[PATCH 4/7] mm: Add thp_size

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

This function returns the number of bytes in a THP.  It is like
page_size(), but compiles to just PAGE_SIZE if CONFIG_TRANSPARENT_HUGEPAGE
is disabled.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 drivers/nvdimm/btt.c    |  4 +---
 drivers/nvdimm/pmem.c   |  6 ++----
 include/linux/huge_mm.h | 11 +++++++++++
 mm/internal.h           |  2 +-
 mm/page_io.c            |  2 +-
 mm/page_vma_mapped.c    |  4 ++--
 6 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
index 48e9d169b6f9..92f25b9e1483 100644
--- a/drivers/nvdimm/btt.c
+++ b/drivers/nvdimm/btt.c
@@ -1490,10 +1490,8 @@ static int btt_rw_page(struct block_device *bdev, sector_t sector,
 {
 	struct btt *btt = bdev->bd_disk->private_data;
 	int rc;
-	unsigned int len;
 
-	len = hpage_nr_pages(page) * PAGE_SIZE;
-	rc = btt_do_bvec(btt, NULL, page, len, 0, op, sector);
+	rc = btt_do_bvec(btt, NULL, page, thp_size(page), 0, op, sector);
 	if (rc == 0)
 		page_endio(page, op_is_write(op), 0);
 
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index d25e66fd942d..d5e86ae144e3 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -238,11 +238,9 @@ static int pmem_rw_page(struct block_device *bdev, sector_t sector,
 	blk_status_t rc;
 
 	if (op_is_write(op))
-		rc = pmem_do_write(pmem, page, 0, sector,
-				   hpage_nr_pages(page) * PAGE_SIZE);
+		rc = pmem_do_write(pmem, page, 0, sector, thp_size(page));
 	else
-		rc = pmem_do_read(pmem, page, 0, sector,
-				   hpage_nr_pages(page) * PAGE_SIZE);
+		rc = pmem_do_read(pmem, page, 0, sector, thp_size(page));
 	/*
 	 * The ->rw_page interface is subtle and tricky.  The core
 	 * retries on any error, so we can only invoke page_endio() in
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index dd19720a8bc2..0ec3b5a73d38 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -469,4 +469,15 @@ static inline bool thp_migration_supported(void)
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
+/**
+ * thp_size - Size of a transparent huge page.
+ * @page: Head page of a transparent huge page.
+ *
+ * Return: Number of bytes in this page.
+ */
+static inline unsigned long thp_size(struct page *page)
+{
+	return PAGE_SIZE << thp_order(page);
+}
+
 #endif /* _LINUX_HUGE_MM_H */
diff --git a/mm/internal.h b/mm/internal.h
index 9886db20d94f..de9f1d0ba5fc 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -395,7 +395,7 @@ vma_address(struct page *page, struct vm_area_struct *vma)
 	unsigned long start, end;
 
 	start = __vma_address(page, vma);
-	end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1);
+	end = start + thp_size(page) - PAGE_SIZE;
 
 	/* page should be within @vma mapping range */
 	VM_BUG_ON_VMA(end < vma->vm_start || start >= vma->vm_end, vma);
diff --git a/mm/page_io.c b/mm/page_io.c
index e8726f3e3820..888000d1a8cc 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -40,7 +40,7 @@ static struct bio *get_swap_bio(gfp_t gfp_flags,
 		bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
 		bio->bi_end_io = end_io;
 
-		bio_add_page(bio, page, PAGE_SIZE * hpage_nr_pages(page), 0);
+		bio_add_page(bio, page, thp_size(page), 0);
 	}
 	return bio;
 }
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 719c35246cfa..e65629c056e8 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -227,7 +227,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 			if (pvmw->address >= pvmw->vma->vm_end ||
 			    pvmw->address >=
 					__vma_address(pvmw->page, pvmw->vma) +
-					hpage_nr_pages(pvmw->page) * PAGE_SIZE)
+					thp_size(pvmw->page))
 				return not_found(pvmw);
 			/* Did we cross page table boundary? */
 			if (pvmw->address % PMD_SIZE == 0) {
@@ -268,7 +268,7 @@ int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
 	unsigned long start, end;
 
 	start = __vma_address(page, vma);
-	end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1);
+	end = start + thp_size(page) - PAGE_SIZE;
 
 	if (unlikely(end < vma->vm_start || start >= vma->vm_end))
 		return 0;
-- 
2.27.0