RDMA/iwcm: Fix WARNING:at_kernel/workqueue.c:#check_flush_dependency

In the commit aee2424246f9 ("RDMA/iwcm: Fix a use-after-free related to destroying CM IDs"), the function flush_workqueue is invoked to flush the work queue iwcm_wq.

But at that time, the work queue iwcm_wq was created via the function alloc_ordered_workqueue without the flag WQ_MEM_RECLAIM.

Because the current process is trying to flush the whole iwcm_wq, if iwcm_wq doesn't have the flag WQ_MEM_RECLAIM, verify that the current process is not reclaiming memory or running on a workqueue which doesn't have the flag WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to a deadlock.

The call trace is as below:
"

[  125.350876][ T1430] Call Trace:
[  125.356281][ T1430]  <TASK>
[ 125.361285][ T1430] ? __warn (kernel/panic.c:693)
[ 125.367640][ T1430] ? check_flush_dependency (kernel/workqueue.c:3706 (discriminator 9))
[ 125.375689][ T1430] ? report_bug (lib/bug.c:180 lib/bug.c:219)
[ 125.382505][ T1430] ? handle_bug (arch/x86/kernel/traps.c:239)
[ 125.388987][ T1430] ? exc_invalid_op (arch/x86/kernel/traps.c:260 (discriminator 1))
[ 125.395831][ T1430] ? asm_exc_invalid_op (arch/x86/include/asm/idtentry.h:621)
[ 125.403125][ T1430] ? check_flush_dependency (kernel/workqueue.c:3706 (discriminator 9))
[ 125.410984][ T1430] ? check_flush_dependency (kernel/workqueue.c:3706 (discriminator 9))
[ 125.418764][ T1430] __flush_workqueue (kernel/workqueue.c:3970)
[ 125.426021][ T1430] ? __pfx___might_resched (kernel/sched/core.c:10151)
[ 125.433431][ T1430] ? destroy_cm_id (drivers/infiniband/core/iwcm.c:375) iw_cm
[  125.440844][ T2411] /usr/bin/wget -q --timeout=3600 --tries=1 --local-encoding=UTF-8 http://internal-lkp-server:80/~lkp/cgi-bin/lkp-jobfile-append-var?job_file=/lkp/jobs/scheduled/lkp-spr-2sp1/blktests-1SSD-rdma-nvme-group-01-debian-12-x86_64-20240206.cgz-aee2424246f9-20240809-69442-1dktaed-4.yaml&job_state=running -O /dev/null
[ 125.441209][ T1430] ? __pfx___flush_workqueue (kernel/workqueue.c:3910)
[  125.441215][ T2411]
[ 125.473900][ T1430] ? _raw_spin_lock_irqsave (arch/x86/include/asm/atomic.h:107 include/linux/atomic/atomic-arch-fallback.h:2170 include/linux/atomic/atomic-instrumented.h:1302 include/asm-generic/qspinlock.h:111 include/linux/spinlock.h:187 include/linux/spinlock_api_smp.h:111 kernel/locking/spinlock.c:162)
[ 125.473909][ T1430] ? __pfx__raw_spin_lock_irqsave (kernel/locking/spinlock.c:161)
[  125.480265][ T2411] target ucode: 0x2b0004b1
[ 125.482537][ T1430] _destroy_id (drivers/infiniband/core/cma.c:2044) rdma_cm
[  125.488511][ T2411]
[ 125.495072][ T1430] nvme_rdma_free_queue (drivers/nvme/host/rdma.c:656 drivers/nvme/host/rdma.c:650) nvme_rdma
[  125.500747][ T2411] LKP: stdout: 2876: current_version: 2b0004b1, target_version: 2b0004b1
[ 125.505827][ T1430] nvme_rdma_reset_ctrl_work (drivers/nvme/host/rdma.c:2180) nvme_rdma
[ 125.505831][ T1430] process_one_work (kernel/workqueue.c:3231)
[  125.508377][ T2411]
[ 125.515122][ T1430] worker_thread (kernel/workqueue.c:3306 kernel/workqueue.c:3393)
[ 125.515127][ T1430] ? __pfx_worker_thread (kernel/workqueue.c:3339)
[  125.524642][ T2411] check_nr_cpu
[ 125.531837][ T1430] kthread (kernel/kthread.c:389)
[  125.537327][ T2411]
[ 125.539864][ T1430] ? __pfx_kthread (kernel/kthread.c:342)
[  125.545392][ T2411] CPU(s):                               224
[ 125.550628][ T1430] ret_from_fork (arch/x86/kernel/process.c:147)
[  125.554342][ T2411]
[ 125.558840][ T1430] ? __pfx_kthread (kernel/kthread.c:342)
[ 125.558844][ T1430] ret_from_fork_asm (arch/x86/entry/entry_64.S:257)
[  125.561843][ T2411] On-line CPU(s) list:                  0-223
[  125.566487][ T1430]  </TASK>
[  125.566488][ T1430] ---[ end trace 0000000000000000 ]---

"

---
V1 -> V2: Modify commit logs based on Bart and Jason' suggestions

---
 drivers/infiniband/core/iwcm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 1a6339f3a63f..7e3a55349e10 100644
@@ -1182,7 +1182,7 @@ static int __init iw_cm_init(void)
 	if (ret)
 		return ret;
 
-	iwcm_wq = alloc_ordered_workqueue("iw_cm_wq", 0);
+	iwcm_wq = alloc_ordered_workqueue("iw_cm_wq", WQ_MEM_RECLAIM);
 	if (!iwcm_wq)
 		goto err_alloc;
 

2.34.1

..

Applied to for-next, thanks

Jason