Linux 5.10 compat: check_disk_change() removed

Kernel 5.10 removed check_disk_change() in favor of callers using
the faster bdev_check_media_change() instead, and explicitly forcing
bdev revalidation when they desire that behavior. To preserve prior
behavior, I have wrapped this into a zfs_check_media_change() macro
that calls an inline function for the new API that mimics the old
behavior when check_disk_change() doesn't exist, and just calls
check_disk_change() if it exists.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes #11085

config/kernel-blkdev-change.m4

@@ -0,0 +1,62 @@
+dnl #
+dnl # check_disk_change() was removed in 5.10
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKDEV_CHECK_DISK_CHANGE], [
+	ZFS_LINUX_TEST_SRC([check_disk_change], [
+		#include <linux/fs.h>
+		#include <linux/blkdev.h>
+	], [
+		struct block_device *bdev = NULL;
+		bool error;
+
+		error = check_disk_change(bdev);
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_CHECK_DISK_CHANGE], [
+	AC_MSG_CHECKING([whether check_disk_change() exists])
+	ZFS_LINUX_TEST_RESULT([check_disk_change], [
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_CHECK_DISK_CHANGE, 1,
+		    [check_disk_change() exists])
+	], [
+		AC_MSG_RESULT(no)
+	])
+])
+
+dnl #
+dnl # 5.10 API, check_disk_change() is removed, in favor of
+dnl # bdev_check_media_change(), which doesn't force revalidation
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKDEV_BDEV_CHECK_MEDIA_CHANGE], [
+	ZFS_LINUX_TEST_SRC([bdev_check_media_change], [
+		#include <linux/fs.h>
+		#include <linux/blkdev.h>
+	], [
+		struct block_device *bdev = NULL;
+		int error;
+
+		error = bdev_check_media_change(bdev);
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_BDEV_CHECK_MEDIA_CHANGE], [
+	AC_MSG_CHECKING([whether bdev_disk_changed() exists])
+	ZFS_LINUX_TEST_RESULT([bdev_check_media_change], [
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_BDEV_CHECK_MEDIA_CHANGE, 1,
+		    [bdev_check_media_change() exists])
+	], [
+		AC_MSG_RESULT(no)
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_SRC_BLKDEV_CHANGE], [
+	ZFS_AC_KERNEL_SRC_BLKDEV_CHECK_DISK_CHANGE
+	ZFS_AC_KERNEL_SRC_BLKDEV_BDEV_CHECK_MEDIA_CHANGE
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_CHANGE], [
+	ZFS_AC_KERNEL_BLKDEV_CHECK_DISK_CHANGE
+	ZFS_AC_KERNEL_BLKDEV_BDEV_CHECK_MEDIA_CHANGE
+])

config/kernel.m4

@@ -144,6 +144,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
 	ZFS_AC_KERNEL_SRC_TOTALRAM_PAGES_FUNC
 	ZFS_AC_KERNEL_SRC_TOTALHIGH_PAGES
 	ZFS_AC_KERNEL_SRC_KSTRTOUL
+	ZFS_AC_KERNEL_SRC_BLKDEV_CHANGE
 
 	AC_MSG_CHECKING([for available kernel interfaces])
 	ZFS_LINUX_TEST_COMPILE_ALL([kabi])
@@ -263,6 +264,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
 	ZFS_AC_KERNEL_TOTALRAM_PAGES_FUNC
 	ZFS_AC_KERNEL_TOTALHIGH_PAGES
 	ZFS_AC_KERNEL_KSTRTOUL
+	ZFS_AC_KERNEL_BLKDEV_CHANGE
 ])
 
 dnl #

include/linux/blkdev_compat.h

@@ -371,12 +371,48 @@ bio_set_bi_error(struct bio *bio, int error)
  *
  * For older kernels trigger a re-reading of the partition table by calling
  * check_disk_change() which calls flush_disk() to invalidate the device.
+ *
+ * For newer kernels (as of 5.10), bdev_check_media_chage is used, in favor of
+ * check_disk_change(), with the modification that invalidation is no longer
+ * forced.
  */
+#ifdef HAVE_CHECK_DISK_CHANGE
+#define	zfs_check_media_change(bdev)	check_disk_change(bdev)
 #ifdef HAVE_BLKDEV_REREAD_PART
 #define	vdev_bdev_reread_part(bdev)	blkdev_reread_part(bdev)
 #else
 #define	vdev_bdev_reread_part(bdev)	check_disk_change(bdev)
 #endif /* HAVE_BLKDEV_REREAD_PART */
+#else
+#ifdef HAVE_BDEV_CHECK_MEDIA_CHANGE
+static inline int
+zfs_check_media_change(struct block_device *bdev)
+{
+	struct gendisk *gd = bdev->bd_disk;
+	const struct block_device_operations *bdo = gd->fops;
+
+	if (!bdev_check_media_change(bdev))
+		return (0);
+
+	/*
+	 * Force revalidation, to mimic the old behavior of
+	 * check_disk_change()
+	 */
+	if (bdo->revalidate_disk)
+		bdo->revalidate_disk(gd);
+
+	return (0);
+}
+#define	vdev_bdev_reread_part(bdev)	zfs_check_media_change(bdev)
+#else
+/*
+ * This is encountered if check_disk_change() and bdev_check_media_change()
+ * are not available in the kernel - likely due to an API change that needs
+ * to be chased down.
+ */
+#error "Unsupported kernel: no usable disk change check"
+#endif /* HAVE_BDEV_CHECK_MEDIA_CHANGE */
+#endif /* HAVE_CHECK_DISK_CHANGE */
 
 /*
  * 2.6.22 API change

module/zfs/vdev_disk.c

@@ -848,7 +848,7 @@ vdev_disk_io_done(zio_t *zio)
 		vdev_t *v = zio->io_vd;
 		vdev_disk_t *vd = v->vdev_tsd;
 
-		if (check_disk_change(vd->vd_bdev)) {
+		if (zfs_check_media_change(vd->vd_bdev)) {
 			vdev_bdev_invalidate(vd->vd_bdev);
 			v->vdev_remove_wanted = B_TRUE;
 			spa_async_request(zio->io_spa, SPA_ASYNC_REMOVE);

module/zfs/zvol.c

@@ -1450,7 +1450,7 @@ zvol_open(struct block_device *bdev, fmode_t flag)
 	if (drop_suspend)
 		rw_exit(&zv->zv_suspend_lock);
 
-	check_disk_change(bdev);
+	zfs_check_media_change(bdev);
 
 	return (0);