RDMA/hns: Fix soft lockup during bt pages loop

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: RDMA/hns: Fix soft lockup during bt pages loop Driver runs a for-loop when allocating bt pages and mapping them with buffer pages. When a large buffer (e.g. MR over 100GB) is being allocated, it may require a considerable loop count. This will lead to soft lockup: watchdog: BUG: soft lockup - CPU#27 stuck for 22s! ... Call trace: hem_list_alloc_mid_bt+0x124/0x394 [hns_roce_hw_v2] hns_roce_hem_list_request+0xf8/0x160 [hns_roce_hw_v2] hns_roce_mtr_create+0x2e4/0x360 [hns_roce_hw_v2] alloc_mr_pbl+0xd4/0x17c [hns_roce_hw_v2] hns_roce_reg_user_mr+0xf8/0x190 [hns_roce_hw_v2] ib_uverbs_reg_mr+0x118/0x290 watchdog: BUG: soft lockup - CPU#35 stuck for 23s! ... Call trace: hns_roce_hem_list_find_mtt+0x7c/0xb0 [hns_roce_hw_v2] mtr_map_bufs+0xc4/0x204 [hns_roce_hw_v2] hns_roce_mtr_create+0x31c/0x3c4 [hns_roce_hw_v2] alloc_mr_pbl+0xb0/0x160 [hns_roce_hw_v2] hns_roce_reg_user_mr+0x108/0x1c0 [hns_roce_hw_v2] ib_uverbs_reg_mr+0x120/0x2bc Add a cond_resched() to fix soft lockup during these loops. In order not to affect the allocation performance of normal-size buffer, set the loop count of a 100GB MR as the threshold to call cond_resched().

References

• https://git.kernel.org/stable/c/461eb4ddede266df8f181f578732bb01742c3fd6
• https://git.kernel.org/stable/c/efe544462fc0b499725364f90bd0f8bbf16f861a
• https://git.kernel.org/stable/c/4104b0023ff66b5df900d23dbf38310893deca79
• https://git.kernel.org/stable/c/975355faba56c0751292ed15a90c3e2c7dc0aad6
• https://git.kernel.org/stable/c/13a52f6c9ff99f7d88f81da535cb4e85eade662b
• https://git.kernel.org/stable/c/9ab20fec7a1ce3057ad86afd27bfd08420b7cd11
• https://git.kernel.org/stable/c/25655580136de59ec89f09089dd28008ea440fc9