From 30a7a9b17c4b0331ec67aadb4b30ff2a951b4ed5 Mon Sep 17 00:00:00 2001 From: Baoquan He Date: Mon, 6 Feb 2023 16:40:18 +0800 Subject: mm/vmalloc: skip the uninitilized vmalloc areas For areas allocated via vmalloc_xxx() APIs, it searches for unmapped area to reserve and allocates new pages to map into, please see function __vmalloc_node_range(). During the process, flag VM_UNINITIALIZED is set in vm->flags to indicate that the pages allocation and mapping haven't been done, until clear_vm_uninitialized_flag() is called to clear VM_UNINITIALIZED. For this kind of area, if VM_UNINITIALIZED is still set, let's ignore it in vread() because pages newly allocated and being mapped in that area only contains zero data. reading them out by aligned_vread() is wasting time. Link: https://lkml.kernel.org/r/20230206084020.174506-6-bhe@redhat.com Signed-off-by: Baoquan He Reviewed-by: Lorenzo Stoakes Reviewed-by: Uladzislau Rezki (Sony) Cc: Dan Carpenter Cc: Stephen Brennan Signed-off-by: Andrew Morton --- mm/vmalloc.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'mm') diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 87d71c783646..3b57260b6d39 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3587,6 +3587,11 @@ long vread(char *buf, char *addr, unsigned long count) if (!vm && !flags) continue; + if (vm && (vm->flags & VM_UNINITIALIZED)) + continue; + /* Pair with smp_wmb() in clear_vm_uninitialized_flag() */ + smp_rmb(); + vaddr = (char *) va->va_start; size = vm ? get_vm_area_size(vm) : va_size(va); -- cgit v1.2.3