On Sat, 3 Aug 2013 12:59:56 -0400 Johannes Weiner <hannes@xxxxxxxxxxx> wrote:
> Unlike global OOM handling, memory cgroup code will invoke the OOM
> killer in any OOM situation because it has no way of telling faults
> occuring in kernel context - which could be handled more gracefully -
> from user-triggered faults.
>
> Pass a flag that identifies faults originating in user space from the
> architecture-specific fault handlers to generic code so that memcg OOM
> handling can be improved.
arch/arm64/mm/fault.c has changed. Here's what I came up with:
--- a/arch/arm64/mm/fault.c~arch-mm-pass-userspace-fault-flag-to-generic-fault-handler
+++ a/arch/arm64/mm/fault.c
@@ -199,13 +199,6 @@ static int __kprobes do_page_fault(unsig
unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC;
unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
- if (esr & ESR_LNX_EXEC) {
- vm_flags = VM_EXEC;
- } else if ((esr & ESR_WRITE) && !(esr & ESR_CM)) {
- vm_flags = VM_WRITE;
- mm_flags |= FAULT_FLAG_WRITE;
- }
-
tsk = current;
mm = tsk->mm;
@@ -220,6 +213,16 @@ static int __kprobes do_page_fault(unsig
if (in_atomic() || !mm)
goto no_context;
+ if (user_mode(regs))
+ mm_flags |= FAULT_FLAG_USER;
+
+ if (esr & ESR_LNX_EXEC) {
+ vm_flags = VM_EXEC;
+ } else if ((esr & ESR_WRITE) && !(esr & ESR_CM)) {
+ vm_flags = VM_WRITE;
+ mm_flags |= FAULT_FLAG_WRITE;
+ }
+
/*
* As per x86, we may deadlock here. However, since the kernel only
* validly references user space from well defined areas of the code,
But I'm not terribly confident in it.
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