linux-kernel - [PATCH 03/16] mm: add vma_desc_size(), vma_desc

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Message-ID: <d8767cda1afd04133e841a819bcedf1e8dda4436.1757329751.git.lorenzo.stoakes@oracle.com>
Date: Mon,  8 Sep 2025 12:10:34 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Jonathan Corbet <corbet@....net>, Matthew Wilcox <willy@...radead.org>,
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Subject: [PATCH 03/16] mm: add vma_desc_size(), vma_desc_pages() helpers

It's useful to be able to determine the size of a VMA descriptor range used
on f_op->mmap_prepare, expressed both in bytes and pages, so add helpers
for both and update code that could make use of it to do so.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 fs/ntfs3/file.c    |  2 +-
 include/linux/mm.h | 10 ++++++++++
 mm/secretmem.c     |  2 +-
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
index c1ece707b195..86eb88f62714 100644
--- a/fs/ntfs3/file.c
+++ b/fs/ntfs3/file.c
@@ -304,7 +304,7 @@ static int ntfs_file_mmap_prepare(struct vm_area_desc *desc)
 
 	if (rw) {
 		u64 to = min_t(loff_t, i_size_read(inode),
-			       from + desc->end - desc->start);
+			       from + vma_desc_size(desc));
 
 		if (is_sparsed(ni)) {
 			/* Allocate clusters for rw map. */
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a6bfa46937a8..9d4508b20be3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3560,6 +3560,16 @@ static inline unsigned long vma_pages(const struct vm_area_struct *vma)
 	return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
 }
 
+static inline unsigned long vma_desc_size(struct vm_area_desc *desc)
+{
+	return desc->end - desc->start;
+}
+
+static inline unsigned long vma_desc_pages(struct vm_area_desc *desc)
+{
+	return vma_desc_size(desc) >> PAGE_SHIFT;
+}
+
 /* Look up the first VMA which exactly match the interval vm_start ... vm_end */
 static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm,
 				unsigned long vm_start, unsigned long vm_end)
diff --git a/mm/secretmem.c b/mm/secretmem.c
index 60137305bc20..62066ddb1e9c 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -120,7 +120,7 @@ static int secretmem_release(struct inode *inode, struct file *file)
 
 static int secretmem_mmap_prepare(struct vm_area_desc *desc)
 {
-	const unsigned long len = desc->end - desc->start;
+	const unsigned long len = vma_desc_size(desc);
 
 	if ((desc->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
 		return -EINVAL;
-- 
2.51.0