x86/mm/numa: Remove uninitialized_var() usage (aecfd220) · Commits · 戴 / test

Using uninitialized_var() is dangerous as it papers over real bugs[1] (or can in the future), and suppresses unrelated compiler warnings (e.g. "unused variable"). If the compiler thinks it is uninitialized, either simply initialize the variable or make compiler changes. As a precursor to removing[2] this[3] macro[4], refactor code to avoid its need. The original reason for its use here was to work around the #ifdef being the only place the variable was used. This is better expressed using IS_ENABLED() and a new code block where the variable can be used unconditionally. [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/ [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/ [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/ [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/ Fixes: ("x86, numa: Implement pfn -> nid mapping granularity check") Signed-off-by:

arch/x86/mm/numa.c

+9 −9

Original line number	Diff line number	Diff line
		@@ -543,7 +543,6 @@ static void __init numa_clear_kernel_node_hotplug(void)

		static int __init numa_register_memblks(struct numa_meminfo *mi)
		{
		unsigned long uninitialized_var(pfn_align);
		int i, nid;

		/* Account for nodes with cpus and no memory */
		@@ -571,15 +570,16 @@ static int __init numa_register_memblks(struct numa_meminfo *mi)
		* If sections array is gonna be used for pfn -> nid mapping, check
		* whether its granularity is fine enough.
		*/
		#ifdef NODE_NOT_IN_PAGE_FLAGS
		pfn_align = node_map_pfn_alignment();
		if (IS_ENABLED(NODE_NOT_IN_PAGE_FLAGS)) {
		unsigned long pfn_align = node_map_pfn_alignment();

		if (pfn_align && pfn_align < PAGES_PER_SECTION) {
		printk(KERN_WARNING "Node alignment %LuMB < min %LuMB, rejecting NUMA config\n",
		pr_warn("Node alignment %LuMB < min %LuMB, rejecting NUMA config\n",
		PFN_PHYS(pfn_align) >> 20,
		PFN_PHYS(PAGES_PER_SECTION) >> 20);
		return -EINVAL;
		}
		#endif
		}
		if (!numa_meminfo_cover_memory(mi))
		return -EINVAL;

+3 −1

Original line number	Diff line number	Diff line
		@@ -98,9 +98,11 @@
		/*
		* We are going to use the flags for the page to node mapping if its in
		* there. This includes the case where there is no node, so it is implicit.
		* Note that this #define MUST have a value so that it can be tested with
		* the IS_ENABLED() macro.
		*/
		#if !(NODES_WIDTH > 0 \|\| NODES_SHIFT == 0)
		#define NODE_NOT_IN_PAGE_FLAGS
		#define NODE_NOT_IN_PAGE_FLAGS 1
		#endif

		#if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0