[PATCH 5/9] mm: vmalloc: Insert busy-VA per-cpu zone

Uladzislau Rezki (Sony)
2023-05-22T11:15:10Z

Store busy-VA objects per a CPU zone. A va->va_start address is
converted into a correct zone where it is placed and resides. An
addr_to_cvz() function is used to do a proper address conversion.

Such approach balances VAs across CPUs. That is why an access
becomes scalable to number of CPUs in a system.

Please note:

Since a zone size is set to ULONG_MAX, i.e. everything is bound
thus accessed to the CPU_0 so far, this patch does not give any
difference comparing with a current behavior.

The global vmap_area_lock, vmap_area_root are removed as there
is no need in it anymore. The vmap_area_list is still kept and
is _empty_. It is exported for a kexec only.

The vmallocinfo and vread() have to be reworked to be able to
handle multiple zones. As a result of this patch it can handle
only one zone, i.e. when cache is disabled.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
mm/vmalloc.c | 127 ++++++++++++++++++++++++++++++++++-----------------
1 file changed, 84 insertions(+), 43 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index f6da2590b4de..a9170fe19909 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -729,11 +729,9 @@ EXPORT_SYMBOL(vmalloc_to_pfn);
#define DEBUG_AUGMENT_LOWEST_MATCH_CHECK 0

-static DEFINE_SPINLOCK(vmap_area_lock);
static DEFINE_SPINLOCK(free_vmap_area_lock);
/* Export for kexec only */
LIST_HEAD(vmap_area_list);
-static struct rb_root vmap_area_root = RB_ROOT;
static bool vmap_initialized __read_mostly;

static struct rb_root purge_vmap_area_root = RB_ROOT;
@@ -823,7 +821,7 @@ addr_to_cpu(unsigned long addr)
}

static inline struct cpu_vmap_zone *
-__maybe_unused addr_to_cvz(unsigned long addr)
+addr_to_cvz(unsigned long addr)
{
return &per_cpu(cpu_vmap_zone, addr_to_cpu(addr));
}
@@ -859,10 +857,10 @@ unsigned long vmalloc_nr_pages(void)
}

/* Look up the first VA which satisfies addr < va_end, NULL if none. */
-static struct vmap_area *find_vmap_area_exceed_addr(unsigned long addr)
+static struct vmap_area *find_vmap_area_exceed_addr(unsigned long addr, struct rb_root *root)
{
struct vmap_area *va = NULL;
- struct rb_node *n = vmap_area_root.rb_node;
+ struct rb_node *n = root->rb_node;

addr = (unsigned long)kasan_reset_tag((void *)addr);

@@ -1608,12 +1606,14 @@ __alloc_vmap_area(struct rb_root *root, struct list_head *head,
*/
static void free_vmap_area(struct vmap_area *va)
{
+ struct cpu_vmap_zone *z = addr_to_cvz(va->va_start);
+
/*
* Remove from the busy tree/list.
*/
- spin_lock(&vmap_area_lock);
- unlink_va(va, &vmap_area_root);
- spin_unlock(&vmap_area_lock);
+ fbl_lock(z, BUSY);
+ unlink_va(va, &fbl_root(z, BUSY));
+ fbl_unlock(z, BUSY);

/*
* Insert/Merge it back to the free tree/list.
@@ -1656,6 +1656,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
int node, gfp_t gfp_mask,
unsigned long va_flags)
{
+ struct cpu_vmap_zone *z;
struct vmap_area *va;
unsigned long freed;
unsigned long addr;
@@ -1701,9 +1702,11 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
va->vm = NULL;
va->flags = va_flags;

- spin_lock(&vmap_area_lock);
- insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
- spin_unlock(&vmap_area_lock);
+ z = addr_to_cvz(va->va_start);
+
+ fbl_lock(z, BUSY);
+ insert_vmap_area(va, &fbl_root(z, BUSY), &fbl_head(z, BUSY));
+ fbl_unlock(z, BUSY);

BUG_ON(!IS_ALIGNED(va->va_start, align));
BUG_ON(va->va_start < vstart);
@@ -1926,24 +1929,26 @@ static void free_unmap_vmap_area(struct vmap_area *va)

struct vmap_area *find_vmap_area(unsigned long addr)
{
+ struct cpu_vmap_zone *z = addr_to_cvz(addr);
struct vmap_area *va;

- spin_lock(&vmap_area_lock);
- va = __find_vmap_area(addr, &vmap_area_root);
- spin_unlock(&vmap_area_lock);
+ fbl_lock(z, BUSY);
+ va = __find_vmap_area(addr, &fbl_root(z, BUSY));
+ fbl_unlock(z, BUSY);

return va;
}

static struct vmap_area *find_unlink_vmap_area(unsigned long addr)
{
+ struct cpu_vmap_zone *z = addr_to_cvz(addr);
struct vmap_area *va;

- spin_lock(&vmap_area_lock);
- va = __find_vmap_area(addr, &vmap_area_root);
+ fbl_lock(z, BUSY);
+ va = __find_vmap_area(addr, &fbl_root(z, BUSY));
if (va)
- unlink_va(va, &vmap_area_root);
- spin_unlock(&vmap_area_lock);
+ unlink_va(va, &fbl_root(z, BUSY));
+ fbl_unlock(z, BUSY);

return va;
}
@@ -2095,14 +2100,17 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)

static void free_vmap_block(struct vmap_block *vb)
{
+ struct cpu_vmap_zone *z;
struct vmap_block *tmp;

tmp = xa_erase(&vmap_blocks, addr_to_vb_idx(vb->va->va_start));
BUG_ON(tmp != vb);

- spin_lock(&vmap_area_lock);
- unlink_va(vb->va, &vmap_area_root);
- spin_unlock(&vmap_area_lock);
+ z = addr_to_cvz(vb->va->va_start);
+
+ fbl_lock(z, BUSY);
+ unlink_va(vb->va, &fbl_root(z, BUSY));
+ fbl_unlock(z, BUSY);

free_vmap_area_noflush(vb->va);
kfree_rcu(vb, rcu_head);
@@ -2484,9 +2492,11 @@ static inline void setup_vmalloc_vm_locked(struct vm_struct *vm,
static void setup_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va,
unsigned long flags, const void *caller)
{
- spin_lock(&vmap_area_lock);
+ struct cpu_vmap_zone *z = addr_to_cvz(va->va_start);
+
+ fbl_lock(z, BUSY);
setup_vmalloc_vm_locked(vm, va, flags, caller);
- spin_unlock(&vmap_area_lock);
+ fbl_unlock(z, BUSY);
}

static void clear_vm_uninitialized_flag(struct vm_struct *vm)
@@ -3605,6 +3615,7 @@ static void vmap_ram_vread(char *buf, char *addr, int count, unsigned long flags
*/
long vread(char *buf, char *addr, unsigned long count)
{
+ struct cpu_vmap_zone *z;
struct vmap_area *va;
struct vm_struct *vm;
char *vaddr, *buf_start = buf;
@@ -3617,8 +3628,11 @@ long vread(char *buf, char *addr, unsigned long count)
if ((unsigned long) addr + count < count)
count = -(unsigned long) addr;

- spin_lock(&vmap_area_lock);
- va = find_vmap_area_exceed_addr((unsigned long)addr);
+ /* Hooked to CPU0 because a cache is not activated. */
+ z = &per_cpu(cpu_vmap_zone, 0);
+ fbl_lock(z, BUSY);
+
+ va = find_vmap_area_exceed_addr((unsigned long)addr, &fbl_root(z, BUSY));
if (!va)
goto finished;

@@ -3626,7 +3640,7 @@ long vread(char *buf, char *addr, unsigned long count)
if ((unsigned long)addr + count <= va->va_start)
goto finished;

- list_for_each_entry_from(va, &vmap_area_list, list) {
+ list_for_each_entry_from(va, &fbl_head(z, BUSY), list) {
if (!count)
break;

@@ -3674,7 +3688,7 @@ long vread(char *buf, char *addr, unsigned long count)
count -= n;
}
finished:
- spin_unlock(&vmap_area_lock);
+ fbl_unlock(z, BUSY);

if (buf == buf_start)
return 0;
@@ -4014,14 +4028,15 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
}

/* insert all vm's */
- spin_lock(&vmap_area_lock);
for (area = 0; area < nr_vms; area++) {
- insert_vmap_area(vas[area], &vmap_area_root, &vmap_area_list);
+ struct cpu_vmap_zone *z = addr_to_cvz(vas[area]->va_start);

+ fbl_lock(z, BUSY);
+ insert_vmap_area(vas[area], &fbl_root(z, BUSY), &fbl_head(z, BUSY));
setup_vmalloc_vm_locked(vms[area], vas[area], VM_ALLOC,
pcpu_get_vm_areas);
+ fbl_unlock(z, BUSY);
}
- spin_unlock(&vmap_area_lock);

/*
* Mark allocated areas as accessible. Do it now as a best-effort
@@ -4145,24 +4160,24 @@ bool vmalloc_dump_obj(void *object)
#ifdef CONFIG_PROC_FS
static void *s_start(struct seq_file *m, loff_t *pos)
__acquires(&vmap_purge_lock)
- __acquires(&vmap_area_lock)
+ __acquires(&fbl(&per_cpu(cpu_vmap_zone, 0), BUSY, lock))
{
mutex_lock(&vmap_purge_lock);
- spin_lock(&vmap_area_lock);
+ fbl_lock((&per_cpu(cpu_vmap_zone, 0)), BUSY);

- return seq_list_start(&vmap_area_list, *pos);
+ return seq_list_start(&fbl_head((&per_cpu(cpu_vmap_zone, 0)), BUSY), *pos);
}

static void *s_next(struct seq_file *m, void *p, loff_t *pos)
{
- return seq_list_next(p, &vmap_area_list, pos);
+ return seq_list_next(p, &fbl_head((&per_cpu(cpu_vmap_zone, 0)), BUSY), pos);
}

static void s_stop(struct seq_file *m, void *p)
- __releases(&vmap_area_lock)
+ __releases(&fbl(&per_cpu(cpu_vmap_zone, 0), BUSY, lock))
__releases(&vmap_purge_lock)
{
- spin_unlock(&vmap_area_lock);
+ fbl_unlock((&per_cpu(cpu_vmap_zone, 0)), BUSY);
mutex_unlock(&vmap_purge_lock);
}

@@ -4258,7 +4273,7 @@ static int s_show(struct seq_file *m, void *p)
* As a final step, dump "unpurged" areas.
*/
final:
- if (list_is_last(&va->list, &vmap_area_list))
+ if (list_is_last(&va->list, &fbl_head((&per_cpu(cpu_vmap_zone, 0)), BUSY)))
show_purge_info(m);

return 0;
@@ -4289,7 +4304,8 @@ static void vmap_init_free_space(void)
{
unsigned long vmap_start = 1;
const unsigned long vmap_end = ULONG_MAX;
- struct vmap_area *busy, *free;
+ struct vmap_area *free;
+ struct vm_struct *busy;

/*
* B F B B B F
@@ -4297,12 +4313,12 @@ static void vmap_init_free_space(void)
* | The KVA space |
* |<--------------------------------->|
*/
- list_for_each_entry(busy, &vmap_area_list, list) {
- if (busy->va_start - vmap_start > 0) {
+ for (busy = vmlist; busy; busy = busy->next) {
+ if (busy->addr - vmap_start > 0) {
free = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
if (!WARN_ON_ONCE(!free)) {
free->va_start = vmap_start;
- free->va_end = busy->va_start;
+ free->va_end = (unsigned long) busy->addr;

insert_vmap_area_augment(free, NULL,
&free_vmap_area_root,
@@ -4310,7 +4326,7 @@ static void vmap_init_free_space(void)
}
}

- vmap_start = busy->va_end;
+ vmap_start = (unsigned long) busy->addr + busy->size;
}

if (vmap_end - vmap_start > 0) {
@@ -4326,6 +4342,22 @@ static void vmap_init_free_space(void)
}
}

+static void vmap_init_pcpu_zones(void)
+{
+ struct cpu_vmap_zone *z;
+ int i, j;
+
+ for_each_possible_cpu(i) {
+ z = per_cpu_ptr(&cpu_vmap_zone, i);
+
+ for (j = 0; j < ARRAY_SIZE(z->fbl); j++) {
+ INIT_LIST_HEAD(&z->fbl[j].head);
+ z->fbl[j].root = RB_ROOT;
+ spin_lock_init(&z->fbl[j].lock);
+ }
+ }
+}
+
void __init vmalloc_init(void)
{
struct vmap_area *va;
@@ -4349,8 +4381,15 @@ void __init vmalloc_init(void)
INIT_WORK(&p->wq, delayed_vfree_work);
}

+ /*
+ * Setup per-cpu data before importing vmlist.
+ */
+ vmap_init_pcpu_zones();
+
/* Import existing vmlist entries. */
for (tmp = vmlist; tmp; tmp = tmp->next) {
+ struct cpu_vmap_zone *z;
+
va = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
if (WARN_ON_ONCE(!va))
continue;
@@ -4358,7 +4397,9 @@ void __init vmalloc_init(void)
va->va_start = (unsigned long)tmp->addr;
va->va_end = va->va_start + tmp->size;
va->vm = tmp;
- insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
+
+ z = addr_to_cvz(va->va_start);
+ insert_vmap_area(va, &fbl_root(z, BUSY), &fbl_head(z, BUSY));
}

/*
--
2.30.2