+ xor-use-static_call-for-xor_gen.patch added to mm-nonmm-unstable branch

+ xor-use-static_call-for-xor_gen.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: xor: use static_call for xor_gen
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     xor-use-static_call-for-xor_gen.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/xor-use-static_call-for-xor_gen.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: Christoph Hellwig <hch@lst.de>
Subject: xor: use static_call for xor_gen
Date: Fri, 27 Mar 2026 07:16:59 +0100

Avoid the indirect call for xor_generation by using a static_call.

Link: https://lkml.kernel.org/r/20260327061704.3707577-28-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Mason <clm@fb.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: David Sterba <dsterba@suse.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jason A. Donenfeld <jason@zx2c4.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Li Nan <linan122@huawei.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Magnus Lindholm <linmag7@gmail.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Song Liu <song@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/raid/xor/xor-core.c |   22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

--- a/lib/raid/xor/xor-core.c~xor-use-static_call-for-xor_gen
+++ a/lib/raid/xor/xor-core.c
@@ -11,10 +11,10 @@
 #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;
+DEFINE_STATIC_CALL_NULL(xor_gen_impl, *xor_block_8regs.xor_gen);
 
 /**
  * xor_gen - generate RAID-style XOR information
@@ -37,13 +37,13 @@ void xor_gen(void *dest, void **srcs, un
 	WARN_ON_ONCE(bytes == 0);
 	WARN_ON_ONCE(bytes & 511);
 
-	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 bool __initdata xor_forced = false;
+static struct xor_block_template *forced_template;
 
 /**
  * xor_register - register a XOR template
@@ -69,7 +69,7 @@ void __init xor_register(struct xor_bloc
  */
 void __init xor_force(struct xor_block_template *tmpl)
 {
-	active_template = tmpl;
+	forced_template = tmpl;
 }
 
 #define BENCH_SIZE	4096
@@ -111,7 +111,7 @@ static int __init calibrate_xor_blocks(v
 	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);
@@ -128,7 +128,7 @@ static int __init calibrate_xor_blocks(v
 		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);
 
@@ -156,10 +156,10 @@ 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;
 	}
 
@@ -170,7 +170,7 @@ static int __init xor_init(void)
 	 * Pick the first template as the temporary default until calibration
 	 * happens.
 	 */
-	active_template = template_list;
+	static_call_update(xor_gen_impl, template_list->xor_gen);
 	return 0;
 #endif
 }
_

Patches currently in -mm which might be from hch@lst.de are

xor-assert-that-xor_blocks-is-not-call-from-interrupt-context.patch
arm-xor-remove-in_interrupt-handling.patch
arm64-xor-fix-conflicting-attributes-for-xor_block_template.patch
um-xor-cleanup-xorh.patch
xor-move-to-lib-raid.patch
xor-small-cleanups.patch
xor-cleanup-registration-and-probing.patch
xor-split-xorh.patch
xor-remove-macro-abuse-for-xor-implementation-registrations.patch
xor-move-generic-implementations-out-of-asm-generic-xorh.patch
alpha-move-the-xor-code-to-lib-raid.patch
arm-move-the-xor-code-to-lib-raid.patch
arm64-move-the-xor-code-to-lib-raid.patch
loongarch-move-the-xor-code-to-lib-raid.patch
powerpc-move-the-xor-code-to-lib-raid.patch
riscv-move-the-xor-code-to-lib-raid.patch
sparc-move-the-xor-code-to-lib-raid.patch
s390-move-the-xor-code-to-lib-raid.patch
x86-move-the-xor-code-to-lib-raid.patch
xor-avoid-indirect-calls-for-arm64-optimized-ops.patch
xor-make-xorko-self-contained-in-lib-raid.patch
xor-add-a-better-public-api.patch
xor-add-a-better-public-api-2.patch
async_xor-use-xor_gen.patch
btrfs-use-xor_gen.patch
xor-pass-the-entire-operation-to-the-low-level-ops.patch
xor-use-static_call-for-xor_gen.patch
xor-add-a-kunit-test-case.patch