1 files changed, 205 insertions, 198 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 1997a7d67f22..58b9c419a2b6 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -291,8 +291,8 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
  *   balance_mutex
  *
  *
- * Exclusive operations, BTRFS_FS_EXCL_OP
- * ======================================
+ * Exclusive operations
+ * ====================
  *
  * Maintains the exclusivity of the following operations that apply to the
  * whole filesystem and cannot run in parallel.
@@ -318,11 +318,11 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
  * - system power-cycle and filesystem mounted as read-only
  * - filesystem or device errors leading to forced read-only
  *
- * BTRFS_FS_EXCL_OP flag is set and cleared using atomic operations.
- * During the course of Paused state, the BTRFS_FS_EXCL_OP remains set.
+ * The status of exclusive operation is set and cleared atomically.
+ * During the course of Paused state, fs_info::exclusive_operation remains set.
  * A device operation in Paused or Running state can be canceled or resumed
  * either by ioctl (Balance only) or when remounted as read-write.
- * BTRFS_FS_EXCL_OP flag is cleared when the device operation is canceled or
+ * The exclusive status is cleared when the device operation is canceled or
  * completed.
  */
 
@@ -356,6 +356,7 @@ static struct btrfs_fs_devices *alloc_fs_devices(const u8 *fsid,
 	INIT_LIST_HEAD(&fs_devs->devices);
 	INIT_LIST_HEAD(&fs_devs->alloc_list);
 	INIT_LIST_HEAD(&fs_devs->fs_list);
+	INIT_LIST_HEAD(&fs_devs->seed_list);
 	if (fsid)
 		memcpy(fs_devs->fsid, fsid, BTRFS_FSID_SIZE);
 
@@ -406,7 +407,7 @@ void __exit btrfs_cleanup_fs_uuids(void)
  * Returned struct is not linked onto any lists and must be destroyed using
  * btrfs_free_device.
  */
-static struct btrfs_device *__alloc_device(void)
+static struct btrfs_device *__alloc_device(struct btrfs_fs_info *fs_info)
 {
 	struct btrfs_device *dev;
 
@@ -433,7 +434,8 @@ static struct btrfs_device *__alloc_device(void)
 	btrfs_device_data_ordered_init(dev);
 	INIT_RADIX_TREE(&dev->reada_zones, GFP_NOFS & ~__GFP_DIRECT_RECLAIM);
 	INIT_RADIX_TREE(&dev->reada_extents, GFP_NOFS & ~__GFP_DIRECT_RECLAIM);
-	extent_io_tree_init(NULL, &dev->alloc_state, 0, NULL);
+	extent_io_tree_init(fs_info, &dev->alloc_state,
+			    IO_TREE_DEVICE_ALLOC_STATE, NULL);
 
 	return dev;
 }
@@ -593,8 +595,6 @@ static int btrfs_free_stale_devices(const char *path,
 			btrfs_free_device(device);
 
 			ret = 0;
-			if (fs_devices->num_devices == 0)
-				break;
 		}
 		mutex_unlock(&fs_devices->device_list_mutex);
 
@@ -941,16 +941,18 @@ static noinline struct btrfs_device *device_list_add(const char *path,
 				bdput(path_bdev);
 				mutex_unlock(&fs_devices->device_list_mutex);
 				btrfs_warn_in_rcu(device->fs_info,
-			"duplicate device fsid:devid for %pU:%llu old:%s new:%s",
-					disk_super->fsid, devid,
-					rcu_str_deref(device->name), path);
+	"duplicate device %s devid %llu generation %llu scanned by %s (%d)",
+						  path, devid, found_transid,
+						  current->comm,
+						  task_pid_nr(current));
 				return ERR_PTR(-EEXIST);
 			}
 			bdput(path_bdev);
 			btrfs_info_in_rcu(device->fs_info,
-				"device fsid %pU devid %llu moved old:%s new:%s",
-				disk_super->fsid, devid,
-				rcu_str_deref(device->name), path);
+	"devid %llu device path %s changed to %s scanned by %s (%d)",
+					  devid, rcu_str_deref(device->name),
+					  path, current->comm,
+					  task_pid_nr(current));
 		}
 
 		name = rcu_string_strdup(path, GFP_NOFS);
@@ -1035,28 +1037,21 @@ error:
 	return ERR_PTR(ret);
 }
 
-/*
- * After we have read the system tree and know devids belonging to
- * this filesystem, remove the device which does not belong there.
- */
-void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step)
+static void __btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices,
+				      int step, struct btrfs_device **latest_dev)
 {
 	struct btrfs_device *device, *next;
-	struct btrfs_device *latest_dev = NULL;
 
-	mutex_lock(&uuid_mutex);
-again:
 	/* This is the initialized path, it is safe to release the devices. */
 	list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
-		if (test_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
-							&device->dev_state)) {
+		if (test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state)) {
 			if (!test_bit(BTRFS_DEV_STATE_REPLACE_TGT,
-			     &device->dev_state) &&
+				      &device->dev_state) &&
 			    !test_bit(BTRFS_DEV_STATE_MISSING,
 				      &device->dev_state) &&
-			     (!latest_dev ||
-			      device->generation > latest_dev->generation)) {
-				latest_dev = device;
+			    (!*latest_dev ||
+			     device->generation > (*latest_dev)->generation)) {
+				*latest_dev = device;
 			}
 			continue;
 		}
@@ -1094,10 +1089,22 @@ again:
 		btrfs_free_device(device);
 	}
 
-	if (fs_devices->seed) {
-		fs_devices = fs_devices->seed;
-		goto again;
-	}
+}
+
+/*
+ * After we have read the system tree and know devids belonging to this
+ * filesystem, remove the device which does not belong there.
+ */
+void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step)
+{
+	struct btrfs_device *latest_dev = NULL;
+	struct btrfs_fs_devices *seed_dev;
+
+	mutex_lock(&uuid_mutex);
+	__btrfs_free_extra_devids(fs_devices, step, &latest_dev);
+
+	list_for_each_entry(seed_dev, &fs_devices->seed_list, seed_list)
+		__btrfs_free_extra_devids(seed_dev, step, &latest_dev);
 
 	fs_devices->latest_bdev = latest_dev->bdev;
 
@@ -1149,47 +1156,41 @@ static void btrfs_close_one_device(struct btrfs_device *device)
 	ASSERT(atomic_read(&device->reada_in_flight) == 0);
 }
 
-static int close_fs_devices(struct btrfs_fs_devices *fs_devices)
+static void close_fs_devices(struct btrfs_fs_devices *fs_devices)
 {
 	struct btrfs_device *device, *tmp;
 
+	lockdep_assert_held(&uuid_mutex);
+
 	if (--fs_devices->opened > 0)
-		return 0;
+		return;
 
-	mutex_lock(&fs_devices->device_list_mutex);
-	list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) {
+	list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list)
 		btrfs_close_one_device(device);
-	}
-	mutex_unlock(&fs_devices->device_list_mutex);
 
 	WARN_ON(fs_devices->open_devices);
 	WARN_ON(fs_devices->rw_devices);
 	fs_devices->opened = 0;
 	fs_devices->seeding = false;
-
-	return 0;
+	fs_devices->fs_info = NULL;
 }
 
-int btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
+void btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
 {
-	struct btrfs_fs_devices *seed_devices = NULL;
-	int ret;
+	LIST_HEAD(list);
+	struct btrfs_fs_devices *tmp;
 
 	mutex_lock(&uuid_mutex);
-	ret = close_fs_devices(fs_devices);
-	if (!fs_devices->opened) {
-		seed_devices = fs_devices->seed;
-		fs_devices->seed = NULL;
-	}
-	mutex_unlock(&uuid_mutex);
+	close_fs_devices(fs_devices);
+	if (!fs_devices->opened)
+		list_splice_init(&fs_devices->seed_list, &list);
 
-	while (seed_devices) {
-		fs_devices = seed_devices;
-		seed_devices = fs_devices->seed;
+	list_for_each_entry_safe(fs_devices, tmp, &list, seed_list) {
 		close_fs_devices(fs_devices);
+		list_del(&fs_devices->seed_list);
 		free_fs_devices(fs_devices);
 	}
-	return ret;
+	mutex_unlock(&uuid_mutex);
 }
 
 static int open_fs_devices(struct btrfs_fs_devices *fs_devices,
@@ -1197,17 +1198,23 @@ static int open_fs_devices(struct btrfs_fs_devices *fs_devices,
 {
 	struct btrfs_device *device;
 	struct btrfs_device *latest_dev = NULL;
+	struct btrfs_device *tmp_device;
 
 	flags |= FMODE_EXCL;
 
-	list_for_each_entry(device, &fs_devices->devices, dev_list) {
-		/* Just open everything we can; ignore failures here */
-		if (btrfs_open_one_device(fs_devices, device, flags, holder))
-			continue;
+	list_for_each_entry_safe(device, tmp_device, &fs_devices->devices,
+				 dev_list) {
+		int ret;
 
-		if (!latest_dev ||
-		    device->generation > latest_dev->generation)
+		ret = btrfs_open_one_device(fs_devices, device, flags, holder);
+		if (ret == 0 &&
+		    (!latest_dev || device->generation > latest_dev->generation)) {
 			latest_dev = device;
+		} else if (ret == -ENODATA) {
+			fs_devices->num_devices--;
+			list_del(&device->dev_list);
+			btrfs_free_device(device);
+		}
 	}
 	if (fs_devices->open_devices == 0)
 		return -EINVAL;
@@ -1961,16 +1968,13 @@ static struct btrfs_device * btrfs_find_next_active_device(
  * this_dev) which is active.
  */
 void __cold btrfs_assign_next_active_device(struct btrfs_device *device,
-				     struct btrfs_device *this_dev)
+					    struct btrfs_device *next_device)
 {
 	struct btrfs_fs_info *fs_info = device->fs_info;
-	struct btrfs_device *next_device;
 
-	if (this_dev)
-		next_device = this_dev;
-	else
+	if (!next_device)
 		next_device = btrfs_find_next_active_device(fs_info->fs_devices,
-								device);
+							    device);
 	ASSERT(next_device);
 
 	if (fs_info->sb->s_bdev &&
@@ -2040,7 +2044,7 @@ void btrfs_scratch_superblocks(struct btrfs_fs_info *fs_info,
 }
 
 int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path,
-		u64 devid)
+		    u64 devid)
 {
 	struct btrfs_device *device;
 	struct btrfs_fs_devices *cur_devices;
@@ -2144,7 +2148,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path,
 	if (device->bdev) {
 		cur_devices->open_devices--;
 		/* remove sysfs entry */
-		btrfs_sysfs_remove_devices_dir(fs_devices, device);
+		btrfs_sysfs_remove_device(device);
 	}
 
 	num_devices = btrfs_super_num_devices(fs_info->super_copy) - 1;
@@ -2165,14 +2169,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path,
 	btrfs_free_device(device);
 
 	if (cur_devices->open_devices == 0) {
-		while (fs_devices) {
-			if (fs_devices->seed == cur_devices) {
-				fs_devices->seed = cur_devices->seed;
-				break;
-			}
-			fs_devices = fs_devices->seed;
-		}
-		cur_devices->seed = NULL;
+		list_del_init(&cur_devices->seed_list);
 		close_fs_devices(cur_devices);
 		free_fs_devices(cur_devices);
 	}
@@ -2221,7 +2218,6 @@ void btrfs_rm_dev_replace_remove_srcdev(struct btrfs_device *srcdev)
 
 void btrfs_rm_dev_replace_free_srcdev(struct btrfs_device *srcdev)
 {
-	struct btrfs_fs_info *fs_info = srcdev->fs_info;
 	struct btrfs_fs_devices *fs_devices = srcdev->fs_devices;
 
 	mutex_lock(&uuid_mutex);
@@ -2232,8 +2228,6 @@ void btrfs_rm_dev_replace_free_srcdev(struct btrfs_device *srcdev)
 
 	/* if this is no devs we rather delete the fs_devices */
 	if (!fs_devices->num_devices) {
-		struct btrfs_fs_devices *tmp_fs_devices;
-
 		/*
 		 * On a mounted FS, num_devices can't be zero unless it's a
 		 * seed. In case of a seed device being replaced, the replace
@@ -2242,15 +2236,7 @@ void btrfs_rm_dev_replace_free_srcdev(struct btrfs_device *srcdev)
 		 */
 		ASSERT(fs_devices->seeding);
 
-		tmp_fs_devices = fs_info->fs_devices;
-		while (tmp_fs_devices) {
-			if (tmp_fs_devices->seed == fs_devices) {
-				tmp_fs_devices->seed = fs_devices->seed;
-				break;
-			}
-			tmp_fs_devices = tmp_fs_devices->seed;
-		}
-		fs_devices->seed = NULL;
+		list_del_init(&fs_devices->seed_list);
 		close_fs_devices(fs_devices);
 		free_fs_devices(fs_devices);
 	}
@@ -2263,7 +2249,7 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev)
 
 	mutex_lock(&fs_devices->device_list_mutex);
 
-	btrfs_sysfs_remove_devices_dir(fs_devices, tgtdev);
+	btrfs_sysfs_remove_device(tgtdev);
 
 	if (tgtdev->bdev)
 		fs_devices->open_devices--;
@@ -2372,10 +2358,20 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info)
 	if (!fs_devices->seeding)
 		return -EINVAL;
 
+	/*
+	 * Private copy of the seed devices, anchored at
+	 * fs_info->fs_devices->seed_list
+	 */
 	seed_devices = alloc_fs_devices(NULL, NULL);
 	if (IS_ERR(seed_devices))
 		return PTR_ERR(seed_devices);
 
+	/*
+	 * It's necessary to retain a copy of the original seed fs_devices in
+	 * fs_uuids so that filesystems which have been seeded can successfully
+	 * reference the seed device from open_seed_devices. This also supports
+	 * multiple fs seed.
+	 */
 	old_devices = clone_fs_devices(fs_devices);
 	if (IS_ERR(old_devices)) {
 		kfree(seed_devices);
@@ -2396,16 +2392,12 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info)
 	list_for_each_entry(device, &seed_devices->devices, dev_list)
 		device->fs_devices = seed_devices;
 
-	mutex_lock(&fs_info->chunk_mutex);
-	list_splice_init(&fs_devices->alloc_list, &seed_devices->alloc_list);
-	mutex_unlock(&fs_info->chunk_mutex);
-
 	fs_devices->seeding = false;
 	fs_devices->num_devices = 0;
 	fs_devices->open_devices = 0;
 	fs_devices->missing_devices = 0;
 	fs_devices->rotating = false;
-	fs_devices->seed = seed_devices;
+	list_add(&seed_devices->seed_list, &fs_devices->seed_list);
 
 	generate_random_uuid(fs_devices->fsid);
 	memcpy(fs_devices->metadata_uuid, fs_devices->fsid, BTRFS_FSID_SIZE);
@@ -2508,7 +2500,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	u64 orig_super_num_devices;
 	int seeding_dev = 0;
 	int ret = 0;
-	bool unlocked = false;
+	bool locked = false;
 
 	if (sb_rdonly(sb) && !fs_devices->seeding)
 		return -EROFS;
@@ -2522,20 +2514,20 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 		seeding_dev = 1;
 		down_write(&sb->s_umount);
 		mutex_lock(&uuid_mutex);
+		locked = true;
 	}
 
-	filemap_write_and_wait(bdev->bd_inode->i_mapping);
+	sync_blockdev(bdev);
 
-	mutex_lock(&fs_devices->device_list_mutex);
-	list_for_each_entry(device, &fs_devices->devices, dev_list) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(device, &fs_devices->devices, dev_list) {
 		if (device->bdev == bdev) {
 			ret = -EEXIST;
-			mutex_unlock(
-				&fs_devices->device_list_mutex);
+			rcu_read_unlock();
 			goto error;
 		}
 	}
-	mutex_unlock(&fs_devices->device_list_mutex);
+	rcu_read_unlock();
 
 	device = btrfs_alloc_device(fs_info, NULL, NULL);
 	if (IS_ERR(device)) {
@@ -2610,9 +2602,6 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	btrfs_set_super_num_devices(fs_info->super_copy,
 				    orig_super_num_devices + 1);
 
-	/* add sysfs device entry */
-	btrfs_sysfs_add_devices_dir(fs_devices, device);
-
 	/*
 	 * we've got more storage, clear any full flags on the space
 	 * infos
@@ -2620,6 +2609,10 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	btrfs_clear_space_info_full(fs_info);
 
 	mutex_unlock(&fs_info->chunk_mutex);
+
+	/* Add sysfs device entry */
+	btrfs_sysfs_add_device(device);
+
 	mutex_unlock(&fs_devices->device_list_mutex);
 
 	if (seeding_dev) {
@@ -2645,8 +2638,11 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 			goto error_sysfs;
 		}
 
-		btrfs_sysfs_update_sprout_fsid(fs_devices,
-				fs_info->fs_devices->fsid);
+		/*
+		 * fs_devices now represents the newly sprouted filesystem and
+		 * its fsid has been changed by btrfs_prepare_sprout
+		 */
+		btrfs_sysfs_update_sprout_fsid(fs_devices);
 	}
 
 	ret = btrfs_commit_transaction(trans);
@@ -2654,7 +2650,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	if (seeding_dev) {
 		mutex_unlock(&uuid_mutex);
 		up_write(&sb->s_umount);
-		unlocked = true;
+		locked = false;
 
 		if (ret) /* transaction commit */
 			return ret;
@@ -2689,7 +2685,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	return ret;
 
 error_sysfs:
-	btrfs_sysfs_remove_devices_dir(fs_devices, device);
+	btrfs_sysfs_remove_device(device);
 	mutex_lock(&fs_info->fs_devices->device_list_mutex);
 	mutex_lock(&fs_info->chunk_mutex);
 	list_del_rcu(&device->dev_list);
@@ -2715,7 +2711,7 @@ error_free_device:
 	btrfs_free_device(device);
 error:
 	blkdev_put(bdev, FMODE_EXCL);
-	if (seeding_dev && !unlocked) {
+	if (locked) {
 		mutex_unlock(&uuid_mutex);
 		up_write(&sb->s_umount);
 	}
@@ -4042,7 +4038,7 @@ int btrfs_balance(struct btrfs_fs_info *fs_info,
 
 	/*
 	 * rw_devices will not change at the moment, device add/delete/replace
-	 * are excluded by EXCL_OP
+	 * are exclusive
 	 */
 	num_devices = fs_info->fs_devices->rw_devices;
 
@@ -4178,7 +4174,7 @@ int btrfs_balance(struct btrfs_fs_info *fs_info,
 	if ((ret && ret != -ECANCELED && ret != -ENOSPC) ||
 	    balance_need_close(fs_info)) {
 		reset_balance_state(fs_info);
-		clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
+		btrfs_exclop_finish(fs_info);
 	}
 
 	wake_up(&fs_info->balance_wait_q);
@@ -4189,7 +4185,7 @@ out:
 		reset_balance_state(fs_info);
 	else
 		kfree(bctl);
-	clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
+	btrfs_exclop_finish(fs_info);
 
 	return ret;
 }
@@ -4291,7 +4287,7 @@ int btrfs_recover_balance(struct btrfs_fs_info *fs_info)
 	 * is in a paused state and must have fs_info::balance_ctl properly
 	 * set up.
 	 */
-	if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags))
+	if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE))
 		btrfs_warn(fs_info,
 	"balance: cannot set exclusive op status, resume manually");
 
@@ -4373,7 +4369,7 @@ int btrfs_cancel_balance(struct btrfs_fs_info *fs_info)
 
 		if (fs_info->balance_ctl) {
 			reset_balance_state(fs_info);
-			clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
+			btrfs_exclop_finish(fs_info);
 			btrfs_info(fs_info, "balance: canceled");
 		}
 	}
@@ -6458,11 +6454,21 @@ struct btrfs_device *btrfs_find_device(struct btrfs_fs_devices *fs_devices,
 				       bool seed)
 {
 	struct btrfs_device *device;
+	struct btrfs_fs_devices *seed_devs;
 
-	while (fs_devices) {
+	if (!fsid || !memcmp(fs_devices->metadata_uuid, fsid, BTRFS_FSID_SIZE)) {
+		list_for_each_entry(device, &fs_devices->devices, dev_list) {
+			if (device->devid == devid &&
+			    (!uuid || memcmp(device->uuid, uuid,
+					     BTRFS_UUID_SIZE) == 0))
+				return device;
+		}
+	}
+
+	list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list) {
 		if (!fsid ||
-		    !memcmp(fs_devices->metadata_uuid, fsid, BTRFS_FSID_SIZE)) {
-			list_for_each_entry(device, &fs_devices->devices,
+		    !memcmp(seed_devs->metadata_uuid, fsid, BTRFS_FSID_SIZE)) {
+			list_for_each_entry(device, &seed_devs->devices,
 					    dev_list) {
 				if (device->devid == devid &&
 				    (!uuid || memcmp(device->uuid, uuid,
@@ -6470,11 +6476,8 @@ struct btrfs_device *btrfs_find_device(struct btrfs_fs_devices *fs_devices,
 					return device;
 			}
 		}
-		if (seed)
-			fs_devices = fs_devices->seed;
-		else
-			return NULL;
 	}
+
 	return NULL;
 }
 
@@ -6529,7 +6532,7 @@ struct btrfs_device *btrfs_alloc_device(struct btrfs_fs_info *fs_info,
 	if (WARN_ON(!devid && !fs_info))
 		return ERR_PTR(-EINVAL);
 
-	dev = __alloc_device();
+	dev = __alloc_device(fs_info);
 	if (IS_ERR(dev))
 		return dev;
 
@@ -6725,13 +6728,11 @@ static struct btrfs_fs_devices *open_seed_devices(struct btrfs_fs_info *fs_info,
 	lockdep_assert_held(&uuid_mutex);
 	ASSERT(fsid);
 
-	fs_devices = fs_info->fs_devices->seed;
-	while (fs_devices) {
+	/* This will match only for multi-device seed fs */
+	list_for_each_entry(fs_devices, &fs_info->fs_devices->seed_list, seed_list)
 		if (!memcmp(fs_devices->fsid, fsid, BTRFS_FSID_SIZE))
 			return fs_devices;
 
-		fs_devices = fs_devices->seed;
-	}
 
 	fs_devices = find_fsid(fsid, NULL);
 	if (!fs_devices) {
@@ -6747,6 +6748,10 @@ static struct btrfs_fs_devices *open_seed_devices(struct btrfs_fs_info *fs_info,
 		return fs_devices;
 	}
 
+	/*
+	 * Upon first call for a seed fs fsid, just create a private copy of the
+	 * respective fs_devices and anchor it at fs_info->fs_devices->seed_list
+	 */
 	fs_devices = clone_fs_devices(fs_devices);
 	if (IS_ERR(fs_devices))
 		return fs_devices;
@@ -6754,20 +6759,17 @@ static struct btrfs_fs_devices *open_seed_devices(struct btrfs_fs_info *fs_info,
 	ret = open_fs_devices(fs_devices, FMODE_READ, fs_info->bdev_holder);
 	if (ret) {
 		free_fs_devices(fs_devices);
-		fs_devices = ERR_PTR(ret);
-		goto out;
+		return ERR_PTR(ret);
 	}
 
 	if (!fs_devices->seeding) {
 		close_fs_devices(fs_devices);
 		free_fs_devices(fs_devices);
-		fs_devices = ERR_PTR(-EINVAL);
-		goto out;
+		return ERR_PTR(-EINVAL);
 	}
 
-	fs_devices->seed = fs_info->fs_devices->seed;
-	fs_info->fs_devices->seed = fs_devices;
-out:
+	list_add(&fs_devices->seed_list, &fs_info->fs_devices->seed_list);
+
 	return fs_devices;
 }
 
@@ -7186,17 +7188,22 @@ error:
 
 void btrfs_init_devices_late(struct btrfs_fs_info *fs_info)
 {
-	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices, *seed_devs;
 	struct btrfs_device *device;
 
-	while (fs_devices) {
-		mutex_lock(&fs_devices->device_list_mutex);
-		list_for_each_entry(device, &fs_devices->devices, dev_list)
+	fs_devices->fs_info = fs_info;
+
+	mutex_lock(&fs_devices->device_list_mutex);
+	list_for_each_entry(device, &fs_devices->devices, dev_list)
+		device->fs_info = fs_info;
+
+	list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list) {
+		list_for_each_entry(device, &seed_devs->devices, dev_list)
 			device->fs_info = fs_info;
-		mutex_unlock(&fs_devices->device_list_mutex);
 
-		fs_devices = fs_devices->seed;
+		seed_devs->fs_info = fs_info;
 	}
+	mutex_unlock(&fs_devices->device_list_mutex);
 }
 
 static u64 btrfs_dev_stats_value(const struct extent_buffer *eb,
@@ -7222,17 +7229,53 @@ static void btrfs_set_dev_stats_value(struct extent_buffer *eb,
 			    sizeof(val));
 }
 
-int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info)
+static int btrfs_device_init_dev_stats(struct btrfs_device *device,
+				       struct btrfs_path *path)
 {
-	struct btrfs_key key;
-	struct btrfs_root *dev_root = fs_info->dev_root;
-	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	struct btrfs_dev_stats_item *ptr;
 	struct extent_buffer *eb;
-	int slot;
-	int ret = 0;
+	struct btrfs_key key;
+	int item_size;
+	int i, ret, slot;
+
+	key.objectid = BTRFS_DEV_STATS_OBJECTID;
+	key.type = BTRFS_PERSISTENT_ITEM_KEY;
+	key.offset = device->devid;
+	ret = btrfs_search_slot(NULL, device->fs_info->dev_root, &key, path, 0, 0);
+	if (ret) {
+		for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
+			btrfs_dev_stat_set(device, i, 0);
+		device->dev_stats_valid = 1;
+		btrfs_release_path(path);
+		return ret < 0 ? ret : 0;
+	}
+	slot = path->slots[0];
+	eb = path->nodes[0];
+	item_size = btrfs_item_size_nr(eb, slot);
+
+	ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_stats_item);
+
+	for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++) {
+		if (item_size >= (1 + i) * sizeof(__le64))
+			btrfs_dev_stat_set(device, i,
+					   btrfs_dev_stats_value(eb, ptr, i));
+		else
+			btrfs_dev_stat_set(device, i, 0);
+	}
+
+	device->dev_stats_valid = 1;
+	btrfs_dev_stat_print_on_load(device);
+	btrfs_release_path(path);
+
+	return 0;
+}
+
+int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices, *seed_devs;
 	struct btrfs_device *device;
 	struct btrfs_path *path = NULL;
-	int i;
+	int ret = 0;
 
 	path = btrfs_alloc_path();
 	if (!path)
@@ -7240,43 +7283,22 @@ int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info)
 
 	mutex_lock(&fs_devices->device_list_mutex);
 	list_for_each_entry(device, &fs_devices->devices, dev_list) {
-		int item_size;
-		struct btrfs_dev_stats_item *ptr;
-
-		key.objectid = BTRFS_DEV_STATS_OBJECTID;
-		key.type = BTRFS_PERSISTENT_ITEM_KEY;
-		key.offset = device->devid;
-		ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
-		if (ret) {
-			for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
-				btrfs_dev_stat_set(device, i, 0);
-			device->dev_stats_valid = 1;
-			btrfs_release_path(path);
-			continue;
-		}
-		slot = path->slots[0];
-		eb = path->nodes[0];
-		item_size = btrfs_item_size_nr(eb, slot);
-
-		ptr = btrfs_item_ptr(eb, slot,
-				     struct btrfs_dev_stats_item);
-
-		for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++) {
-			if (item_size >= (1 + i) * sizeof(__le64))
-				btrfs_dev_stat_set(device, i,
-					btrfs_dev_stats_value(eb, ptr, i));
-			else
-				btrfs_dev_stat_set(device, i, 0);
+		ret = btrfs_device_init_dev_stats(device, path);
+		if (ret)
+			goto out;
+	}
+	list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list) {
+		list_for_each_entry(device, &seed_devs->devices, dev_list) {
+			ret = btrfs_device_init_dev_stats(device, path);
+			if (ret)
+				goto out;
 		}
-
-		device->dev_stats_valid = 1;
-		btrfs_dev_stat_print_on_load(device);
-		btrfs_release_path(path);
 	}
+out:
 	mutex_unlock(&fs_devices->device_list_mutex);
 
 	btrfs_free_path(path);
-	return ret < 0 ? ret : 0;
+	return ret;
 }
 
 static int update_dev_stat_item(struct btrfs_trans_handle *trans,
@@ -7493,24 +7515,6 @@ void btrfs_commit_device_sizes(struct btrfs_transaction *trans)
 	mutex_unlock(&trans->fs_info->chunk_mutex);
 }
 
-void btrfs_set_fs_info_ptr(struct btrfs_fs_info *fs_info)
-{
-	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
-	while (fs_devices) {
-		fs_devices->fs_info = fs_info;
-		fs_devices = fs_devices->seed;
-	}
-}
-
-void btrfs_reset_fs_info_ptr(struct btrfs_fs_info *fs_info)
-{
-	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
-	while (fs_devices) {
-		fs_devices->fs_info = NULL;
-		fs_devices = fs_devices->seed;
-	}
-}
-
 /*
  * Multiplicity factor for simple profiles: DUP, RAID1-like and RAID10.
  */
@@ -7591,8 +7595,11 @@ static int verify_one_dev_extent(struct btrfs_fs_info *fs_info,
 
 	/* It's possible this device is a dummy for seed device */
 	if (dev->disk_total_bytes == 0) {
-		dev = btrfs_find_device(fs_info->fs_devices->seed, devid, NULL,
-					NULL, false);
+		struct btrfs_fs_devices *devs;
+
+		devs = list_first_entry(&fs_info->fs_devices->seed_list,
+					struct btrfs_fs_devices, seed_list);
+		dev = btrfs_find_device(devs, devid, NULL, NULL, false);
 		if (!dev) {
 			btrfs_err(fs_info, "failed to find seed devid %llu",
 				  devid);