Merge tag 'for-6.9-part2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Pull btrfs fix from David Sterba:
 "Fix a problem found in 6.7 after adding the temp-fsid feature which
  changed device tracking in memory and broke grub-probe. This is used
  on initrd-less systems. There were several iterations of the fix and
  it took longer than expected"

* tag 'for-6.9-part2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: do not skip re-registration for the mounted device

Author: torvalds

fs/btrfs/volumes.c

@@ -1303,6 +1303,47 @@ int btrfs_forget_devices(dev_t devt)
 	return ret;
 }
 
+static bool btrfs_skip_registration(struct btrfs_super_block *disk_super,
+				    const char *path, dev_t devt,
+				    bool mount_arg_dev)
+{
+	struct btrfs_fs_devices *fs_devices;
+
+	/*
+	 * Do not skip device registration for mounted devices with matching
+	 * maj:min but different paths. Booting without initrd relies on
+	 * /dev/root initially, later replaced with the actual root device.
+	 * A successful scan ensures grub2-probe selects the correct device.
+	 */
+	list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
+		struct btrfs_device *device;
+
+		mutex_lock(&fs_devices->device_list_mutex);
+
+		if (!fs_devices->opened) {
+			mutex_unlock(&fs_devices->device_list_mutex);
+			continue;
+		}
+
+		list_for_each_entry(device, &fs_devices->devices, dev_list) {
+			if (device->bdev && (device->bdev->bd_dev == devt) &&
+			    strcmp(device->name->str, path) != 0) {
+				mutex_unlock(&fs_devices->device_list_mutex);
+
+				/* Do not skip registration. */
+				return false;
+			}
+		}
+		mutex_unlock(&fs_devices->device_list_mutex);
+	}
+
+	if (!mount_arg_dev && btrfs_super_num_devices(disk_super) == 1 &&
+	    !(btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_SEEDING))
+		return true;
+
+	return false;
+}
+
 /*
  * Look for a btrfs signature on a device. This may be called out of the mount path
  * and we are not allowed to call set_blocksize during the scan. The superblock
@@ -1320,6 +1361,7 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, blk_mode_t flags,
 	struct btrfs_device *device = NULL;
 	struct file *bdev_file;
 	u64 bytenr, bytenr_orig;
+	dev_t devt;
 	int ret;
 
 	lockdep_assert_held(&uuid_mutex);
@@ -1359,19 +1401,13 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, blk_mode_t flags,
 		goto error_bdev_put;
 	}
 
-	if (!mount_arg_dev && btrfs_super_num_devices(disk_super) == 1 &&
-	    !(btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_SEEDING)) {
-		dev_t devt;
+	devt = file_bdev(bdev_file)->bd_dev;
+	if (btrfs_skip_registration(disk_super, path, devt, mount_arg_dev)) {
+		pr_debug("BTRFS: skip registering single non-seed device %s (%d:%d)\n",
+			  path, MAJOR(devt), MINOR(devt));
 
-		ret = lookup_bdev(path, &devt);
-		if (ret)
-			btrfs_warn(NULL, "lookup bdev failed for path %s: %d",
-				   path, ret);
-		else
-			btrfs_free_stale_devices(devt, NULL);
+		btrfs_free_stale_devices(devt, NULL);
 
-	pr_debug("BTRFS: skip registering single non-seed device %s (%d:%d)\n",
-			path, MAJOR(devt), MINOR(devt));
 		device = NULL;
 		goto free_disk_super;
 	}