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...
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);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.