vcsm: Treat EBUSY as success rather than SIGBUS

Currently if two cores access the same page concurrently one will return VM_FAULT_NOPAGE
and the other VM_FAULT_SIGBUS crashing the user code.

Also report when mapping fails.

Signed-off-by: popcornmix <popcornmix@gmail.com>

diff --git a/drivers/char/broadcom/vc_sm/vmcs_sm.c b/drivers/char/broadcom/vc_sm/vmcs_sm.c
index 1db6716c2c0c8b2013203391501f92d09db258af..ee4e05948c439a9045e0b65566d57587177a32e2 100644 (file)
--- a/drivers/char/broadcom/vc_sm/vmcs_sm.c
+++ b/drivers/char/broadcom/vc_sm/vmcs_sm.c
@@ -1181,11 +1181,20 @@ static int vcsm_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
        switch (ret) {
        case 0:
        case -ERESTARTSYS:
+       /*
+       * EBUSY is ok: this just means that another thread
+       * already did the job.
+       */
+       case -EBUSY:
                return VM_FAULT_NOPAGE;
        case -ENOMEM:
        case -EAGAIN:
+               pr_err("[%s]: failed to map page pfn:%lx virt:%lx ret:%d\n", __func__,
+                       pfn, (unsigned long)vmf->virtual_address, ret);
                return VM_FAULT_OOM;
        default:
+               pr_err("[%s]: failed to map page pfn:%lx virt:%lx ret:%d\n", __func__,
+                       pfn, (unsigned long)vmf->virtual_address, ret);
                return VM_FAULT_SIGBUS;
        }
 }