From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Try a speculative fault before acquiring mmap_sem, if it returns with
VM_FAULT_RETRY continue with the mmap_sem acquisition and do the
traditional fault.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/x86/mm/fault.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index e3254ca0eec4..ee6d8799d958 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1316,6 +1316,16 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
if (error_code & PF_INSTR)
flags |= FAULT_FLAG_INSTRUCTION;
+ if (error_code & PF_USER) {
+ fault = handle_speculative_fault(mm, address,
+ flags & ~FAULT_FLAG_ALLOW_RETRY);
+
+ if (fault & VM_FAULT_RETRY)
+ goto retry;
+
+ goto done;
+ }
+
/*
* When running in the kernel we expect faults to occur only to
* addresses in user space. All other faults represent errors in
@@ -1419,7 +1429,15 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
return;
}
+ if (unlikely(fault & VM_FAULT_RETRY)) {
+ if (fatal_signal_pending(current))
+ return;
+
+ goto done;
+ }
+
up_read(&mm->mmap_sem);
+done:
if (unlikely(fault & VM_FAULT_ERROR)) {
mm_fault_error(regs, error_code, address, vma, fault);
return;
--
2.7.4
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