linux-kernel - [PATCH v2 1/5] mm: introduce num_pages

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Message-ID: <20250704062602.33500-2-lizhe.67@bytedance.com>
Date: Fri,  4 Jul 2025 14:25:58 +0800
From: lizhe.67@...edance.com
To: alex.williamson@...hat.com,
	akpm@...ux-foundation.org,
	david@...hat.com,
	peterx@...hat.com,
	jgg@...pe.ca
Cc: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	lizhe.67@...edance.com
Subject: [PATCH v2 1/5] mm: introduce num_pages_contiguous()

From: Li Zhe <lizhe.67@...edance.com>

Function num_pages_contiguous() determine the number of contiguous
pages starting from the first page in the given array of page pointers.
VFIO will utilize this interface to accelerate the VFIO DMA map process.

Suggested-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Li Zhe <lizhe.67@...edance.com>
---
 include/linux/mm.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0ef2ba0c667a..1d26203d1ced 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -205,6 +205,26 @@ extern unsigned long sysctl_admin_reserve_kbytes;
 #define folio_page_idx(folio, p)	((p) - &(folio)->page)
 #endif
 
+/*
+ * num_pages_contiguous() - determine the number of contiguous pages
+ * starting from the first page.
+ *
+ * @pages: an array of page pointers
+ * @nr_pages: length of the array
+ */
+static inline unsigned long num_pages_contiguous(struct page **pages,
+						 unsigned long nr_pages)
+{
+	struct page *first_page = pages[0];
+	unsigned long i;
+
+	for (i = 1; i < nr_pages; i++)
+		if (pages[i] != nth_page(first_page, i))
+			break;
+
+	return i;
+}
+
 /* to align the pointer to the (next) page boundary */
 #define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE)
 
-- 
2.20.1