arm64: mte: simplify swap tag restoration logic

As a result of the patches "mm: Call arch_swap_restore() from
do_swap_page()" and "mm: Call arch_swap_restore() from unuse_pte()", there
are no circumstances in which a swapped-in page is installed in a page
table without first having arch_swap_restore() called on it.  Therefore,
we no longer need the logic in set_pte_at() that restores the tags, so
remove it.

Link: https://lkml.kernel.org/r/20230523004312.1807357-4-pcc@google.com
Link: https://linux-review.googlesource.com/id/I8ad54476f3b2d0144ccd8ce0c1d7a2963e5ff6f3
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: kasan-dev@googlegroups.com
Cc: kasan-dev <kasan-dev@googlegroups.com>
Cc: "Kuan-Ying Lee (李冠穎)" <Kuan-Ying.Lee@mediatek.com>
Cc: Qun-Wei Lin <qun-wei.lin@mediatek.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 7 insertions, 30 deletions

diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index 4c5ef9b20065..4edecaac8f91 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -35,41 +35,18 @@ DEFINE_STATIC_KEY_FALSE(mte_async_or_asymm_mode);
 EXPORT_SYMBOL_GPL(mte_async_or_asymm_mode);
 #endif
 
-static void mte_sync_page_tags(struct page *page, pte_t old_pte,
-			       bool check_swap, bool pte_is_tagged)
-{
-	if (check_swap && is_swap_pte(old_pte)) {
-		swp_entry_t entry = pte_to_swp_entry(old_pte);
-
-		if (!non_swap_entry(entry))
-			mte_restore_tags(entry, page);
-	}
-
-	if (!pte_is_tagged)
-		return;
-
-	if (try_page_mte_tagging(page)) {
-		mte_clear_page_tags(page_address(page));
-		set_page_mte_tagged(page);
-	}
-}
-
-void mte_sync_tags(pte_t old_pte, pte_t pte)
+void mte_sync_tags(pte_t pte)
 {
 	struct page *page = pte_page(pte);
 	long i, nr_pages = compound_nr(page);
-	bool check_swap = nr_pages == 1;
-	bool pte_is_tagged = pte_tagged(pte);
-
-	/* Early out if there's nothing to do */
-	if (!check_swap && !pte_is_tagged)
-		return;
 
 	/* if PG_mte_tagged is set, tags have already been initialised */
-	for (i = 0; i < nr_pages; i++, page++)
-		if (!page_mte_tagged(page))
-			mte_sync_page_tags(page, old_pte, check_swap,
-					   pte_is_tagged);
+	for (i = 0; i < nr_pages; i++, page++) {
+		if (try_page_mte_tagging(page)) {
+			mte_clear_page_tags(page_address(page));
+			set_page_mte_tagged(page);
+		}
+	}
 
 	/* ensure the tags are visible before the PTE is set */
 	smp_wmb();