On Tue, Jan 02, 2024 at 03:32:56PM -0800, Suren Baghdasaryan wrote:
While testing the split PMD path with lockdep enabled I've got an "Invalid wait context" error caused by split_huge_page_to_list() trying to lock anon_vma->rwsem while inside RCU read section. The issues is due to move_pages_pte() calling split_folio() under RCU read lock. Fix this by unmapping the PTEs and exiting RCU read section before splitting the folio and then retrying. The same retry pattern is used when locking the folio or anon_vma in this function. After splitting the large folio we unlock and release it because after the split the old folio might not be the one that contains the src_addr.
Fixes: 94b01c885131 ("userfaultfd: UFFDIO_MOVE uABI") Signed-off-by: Suren Baghdasaryan surenb@google.com
Reviewed-by: Peter Xu peterx@redhat.com
Thanks,