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mm/rmap: batch unmap file folios belonging to uffd-wp VMAs

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Commit a67fe41e21 ("mm: rmap: support batched unmapping for file large
folios") extended batched unmapping for file folios.  That also required
making pte_install_uffd_wp_if_needed() support batching, but that was left
out for the time being.  Correctness was maintained by stopping batching
if the VMA the folio belongs to is marked uffd-wp.

Now that cond_install_uffd_wp_ptes() supports batching, call it with the
full batch length and allow folio_unmap_pte_batch() to batch file folios
belonging to uffd-wp VMAs.

For file folios, if the uffd-wp bit is set, unmapping converts present
PTEs into uffd-wp markers.  We must ensure that the same PTE range is not
reprocessed by the try_to_unmap_one() loop.

The page_vma_mapped_walk API ensures this: check_pte() only returns true
if any PFN in [pvmw->pfn, pvmw->pfn + nr_pages) is mapped by the PTE. 
There is no PFN underlying a uffd-wp marker PTE, so check_pte() returns
false and the walk skips ahead until it reaches a present entry again.

Link: https://lore.kernel.org/20260720065508.2695106-4-dev.jain@arm.com
Signed-off-by: Dev Jain <dev.jain@arm.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Harry Yoo <harry@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Dev Jain 2026-07-20 06:55:07 +00:00 • committed by Andrew Morton
commit 4fe4ea4cbe
1 changed files with 2 additions and 4 deletions
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