Linux 5.14 compat: blk_alloc_disk()

In Linux 5.14, blk_alloc_queue is no longer exported, and its usage
has been superseded by blk_alloc_disk, which returns a gendisk struct
from which we can still retrieve the struct request_queue* that is
needed in the one place where it is used. This also replaces the call
to alloc_disk(minors), and minors is now set via struct member
assignment.

Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Reviewed-by: Olaf Faaland <faaland1@llnl.gov>
Reviewed-by: Coleman Kane <ckane@colemankane.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes openzfs#12362
Closes openzfs#12409

config/kernel-make-request-fn.m4

@@ -42,6 +42,13 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_MAKE_REQUEST_FN], [
 		struct block_device_operations o;
 		o.submit_bio = NULL;
 	])
+
+	ZFS_LINUX_TEST_SRC([blk_alloc_disk], [
+		#include <linux/blkdev.h>
+	],[
+		struct gendisk *disk  __attribute__ ((unused));
+		disk = blk_alloc_disk(NUMA_NO_NODE);
+	])
 ])
 
 AC_DEFUN([ZFS_AC_KERNEL_MAKE_REQUEST_FN], [
@@ -56,6 +63,19 @@ AC_DEFUN([ZFS_AC_KERNEL_MAKE_REQUEST_FN], [
 
 		AC_DEFINE(HAVE_SUBMIT_BIO_IN_BLOCK_DEVICE_OPERATIONS, 1,
 		    [submit_bio is member of struct block_device_operations])
+
+		dnl #
+		dnl # Linux 5.14 API Change:
+		dnl # blk_alloc_queue() + alloc_disk() combo replaced by
+		dnl # a single call to blk_alloc_disk().
+		dnl #
+		AC_MSG_CHECKING([whether blk_alloc_disk() exists])
+		ZFS_LINUX_TEST_RESULT([blk_alloc_disk], [
+			AC_MSG_RESULT(yes)
+			AC_DEFINE([HAVE_BLK_ALLOC_DISK], 1, [blk_alloc_disk() exists])
+		], [
+			AC_MSG_RESULT(no)
+		])
 	],[
 		AC_MSG_RESULT(no)
 

module/os/linux/zfs/zvol_os.c

@@ -762,7 +762,7 @@ static struct block_device_operations zvol_ops = {
 	.getgeo			= zvol_getgeo,
 	.owner			= THIS_MODULE,
 #ifdef HAVE_SUBMIT_BIO_IN_BLOCK_DEVICE_OPERATIONS
-    .submit_bio		= zvol_submit_bio,
+	.submit_bio		= zvol_submit_bio,
 #endif
 };
 
@@ -795,13 +795,40 @@ zvol_alloc(dev_t dev, const char *name)
 	mutex_init(&zv->zv_state_lock, NULL, MUTEX_DEFAULT, NULL);
 
 #ifdef HAVE_SUBMIT_BIO_IN_BLOCK_DEVICE_OPERATIONS
+#ifdef HAVE_BLK_ALLOC_DISK
+	zso->zvo_disk = blk_alloc_disk(NUMA_NO_NODE);
+	if (zso->zvo_disk == NULL)
+		goto out_kmem;
+
+	zso->zvo_disk->minors = ZVOL_MINORS;
+	zso->zvo_queue = zso->zvo_disk->queue;
+#else
 	zso->zvo_queue = blk_alloc_queue(NUMA_NO_NODE);
+	if (zso->zvo_queue == NULL)
+		goto out_kmem;
+
+	zso->zvo_disk = alloc_disk(ZVOL_MINORS);
+	if (zso->zvo_disk == NULL) {
+		blk_cleanup_queue(zso->zvo_queue);
+		goto out_kmem;
+	}
+
+	zso->zvo_disk->queue = zso->zvo_queue;
+#endif /* HAVE_BLK_ALLOC_DISK */
 #else
 	zso->zvo_queue = blk_generic_alloc_queue(zvol_request, NUMA_NO_NODE);
-#endif
 	if (zso->zvo_queue == NULL)
 		goto out_kmem;
 
+	zso->zvo_disk = alloc_disk(ZVOL_MINORS);
+	if (zso->zvo_disk == NULL) {
+		blk_cleanup_queue(zso->zvo_queue);
+		goto out_kmem;
+	}
+
+	zso->zvo_disk->queue = zso->zvo_queue;
+#endif /* HAVE_SUBMIT_BIO_IN_BLOCK_DEVICE_OPERATIONS */
+
 	blk_queue_set_write_cache(zso->zvo_queue, B_TRUE, B_TRUE);
 
 	/* Limit read-ahead to a single page to prevent over-prefetching. */
@@ -810,10 +837,6 @@ zvol_alloc(dev_t dev, const char *name)
 	/* Disable write merging in favor of the ZIO pipeline. */
 	blk_queue_flag_set(QUEUE_FLAG_NOMERGES, zso->zvo_queue);
 
-	zso->zvo_disk = alloc_disk(ZVOL_MINORS);
-	if (zso->zvo_disk == NULL)
-		goto out_queue;
-
 	zso->zvo_queue->queuedata = zv;
 	zso->zvo_dev = dev;
 	zv->zv_open_count = 0;
@@ -844,14 +867,11 @@ zvol_alloc(dev_t dev, const char *name)
 	zso->zvo_disk->first_minor = (dev & MINORMASK);
 	zso->zvo_disk->fops = &zvol_ops;
 	zso->zvo_disk->private_data = zv;
-	zso->zvo_disk->queue = zso->zvo_queue;
 	snprintf(zso->zvo_disk->disk_name, DISK_NAME_LEN, "%s%d",
 	    ZVOL_DEV_NAME, (dev & MINORMASK));
 
 	return (zv);
 
-out_queue:
-	blk_cleanup_queue(zso->zvo_queue);
 out_kmem:
 	kmem_free(zso, sizeof (struct zvol_state_os));
 	kmem_free(zv, sizeof (zvol_state_t));
@@ -882,8 +902,13 @@ zvol_free(zvol_state_t *zv)
 	zfs_rangelock_fini(&zv->zv_rangelock);
 
 	del_gendisk(zv->zv_zso->zvo_disk);
+#if defined(HAVE_SUBMIT_BIO_IN_BLOCK_DEVICE_OPERATIONS) && \
+	defined(HAVE_BLK_ALLOC_DISK)
+	blk_cleanup_disk(zv->zv_zso->zvo_disk);
+#else
 	blk_cleanup_queue(zv->zv_zso->zvo_queue);
 	put_disk(zv->zv_zso->zvo_disk);
+#endif
 
 	ida_simple_remove(&zvol_ida,
 	    MINOR(zv->zv_zso->zvo_dev) >> ZVOL_MINOR_BITS);