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Anthony. > > Yep, I checked the comments in arch/mm/x86/fault.c file which says as your > advices in previous email. > > > I changed my code in kernel 5.5 as below: > > if (unlikely(is_shared_vma) && ((fault & VM_FAULT_RETRY) && > (flags & FAULT_FLAG_ALLOW_RETRY) || fault_signal_pending(fault, regs))) > mmap_read_unlock(mm); > > BTW: I wrote some selftests in my github repostory, which perform > the basic function of mshare, and I will write some complicated cases > to support the new functions or defect found in mshare. For example, > once you support mshare as a VMA in KVM (just as the defeat viewed by > Jann Horn), I will add extra test cases to verify its correctiness for > this scenario. This is great! I'll take a look at them in more detail. I just sent out an updated series. > > From Jann Horn's review: > https://lore.kernel.org/all/CAG48ez3cUZf+xOtP6UkkS2-CmOeo+3K5pvny0AFL_XBkHh5q_g@mail.gmail.com/ My new series does not yet have support for mmu notifiers. It's something I'm working on, but there are key issues to overcome. One is that I need to update the implementation of mm_take_all_locks() to also carefully take all locks in any mapped mshare regions. The other is that passing through mmu notifier calls for arch_invalidate_secondary_tlbs callbacks is especially tricky because the callback is not allowed to sleep due to holding a ptl spin lock. > > Currently, I put my selftest in my github repostory, and you could retrieve it > as below: > > git remote add yongting-mshare-selftests https://github.com/ivanalgo/linux-kernel-develop/ > git fetch yongting-mshare-selftests dev-mshare-v2-selftest-v1 > git cherry-pick a64f2ff6497d13c09badc0fc68c44d9995bc2fef > > At this stage, I am not sure what is the best way to proceed: > - Should I send them as part of your next version (v3)? > - Or should I post them separately as [RFC PATCH] for early review? > > Please let me know your preference and any sugestion is welcome. > I am happy to rebase and resend in the format that works best for > the community. I may have more feedback once I take look. I suggest starting by updating them to work with the series I just sent out. Thanks, Anthony > > Thanks > Yongting > >> Anthony >> >>> >>> As a result, needs to release vma->vm_mm.mmap_lock as well. >>> >>> So it is supposed to be like below: >>> >>> - fault = handle_mm_fault(vma, address, flags, regs); >>> + fault = handle_mm_fault(vma, addr, flags, regs); >>> + >>> + if (unlikely(is_shared_vma) && ((fault & VM_FAULT_COMPLETED) || >>> + (fault & VM_FAULT_RETRY) || fault_signal_pending(fault, regs))) { >>> + mmap_read_unlock(vma->vm_mm); >>> + mmap_read_unlock(mm); >>> + } >>> >>>> if (fault_signal_pending(fault, regs)) { >>>> /* >>>> @@ -1413,6 +1446,8 @@ void do_user_addr_fault(struct pt_regs *regs, >>>> goto retry; >>>> } >>>> + if (unlikely(is_shared_vma)) >>>> + mmap_read_unlock(vma->vm_mm); >>>> mmap_read_unlock(mm); >>>> done: >>>> if (likely(!(fault & VM_FAULT_ERROR))) >>>> diff --git a/mm/Kconfig b/mm/Kconfig >>>> index e6c90db83d01..8a5a159457f2 100644 >>>> --- a/mm/Kconfig >>>> +++ b/mm/Kconfig >>>> @@ -1344,7 +1344,7 @@ config PT_RECLAIM >>>> config MSHARE >>>> bool "Mshare" >>>> - depends on MMU >>>> + depends on MMU && ARCH_SUPPORTS_MSHARE >>>> help >>>> Enable msharefs: A ram-based filesystem that allows multiple >>>> processes to share page table entries for shared pages. A file >>> >>> Yongting Lin. >> >>