Tejun Heo wrote:
> Hello,
>
> Sachin Sant wrote:
>> <4>PERCPU: chunk 1 relocating -1 -> 18 c0000000db70fb00
>> <c0000000db70fb00:c0000000db70fb00>
>> <4>PERCPU: relocated <c000000001120320:c000000001120320>
>> <4>PERCPU: chunk 1 relocating 18 -> 16 c0000000db70fb00
>> <c000000001120320:c000000001120320>
>> <4>PERCPU: relocated <c000000001120300:c000000001120300>
>> <4>PERCPU: chunk 1, alloc pages [0,1)
>> <4>PERCPU: chunk 1, map pages [0,1)
>> <4>PERCPU: map 0xd00007fffff00000, 1 pages 53544
>> <4>PERCPU: map 0xd00007fffff80000, 1 pages 53545
>> <4>PERCPU: chunk 1, will clear 4096b/unit d00007fffff00000 d00007fffff80000
>> <3>INFO: RCU detected CPU 0 stall (t=1000 jiffies)
>
> This supports my hypothesis. This is the first area being allocated
> from a dynamic chunk and cleared. PFN 53544 and 53545 have been
> allocated and successfully mapped to 0xd00007fffff00000 and
> 0xd00007fffff80000 using map_kernel_range_noflush() but when those
> addresses are actually accessed, we end up with infinite faults. The
> fault handler probably thinks that the fault has been handled
> correctly but, when the control is returned, the processor faults
> again. Benjamin, I'm way out of my depth here, can you please help?
>
> Oh, one more simple experiment. Sachin, does the following patch make
> any difference?
Oops, the patch should look like the following.
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 69511e6..37ab9e2 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2056,7 +2056,8 @@ static unsigned long pvm_determine_end(struct vmap_area
**pnext,
struct vmap_area **pprev,
unsigned long align)
{
- const unsigned long vmalloc_end = VMALLOC_END & ~(align - 1);
+ const unsigned long vmalloc_start = ALIGN(VMALLOC_START, align);
+ const unsigned long vmalloc_end = vmalloc_start + (512 << 20);
unsigned long addr;
if (*pnext)
@@ -2102,7 +2103,7 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long
*offsets,
size_t align, gfp_t gfp_mask)
{
const unsigned long vmalloc_start = ALIGN(VMALLOC_START, align);
- const unsigned long vmalloc_end = VMALLOC_END & ~(align - 1);
+ const unsigned long vmalloc_end = vmalloc_start + (512 << 20);
struct vmap_area **vas, *prev, *next;
struct vm_struct **vms;
int area, area2, last_area, term_area;
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