Add a host_zeroes_pages flag to page_reporting_dev_info, allowing drivers to declare that their host zeros reported pages on reclaim. A static key gates the fast path.
Set PG_zeroed alongside PageReported in page_reporting_drain() when host_zeroes_pages is enabled, so reported pages are marked as known-zero at reporting time. Signed-off-by: Michael S. Tsirkin <[email protected]> Assisted-by: Claude:claude-opus-4-6 Assisted-by: cursor-agent:GPT-5.4-xhigh --- include/linux/page_reporting.h | 3 +++ mm/page_reporting.c | 13 ++++++++++++- mm/page_reporting.h | 11 +++++++++++ 3 files changed, 26 insertions(+), 1 deletion(-) diff --git a/include/linux/page_reporting.h b/include/linux/page_reporting.h index fe648dfa3a7c..10faadfeb4fb 100644 --- a/include/linux/page_reporting.h +++ b/include/linux/page_reporting.h @@ -13,6 +13,9 @@ struct page_reporting_dev_info { int (*report)(struct page_reporting_dev_info *prdev, struct scatterlist *sg, unsigned int nents); + /* If true, host zeros reported pages on reclaim */ + bool host_zeroes_pages; + /* work struct for processing reports */ struct delayed_work work; diff --git a/mm/page_reporting.c b/mm/page_reporting.c index f0042d5743af..5e1e1a924b0c 100644 --- a/mm/page_reporting.c +++ b/mm/page_reporting.c @@ -50,6 +50,8 @@ EXPORT_SYMBOL_GPL(page_reporting_order); #define PAGE_REPORTING_DELAY (2 * HZ) static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly; +DEFINE_STATIC_KEY_FALSE(page_reporting_host_zeroes); + enum { PAGE_REPORTING_IDLE = 0, PAGE_REPORTING_REQUESTED, @@ -129,8 +131,11 @@ page_reporting_drain(struct page_reporting_dev_info *prdev, * report on the new larger page when we make our way * up to that higher order. */ - if (PageBuddy(page) && buddy_order(page) == order) + if (PageBuddy(page) && buddy_order(page) == order) { __SetPageReported(page); + if (page_reporting_host_zeroes_pages()) + __SetPageZeroed(page); + } } while ((sg = sg_next(sg))); /* reinitialize scatterlist now that it is empty */ @@ -386,6 +391,9 @@ int page_reporting_register(struct page_reporting_dev_info *prdev) /* Assign device to allow notifications */ rcu_assign_pointer(pr_dev_info, prdev); + if (prdev->host_zeroes_pages) + static_branch_enable(&page_reporting_host_zeroes); + /* enable page reporting notification */ if (!static_key_enabled(&page_reporting_enabled)) { static_branch_enable(&page_reporting_enabled); @@ -410,6 +418,9 @@ void page_reporting_unregister(struct page_reporting_dev_info *prdev) /* Flush any existing work, and lock it out */ cancel_delayed_work_sync(&prdev->work); + + if (prdev->host_zeroes_pages) + static_branch_disable(&page_reporting_host_zeroes); } mutex_unlock(&page_reporting_mutex); diff --git a/mm/page_reporting.h b/mm/page_reporting.h index c51dbc228b94..a53ab22f4c49 100644 --- a/mm/page_reporting.h +++ b/mm/page_reporting.h @@ -12,9 +12,15 @@ #ifdef CONFIG_PAGE_REPORTING DECLARE_STATIC_KEY_FALSE(page_reporting_enabled); +DECLARE_STATIC_KEY_FALSE(page_reporting_host_zeroes); extern unsigned int page_reporting_order; void __page_reporting_notify(void); +static inline bool page_reporting_host_zeroes_pages(void) +{ + return static_branch_unlikely(&page_reporting_host_zeroes); +} + static inline bool page_reported(struct page *page) { return static_branch_unlikely(&page_reporting_enabled) && @@ -46,6 +52,11 @@ static inline void page_reporting_notify_free(unsigned int order) #else /* CONFIG_PAGE_REPORTING */ #define page_reported(_page) false +static inline bool page_reporting_host_zeroes_pages(void) +{ + return false; +} + static inline void page_reporting_notify_free(unsigned int order) { } -- MST
