On Tue, 30 Jun 2020, Peter Xu wrote: > @@ -4408,6 +4440,34 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, > unsigned long address, > mem_cgroup_oom_synchronize(false); > } > > + if (ret & (VM_FAULT_RETRY | VM_FAULT_ERROR)) > + return ret; > + > + /* > + * Do accounting in the common code, to avoid unnecessary > + * architecture differences or duplicated code. > + * > + * We arbitrarily make the rules be: > + * > + * - Unsuccessful faults do not count (e.g. when the address wasn't > + * valid). That includes arch_vma_access_permitted() failing above. > + * > + * So this is expressly not a "this many hardware page faults" > + * counter. Use the hw profiling for that. > + * > + * - Incomplete faults do not count (e.g. RETRY). They will only > + * count once completed. > + * > + * - The fault counts as a "major" fault when the final successful > + * fault is VM_FAULT_MAJOR, or if it was a retry (which implies that > + * we couldn't handle it immediately previously). > + * > + * - If the fault is done for GUP, regs will be NULL and no accounting > + * will be done. > + */ > + mm_account_fault(regs, address, (ret & VM_FAULT_MAJOR) || > + (flags & FAULT_FLAG_TRIED)); > + > return ret; > } > EXPORT_SYMBOL_GPL(handle_mm_fault);
Just a nit, likely not important: I wonder if it would be cleaner to pass the vm_fault_t into mm_account_fault() and then do the VM_FAULT_RETRY and VM_FAULT_ERROR checks there as well as putting the comment about how accounting is handled in that function. Your comment is great.
