From: Suren Baghdasaryan <surenb@google.com>
Date: Sun, 29 May 2022 20:20:27 +0000 (-0700)
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=eced6b36c3905aaccb003b499acf66212c28dedc;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.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Laurent Dufour <laurent.dufour@fr.ibm.com>
---

diff --git a/mm/memory.c b/mm/memory.c
index 6640b8cba622..57279e03f888 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3744,6 +3744,11 @@ 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)) {