A kernel panic was observed when passing the sc->request->cpu = -1 to
retrieve the per_cpu variable pointer:
#0 [ffff880011203960] machine_kexec at ffffffff81022bc3
#1 [ffff8800112039b0] crash_kexec at ffffffff81088630
#2 [ffff880011203a80] __die at ffffffff8139ea20
#3 [ffff880011203aa0] no_context at ffffffff8102f3a7
#4 [ffff880011203ae0] __bad_area_nosemaphore at ffffffff8102f665
#5 [ffff880011203ba0] retint_signal at ffffffff8139dd1f
#6 [ffff880011203cc8] bnx2i_indicate_kcqe at ffffffffa03dc4f2
#7 [ffff880011203da8] service_kcqes at ffffffffa03cb04f
#8 [ffff880011203e68] cnic_service_bnx2x_kcq at ffffffffa03cb14a
#9 [ffff880011203e88] cnic_service_bnx2x_bh at ffffffffa03cb1b3
The problem lies in the slow path sg_io (and perhaps sg_scsi_ioctl) call to
blk_get_request->get_request/wait->blk_alloc_request->blk_rq_init which
re-initializes the request->cpu to -1. There is no assignment for cpu from
that to the request_fn call to low level drivers.
When this happens, the sc->request->cpu will be using the init value of
-1. This will create a kernel panic when it hits bnx2i because the code
refers it to get the per_cpu variables ptr.
This change is to put in a guard against that and also for cases when
bio affinity/queue completion to the same cpu is not enabled. In those
cases, the request->cpu will remain a -1 also.
This bug was created from commit: b5cf6b63f73abdc051035f0050b367beeb2ef94c
For the case when the blk layer did not setup the request->cpu, bnx2i
will complete the sc with the current CPU of the thread.
Signed-off-by: Eddie Wai <eddie.wai@xxxxxxxxxxxx>
---
drivers/scsi/bnx2i/bnx2i_hwi.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/drivers/scsi/bnx2i/bnx2i_hwi.c b/drivers/scsi/bnx2i/bnx2i_hwi.c
index 54978c1..28c6693 100644
--- a/drivers/scsi/bnx2i/bnx2i_hwi.c
+++ b/drivers/scsi/bnx2i/bnx2i_hwi.c
@@ -1901,6 +1901,7 @@ static int bnx2i_queue_scsi_cmd_resp(struct iscsi_session *session,
struct iscsi_task *task;
struct scsi_cmnd *sc;
int rc = 0;
+ int cpu;
spin_lock(&session->lock);
task = iscsi_itt_to_task(bnx2i_conn->cls_conn->dd_data,
@@ -1912,7 +1913,12 @@ static int bnx2i_queue_scsi_cmd_resp(struct iscsi_session *session,
sc = task->sc;
spin_unlock(&session->lock);
- p = &per_cpu(bnx2i_percpu, sc->request->cpu);
+ if (!blk_rq_cpu_valid(sc->request))
+ cpu = smp_processor_id();
+ else
+ cpu = sc->request->cpu;
+
+ p = &per_cpu(bnx2i_percpu, cpu);
spin_lock(&p->p_work_lock);
if (unlikely(!p->iothread)) {
rc = -EINVAL;
--
1.7.0.5
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