Messages in this thread | | | Date | Thu, 08 Feb 2018 09:44:29 +0800 | From | Wei Wang <> | Subject | Re: [PATCH v27 3/4] mm/page_poison: expose page_poisoning_enabled to kernel modules |
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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 <wei.w.wang@intel.com> >> Cc: Andrew Morton <akpm@linux-foundation.org> >> Cc: Michal Hocko <mhocko@kernel.org> >> Cc: Michael S. Tsirkin <mst@redhat.com> >> --- >> 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
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