mm/khugepaged: fix GUP-fast interaction by sending IPI

Since commit 70cbc3cc78a99 ("mm: gup: fix the fast GUP race against THP
collapse"), the lockless_pages_from_mm() fastpath rechecks the pmd_t to
ensure that the page table was not removed by khugepaged in between.

However, lockless_pages_from_mm() still requires that the page table is
not concurrently freed.  Fix it by sending IPIs (if the architecture uses
semi-RCU-style page table freeing) before freeing/reusing page tables.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Fixes: ba76149f47d8 ("thp: khugepaged")
Signed-off-by: Jann Horn <[email protected]>
Reviewed-by: Yang Shi <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions