On Tue, 3 Dec 2019 14:22:33 +0100 Thomas Hellström (VMware) thomas_os@shipmail.org wrote:
We currently only do COW and write-notify on the PTE level, so if the huge_fault() handler returns VM_FAULT_FALLBACK on wp faults, split the huge pages and page-table entries. Also do this for huge PUDs if there is no huge_fault() handler and the vma is not anonymous, similar to how it's done for PMDs.
There is no description here of *why* we are making this change?
Note that fs/dax.c does the splitting in the huge_fault() handler, but as huge_fault() is implemented by modules we need to consider whether to export the splitting functions for use in the modules or whether to try to keep calls in the core. Opt for the latter. A follow-up patch can remove the dax.c split_huge_pmd() if needed.