let mut n = 0;
                // Delete the pages allocated during this transaction
                // from the free db. If these pages have been freed
                // again, they will be reinserted below.
                while let Some(p) = self.initial_allocated.pop() {
                    debug!("del initial {} {:x} {:x}", n, free_db.db, p);
                    btree::del(&mut self, &mut free_db, &p.to_le(), None)?;
                    if cfg!(debug_assertions) {
                        crate::debug::debug(&self, &[&free_db], &format!("/tmp/free_{}", n), true);
                        n += 1;

                let mut changed = true;
                // Fix point on the freed and allocated pages.
                while changed {
                    changed = false;
                    // Delete the pages allocated during this transaction
                    // from the free db. If these pages have been freed
                    // again, they will be reinserted below.
                    while let Some(p) = self.initial_allocated.pop() {
                        btree::del(&mut self, &mut free_db, &p.to_le(), None)?;
                        changed = true;

                }

                // Adding all the pages freed during the transaction to the
                // tree of free pages. If this call to `btree::put` frees
                // pages, add them again. This converges in at most log n
                // iterations (where n is the total number of free pages).
                while !self.free_pages.is_empty() || !self.free_owned_pages.is_empty() {
                    while let Some(p) = self.free_pages.pop() {
                        let p = p & !0xfff;
                        debug!("put free {} {:x}", n, p);
                        btree::put(&mut self, &mut free_db, &p.to_le(), &())?;
                        if cfg!(debug_assertions) {
                            crate::debug::debug(&self, &[&free_db], &format!("/tmp/free_{}", n), true);
                            n += 1;

                    // Adding all the pages freed during the transaction to the
                    // tree of free pages. If this call to `btree::put` frees
                    // pages, add them again. This converges in at most log n
                    // iterations (where n is the total number of free pages).
                    while !self.free_pages.is_empty() || !self.free_owned_pages.is_empty() {
                        while let Some(p) = self.free_pages.pop() {
                            let p = p & !0xfff;
                            btree::put(&mut self, &mut free_db, &p.to_le(), &())?;
                            changed = true;

                    }
                    while let Some(p) = self.free_owned_pages.pop() {
                        let p = p & !0xfff;
                        debug!("put owned free {} {:x}", n, p);
                        btree::put(&mut self, &mut free_db, &p.to_le(), &())?;
                        if cfg!(debug_assertions) {
                            crate::debug::debug(&self, &[&free_db], &format!("/tmp/free_{}", n), true);
                            n += 1;

                        while let Some(p) = self.free_owned_pages.pop() {
                            let p = p & !0xfff;
                            btree::put(&mut self, &mut free_db, &p.to_le(), &())?;
                            changed = true;

                // Delete the pages allocated during in the calls to
                // `put` just above. Note that this is the same code
                // as just before the `put`s. We need this duplication
                // because doing this only here could potentially
                // delete pages we just inserted, causing leaks.
                //
                // Conversely, doing it only above could result in
                // pages being allocated in the calls to `put` above,
                // and still counted as free.
                while let Some(p) = self.initial_allocated.pop() {
                    debug!("del initial {} {:x} {:x}", n, free_db.db, p);
                    btree::del(&mut self, &mut free_db, &p.to_le(), None)?;
                    if cfg!(debug_assertions) {
                        crate::debug::debug(&self, &[&free_db], &format!("/tmp/free_{}", n), true);
                        n += 1;
                    }
                }