[PATCH] s390/mm: Use pmd_pgtable_page() helper in __gmap_segment_gaddr()

[Anshuman Khandual <anshuman.khandual@arm.com>]

In __gmap_segment_gaddr() pmd level page table page is being extracted from
the pmd pointer, similar to pmd_pgtable_page() implementation. This reduces
some redundancy by directly using pmd_pgtable_page() instead,  though first
making it available.

Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: kvm@vger.kernel.org
Cc: linux-s390@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
This applies on v6.1-rc6 but after the following patch. Build tested for
s390 plaform (defconfig).

https://lore.kernel.org/all/20221124131641.1523772-1-anshuman.khandual@arm.com/

 arch/s390/mm/gmap.c | 5 ++---
 include/linux/mm.h  | 2 +-
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 02d15c8dc92e..8947451ae021 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -336,12 +336,11 @@ static int gmap_alloc_table(struct gmap *gmap, unsigned long *table,
 static unsigned long __gmap_segment_gaddr(unsigned long *entry)
 {
 	struct page *page;
-	unsigned long offset, mask;
+	unsigned long offset;
 
 	offset = (unsigned long) entry / sizeof(unsigned long);
 	offset = (offset & (PTRS_PER_PMD - 1)) * PMD_SIZE;
-	mask = ~(PTRS_PER_PMD * sizeof(pmd_t) - 1);
-	page = virt_to_page((void *)((unsigned long) entry & mask));
+	page = pmd_pgtable_page((pmd_t *) entry);
 	return page->index + offset;
 }
 
diff --git a/include/linux/mm.h b/include/linux/mm.h
index e9e387caffac..5ead9e997510 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2403,7 +2403,7 @@ static inline void pgtable_pte_page_dtor(struct page *page)
 
 #if USE_SPLIT_PMD_PTLOCKS
 
-static struct page *pmd_pgtable_page(pmd_t *pmd)
+static inline struct page *pmd_pgtable_page(pmd_t *pmd)
 {
 	unsigned long mask = ~(PTRS_PER_PMD * sizeof(pmd_t) - 1);
 	return virt_to_page((void *)((unsigned long) pmd & mask));
-- 
2.25.1