percpu: introduce start_offset to pcpu_chunk

The reserved chunk arithmetic uses a global variable
pcpu_reserved_chunk_limit that is set in the first chunk init code to
hide a portion of the area map. The bitmap allocator to come will
eventually move the base_addr up and require both the reserved chunk
and static chunk to maintain this offset. pcpu_reserved_chunk_limit is
removed and start_offset is added.

The first chunk that is circulated and is pcpu_first_chunk serves the
dynamic region, the region following the reserved region. The reserved
chunk address check will temporarily use the first chunk to identify its
address range. A following patch will increase the base_addr and remove
this. If there is no reserved chunk, this will check the static region
and return false because those values should never be passed into the
allocator.

Lastly, when linking in the first chunk, make sure to count the right
free region for the number of empty populated pages.

Signed-off-by: Dennis Zhou <dennisszhou@gmail.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h
index c9158a48ca05..92fc0121dfff 100644
--- a/mm/percpu-internal.h
+++ b/mm/percpu-internal.h
@@ -28,6 +28,9 @@ struct pcpu_chunk {
 						   contain reservation for static chunk.
 						   Dynamic chunk will contain reservation
 						   for static and reserved chunks. */
+	int			start_offset;	/* the overlap with the previous
+						   region to have a page aligned
+						   base_addr */
 	int			nr_populated;	/* # of populated pages */
 	unsigned long		populated[];	/* populated bitmap */
 };