0ba0 R14: 0000000001399930 R15: 00000000013a1030
[ 171.667209] </TASK>
[ 171.667210] ---[ end trace f5dbd6afa41e60aa ]---

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>