Re: Panic when make check for ndctl

[Yasunori Goto <y-goto@jp.fujitsu.com>]

Hi, Dan-san, Linda-san,

I had chased the root cause of this panic problem, and maybe I found it.

> > > Hmmm, though I made Fedora 25 environment, this panic still occurs...
> > > I'll attach syslog and .config again.
> > >
> > >
> > [..]
> > > [  117.804948] general protection fault: 0000 [#1] SMP
> > [..]
> > > [  117.820866] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
> > [..]
> > > [  117.843262] Call Trace:
> > > [  117.843985]  release_nodes+0x76/0x260
> > > [  117.845062]  devres_release_all+0x3c/0x50
> > > [  117.846225]  device_release_driver_internal+0x159/0x200
> > > [  117.847748]  device_release_driver+0x12/0x20
> > > [  117.849029]  bus_remove_device+0xfd/0x170
> > > [  117.850192]  device_del+0x1e8/0x330
> > > [  117.851284]  platform_device_del+0x28/0x90
> > > [  117.852485]  platform_device_unregister+0x12/0x30
> > > [  117.853846]  nfit_test_exit+0x2a/0x93b [nfit_test]
> > > [  117.855219]  SyS_delete_module+0x171/0x250
> > > [  117.856403]  entry_SYSCALL_64_fastpath+0x1a/0xa5
> > 
> > Can you also attach the qemu-kvm command line you are using?
> > 
> >     ps aux | grep qemu


The cause of this problem is the num_pm of nfit_test1 is wrong.
Though 1 is specified for num_pm at nfit_test_init(), it must be 2.

----
static __init int nfit_test_init(void)
{
        int rc, i;
        :
        :
                case 1:
                        nfit_test->num_pm = 1;            <---- !!!
                        nfit_test->dcr_idx = NUM_DCR;
-----

The num_pm affects size of devm_kcalloc() at nfit_test_probe().

----
static int nfit_test_probe(struct platform_device *pdev)
{
        if (nfit_test->num_pm) {
                int num = nfit_test->num_pm;   <----!!!

                nfit_test->spa_set = devm_kcalloc(dev, num, sizeof(void *),
                                GFP_KERNEL);   <---!!!!
                nfit_test->spa_set_dma = devm_kcalloc(dev, num,   
                                sizeof(dma_addr_t), GFP_KERNEL);
-----

However,  spa_set[] array needs 2 elements at nfit_test1_alloc().

---
static int nfit_test1_alloc(struct nfit_test *t)
{
               :
        t->spa_set[0] = test_alloc(t, SPA2_SIZE, &t->spa_set_dma[0]);  <--- first element
        if (!t->spa_set[0])
                return -ENOMEM;
               :

       t->spa_set[1] = test_alloc(t, SPA_VCD_SIZE, &t->spa_set_dma[1]);  <---- The second element!!!!
-----

This breaks other area, and the area is often the link list of devres.
As a result, the panic occured on release_nodes().

I confirmed that this panic never occurred with the following patch.

---
diff --git a/tools/testing/nvdimm/test/nfit.c b/tools/testing/nvdimm/test/nfit.c
index c218717..548b6d4 100644
--- a/tools/testing/nvdimm/test/nfit.c
+++ b/tools/testing/nvdimm/test/nfit.c
@@ -1943,7 +1943,7 @@ static __init int nfit_test_init(void)
                        nfit_test->setup = nfit_test0_setup;
                        break;
                case 1:
-                       nfit_test->num_pm = 1;
+                       nfit_test->num_pm = 2;
                        nfit_test->dcr_idx = NUM_DCR;
                        nfit_test->num_dcr = 2;
                        nfit_test->alloc = nfit_test1_alloc;
----

Thanks,
Yasunori Goto


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