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@@ -280,7 +280,8 @@ static inline int do_exception(struct pt_regs *regs, int access,
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struct mm_struct *mm;
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struct vm_area_struct *vma;
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unsigned long address;
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- int fault, write;
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+ unsigned int flags;
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+ int fault;
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if (notify_page_fault(regs))
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return 0;
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@@ -299,6 +300,10 @@ static inline int do_exception(struct pt_regs *regs, int access,
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address = trans_exc_code & __FAIL_ADDR_MASK;
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perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, address);
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+ flags = FAULT_FLAG_ALLOW_RETRY;
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+ if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400)
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+ flags |= FAULT_FLAG_WRITE;
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+retry:
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down_read(&mm->mmap_sem);
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fault = VM_FAULT_BADMAP;
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@@ -328,21 +333,31 @@ static inline int do_exception(struct pt_regs *regs, int access,
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* make sure we exit gracefully rather than endlessly redo
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* the fault.
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*/
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- write = (access == VM_WRITE ||
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- (trans_exc_code & store_indication) == 0x400) ?
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- FAULT_FLAG_WRITE : 0;
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- fault = handle_mm_fault(mm, vma, address, write);
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+ fault = handle_mm_fault(mm, vma, address, flags);
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if (unlikely(fault & VM_FAULT_ERROR))
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goto out_up;
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- if (fault & VM_FAULT_MAJOR) {
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- tsk->maj_flt++;
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- perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0,
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- regs, address);
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- } else {
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- tsk->min_flt++;
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- perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0,
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- regs, address);
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+ /*
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+ * Major/minor page fault accounting is only done on the
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+ * initial attempt. If we go through a retry, it is extremely
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+ * likely that the page will be found in page cache at that point.
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+ */
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+ if (flags & FAULT_FLAG_ALLOW_RETRY) {
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+ if (fault & VM_FAULT_MAJOR) {
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+ tsk->maj_flt++;
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+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0,
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+ regs, address);
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+ } else {
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+ tsk->min_flt++;
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+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0,
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+ regs, address);
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+ }
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+ if (fault & VM_FAULT_RETRY) {
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+ /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
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+ * of starvation. */
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+ flags &= ~FAULT_FLAG_ALLOW_RETRY;
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+ goto retry;
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+ }
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}
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/*
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* The instruction that caused the program check will
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