Thank you! 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.
>From Jann Horn's review:
https://lore.kernel.org/all/cag48ez3cuzf+xotp6ukks2-cmoeo+3k5pvny0afl_xbkhh5...@mail.gmail.com/
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.
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.
>
>
