mm: userfaultfd: correct dirty flags set for both present and swap pte

As David pointed out, what truly matters for mremap and userfaultfd move
operations is the soft dirty bit.  The current comment and
implementation—which always sets the dirty bit for present PTEs and
fails to set the soft dirty bit for swap PTEs—are incorrect.  This could
break features like Checkpoint-Restore in Userspace (CRIU).

This patch updates the behavior to correctly set the soft dirty bit for
both present and swap PTEs in accordance with mremap.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI")
Signed-off-by: Barry Song <[email protected]>
Reported-by: David Hildenbrand <[email protected]>
Closes: https://lore.kernel.org/linux-mm/[email protected]/
Acked-by: Peter Xu <[email protected]>
Reviewed-by: Suren Baghdasaryan <[email protected]>
Cc: Lokesh Gidra <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions