Linux 5.12 compat: bio->bi_disk member moved

The struct bio member bi_disk was moved underneath a new member named
bi_bdev. So all attempts to reference bio->bi_disk need to now become
bio->bi_bdev->bd_disk.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes #11639

config/kernel-bio.m4

@@ -369,6 +369,33 @@ AC_DEFUN([ZFS_AC_KERNEL_BLKG_TRYGET], [
 	])
 ])
 
+dnl #
+dnl # Linux 5.12 API,
+dnl #
+dnl # The Linux 5.12 kernel updated struct bio to create a new bi_bdev member
+dnl # and bio->bi_disk was moved to bio->bi_bdev->bd_disk
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_BIO_BDEV_DISK], [
+	ZFS_LINUX_TEST_SRC([bio_bdev_disk], [
+		#include <linux/blk_types.h>
+		#include <linux/blkdev.h>
+	],[
+		struct bio *b = NULL;
+		struct gendisk *d = b->bi_bdev->bd_disk;
+		blk_register_queue(d);
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_BIO_BDEV_DISK], [
+	AC_MSG_CHECKING([whether bio->bi_bdev->bd_disk exists])
+	ZFS_LINUX_TEST_RESULT([bio_bdev_disk], [
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_BIO_BDEV_DISK, 1, [bio->bi_bdev->bd_disk exists])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])
+
 AC_DEFUN([ZFS_AC_KERNEL_SRC_BIO], [
 	ZFS_AC_KERNEL_SRC_REQ
 	ZFS_AC_KERNEL_SRC_BIO_OPS
@@ -379,6 +406,7 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_BIO], [
 	ZFS_AC_KERNEL_SRC_BIO_SUBMIT_BIO
 	ZFS_AC_KERNEL_SRC_BIO_CURRENT_BIO_LIST
 	ZFS_AC_KERNEL_SRC_BLKG_TRYGET
+	ZFS_AC_KERNEL_SRC_BIO_BDEV_DISK
 ])
 
 AC_DEFUN([ZFS_AC_KERNEL_BIO], [
@@ -400,4 +428,5 @@ AC_DEFUN([ZFS_AC_KERNEL_BIO], [
 	ZFS_AC_KERNEL_BIO_SUBMIT_BIO
 	ZFS_AC_KERNEL_BIO_CURRENT_BIO_LIST
 	ZFS_AC_KERNEL_BLKG_TRYGET
+	ZFS_AC_KERNEL_BIO_BDEV_DISK
 ])

module/os/linux/zfs/vdev_disk.c

@@ -494,7 +494,11 @@ vdev_blkg_tryget(struct blkcg_gq *blkg)
 static inline void
 vdev_bio_associate_blkg(struct bio *bio)
 {
+#if defined(HAVE_BIO_BDEV_DISK)
+	struct request_queue *q = bio->bi_bdev->bd_disk->queue;
+#else
 	struct request_queue *q = bio->bi_disk->queue;
+#endif
 
 	ASSERT3P(q, !=, NULL);
 	ASSERT3P(bio->bi_blkg, ==, NULL);

module/os/linux/zfs/zvol_os.c

@@ -307,7 +307,11 @@ zvol_request(struct request_queue *q, struct bio *bio)
 #endif
 {
 #ifdef HAVE_SUBMIT_BIO_IN_BLOCK_DEVICE_OPERATIONS
+#if defined(HAVE_BIO_BDEV_DISK)
+	struct request_queue *q = bio->bi_bdev->bd_disk->queue;
+#else
 	struct request_queue *q = bio->bi_disk->queue;
+#endif
 #endif
 	zvol_state_t *zv = q->queuedata;
 	fstrans_cookie_t cookie = spl_fstrans_mark();