percpu, module: implement reserved allocation and use it for module percpu variables

Impact: add reserved allocation functionality and use it for module
	percpu variables

This patch implements reserved allocation from the first chunk.  When
setting up the first chunk, arch can ask to set aside certain number
of bytes right after the core static area which is available only
through a separate reserved allocator.  This will be used primarily
for module static percpu variables on architectures with limited
relocation range to ensure that the module perpcu symbols are inside
the relocatable range.

If reserved area is requested, the first chunk becomes reserved and
isn't available for regular allocation.  If the first chunk also
includes piggy-back dynamic allocation area, a separate chunk mapping
the same region is created to serve dynamic allocation.  The first one
is called static first chunk and the second dynamic first chunk.
Although they share the page map, their different area map
initializations guarantee they serve disjoint areas according to their
purposes.

If arch doesn't setup reserved area, reserved allocation is handled
like any other allocation.

Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index 38e2b2a..dd4eabc 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -217,7 +217,7 @@ proceed:
 	pr_info("PERCPU: Remapped at %p with large pages, static data "
 		"%zu bytes\n", vm.addr, static_size);
 
-	ret = pcpu_setup_first_chunk(pcpur_get_page, static_size, PMD_SIZE,
+	ret = pcpu_setup_first_chunk(pcpur_get_page, static_size, 0, PMD_SIZE,
 				     pcpur_size - static_size, vm.addr, NULL);
 	goto out_free_ar;
 
@@ -297,7 +297,7 @@ static ssize_t __init setup_pcpu_embed(size_t static_size)
 	pr_info("PERCPU: Embedded %zu pages at %p, static data %zu bytes\n",
 		pcpue_size >> PAGE_SHIFT, pcpue_ptr, static_size);
 
-	return pcpu_setup_first_chunk(pcpue_get_page, static_size,
+	return pcpu_setup_first_chunk(pcpue_get_page, static_size, 0,
 				      pcpue_unit_size, dyn_size,
 				      pcpue_ptr, NULL);
 }
@@ -356,8 +356,8 @@ static ssize_t __init setup_pcpu_4k(size_t static_size)
 	pr_info("PERCPU: Allocated %d 4k pages, static data %zu bytes\n",
 		pcpu4k_nr_static_pages, static_size);
 
-	ret = pcpu_setup_first_chunk(pcpu4k_get_page, static_size, -1, -1, NULL,
-				     pcpu4k_populate_pte);
+	ret = pcpu_setup_first_chunk(pcpu4k_get_page, static_size, 0, -1, -1,
+				     NULL, pcpu4k_populate_pte);
 	goto out_free_ar;
 
 enomem: