linux-kernel - [PATCH 31/41] mm: prevent do_swap_page from handling page faults under VMA lock

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Message-ID: <20230109205336.3665937-32-surenb@google.com>
Date:   Mon,  9 Jan 2023 12:53:26 -0800
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     akpm@...ux-foundation.org
Cc:     michel@...pinasse.org, jglisse@...gle.com, mhocko@...e.com,
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Subject: [PATCH 31/41] 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@...gle.com>
Reviewed-by: Laurent Dufour <laurent.dufour@...ibm.com>
---
 mm/memory.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/memory.c b/mm/memory.c
index 2560524ad7f4..20806bc8b4eb 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3707,6 +3707,11 @@ 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)) {
-- 
2.39.0