+ mm-call-arch_swap_restore-from-unuse_pte.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

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The patch titled
     Subject: mm: call arch_swap_restore() from unuse_pte()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-call-arch_swap_restore-from-unuse_pte.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-call-arch_swap_restore-from-unuse_pte.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Peter Collingbourne <pcc@google.com>
Subject: mm: call arch_swap_restore() from unuse_pte()
Date: Mon, 22 May 2023 17:43:09 -0700

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.

Link: https://lkml.kernel.org/r/20230523004312.1807357-3-pcc@google.com
Link: https://linux-review.googlesource.com/id/I68276653e612d64cde271ce1b5a99ae05d6bbc4f
Signed-off-by: Peter Collingbourne <pcc@google.com>
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>
Cc: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/swapfile.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/mm/swapfile.c~mm-call-arch_swap_restore-from-unuse_pte
+++ a/mm/swapfile.c
@@ -1778,6 +1778,13 @@ static int unuse_pte(struct vm_area_stru
 		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));
_

Patches currently in -mm which might be from pcc@google.com are

mm-call-arch_swap_restore-from-do_swap_page.patch
mm-call-arch_swap_restore-from-unuse_pte.patch
arm64-mte-simplify-swap-tag-restoration-logic.patch