[PATCH v2 0/2] mm/hugetlb: dissolve gigantic pages without runtime support

From: Longlong Xia <[email protected]>

v2 of the dissolve fix. It now carries the cleanup David asked for as a
separate patch, and is split so the minimal bug fix can go to -stable on
its own.

  1/2 - mm/hugetlb: do not dissolve gigantic pages without runtime support
        dissolve_free_hugetlb_folio() doesn't check
        hstate_is_gigantic_no_runtime(h); the helpers bail for such
        hstates, so dissolving leaves the folio on the free list and the
        add_hugetlb_folio() rollback on vmemmap restore failure corrupts
        that list. Bail out before touching the accounting. (Fixes,
        -stable candidate.)

  2/2 - mm/hugetlb: warn instead of silently bailing gigantic pages
        without runtime support
        Per David's review: turn the silent bail in
        remove_hugetlb_folio()/__update_and_free_hugetlb_folio() into a
        VM_WARN_ON_ONCE. All callers already filter
        gigantic_no_runtime upstream. (no Fixes, -next only.)

Changes in v2 (vs the single v1 patch):
  - Split into [1/2] bug fix and [2/2] cleanup so the fix stays minimal
    for -stable and the diagnostic cleanup is -next only.
  - [2/2] is new, per David's review ("VM_WARN_ON() instead of handling
    it silently").
  - [1/2] differs from v1 only by a comment reword.

Link: https://lore.kernel.org/r/[email protected]
Link: https://sashiko.dev/#/patchset/[email protected]

Longlong Xia (2):
  mm/hugetlb: do not dissolve gigantic pages without runtime support
  mm/hugetlb: warn instead of silently bailing gigantic pages without
    runtime support

 mm/hugetlb.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

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2.43.0