[PATCH v3 2/7] mm/vmalloc.c: add flags to mark vm_map_ram area

Baoquan He
2023-01-13T03:20:42Z

Through vmalloc API, a virtual kernel area is reserved for physical
address mapping. And vmap_area is used to track them, while vm_struct
is allocated to associate with the vmap_area to store more information
and passed out.

However, area reserved via vm_map_ram() is an exception. It doesn't have
vm_struct to associate with vmap_area. And we can't recognize the
vmap_area with '->vm == NULL' as a vm_map_ram() area because the normal
freeing path will set va->vm = NULL before unmapping, please see
function remove_vm_area().

Meanwhile, there are two kinds of handling for vm_map_ram area. One is
the whole vmap_area being reserved and mapped at one time through
vm_map_area() interface; the other is the whole vmap_area with
VMAP_BLOCK_SIZE size being reserved, while mapped into split regions
with smaller size via vb_alloc().

To mark the area reserved through vm_map_ram(), add flags field into
struct vmap_area. Bit 0 indicates this is vm_map_ram area created
through vm_map_ram() interface, while bit 1 marks out the type of
vm_map_ram area which makes use of vmap_block to manage split regions
via vb_alloc/free().

This is a preparatoin for later use.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
include/linux/vmalloc.h | 1 +
mm/vmalloc.c | 16 ++++++++++++----
2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 096d48aa3437..69250efa03d1 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -76,6 +76,7 @@ struct vmap_area {
unsigned long subtree_max_size; /* in "free" tree */
struct vm_struct *vm; /* in "busy" tree */
};
+ unsigned long flags; /* mark type of vm_map_ram area */
};

/* archs that select HAVE_ARCH_HUGE_VMAP should override one or more of these */
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index d6ff058ef4d0..ab4825050b5c 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1589,7 +1589,8 @@ preload_this_cpu_lock(spinlock_t *lock, gfp_t gfp_mask, int node)
static struct vmap_area *alloc_vmap_area(unsigned long size,
unsigned long align,
unsigned long vstart, unsigned long vend,
- int node, gfp_t gfp_mask)
+ int node, gfp_t gfp_mask,
+ unsigned long va_flags)
{
struct vmap_area *va;
unsigned long freed;
@@ -1635,6 +1636,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
va->va_start = addr;
va->va_end = addr + size;
va->vm = NULL;
+ va->flags = va_flags;

spin_lock(&vmap_area_lock);
insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
@@ -1913,6 +1915,10 @@ static struct vmap_area *find_unlink_vmap_area(unsigned long addr)

#define VMAP_BLOCK_SIZE (VMAP_BBMAP_BITS * PAGE_SIZE)

+#define VMAP_RAM 0x1 /* indicates vm_map_ram area*/
+#define VMAP_BLOCK 0x2 /* mark out the vmap_block sub-type*/
+#define VMAP_FLAGS_MASK 0x3
+
struct vmap_block_queue {
spinlock_t lock;
struct list_head free;
@@ -1988,7 +1994,8 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)

va = alloc_vmap_area(VMAP_BLOCK_SIZE, VMAP_BLOCK_SIZE,
VMALLOC_START, VMALLOC_END,
- node, gfp_mask);
+ node, gfp_mask,
+ VMAP_RAM|VMAP_BLOCK);
if (IS_ERR(va)) {
kfree(vb);
return ERR_CAST(va);
@@ -2297,7 +2304,8 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node)
} else {
struct vmap_area *va;
va = alloc_vmap_area(size, PAGE_SIZE,
- VMALLOC_START, VMALLOC_END, node, GFP_KERNEL);
+ VMALLOC_START, VMALLOC_END,
+ node, GFP_KERNEL, VMAP_RAM);
if (IS_ERR(va))
return NULL;

@@ -2537,7 +2545,7 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
if (!(flags & VM_NO_GUARD))
size += PAGE_SIZE;

- va = alloc_vmap_area(size, align, start, end, node, gfp_mask);
+ va = alloc_vmap_area(size, align, start, end, node, gfp_mask, 0);
if (IS_ERR(va)) {
kfree(area);
return NULL;
--
2.34.1