From ec867977fed07b599fd9f24c6950628f88cbc29a Mon Sep 17 00:00:00 2001 From: Yosry Ahmed Date: Wed, 4 Sep 2024 20:54:19 +0000 Subject: [PATCH] mm: page_alloc: fix missed updates of PGFREE in free_unref_{page/folios} PGFREE is currently updated in two code paths: - __free_pages_ok(): for pages freed to the buddy allocator. - free_unref_page_commit(): for pages freed to the pcplists. Before commit df1acc856923 ("mm/page_alloc: avoid conflating IRQs disabled with zone->lock"), free_unref_page_commit() used to fallback to freeing isolated pages directly to the buddy allocator through free_one_page(). This was done _after_ updating PGFREE, so the counter was correctly updated. However, that commit moved the fallback logic to its callers (now called free_unref_page() and free_unref_folios()), so PGFREE was no longer updated in this fallback case. Now that the code has developed, there are more cases in free_unref_page() and free_unref_folios() where we fallback to calling free_one_page() (e.g. !pcp_allowed_order(), pcp_spin_trylock() fails). These cases also miss updating PGFREE. To make sure PGFREE is updated in all cases where pages are freed to the buddy allocator, move the update down the stack to free_one_page(). This was noticed through code inspection, although it should be noticeable at runtime (at least with some workloads). Link: https://lkml.kernel.org/r/20240904205419.821776-1-yosryahmed@google.com Fixes: df1acc856923 ("mm/page_alloc: avoid conflating IRQs disabled with zone->lock") Signed-off-by: Yosry Ahmed Cc: Brendan Jackman Cc: Mel Gorman Cc: Peter Zijlstra Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/page_alloc.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ee377bf5c033..a6adc8f4b7c0 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1231,6 +1231,8 @@ static void free_one_page(struct zone *zone, struct page *page, spin_lock_irqsave(&zone->lock, flags); split_large_buddy(zone, page, pfn, order, fpi_flags); spin_unlock_irqrestore(&zone->lock, flags); + + __count_vm_events(PGFREE, 1 << order); } static void __free_pages_ok(struct page *page, unsigned int order, @@ -1239,12 +1241,8 @@ static void __free_pages_ok(struct page *page, unsigned int order, unsigned long pfn = page_to_pfn(page); struct zone *zone = page_zone(page); - if (!free_pages_prepare(page, order)) - return; - - free_one_page(zone, page, pfn, order, fpi_flags); - - __count_vm_events(PGFREE, 1 << order); + if (free_pages_prepare(page, order)) + free_one_page(zone, page, pfn, order, fpi_flags); } void __meminit __free_pages_core(struct page *page, unsigned int order,