diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 1db24e6d6d906d462e29fc8c50523ae71e685780..8202ad6aa131740ec44474f0f82cb451f43eaebc 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -124,7 +124,16 @@ void btrfs_put_block_group(struct btrfs_block_group *cache)
 {
 	if (refcount_dec_and_test(&cache->refs)) {
 		WARN_ON(cache->pinned > 0);
-		WARN_ON(cache->reserved > 0);
+		/*
+		 * If there was a failure to cleanup a log tree, very likely due
+		 * to an IO failure on a writeback attempt of one or more of its
+		 * extent buffers, we could not do proper (and cheap) unaccounting
+		 * of their reserved space, so don't warn on reserved > 0 in that
+		 * case.
+		 */
+		if (!(cache->flags & BTRFS_BLOCK_GROUP_METADATA) ||
+		    !BTRFS_FS_LOG_CLEANUP_ERROR(cache->fs_info))
+			WARN_ON(cache->reserved > 0);
 
 		/*
 		 * A block_group shouldn't be on the discard_list anymore.
@@ -2544,6 +2553,19 @@ int btrfs_inc_block_group_ro(struct btrfs_block_group *cache,
 	int ret;
 	bool dirty_bg_running;
 
+	/*
+	 * This can only happen when we are doing read-only scrub on read-only
+	 * mount.
+	 * In that case we should not start a new transaction on read-only fs.
+	 * Thus here we skip all chunk allocations.
+	 */
+	if (sb_rdonly(fs_info->sb)) {
+		mutex_lock(&fs_info->ro_block_group_mutex);
+		ret = inc_block_group_ro(cache, 0);
+		mutex_unlock(&fs_info->ro_block_group_mutex);
+		return ret;
+	}
+
 	do {
 		trans = btrfs_join_transaction(root);
 		if (IS_ERR(trans))
@@ -3974,9 +3996,22 @@ int btrfs_free_block_groups(struct btrfs_fs_info *info)
 		 * important and indicates a real bug if this happens.
 		 */
 		if (WARN_ON(space_info->bytes_pinned > 0 ||
-			    space_info->bytes_reserved > 0 ||
 			    space_info->bytes_may_use > 0))
 			btrfs_dump_space_info(info, space_info, 0, 0);
+
+		/*
+		 * If there was a failure to cleanup a log tree, very likely due
+		 * to an IO failure on a writeback attempt of one or more of its
+		 * extent buffers, we could not do proper (and cheap) unaccounting
+		 * of their reserved space, so don't warn on bytes_reserved > 0 in
+		 * that case.
+		 */
+		if (!(space_info->flags & BTRFS_BLOCK_GROUP_METADATA) ||
+		    !BTRFS_FS_LOG_CLEANUP_ERROR(info)) {
+			if (WARN_ON(space_info->bytes_reserved > 0))
+				btrfs_dump_space_info(info, space_info, 0, 0);
+		}
+
 		WARN_ON(space_info->reclaim_size > 0);
 		list_del(&space_info->list);
 		btrfs_sysfs_remove_space_info(space_info);
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index b4a9b1c58d2286efb3f2e159dc16f31df2cf2b81..8992e0096163e2c4bc6b9c86b180ef0a47232691 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -145,6 +145,9 @@ enum {
 	BTRFS_FS_STATE_DUMMY_FS_INFO,
 
 	BTRFS_FS_STATE_NO_CSUMS,
+
+	/* Indicates there was an error cleaning up a log tree. */
+	BTRFS_FS_STATE_LOG_CLEANUP_ERROR,
 };
 
 #define BTRFS_BACKREF_REV_MAX		256
@@ -3593,6 +3596,9 @@ do {								\
 
 #define BTRFS_FS_ERROR(fs_info)	(unlikely(test_bit(BTRFS_FS_STATE_ERROR, \
 						   &(fs_info)->fs_state)))
+#define BTRFS_FS_LOG_CLEANUP_ERROR(fs_info)				\
+	(unlikely(test_bit(BTRFS_FS_STATE_LOG_CLEANUP_ERROR,		\
+			   &(fs_info)->fs_state)))
 
 __printf(5, 6)
 __cold
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index d8af6620a9413752dfced63f5fae2e936314aab1..33eda39df685f7607e57a886a7a53b59f1fe6347 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -805,10 +805,7 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
 		goto fail;
 	}
 
-	spin_lock(&fs_info->trans_lock);
-	list_add(&pending_snapshot->list,
-		 &trans->transaction->pending_snapshots);
-	spin_unlock(&fs_info->trans_lock);
+	trans->pending_snapshot = pending_snapshot;
 
 	ret = btrfs_commit_transaction(trans);
 	if (ret)
@@ -3354,7 +3351,7 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
 	struct block_device *bdev = NULL;
 	fmode_t mode;
 	int ret;
-	bool cancel;
+	bool cancel = false;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 8928275823a1708779fe5edad275971f9de25c4e..f12dc687350c71cd103e7e0156dcb2dd903c1162 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1185,9 +1185,24 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info)
 	struct btrfs_trans_handle *trans = NULL;
 	int ret = 0;
 
+	/*
+	 * We need to have subvol_sem write locked, to prevent races between
+	 * concurrent tasks trying to disable quotas, because we will unlock
+	 * and relock qgroup_ioctl_lock across BTRFS_FS_QUOTA_ENABLED changes.
+	 */
+	lockdep_assert_held_write(&fs_info->subvol_sem);
+
 	mutex_lock(&fs_info->qgroup_ioctl_lock);
 	if (!fs_info->quota_root)
 		goto out;
+
+	/*
+	 * Request qgroup rescan worker to complete and wait for it. This wait
+	 * must be done before transaction start for quota disable since it may
+	 * deadlock with transaction by the qgroup rescan worker.
+	 */
+	clear_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
+	btrfs_qgroup_wait_for_completion(fs_info, false);
 	mutex_unlock(&fs_info->qgroup_ioctl_lock);
 
 	/*
@@ -1205,14 +1220,13 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info)
 	if (IS_ERR(trans)) {
 		ret = PTR_ERR(trans);
 		trans = NULL;
+		set_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
 		goto out;
 	}
 
 	if (!fs_info->quota_root)
 		goto out;
 
-	clear_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
-	btrfs_qgroup_wait_for_completion(fs_info, false);
 	spin_lock(&fs_info->qgroup_lock);
 	quota_root = fs_info->quota_root;
 	fs_info->quota_root = NULL;
@@ -3383,6 +3397,9 @@ qgroup_rescan_init(struct btrfs_fs_info *fs_info, u64 progress_objectid,
 			btrfs_warn(fs_info,
 			"qgroup rescan init failed, qgroup is not enabled");
 			ret = -EINVAL;
+		} else if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)) {
+			/* Quota disable is in progress */
+			ret = -EBUSY;
 		}
 
 		if (ret) {
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 03de89b45f279e0b1e960af1013fe50ac88a6bf0..c43bbc7f623eec272adaf2a283ef222885833365 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -2000,6 +2000,27 @@ static inline void btrfs_wait_delalloc_flush(struct btrfs_fs_info *fs_info)
 		btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 }
 
+/*
+ * Add a pending snapshot associated with the given transaction handle to the
+ * respective handle. This must be called after the transaction commit started
+ * and while holding fs_info->trans_lock.
+ * This serves to guarantee a caller of btrfs_commit_transaction() that it can
+ * safely free the pending snapshot pointer in case btrfs_commit_transaction()
+ * returns an error.
+ */
+static void add_pending_snapshot(struct btrfs_trans_handle *trans)
+{
+	struct btrfs_transaction *cur_trans = trans->transaction;
+
+	if (!trans->pending_snapshot)
+		return;
+
+	lockdep_assert_held(&trans->fs_info->trans_lock);
+	ASSERT(cur_trans->state >= TRANS_STATE_COMMIT_START);
+
+	list_add(&trans->pending_snapshot->list, &cur_trans->pending_snapshots);
+}
+
 int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
@@ -2073,6 +2094,8 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	if (cur_trans->state >= TRANS_STATE_COMMIT_START) {
 		enum btrfs_trans_state want_state = TRANS_STATE_COMPLETED;
 
+		add_pending_snapshot(trans);
+
 		spin_unlock(&fs_info->trans_lock);
 		refcount_inc(&cur_trans->use_count);
 
@@ -2163,6 +2186,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	 * COMMIT_DOING so make sure to wait for num_writers to == 1 again.
 	 */
 	spin_lock(&fs_info->trans_lock);
+	add_pending_snapshot(trans);
 	cur_trans->state = TRANS_STATE_COMMIT_DOING;
 	spin_unlock(&fs_info->trans_lock);
 	wait_event(cur_trans->writer_wait,
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 1852ed9de7fd56bf9f0d9b41d96a29e5a3e66cac..9402d8d944846f2ab398d46125b5448e2b6dc538 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -123,6 +123,8 @@ struct btrfs_trans_handle {
 	struct btrfs_transaction *transaction;
 	struct btrfs_block_rsv *block_rsv;
 	struct btrfs_block_rsv *orig_rsv;
+	/* Set by a task that wants to create a snapshot. */
+	struct btrfs_pending_snapshot *pending_snapshot;
 	refcount_t use_count;
 	unsigned int type;
 	/*
diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index 72e1c942197df816bb07f08dc686467900ae3c56..9fd145f1c4bc265da7362a6acb3fb693ec4b817d 100644
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -965,6 +965,7 @@ static int check_dev_item(struct extent_buffer *leaf,
 			  struct btrfs_key *key, int slot)
 {
 	struct btrfs_dev_item *ditem;
+	const u32 item_size = btrfs_item_size(leaf, slot);
 
 	if (unlikely(key->objectid != BTRFS_DEV_ITEMS_OBJECTID)) {
 		dev_item_err(leaf, slot,
@@ -972,6 +973,13 @@ static int check_dev_item(struct extent_buffer *leaf,
 			     key->objectid, BTRFS_DEV_ITEMS_OBJECTID);
 		return -EUCLEAN;
 	}
+
+	if (unlikely(item_size != sizeof(*ditem))) {
+		dev_item_err(leaf, slot, "invalid item size: has %u expect %zu",
+			     item_size, sizeof(*ditem));
+		return -EUCLEAN;
+	}
+
 	ditem = btrfs_item_ptr(leaf, slot, struct btrfs_dev_item);
 	if (unlikely(btrfs_device_id(leaf, ditem) != key->offset)) {
 		dev_item_err(leaf, slot,
@@ -1007,6 +1015,7 @@ static int check_inode_item(struct extent_buffer *leaf,
 	struct btrfs_inode_item *iitem;
 	u64 super_gen = btrfs_super_generation(fs_info->super_copy);
 	u32 valid_mask = (S_IFMT | S_ISUID | S_ISGID | S_ISVTX | 0777);
+	const u32 item_size = btrfs_item_size(leaf, slot);
 	u32 mode;
 	int ret;
 	u32 flags;
@@ -1016,6 +1025,12 @@ static int check_inode_item(struct extent_buffer *leaf,
 	if (unlikely(ret < 0))
 		return ret;
 
+	if (unlikely(item_size != sizeof(*iitem))) {
+		generic_err(leaf, slot, "invalid item size: has %u expect %zu",
+			    item_size, sizeof(*iitem));
+		return -EUCLEAN;
+	}
+
 	iitem = btrfs_item_ptr(leaf, slot, struct btrfs_inode_item);
 
 	/* Here we use super block generation + 1 to handle log tree */
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index c1ddbe800897578c587e5b376a49bcb6060b2e66..3ee014c06b82a544df86c9df228bbcc72d5f3b56 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3414,6 +3414,29 @@ static void free_log_tree(struct btrfs_trans_handle *trans,
 	if (log->node) {
 		ret = walk_log_tree(trans, log, &wc);
 		if (ret) {
+			/*
+			 * We weren't able to traverse the entire log tree, the
+			 * typical scenario is getting an -EIO when reading an
+			 * extent buffer of the tree, due to a previous writeback
+			 * failure of it.
+			 */
+			set_bit(BTRFS_FS_STATE_LOG_CLEANUP_ERROR,
+				&log->fs_info->fs_state);
+
+			/*
+			 * Some extent buffers of the log tree may still be dirty
+			 * and not yet written back to storage, because we may
+			 * have updates to a log tree without syncing a log tree,
+			 * such as during rename and link operations. So flush
+			 * them out and wait for their writeback to complete, so
+			 * that we properly cleanup their state and pages.
+			 */
+			btrfs_write_marked_extents(log->fs_info,
+						   &log->dirty_log_pages,
+						   EXTENT_DIRTY | EXTENT_NEW);
+			btrfs_wait_tree_log_extents(log,
+						    EXTENT_DIRTY | EXTENT_NEW);
+
 			if (trans)
 				btrfs_abort_transaction(trans, ret);
 			else