On Tue, Sep 6, 2022 at 12:39 PM Peter Xu [off-list ref] wrote:

On Thu, Sep 01, 2022 at 10:35:07AM -0700, Suren Baghdasaryan wrote:

quoted

Due to the possibility of do_swap_page dropping mmap_lock, abort fault
handling under VMA lock and retry holding mmap_lock. This can be handled
more gracefully in the future.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 mm/memory.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/memory.c b/mm/memory.c
index 9ac9944e8c62..29d2f49f922a 100644
--- a/mm/memory.c
+++ b/mm/memory.c

@@ -3738,6 +3738,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
      vm_fault_t ret = 0;
      void *shadow = NULL;

+     if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
+             ret = VM_FAULT_RETRY;
+             goto out;
+     }
+

May want to fail early similarly for handle_userfault() too for similar
reason.  Thanks,

I wasn't aware of a similar issue there. Will have a closer look. Thanks!

--
Peter Xu