percpu: add pcpu_unit_offsets[]

Currently units are mapped sequentially into address space.  This
patch adds pcpu_unit_offsets[] which allows units to be mapped to
arbitrary offsets from the chunk base address.  This is necessary to
allow sparse embedding which might would need to allocate address
ranges and memory areas which aren't aligned to unit size but
allocation atom size (page or large page size).  This also simplifies
things a bit by removing the need to calculate offset from unit
number.

With this change, there's no need for the arch code to know
pcpu_unit_size.  Update pcpu_setup_first_chunk() and first chunk
allocators to return regular 0 or -errno return code instead of unit
size or -errno.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 5 deletions

diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index a42a4a7..b03fd36 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -1478,9 +1478,10 @@ void __init setup_per_cpu_areas(void)
 	static struct vm_struct vm;
 	struct pcpu_alloc_info *ai;
 	unsigned long delta, cpu;
-	size_t size_sum, pcpu_unit_size;
+	size_t size_sum;
 	size_t ptrs_size;
 	void **ptrs;
+	int rc;
 
 	ai = pcpu_alloc_alloc_info(1, nr_cpu_ids);
 
@@ -1526,14 +1527,15 @@ void __init setup_per_cpu_areas(void)
 		pcpu_map_range(start, end, virt_to_page(ptrs[cpu]));
 	}
 
-	pcpu_unit_size = pcpu_setup_first_chunk(ai, vm.addr);
+	rc = pcpu_setup_first_chunk(ai, vm.addr);
+	if (rc)
+		panic("failed to setup percpu first chunk (%d)", rc);
 
 	free_bootmem(__pa(ptrs), ptrs_size);
 
 	delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
-	for_each_possible_cpu(cpu) {
-		__per_cpu_offset(cpu) = delta + cpu * pcpu_unit_size;
-	}
+	for_each_possible_cpu(cpu)
+		__per_cpu_offset(cpu) = delta + pcpu_unit_offsets[cpu];
 
 	/* Setup %g5 for the boot cpu.  */
 	__local_per_cpu_offset = __per_cpu_offset(smp_processor_id());