mm: call arch_swap_restore() from unuse_pte()

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>

diff --git a/mm/swapfile.c b/mm/swapfile.c
index cad0209..d996c33 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1778,6 +1778,13 @@ 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));