On 06.10.23 19:58, Andrew Morton wrote:
On Mon, 25 Sep 2023 13:01:10 -0700 "Zach O'Keefe" <zokeefe@xxxxxxxxxx> 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, this was a bad assumption to make as it assumes the only reason to support ->huge_fault was for DAX (which is not true in general). Remove the VM_NO_KHUGEPAGED check when not in collapse path and give any ->huge_fault handler a chance to handle the fault. Note that we don't validate the file mode or mapping alignment, which is consistent with the behavior before the aforementioned commits. ... @@ -100,11 +100,11 @@ bool hugepage_vma_check(struct vm_area_struct *vma, unsigned long vm_flags, return in_pf;Ryan's "mm: thp: introduce anon_orders and anon_always_mask sysfs files" changes hugepage_vma_check() to return an unsigned int, so this patch will need some rework to fit in after that. However Ryan's overall series "variable-order, large folios for anonymous memory" is in early days and might not make it. And as I don't know what is the urgency of this patch ("mm/thp: fix "mm: thp: kill __transhuge_page_enabled()"), I'm unable to decide which patch needs to come first (thus requiring rework of the other patch). Please discuss!
IMHO clearly this one. -- Cheers, David / dhildenb
