vm_area_add_early/vm_area_register_early() are used to reserve vmalloc area
during boot process and those virtually mapped areas are never unmapped.
So `OR` VM_STATIC flag to the areas in vmalloc_init() when importing
existing vmlist entries and prevent those areas from being removed from the
rbtree by accident.
Signed-off-by: Hoeun Ryu <[email protected]>
---
include/linux/vmalloc.h | 1 +
mm/vmalloc.c | 9 ++++++---
2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 46991ad..3df53fc 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -19,6 +19,7 @@ struct notifier_block; /* in notifier.h */
#define VM_UNINITIALIZED 0x00000020 /* vm_struct is not fully initialized */
#define VM_NO_GUARD 0x00000040 /* don't add guard page */
#define VM_KASAN 0x00000080 /* has allocated kasan shadow memory */
+#define VM_STATIC 0x00000200
/* bits [20..32] reserved for arch specific ioremap internals */
/*
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 8ef8ea1..fb5049a 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1262,7 +1262,7 @@ void __init vmalloc_init(void)
/* Import existing vmlist entries. */
for (tmp = vmlist; tmp; tmp = tmp->next) {
va = kzalloc(sizeof(struct vmap_area), GFP_NOWAIT);
- va->flags = VM_VM_AREA;
+ va->flags = VM_VM_AREA | VM_STATIC;
va->va_start = (unsigned long)tmp->addr;
va->va_end = va->va_start + tmp->size;
va->vm = tmp;
@@ -1480,7 +1480,7 @@ struct vm_struct *remove_vm_area(const void *addr)
might_sleep();
va = find_vmap_area((unsigned long)addr);
- if (va && va->flags & VM_VM_AREA) {
+ if (va && va->flags & VM_VM_AREA && likely(!(va->flags & VM_STATIC))) {
struct vm_struct *vm = va->vm;
spin_lock(&vmap_area_lock);
@@ -1510,7 +1510,7 @@ static void __vunmap(const void *addr, int deallocate_pages)
area = remove_vm_area(addr);
if (unlikely(!area)) {
- WARN(1, KERN_ERR "Trying to vfree() nonexistent vm area (%p)\n",
+ WARN(1, KERN_ERR "Trying to vfree() nonexistent or static vm area (%p)\n",
addr);
return;
}
@@ -2708,6 +2708,9 @@ static int s_show(struct seq_file *m, void *p)
if (v->phys_addr)
seq_printf(m, " phys=%pa", &v->phys_addr);
+ if (v->flags & VM_STATIC)
+ seq_puts(m, " static");
+
if (v->flags & VM_IOREMAP)
seq_puts(m, " ioremap");
--
2.7.4
On Wed, Apr 12, 2017 at 02:01:59PM +0900, Hoeun Ryu wrote:
> vm_area_add_early/vm_area_register_early() are used to reserve vmalloc area
> during boot process and those virtually mapped areas are never unmapped.
> So `OR` VM_STATIC flag to the areas in vmalloc_init() when importing
> existing vmlist entries and prevent those areas from being removed from the
> rbtree by accident.
How would they be removed "by accident"?
> On Apr 12, 2017, at 3:02 PM, Christoph Hellwig <[email protected]> wrote:
>
>> On Wed, Apr 12, 2017 at 02:01:59PM +0900, Hoeun Ryu wrote:
>> vm_area_add_early/vm_area_register_early() are used to reserve vmalloc area
>> during boot process and those virtually mapped areas are never unmapped.
>> So `OR` VM_STATIC flag to the areas in vmalloc_init() when importing
>> existing vmlist entries and prevent those areas from being removed from the
>> rbtree by accident.
>
> How would they be removed "by accident"?
I don't mean actual use-cases, but I just want to make it robust against like programming errors.
On Wed, Apr 12, 2017 at 08:42:08PM +0900, Hoeun Ryu wrote:
>
> > On Apr 12, 2017, at 3:02 PM, Christoph Hellwig <[email protected]> wrote:
> >
> >> On Wed, Apr 12, 2017 at 02:01:59PM +0900, Hoeun Ryu wrote:
> >> vm_area_add_early/vm_area_register_early() are used to reserve vmalloc area
> >> during boot process and those virtually mapped areas are never unmapped.
> >> So `OR` VM_STATIC flag to the areas in vmalloc_init() when importing
> >> existing vmlist entries and prevent those areas from being removed from the
> >> rbtree by accident.
> >
> > How would they be removed "by accident"?
>
> I don't mean actual use-cases, but I just want to make it robust against like programming errors.
Oh, ok. The patch makes sense then, although the changelog could use
a little update.
> On 13 Apr 2017, at 2:31 AM, Christoph Hellwig <[email protected]> wrote:
>
> On Wed, Apr 12, 2017 at 08:42:08PM +0900, Hoeun Ryu wrote:
>>
>>> On Apr 12, 2017, at 3:02 PM, Christoph Hellwig <[email protected]> wrote:
>>>
>>>> On Wed, Apr 12, 2017 at 02:01:59PM +0900, Hoeun Ryu wrote:
>>>> vm_area_add_early/vm_area_register_early() are used to reserve vmalloc area
>>>> during boot process and those virtually mapped areas are never unmapped.
>>>> So `OR` VM_STATIC flag to the areas in vmalloc_init() when importing
>>>> existing vmlist entries and prevent those areas from being removed from the
>>>> rbtree by accident.
>>>
>>> How would they be removed "by accident"?
>>
>> I don't mean actual use-cases, but I just want to make it robust against like programming errors.
>
> Oh, ok. The patch makes sense then, although the changelog could use
> a little update.
OK, I will.
Any other suggestions for code itself ?
On 04/12/2017 10:31 AM, Hoeun Ryu wrote:
> vm_area_add_early/vm_area_register_early() are used to reserve vmalloc area
> during boot process and those virtually mapped areas are never unmapped.
> So `OR` VM_STATIC flag to the areas in vmalloc_init() when importing
> existing vmlist entries and prevent those areas from being removed from the
> rbtree by accident.
I am wondering whether protection against accidental deletion
of any vmap area should be done in remove_vm_area() function
or the callers should take care of it. But I guess either way
it works.
>
> Signed-off-by: Hoeun Ryu <[email protected]>
> ---
> include/linux/vmalloc.h | 1 +
> mm/vmalloc.c | 9 ++++++---
> 2 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 46991ad..3df53fc 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -19,6 +19,7 @@ struct notifier_block; /* in notifier.h */
> #define VM_UNINITIALIZED 0x00000020 /* vm_struct is not fully initialized */
> #define VM_NO_GUARD 0x00000040 /* don't add guard page */
> #define VM_KASAN 0x00000080 /* has allocated kasan shadow memory */
> +#define VM_STATIC 0x00000200
You might want to add some description in the comment saying
its a sticky VM area which will never go away or something.
> /* bits [20..32] reserved for arch specific ioremap internals */
>
> /*
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 8ef8ea1..fb5049a 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1262,7 +1262,7 @@ void __init vmalloc_init(void)
> /* Import existing vmlist entries. */
> for (tmp = vmlist; tmp; tmp = tmp->next) {
> va = kzalloc(sizeof(struct vmap_area), GFP_NOWAIT);
> - va->flags = VM_VM_AREA;
> + va->flags = VM_VM_AREA | VM_STATIC;
> va->va_start = (unsigned long)tmp->addr;
> va->va_end = va->va_start + tmp->size;
> va->vm = tmp;
> @@ -1480,7 +1480,7 @@ struct vm_struct *remove_vm_area(const void *addr)
> might_sleep();
>
> va = find_vmap_area((unsigned long)addr);
> - if (va && va->flags & VM_VM_AREA) {
> + if (va && va->flags & VM_VM_AREA && likely(!(va->flags & VM_STATIC))) {
You might want to move the VM_STATIC check before the VM_VM_AREA
check so in cases where the former is set we can save one more
conditional check.
> On Apr 13, 2017, at 1:17 PM, Anshuman Khandual <[email protected]> wrote:
>
>> On 04/12/2017 10:31 AM, Hoeun Ryu wrote:
>> vm_area_add_early/vm_area_register_early() are used to reserve vmalloc area
>> during boot process and those virtually mapped areas are never unmapped.
>> So `OR` VM_STATIC flag to the areas in vmalloc_init() when importing
>> existing vmlist entries and prevent those areas from being removed from the
>> rbtree by accident.
>
> I am wondering whether protection against accidental deletion
> of any vmap area should be done in remove_vm_area() function
> or the callers should take care of it. But I guess either way
> it works.
>
>>
>> Signed-off-by: Hoeun Ryu <[email protected]>
>> ---
>> include/linux/vmalloc.h | 1 +
>> mm/vmalloc.c | 9 ++++++---
>> 2 files changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
>> index 46991ad..3df53fc 100644
>> --- a/include/linux/vmalloc.h
>> +++ b/include/linux/vmalloc.h
>> @@ -19,6 +19,7 @@ struct notifier_block; /* in notifier.h */
>> #define VM_UNINITIALIZED 0x00000020 /* vm_struct is not fully initialized */
>> #define VM_NO_GUARD 0x00000040 /* don't add guard page */
>> #define VM_KASAN 0x00000080 /* has allocated kasan shadow memory */
>> +#define VM_STATIC 0x00000200
>
> You might want to add some description in the comment saying
> its a sticky VM area which will never go away or something.
>
OK. I will add some description.
>> /* bits [20..32] reserved for arch specific ioremap internals */
>>
>> /*
>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>> index 8ef8ea1..fb5049a 100644
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -1262,7 +1262,7 @@ void __init vmalloc_init(void)
>> /* Import existing vmlist entries. */
>> for (tmp = vmlist; tmp; tmp = tmp->next) {
>> va = kzalloc(sizeof(struct vmap_area), GFP_NOWAIT);
>> - va->flags = VM_VM_AREA;
>> + va->flags = VM_VM_AREA | VM_STATIC;
>> va->va_start = (unsigned long)tmp->addr;
>> va->va_end = va->va_start + tmp->size;
>> va->vm = tmp;
>> @@ -1480,7 +1480,7 @@ struct vm_struct *remove_vm_area(const void *addr)
>> might_sleep();
>>
>> va = find_vmap_area((unsigned long)addr);
>> - if (va && va->flags & VM_VM_AREA) {
>> + if (va && va->flags & VM_VM_AREA && likely(!(va->flags & VM_STATIC))) {
>
>
> You might want to move the VM_STATIC check before the VM_VM_AREA
> check so in cases where the former is set we can save one more
> conditional check.
>
OK, I'll fix this in the next version
Thank you for the review.