mm/swapops: make is_pmd_migration_entry more strict

A pmd migration entry should first be a swap pmd,so use is_swap_pmd(pmd)
instead of !pmd_present(pmd).

On the other hand, some architecture (MIPS for example) may misjudge a
pmd_none entry as a pmd migration entry.

Link: https://lkml.kernel.org/r/1651131333-6386-1-git-send-email-zhanghongchen@loongson.cn
Signed-off-by: Hongchen Zhang <zhanghongchen@loongson.cn>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index d1b7289..82265b0 100644 (file)
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -331,7 +331,7 @@ static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
 
 static inline int is_pmd_migration_entry(pmd_t pmd)
 {
-       return !pmd_present(pmd) && is_migration_entry(pmd_to_swp_entry(pmd));
+       return is_swap_pmd(pmd) && is_migration_entry(pmd_to_swp_entry(pmd));
 }
 #else
 static inline int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,