From 17fcdd8699b2439e83e3c3aa6cf0f55bd35b4053 Mon Sep 17 00:00:00 2001 From: Kaitao Cheng Date: Thu, 18 Jun 2026 21:04:13 +0800 Subject: [PATCH] mm/percpu: make cached pages lookup explicit pcpu_depopulate_chunk() only needs the temporary pages array that was already allocated by an earlier successful population attempt. Passing GFP_KERNEL to pcpu_get_pages() in this path is misleading because the depopulation path is not expected to allocate the array. Teach pcpu_get_pages() to treat a zero gfp mask as a cached-only lookup and add pcpu_get_pages_cached() for that use case. This keeps allocation on the populate path tied to the caller supplied GFP mask while making the depopulate path's dependency on the cached array explicit. Link: https://lore.kernel.org/20260618130414.96383-4-kaitao.cheng@linux.dev Signed-off-by: Kaitao Cheng Suggested-by: Dennis Zhou Acked-by: Michal Hocko Cc: Christoph Lameter Cc: Pedro Falcato Cc: Shivam Kalra Cc: Tejun Heo Cc: Uladzislau Rezki (Sony) Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/percpu-vm.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c index ccd03cc152d4..7ed216192fc0 100644 --- a/mm/percpu-vm.c +++ b/mm/percpu-vm.c @@ -21,7 +21,8 @@ static struct page *pcpu_chunk_page(struct pcpu_chunk *chunk, /** * pcpu_get_pages - get temp pages array - * @gfp: allocation flags passed to the underlying allocator + * @gfp: allocation flags passed to the underlying allocator, 0 to only + * return the cached array * * Returns pointer to array of pointers to struct page which can be indexed * with pcpu_page_idx(). Note that there is only one array and accesses @@ -37,11 +38,16 @@ static struct page **pcpu_get_pages(gfp_t gfp) lockdep_assert_held(&pcpu_alloc_mutex); - if (!pages) + if (!pages && gfp) pages = pcpu_mem_zalloc(pages_size, gfp); return pages; } +static struct page **pcpu_get_pages_cached(void) +{ + return pcpu_get_pages(0); +} + /** * pcpu_free_pages - free pages which were allocated for @chunk * @chunk: chunk pages were allocated for @@ -333,7 +339,7 @@ static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, * successful population attempt so the temp pages array must * be available now. */ - pages = pcpu_get_pages(GFP_KERNEL); + pages = pcpu_get_pages_cached(); BUG_ON(!pages); /* unmap and free */