From: Suren Baghdasaryan <surenb@google.com>
Date: Mon, 27 Feb 2023 17:36:25 +0000 (-0800)
Subject: mm: prevent do_swap_page from handling page faults under VMA lock
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=2d9f306b5854dd50275f303ed24755134ea836ea;p=users%2Fjedix%2Flinux-maple.git

mm: prevent do_swap_page from handling page faults under VMA lock

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.

Link: https://lkml.kernel.org/r/20230227173632.3292573-27-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Laurent Dufour <laurent.dufour@fr.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/memory.c b/mm/memory.c
index 480e96af0407..f76bd6c05d51 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3701,6 +3701,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	if (!pte_unmap_same(vmf))
 		goto out;
 
+	if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
+		ret = VM_FAULT_RETRY;
+		goto out;
+	}
+
 	entry = pte_to_swp_entry(vmf->orig_pte);
 	if (unlikely(non_swap_entry(entry))) {
 		if (is_migration_entry(entry)) {