diff options
| author | Jann Horn <[email protected]> | 2024-08-13 22:25:22 +0200 |
|---|---|---|
| committer | Andrew Morton <[email protected]> | 2024-09-01 17:59:00 -0700 |
| commit | 4828d207dc5161dc7ddf9a4f6dcfd80c7dd7d20a (patch) | |
| tree | 8dc1897967f79d74885f6abd07af6de02c538d60 | |
| parent | 71c186efc1b2cf1aeabfeff3b9bd5ac4c5ac14d8 (diff) | |
userfaultfd: don't BUG_ON() if khugepaged yanks our page table
Since khugepaged was changed to allow retracting page tables in file
mappings without holding the mmap lock, these BUG_ON()s are wrong - get
rid of them.
We could also remove the preceding "if (unlikely(...))" block, but then we
could reach pte_offset_map_lock() with transhuge pages not just for file
mappings but also for anonymous mappings - which would probably be fine
but I think is not necessarily expected.
Link: https://lkml.kernel.org/r/[email protected]
Fixes: 1d65b771bc08 ("mm/khugepaged: retract_page_tables() without mmap or vma lock")
Signed-off-by: Jann Horn <[email protected]>
Reviewed-by: Qi Zheng <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
| -rw-r--r-- | mm/userfaultfd.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 290b2a0d84ac..acc56c75ba99 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -807,9 +807,10 @@ retry: err = -EFAULT; break; } - - BUG_ON(pmd_none(*dst_pmd)); - BUG_ON(pmd_trans_huge(*dst_pmd)); + /* + * For shmem mappings, khugepaged is allowed to remove page + * tables under us; pte_offset_map_lock() will deal with that. + */ err = mfill_atomic_pte(dst_pmd, dst_vma, dst_addr, src_addr, flags, &folio); |