On 22.08.23 01:48, Zach O'Keefe wrote:
The 6.0 commits:
commit 9fec51689ff6 ("mm: thp: kill transparent_hugepage_active()")
commit 7da4e2cb8b1f ("mm: thp: kill __transhuge_page_enabled()")
merged "can we have THPs in this VMA?" logic that was previously done
separately by fault-path, khugepaged, and smaps "THPeligible" checks.
During the process, the semantics of the fault path check changed in two
ways:
1) A VM_NO_KHUGEPAGED check was introduced (also added to smaps path).
2) We no longer checked if non-anonymous memory had a vm_ops->huge_fault
handler that could satisfy the fault. Previously, this check had been
done in create_huge_pud() and create_huge_pmd() routines, but after
the changes, we never reach those routines.
During the review of the above commits, it was determined that in-tree
users weren't affected by the change; most notably, since the only relevant
user (in terms of THP) of VM_MIXEDMAP or ->huge_fault is DAX, which is
explicitly approved early in approval logic. However, there is at least
one occurrence where an out-of-tree driver that used
VM_HUGEPAGE|VM_MIXEDMAP with a vm_ops->huge_fault handler, was broken.
... so all we did is break an arbitrary out-of-tree driver? Sorry to
say, but why should we care?
Is there any in-tree code affected and needs a "Fixes:" ?
--
Cheers,
David / dhildenb
