Re: [PATCH v27 3/4] mm/page_poison: expose page_poisoning_enabled to kernel modules
On Thu, Feb 08, 2018 at 09:44:29AM +0800, Wei Wang wrote:
> On 02/08/2018 02:34 AM, Michael S. Tsirkin wrote:
> > On Wed, Feb 07, 2018 at 02:54:30PM +0800, Wei Wang wrote:
> > > In some usages, e.g. virtio-balloon, a kernel module needs to know if
> > > page poisoning is in use. This patch exposes the page_poisoning_enabled
> > > function to kernel modules.
> > >
> > > Signed-off-by: Wei Wang
> > > Cc: Andrew Morton
> > > Cc: Michal Hocko
> > > Cc: Michael S. Tsirkin
> > > ---
> > > mm/page_poison.c | 6 ++
> > > 1 file changed, 6 insertions(+)
> > >
> > > diff --git a/mm/page_poison.c b/mm/page_poison.c
> > > index e83fd44..c08d02a 100644
> > > --- a/mm/page_poison.c
> > > +++ b/mm/page_poison.c
> > > @@ -30,6 +30,11 @@ bool page_poisoning_enabled(void)
> > > debug_pagealloc_enabled()));
> > > }
> > > +/**
> > > + * page_poisoning_enabled - check if page poisoning is enabled
> > > + *
> > > + * Return true if page poisoning is enabled, or false if not.
> > > + */
> > > static void poison_page(struct page *page)
> > > {
> > > void *addr = kmap_atomic(page);
> > > @@ -37,6 +42,7 @@ static void poison_page(struct page *page)
> > > memset(addr, PAGE_POISON, PAGE_SIZE);
> > > kunmap_atomic(addr);
> > > }
> > > +EXPORT_SYMBOL_GPL(page_poisoning_enabled);
> > > static void poison_pages(struct page *page, int n)
> > > {
> > Looks like both the comment and the export are in the wrong place.
>
> Thanks. Will be more careful.
>
> > I'm a bit concerned that callers also in fact poke at the
> > PAGE_POISON - exporting that seems to be more of an accident
> > as it's only used without page_poisoning.c - it might be
> > better to have page_poisoning_enabled get u8 * and set it.
> >
>
> PAGE_POISON is a macro defined in the header, why would callers using it be
> a concern?
It might be a good idea to move it out of there though.
> Do you suggest to have:
>
> bool page_poisoning_get(u8 *val)
> {
> if (page_poisoning_enabled()) {
> *val = PAGE_POISON;
> return true;
> }
>
> return false;
> }
> EXPORT_SYMBOL_GPL(page_poisoning_get);
>
>
> Best,
> Wei
Something like this, yes.
--
MST
Re: [PATCH v27 3/4] mm/page_poison: expose page_poisoning_enabled to kernel modules
On 02/08/2018 02:34 AM, Michael S. Tsirkin wrote:
On Wed, Feb 07, 2018 at 02:54:30PM +0800, Wei Wang wrote:
In some usages, e.g. virtio-balloon, a kernel module needs to know if
page poisoning is in use. This patch exposes the page_poisoning_enabled
function to kernel modules.
Signed-off-by: Wei Wang
Cc: Andrew Morton
Cc: Michal Hocko
Cc: Michael S. Tsirkin
---
mm/page_poison.c | 6 ++
1 file changed, 6 insertions(+)
diff --git a/mm/page_poison.c b/mm/page_poison.c
index e83fd44..c08d02a 100644
--- a/mm/page_poison.c
+++ b/mm/page_poison.c
@@ -30,6 +30,11 @@ bool page_poisoning_enabled(void)
debug_pagealloc_enabled()));
}
+/**
+ * page_poisoning_enabled - check if page poisoning is enabled
+ *
+ * Return true if page poisoning is enabled, or false if not.
+ */
static void poison_page(struct page *page)
{
void *addr = kmap_atomic(page);
@@ -37,6 +42,7 @@ static void poison_page(struct page *page)
memset(addr, PAGE_POISON, PAGE_SIZE);
kunmap_atomic(addr);
}
+EXPORT_SYMBOL_GPL(page_poisoning_enabled);
static void poison_pages(struct page *page, int n)
{
Looks like both the comment and the export are in the wrong place.
Thanks. Will be more careful.
I'm a bit concerned that callers also in fact poke at the
PAGE_POISON - exporting that seems to be more of an accident
as it's only used without page_poisoning.c - it might be
better to have page_poisoning_enabled get u8 * and set it.
PAGE_POISON is a macro defined in the header, why would callers using it
be a concern?
Do you suggest to have:
bool page_poisoning_get(u8 *val)
{
if (page_poisoning_enabled()) {
*val = PAGE_POISON;
return true;
}
return false;
}
EXPORT_SYMBOL_GPL(page_poisoning_get);
Best,
Wei
Re: [PATCH v27 3/4] mm/page_poison: expose page_poisoning_enabled to kernel modules
On Wed, Feb 07, 2018 at 02:54:30PM +0800, Wei Wang wrote:
> In some usages, e.g. virtio-balloon, a kernel module needs to know if
> page poisoning is in use. This patch exposes the page_poisoning_enabled
> function to kernel modules.
>
> Signed-off-by: Wei Wang
> Cc: Andrew Morton
> Cc: Michal Hocko
> Cc: Michael S. Tsirkin
> ---
> mm/page_poison.c | 6 ++
> 1 file changed, 6 insertions(+)
>
> diff --git a/mm/page_poison.c b/mm/page_poison.c
> index e83fd44..c08d02a 100644
> --- a/mm/page_poison.c
> +++ b/mm/page_poison.c
> @@ -30,6 +30,11 @@ bool page_poisoning_enabled(void)
> debug_pagealloc_enabled()));
> }
>
> +/**
> + * page_poisoning_enabled - check if page poisoning is enabled
> + *
> + * Return true if page poisoning is enabled, or false if not.
> + */
> static void poison_page(struct page *page)
> {
> void *addr = kmap_atomic(page);
> @@ -37,6 +42,7 @@ static void poison_page(struct page *page)
> memset(addr, PAGE_POISON, PAGE_SIZE);
> kunmap_atomic(addr);
> }
> +EXPORT_SYMBOL_GPL(page_poisoning_enabled);
>
> static void poison_pages(struct page *page, int n)
> {
Looks like both the comment and the export are in the wrong place.
I'm a bit concerned that callers also in fact poke at the
PAGE_POISON - exporting that seems to be more of an accident
as it's only used without page_poisoning.c - it might be
better to have page_poisoning_enabled get u8 * and set it.
> --
> 2.7.4
[PATCH v27 3/4] mm/page_poison: expose page_poisoning_enabled to kernel modules
In some usages, e.g. virtio-balloon, a kernel module needs to know if
page poisoning is in use. This patch exposes the page_poisoning_enabled
function to kernel modules.
Signed-off-by: Wei Wang
Cc: Andrew Morton
Cc: Michal Hocko
Cc: Michael S. Tsirkin
---
mm/page_poison.c | 6 ++
1 file changed, 6 insertions(+)
diff --git a/mm/page_poison.c b/mm/page_poison.c
index e83fd44..c08d02a 100644
--- a/mm/page_poison.c
+++ b/mm/page_poison.c
@@ -30,6 +30,11 @@ bool page_poisoning_enabled(void)
debug_pagealloc_enabled()));
}
+/**
+ * page_poisoning_enabled - check if page poisoning is enabled
+ *
+ * Return true if page poisoning is enabled, or false if not.
+ */
static void poison_page(struct page *page)
{
void *addr = kmap_atomic(page);
@@ -37,6 +42,7 @@ static void poison_page(struct page *page)
memset(addr, PAGE_POISON, PAGE_SIZE);
kunmap_atomic(addr);
}
+EXPORT_SYMBOL_GPL(page_poisoning_enabled);
static void poison_pages(struct page *page, int n)
{
--
2.7.4
