[5.10] [Bugfix] swiotlb: fix the deadlock in swiotlb_do_find_slots · Pull Request !1191 · anolis/cloud-kernel

bugzilla: https://bugzilla.openanolis.cn/show_bug.cgi?id=4078

In general, if swiotlb is sufficient, the logic of index =
wrap_area_index(mem, index + 1) is fine, it will quickly take a slot and
release the area->lock; But if swiotlb is insufficient and the device
has min_align_mask requirements, such as NVME, we may not be able to
satisfy index == wrap and exit the loop properly. In this case, other
kernel threads will not be able to acquire the area->lock and release
the slot, resulting in a deadlock.

The current implementation of wrap_area_index does not involve a modulo
operation, so adjusting the wrap to ensure the loop ends is not trivial.
Introduce the index_nowrap variable to record the number of loops and
exit the loop after completing the traversal.

Backtraces:
Every other CPU are waiting this core to exit the swiotlb_do_find_slots 
loop.

[10199.924385] NMI backtrace for cpu 49
[10199.924403] Call Trace:
[10199.924404]  <TASK>
[10199.924405]  swiotlb_tbl_map_single+0xec/0x1f0
[10199.924407]  swiotlb_map+0x5c/0x260
[10199.924409]  ? nvme_pci_setup_prps+0x1ed/0x340
[10199.924411]  dma_direct_map_page+0x12e/0x1c0
[10199.924413]  nvme_map_data+0x304/0x370
[10199.924415]  nvme_prep_rq.part.0+0x31/0x120
[10199.924417]  nvme_queue_rq+0x77/0x1f0
[10199.924420]  blk_mq_dispatch_rq_list+0x17e/0x670
[10199.924422]  __blk_mq_sched_dispatch_requests+0x129/0x140
[10199.924424]  blk_mq_sched_dispatch_requests+0x34/0x60
[10199.924426]  __blk_mq_run_hw_queue+0x91/0xb0
[10199.924428]  process_one_work+0x1df/0x3b0
[10199.924430]  worker_thread+0x49/0x2e0
[10199.924432]  ? rescuer_thread+0x390/0x390
[10199.924433]  kthread+0xe5/0x110
[10199.924435]  ? kthread_complete_and_exit+0x20/0x20
[10199.924436]  ret_from_fork+0x1f/0x30
[10199.924439]  </TASK>

...
[ 9639.596311] NMI backtrace for cpu 48
[ 9639.596336] Call Trace:
[ 9639.596337]  <TASK>
[ 9639.596338]  _raw_spin_lock_irqsave+0x37/0x40
[ 9639.596341]  swiotlb_do_find_slots+0xef/0x3e0
[ 9639.596344]  swiotlb_tbl_map_single+0xec/0x1f0
[ 9639.596347]  swiotlb_map+0x5c/0x260
[ 9639.596349]  dma_direct_map_sg+0x7a/0x280
[ 9639.596352]  __dma_map_sg_attrs+0x30/0x70
[ 9639.596355]  dma_map_sgtable+0x1d/0x30
[ 9639.596356]  nvme_map_data+0xce/0x370
[ 9639.596359]  nvme_prep_rq.part.0+0x31/0x120
[ 9639.596362]  nvme_queue_rq+0x77/0x1f0
[ 9639.596364]  blk_mq_dispatch_rq_list+0x17e/0x670
[ 9639.596367]  __blk_mq_sched_dispatch_requests+0x129/0x140
[ 9639.596370]  blk_mq_sched_dispatch_requests+0x34/0x60
[ 9639.596372]  __blk_mq_run_hw_queue+0x91/0xb0
[ 9639.596374]  process_one_work+0x1df/0x3b0
[ 9639.596377]  worker_thread+0x49/0x2e0
[ 9639.596379]  ? rescuer_thread+0x390/0x390
[ 9639.596380]  kthread+0xe5/0x110
[ 9639.596382]  ? kthread_complete_and_exit+0x20/0x20
[ 9639.596383]  ret_from_fork+0x1f/0x30
[ 9639.596387]  </TASK>

...

[ 9639.595665] NMI backtrace for cpu 50
[ 9639.595682] Call Trace:
[ 9639.595682]  <IRQ>
[ 9639.595683]  _raw_spin_lock_irqsave+0x37/0x40
[ 9639.595686]  swiotlb_release_slots.isra.0+0x86/0x180
[ 9639.595688]  dma_direct_unmap_sg+0xcf/0x1a0
[ 9639.595690]  nvme_unmap_data.part.0+0x43/0xc0
[ 9639.595693]  nvme_pci_complete_batch+0x71/0xe0
[ 9639.595695]  nvme_irq+0x7b/0x90
[ 9639.595697]  ? nvme_prep_rq_batch+0xc0/0xc0
[ 9639.595700]  __handle_irq_event_percpu+0x46/0x170
[ 9639.595701]  handle_irq_event+0x3a/0x80
[ 9639.595703]  handle_edge_irq+0xae/0x290
[ 9639.595705]  __common_interrupt+0x62/0x100
[ 9639.595707]  common_interrupt+0xb3/0xd0
[ 9639.595709]  </IRQ>
[ 9639.595709]  <TASK>
[ 9639.595710]  asm_common_interrupt+0x22/0x40
[ 9639.595712] RIP: 0010:__tdx_hypercall+0x34/0x80

Fixes: 1f221a0d0dbf ("swiotlb: respect min_align_mask")
Signed-off-by: Guorui Yu <GuoRui.Yu@linux.alibaba.com>
Signed-off-by: Xiaokang Hu <xiaokang.hxk@alibaba-inc.com>

类型	指派人员	状态
审查	Artie Ding zelindeng	已完成 (0/0人)
测试	小龙已测试通过	已完成 (1/1人)

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