From 0272d07ef6ebc574e62d6423e5efa5b975f9f910 Mon Sep 17 00:00:00 2001 From: "Uladzislau Rezki (Sony)" Date: Tue, 15 Apr 2025 13:26:46 +0200 Subject: [PATCH] vmalloc: use atomic_long_add_return_relaxed() Switch from the atomic_long_add_return() to its relaxed version. We do not need a full memory barrier or any memory ordering during increasing the "vmap_lazy_nr" variable. What we only need is to do it atomically. This is what atomic_long_add_return_relaxed() guarantees. AARCH64: Default: 40ec: d34cfe94 lsr x20, x20, #12 40f0: 14000044 b 4200 40f4: 94000000 bl 0 <__sanitizer_cov_trace_pc> 40f8: 90000000 adrp x0, 0 <__traceiter_alloc_vmap_area> 40fc: 91000000 add x0, x0, #0x0 4100: f8f40016 ldaddal x20, x22, [x0] 4104: 8b160296 add x22, x20, x22 Relaxed: 40ec: d34cfe94 lsr x20, x20, #12 40f0: 14000044 b 4200 40f4: 94000000 bl 0 <__sanitizer_cov_trace_pc> 40f8: 90000000 adrp x0, 0 <__traceiter_alloc_vmap_area> 40fc: 91000000 add x0, x0, #0x0 4100: f8340016 ldadd x20, x22, [x0] 4104: 8b160296 add x22, x20, x22 Link: https://lkml.kernel.org/r/20250415112646.113091-1-urezki@gmail.com Signed-off-by: Uladzislau Rezki (Sony) Reviewed-by: Baoquan He Cc: Christop Hellwig Cc: Mateusz Guzik Signed-off-by: Andrew Morton --- mm/vmalloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 9eb3880887b6..dc33ebeb8b1b 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2370,7 +2370,7 @@ static void free_vmap_area_noflush(struct vmap_area *va) if (WARN_ON_ONCE(!list_empty(&va->list))) return; - nr_lazy = atomic_long_add_return(va_size(va) >> PAGE_SHIFT, + nr_lazy = atomic_long_add_return_relaxed(va_size(va) >> PAGE_SHIFT, &vmap_lazy_nr); /* -- 2.50.1