[PATCH v3 03/13] mm: add vma_desc_size(), vma_desc_pages() helpers

Lorenzo Stoakes
2025-09-16T14:13:29Z

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@oracle.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: David Hildenbrand <david@redhat.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 da6e0abad2cb..dd1fec5f028a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3571,6 +3571,16 @@ 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(const struct vm_area_desc *desc)
+{
+ return desc->end - desc->start;
+}
+
+static inline unsigned long vma_desc_pages(const 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