linux-kernel - [RFC PATCH RESEND 19/28] mm: disallow do_swap_page to handle page faults under VMA lock

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Message-ID: <20220901173516.702122-20-surenb@google.com>
Date:   Thu,  1 Sep 2022 10:35:07 -0700
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@...e.de,
        dave@...olabs.net, willy@...radead.org, liam.howlett@...cle.com,
        peterz@...radead.org, ldufour@...ux.ibm.com,
        laurent.dufour@...ibm.com, paulmck@...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, rientjes@...gle.com,
        axelrasmussen@...gle.com, joelaf@...gle.com, minchan@...gle.com,
        surenb@...gle.com, kernel-team@...roid.com, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [RFC PATCH RESEND 19/28] mm: disallow do_swap_page to handle 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>
---
 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;
+	}
+
 	if (!pte_unmap_same(vmf))
 		goto out;
 
-- 
2.37.2.789.g6183377224-goog