[Deepin-Kernel-SIG] [linux 6.6.y] [Upstream] sync bugfixes for mm/rmap: interface overhaul

[opsiff]

#1969

Summary by Sourcery

Align rmap and hugepage handling with upstream fixes to improve correctness of THP and folio dirty accounting.

Bug Fixes:

• Relax rmap sanity checks for large folios to account for driver-allocated folios in mixed VMAs.
• Ensure do_set_pmd uses the folio order consistently and correctly derives the page from the folio when installing PMD-sized THPs.
• Fix THP and migration entry paths to correctly mark backing folios dirty based on pmd state.

Enhancements:

• Replace legacy folio_set_dirty uses with folio_mark_dirty to match the updated folio dirty-tracking interface.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Synchronizes rmap-related bugfixes and interface changes from upstream by relaxing folio rmap sanity checks, switching several MM paths from folio_set_dirty() to folio_mark_dirty(), and fixing THP PMD setup to consistently derive the page from the folio after order validation.

File-Level Changes

Change	Details	Files
Relax rmap folio sanity checking to accommodate driver-allocated large folios and document required future handling.	Remove strict assertion tying large folios to folio_test_large_rmappable() in rmap sanity checks. Add explanatory TODO comment about VM_MIXEDMAP VMA handling and rmap-compatible folios. Keep other folio/page consistency checks and nr_pages validation unchanged.	include/linux/rmap.h
Use folio_mark_dirty() instead of folio_set_dirty() in key MM code paths handling PTE/PMD dirty state propagation.	Change zap_pte_range to mark folios dirty with folio_mark_dirty() when a dirty PTE is zapped for non-anon folios. Update huge PMD split path to call folio_mark_dirty() when pmd_dirty() but folio is not yet dirty. Update PMD migration entry setup to call folio_mark_dirty() on dirty PMDs before creating migration entries.	mm/memory.c mm/huge_memory.c
Correct THP PMD setup logic to rely solely on folio order and to consistently set the page pointer from the folio after validation.	Remove redundant check comparing the incoming page pointer to &folio->page when setting a PMD for THP. Require only that folio_order(folio) matches HPAGE_PMD_ORDER before proceeding. Explicitly assign page = &folio->page once order is validated to ensure consistent page/folio pairing.	mm/memory.c

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[sourcery-ai]

Hey - I've left some high level feedback:

• In __folio_rmap_sanity_checks(), the previous large_rmappable check is dropped entirely and replaced with a TODO; consider either tightening the comment to describe the current expected invariants for VM_MIXEDMAP folios or adding a targeted VM_WARN_ON for clearly invalid cases to avoid silently masking real bugs.
• In do_set_pmd(), you now unconditionally derive page from the folio after only checking the folio order; if non-head pages can still legitimately reach this path, it may be safer to assert that page == &folio->page (e.g. via VM_WARN_ON) or otherwise document the invariant that only head pages are expected here.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In __folio_rmap_sanity_checks(), the previous large_rmappable check is dropped entirely and replaced with a TODO; consider either tightening the comment to describe the current expected invariants for VM_MIXEDMAP folios or adding a targeted VM_WARN_ON for clearly invalid cases to avoid silently masking real bugs.
- In do_set_pmd(), you now unconditionally derive `page` from the folio after only checking the folio order; if non-head pages can still legitimately reach this path, it may be safer to assert that `page == &folio->page` (e.g. via VM_WARN_ON) or otherwise document the invariant that only head pages are expected here.

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