percpu: don't implicitly include slab.h from percpu.h

percpu.h has always been including slab.h to get k[mz]alloc/free() for
UP inline implementation.  percpu.h being used by very low level
headers including module.h and sched.h, this meant that a lot files
unintentionally got slab.h inclusion.

Lee Schermerhorn was trying to make topology.h use percpu.h and got
bitten by this implicit inclusion.  The right thing to do is break
this ultimately unnecessary dependency.  The previous patch added
explicit inclusion of either gfp.h or slab.h to the source files using
them.  This patch updates percpu.h such that slab.h is no longer
included from percpu.h.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>

2 files changed, 35 insertions, 1 deletions

diff --git a/mm/Makefile b/mm/Makefile
index 7a68d2ab5560..6c2a73a54a43 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -33,7 +33,11 @@ obj-$(CONFIG_FAILSLAB) += failslab.o
 obj-$(CONFIG_MEMORY_HOTPLUG) += memory_hotplug.o
 obj-$(CONFIG_FS_XIP) += filemap_xip.o
 obj-$(CONFIG_MIGRATION) += migrate.o
-obj-$(CONFIG_SMP) += percpu.o
+ifdef CONFIG_SMP
+obj-y += percpu.o
+else
+obj-y += percpu_up.o
+endif
 obj-$(CONFIG_QUICKLIST) += quicklist.o
 obj-$(CONFIG_CGROUP_MEM_RES_CTLR) += memcontrol.o page_cgroup.o
 obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o
diff --git a/mm/percpu_up.c b/mm/percpu_up.c
new file mode 100644
index 000000000000..c4351c7f57d2
--- /dev/null
+++ b/mm/percpu_up.c
@@ -0,0 +1,30 @@
+/*
+ * mm/percpu_up.c - dummy percpu memory allocator implementation for UP
+ */
+
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/slab.h>
+
+void __percpu *__alloc_percpu(size_t size, size_t align)
+{
+	/*
+	 * Can't easily make larger alignment work with kmalloc.  WARN
+	 * on it.  Larger alignment should only be used for module
+	 * percpu sections on SMP for which this path isn't used.
+	 */
+	WARN_ON_ONCE(align > SMP_CACHE_BYTES);
+	return kzalloc(size, GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(__alloc_percpu);
+
+void free_percpu(void __percpu *p)
+{
+	kfree(p);
+}
+EXPORT_SYMBOL_GPL(free_percpu);
+
+phys_addr_t per_cpu_ptr_to_phys(void *addr)
+{
+	return __pa(addr);
+}