[PATCH v2 05/13] mm/vmalloc: Add a get_vm_area_node() and vmap_pages_range() public functions

David Stevens
2026-04-24T19:17:03Z

From: Pasha Tatashin <pasha.tatashin@soleen.com>

get_vm_area_node()
Unlike the other public get_vm_area_* variants, this one accepts node
from which to allocate data structure, and also the align, which allows
to create vm area with a specific alignment.

This call is going to be used by dynamic stacks in order to ensure that
the stack VM area of a specific alignment, and that even if there is
only one page mapped, no page table allocations are going to be needed
to map the other stack pages.

vmap_pages_range()
We will need it from kernel/fork.c in order to map the initial stack
pages, so export the function and add a forward declaration of this
function to the linux/vmalloc.h header.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
[Switched to vmap_pages_range instead of noflush variant, fix typos]
Signed-off-by: David Stevens <stevensd@google.com>
---
include/linux/vmalloc.h | 14 ++++++++++++++
mm/vmalloc.c | 25 +++++++++++++++++++++++++
2 files changed, 39 insertions(+)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index e8e94f90d686..7b56a0b998ab 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -250,6 +250,9 @@ extern struct vm_struct *__get_vm_area_caller(unsigned long size,
unsigned long flags,
unsigned long start, unsigned long end,
const void *caller);
+struct vm_struct *get_vm_area_node(unsigned long size, unsigned long align,
+ unsigned long flags, int node, gfp_t gfp,
+ const void *caller);
void free_vm_area(struct vm_struct *area);
extern struct vm_struct *remove_vm_area(const void *addr);
extern struct vm_struct *find_vm_area(const void *addr);
@@ -301,11 +304,22 @@ static inline void set_vm_flush_reset_perms(void *addr)
if (vm)
vm->flags |= VM_FLUSH_RESET_PERMS;
}
+
+int __must_check vmap_pages_range(unsigned long addr, unsigned long end,
+ pgprot_t prot, struct page **pages, unsigned int page_shift);
+
#else /* !CONFIG_MMU */
#define VMALLOC_TOTAL 0UL

static inline unsigned long vmalloc_nr_pages(void) { return 0; }
static inline void set_vm_flush_reset_perms(void *addr) {}
+static inline
+int __must_check vmap_pages_range(unsigned long addr, unsigned long end,
+ pgprot_t prot, struct page **pages, unsigned int page_shift)
+{
+ return -EINVAL;
+}
+
#endif /* CONFIG_MMU */

#if defined(CONFIG_MMU) && defined(CONFIG_SMP)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 61caa55a4402..39b7e118cbce 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -722,6 +722,7 @@ int vmap_pages_range(unsigned long addr, unsigned long end,
{
return __vmap_pages_range(addr, end, prot, pages, page_shift, GFP_KERNEL);
}
+EXPORT_SYMBOL_GPL(vmap_pages_range);

static int check_sparse_vm_area(struct vm_struct *area, unsigned long start,
unsigned long end)
@@ -3285,6 +3286,30 @@ struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags,
NUMA_NO_NODE, GFP_KERNEL, caller);
}

+/**
+ * get_vm_area_node - reserve a contiguous and aligned kernel virtual area
+ * @size: size of the area
+ * @align: alignment of the start address of the area
+ * @flags: %VM_IOREMAP for I/O mappings
+ * @node: NUMA node from which to allocate the area data structure
+ * @gfp: Flags to pass to the allocator
+ * @caller: Caller to be stored in the vm area data structure
+ *
+ * Search for an area of @size/align in the kernel virtual mapping area and
+ * reserve it for our purposes. Returns the area descriptor on success or %NULL
+ * on failure.
+ *
+ * Return: the area descriptor on success or %NULL on failure.
+ */
+struct vm_struct *get_vm_area_node(unsigned long size, unsigned long align,
+ unsigned long flags, int node, gfp_t gfp,
+ const void *caller)
+{
+ return __get_vm_area_node(size, align, PAGE_SHIFT, flags,
+ VMALLOC_START, VMALLOC_END,
+ node, gfp, caller);
+}
+
/**
* find_vm_area - find a continuous kernel virtual area
* @addr: base address