[PATCH 25/25] xor: use static_call for xor_gen

[Christoph Hellwig]

Avoid the indirect call for xor_generation by using a static_call.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 lib/raid/xor/xor-32regs.c |  2 +-
 lib/raid/xor/xor-core.c   | 29 ++++++++++++++---------------
 lib/raid/xor/xor_impl.h   |  4 ++++
 3 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/lib/raid/xor/xor-32regs.c b/lib/raid/xor/xor-32regs.c
index acb4a10d1e95..759a31f76414 100644
--- a/lib/raid/xor/xor-32regs.c
+++ b/lib/raid/xor/xor-32regs.c
@@ -209,7 +209,7 @@ xor_32regs_5(unsigned long bytes, unsigned long * __restrict p1,
 	} while (--lines > 0);
 }
 
-DO_XOR_BLOCKS(32regs, xor_32regs_2, xor_32regs_3, xor_32regs_4, xor_32regs_5);
+__DO_XOR_BLOCKS(32regs, xor_32regs_2, xor_32regs_3, xor_32regs_4, xor_32regs_5);
 
 struct xor_block_template xor_block_32regs = {
 	.name		= "32regs",
diff --git a/lib/raid/xor/xor-core.c b/lib/raid/xor/xor-core.c
index f18dcc57004b..2ab03dd294bf 100644
--- a/lib/raid/xor/xor-core.c
+++ b/lib/raid/xor/xor-core.c
@@ -11,10 +11,14 @@
 #include <linux/raid/xor.h>
 #include <linux/jiffies.h>
 #include <linux/preempt.h>
+#include <linux/static_call.h>
 #include "xor_impl.h"
 
-/* The xor routine to use.  */
-static struct xor_block_template *active_template;
+/*
+ * Provide a temporary default until the fastest or forced implementation is
+ * picked.
+ */
+DEFINE_STATIC_CALL(xor_gen_impl, xor_gen_32regs);
 
 /**
  * xor_gen - generate RAID-style XOR information
@@ -32,13 +36,13 @@ static struct xor_block_template *active_template;
 void xor_gen(void *dest, void **srcs, unsigned int src_cnt, unsigned int bytes)
 {
 	WARN_ON_ONCE(in_interrupt());
-	active_template->xor_gen(dest, srcs, src_cnt, bytes);
+	static_call(xor_gen_impl)(dest, srcs, src_cnt, bytes);
 }
 EXPORT_SYMBOL(xor_gen);
 
 /* Set of all registered templates.  */
 static struct xor_block_template *__initdata template_list;
-static int __initdata xor_forced = false;
+static struct xor_block_template *forced_template;
 
 /**
  * xor_register - register a XOR template
@@ -64,7 +68,7 @@ void __init xor_register(struct xor_block_template *tmpl)
  */
 void __init xor_force(struct xor_block_template *tmpl)
 {
-	active_template = tmpl;
+	forced_template = tmpl;
 }
 
 #define BENCH_SIZE	4096
@@ -106,7 +110,7 @@ static int __init calibrate_xor_blocks(void)
 	void *b1, *b2;
 	struct xor_block_template *f, *fastest;
 
-	if (xor_forced)
+	if (forced_template)
 		return 0;
 
 	b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
@@ -123,7 +127,7 @@ static int __init calibrate_xor_blocks(void)
 		if (f->speed > fastest->speed)
 			fastest = f;
 	}
-	active_template = fastest;
+	static_call_update(xor_gen_impl, fastest->xor_gen);
 	pr_info("xor: using function: %s (%d MB/sec)\n",
 	       fastest->name, fastest->speed);
 
@@ -151,21 +155,16 @@ static int __init xor_init(void)
 	 * If this arch/cpu has a short-circuited selection, don't loop through
 	 * all the possible functions, just use the best one.
 	 */
-	if (active_template) {
+	if (forced_template) {
 		pr_info("xor: automatically using best checksumming function   %-10s\n",
-			active_template->name);
-		xor_forced = true;
+			forced_template->name);
+		static_call_update(xor_gen_impl, forced_template->xor_gen);
 		return 0;
 	}
 
 #ifdef MODULE
 	return calibrate_xor_blocks();
 #else
-	/*
-	 * Pick the first template as the temporary default until calibration
-	 * happens.
-	 */
-	active_template = template_list;
 	return 0;
 #endif
 }
diff --git a/lib/raid/xor/xor_impl.h b/lib/raid/xor/xor_impl.h
index 968dd07df627..f11910162b08 100644
--- a/lib/raid/xor/xor_impl.h
+++ b/lib/raid/xor/xor_impl.h
@@ -50,6 +50,10 @@ extern struct xor_block_template xor_block_32regs;
 extern struct xor_block_template xor_block_8regs_p;
 extern struct xor_block_template xor_block_32regs_p;
 
+/* default call until updated */
+void xor_gen_32regs(void *dest, void **srcs, unsigned int src_cnt,
+		unsigned int bytes);
+
 void __init xor_register(struct xor_block_template *tmpl);
 void __init xor_force(struct xor_block_template *tmpl);
 
-- 
2.47.3