Linux 5.16: bio_set_dev is no longer a helper macro

This change adds a confiugre check to determine if bio_set_dev is a
helper macro or not. If not, then the attempt to override its internal
call to bio_associate_blkg(), with a macro definition to our own
version, is no longer possible, as the compiler won't use it when
compiling the new inline function replacement implemented in the header.
This change also creates a new vdev_bio_set_dev() function that performs
the same work, and also performs the work implemented in
vdev_bio_associate_blkg(), as it is the only thing calling that function
in our code. Our custom vdev_bio_associate_blkg() is now only compiled
if the bio_set_dev() is a macro in the Linux headers.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes openzfs#12819

config/kernel-bio.m4

@@ -191,6 +191,24 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_BIO_SET_DEV], [
 	], [], [ZFS_META_LICENSE])
 ])
 
+dnl #
+dnl # Linux 5.16 API
+dnl #
+dnl # bio_set_dev is no longer a helper macro and is now an inline function,
+dnl # meaning that the function it calls internally can no longer be overridden
+dnl # by our code
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_BIO_SET_DEV_MACRO], [
+	ZFS_LINUX_TEST_SRC([bio_set_dev_macro], [
+		#include <linux/bio.h>
+		#include <linux/fs.h>
+	],[
+		#ifndef bio_set_dev
+		#error Not a macro
+		#endif
+	], [], [ZFS_META_LICENSE])
+])
+
 AC_DEFUN([ZFS_AC_KERNEL_BIO_SET_DEV], [
 	AC_MSG_CHECKING([whether bio_set_dev() is available])
 	ZFS_LINUX_TEST_RESULT([bio_set_dev], [
@@ -205,6 +223,15 @@ AC_DEFUN([ZFS_AC_KERNEL_BIO_SET_DEV], [
 			AC_DEFINE(HAVE_BIO_SET_DEV_GPL_ONLY, 1,
 			    [bio_set_dev() GPL-only])
 		])
+
+		AC_MSG_CHECKING([whether bio_set_dev() is a macro])
+		ZFS_LINUX_TEST_RESULT([bio_set_dev_macro], [
+			AC_MSG_RESULT(yes)
+			AC_DEFINE(HAVE_BIO_SET_DEV_MACRO, 1,
+			    [bio_set_dev() is a macro])
+		],[
+			AC_MSG_RESULT(no)
+		])
 	],[
 		AC_MSG_RESULT(no)
 	])
@@ -434,6 +461,7 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_BIO], [
 	ZFS_AC_KERNEL_SRC_BLKG_TRYGET
 	ZFS_AC_KERNEL_SRC_BIO_BDEV_DISK
 	ZFS_AC_KERNEL_SRC_BDEV_SUBMIT_BIO_RETURNS_VOID
+	ZFS_AC_KERNEL_SRC_BIO_SET_DEV_MACRO
 ])
 
 AC_DEFUN([ZFS_AC_KERNEL_BIO], [

module/os/linux/zfs/vdev_disk.c

@@ -493,6 +493,7 @@ vdev_blkg_tryget(struct blkcg_gq *blkg)
 #elif defined(HAVE_BLKG_TRYGET)
 #define	vdev_blkg_tryget(bg)	blkg_tryget(bg)
 #endif
+#ifdef HAVE_BIO_SET_DEV_MACRO
 /*
  * The Linux 5.0 kernel updated the bio_set_dev() macro so it calls the
  * GPL-only bio_associate_blkg() symbol thus inadvertently converting
@@ -514,7 +515,30 @@ vdev_bio_associate_blkg(struct bio *bio)
 	if (q->root_blkg && vdev_blkg_tryget(q->root_blkg))
 		bio->bi_blkg = q->root_blkg;
 }
+
 #define	bio_associate_blkg vdev_bio_associate_blkg
+#else
+static inline void
+vdev_bio_set_dev(struct bio *bio, struct block_device *bdev)
+{
+#if defined(HAVE_BIO_BDEV_DISK)
+	struct request_queue *q = bdev->bd_disk->queue;
+#else
+	struct request_queue *q = bio->bi_disk->queue;
+#endif
+	bio_clear_flag(bio, BIO_REMAPPED);
+	if (bio->bi_bdev != bdev)
+		bio_clear_flag(bio, BIO_THROTTLED);
+	bio->bi_bdev = bdev;
+
+	ASSERT3P(q, !=, NULL);
+	ASSERT3P(bio->bi_blkg, ==, NULL);
+
+	if (q->root_blkg && vdev_blkg_tryget(q->root_blkg))
+		bio->bi_blkg = q->root_blkg;
+}
+#define	bio_set_dev		vdev_bio_set_dev
+#endif
 #endif
 #else
 /*