linux-kernel - [PATCH v2 26/33] mm: prevent do_swap_page from handling page faults under VMA lock

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Message-ID: <20230127194110.533103-27-surenb@google.com>
Date:   Fri, 27 Jan 2023 11:41:03 -0800
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     akpm@...ux-foundation.org
Cc:     michel@...pinasse.org, jglisse@...gle.com, mhocko@...e.com,
        vbabka@...e.cz, hannes@...xchg.org, mgorman@...hsingularity.net,
        dave@...olabs.net, willy@...radead.org, liam.howlett@...cle.com,
        peterz@...radead.org, ldufour@...ux.ibm.com, paulmck@...nel.org,
        mingo@...hat.com, will@...nel.org, luto@...nel.org,
        songliubraving@...com, peterx@...hat.com, david@...hat.com,
        dhowells@...hat.com, hughd@...gle.com, bigeasy@...utronix.de,
        kent.overstreet@...ux.dev, punit.agrawal@...edance.com,
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        rppt@...nel.org, jannh@...gle.com, shakeelb@...gle.com,
        tatashin@...gle.com, edumazet@...gle.com, gthelen@...gle.com,
        gurua@...gle.com, arjunroy@...gle.com, soheil@...gle.com,
        leewalsh@...gle.com, posk@...gle.com, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        surenb@...gle.com, Laurent Dufour <laurent.dufour@...ibm.com>
Subject: [PATCH v2 26/33] 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 593548f24007..33ecc850d3cb 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3690,6 +3690,11 @@ 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)) {
-- 
2.39.1