[PATCH v4 2/3] mm: Call arch_swap_restore() from unuse_pte()

From: Peter Collingbourne <pcc@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: "Peter Collingbourne" <pcc@google.com>,
	"Qun-wei Lin (林群崴)" <Qun-wei.Lin@mediatek.com>,
	linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org,
	"surenb@google.com" <surenb@google.com>,
	"david@redhat.com" <david@redhat.com>,
	"Chinwen Chang (張錦文)" <chinwen.chang@mediatek.com>,
	"kasan-dev@googlegroups.com" <kasan-dev@googlegroups.com>,
	"Kuan-Ying Lee (李冠穎)" <Kuan-Ying.Lee@mediatek.com>,
	"Casper Li (李中榮)" <casper.li@mediatek.com>,
	"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	vincenzo.frascino@arm.com,
	"Alexandru Elisei" <alexandru.elisei@arm.com>,
	will@kernel.org, eugenis@google.com,
	"Steven Price" <steven.price@arm.com>
Subject: [PATCH v4 2/3] mm: Call arch_swap_restore() from unuse_pte()
Date: Mon, 22 May 2023 17:43:09 -0700	[thread overview]
Message-ID: <20230523004312.1807357-3-pcc@google.com> (raw)
In-Reply-To: <20230523004312.1807357-1-pcc@google.com>

We would like to move away from requiring architectures to restore
metadata from swap in the set_pte_at() implementation, as this is not only
error-prone but adds complexity to the arch-specific code. This requires
us to call arch_swap_restore() before calling swap_free() whenever pages
are restored from swap. We are currently doing so everywhere except in
unuse_pte(); do so there as well.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/I68276653e612d64cde271ce1b5a99ae05d6bbc4f
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
---
 mm/swapfile.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 274bbf797480..e9843fadecd6 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1794,6 +1794,13 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
 		goto setpte;
 	}
 
+	/*
+	 * Some architectures may have to restore extra metadata to the page
+	 * when reading from swap. This metadata may be indexed by swap entry
+	 * so this must be called before swap_free().
+	 */
+	arch_swap_restore(entry, page_folio(page));
+
 	/* See do_swap_page() */
 	BUG_ON(!PageAnon(page) && PageMappedToDisk(page));
 	BUG_ON(PageAnon(page) && PageAnonExclusive(page));
-- 
2.40.1.698.g37aff9b760-goog

