diff --git a/include/libtorrent/alert_types.hpp b/include/libtorrent/alert_types.hpp
index a65d5624cca..9615eb7cbfd 100644
--- a/include/libtorrent/alert_types.hpp
+++ b/include/libtorrent/alert_types.hpp
@@ -13,6 +13,7 @@ Copyright (c) 2019, ghbplayer
 Copyright (c) 2020, AllSeeingEyeTolledEweSew
 Copyright (c) 2020, Fonic
 Copyright (c) 2020, Viktor Elofsson
+Copyright (c) 2023, Joris Carrier
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
@@ -1891,11 +1892,16 @@ TORRENT_VERSION_NAMESPACE_3
 	struct TORRENT_EXPORT cache_flushed_alert final : torrent_alert
 	{
 		// internal
-		TORRENT_UNEXPORT cache_flushed_alert(aux::stack_allocator& alloc, torrent_handle const& h);
+		TORRENT_UNEXPORT cache_flushed_alert(aux::stack_allocator& alloc,
+			torrent_handle const& h, client_data_t userdata = {});
 
 		TORRENT_DEFINE_ALERT_PRIO(cache_flushed_alert, 58, alert_priority::high)
 
 		static constexpr alert_category_t static_category = alert_category::storage;
+
+		// '`userdata`` as set in torrent_handle::flush_cache on call.
+		// This can be used to associate the call with related data.
+		client_data_t userdata;
 	};
 
 #if TORRENT_ABI_VERSION == 1
diff --git a/include/libtorrent/torrent.hpp b/include/libtorrent/torrent.hpp
index ecca52f34ea..d8f4d9f50c4 100644
--- a/include/libtorrent/torrent.hpp
+++ b/include/libtorrent/torrent.hpp
@@ -12,6 +12,7 @@ Copyright (c) 2018, d-komarov
 Copyright (c) 2019, ghbplayer
 Copyright (c) 2020, Paul-Louis Ageneau
 Copyright (c) 2021, AdvenT
+Copyright (c) 2023, Joris Carrier
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
@@ -563,7 +564,7 @@ namespace libtorrent {
 		bool has_error() const { return !!m_error; }
 		error_code error() const { return m_error; }
 
-		void flush_cache();
+		void flush_cache(client_data_t userdata = {});
 		void pause(pause_flags_t flags = {});
 		void resume();
 
@@ -1307,7 +1308,7 @@ namespace libtorrent {
 		void on_file_renamed(std::string const& filename
 			, file_index_t file_idx
 			, storage_error const& error);
-		void on_cache_flushed(bool manually_triggered);
+		void on_cache_flushed(bool manually_triggered, client_data_t userdata = {});
 
 		// this is used when a torrent is being removed.It synchronizes with the
 		// disk thread
diff --git a/include/libtorrent/torrent_handle.hpp b/include/libtorrent/torrent_handle.hpp
index 6ffd49fb9f0..ad6f2ef0f9f 100644
--- a/include/libtorrent/torrent_handle.hpp
+++ b/include/libtorrent/torrent_handle.hpp
@@ -9,6 +9,7 @@ Copyright (c) 2017, 2020, AllSeeingEyeTolledEweSew
 Copyright (c) 2017, Falcosc
 Copyright (c) 2019, Andrei Kurushin
 Copyright (c) 2019, ghbplayer
+Copyright (c) 2023, Joris Carrier
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
@@ -652,13 +653,15 @@ namespace aux {
 
 		// Instructs libtorrent to flush all the disk caches for this torrent and
 		// close all file handles. This is done asynchronously and you will be
-		// notified that it's complete through cache_flushed_alert.
+		// notified that it's complete through cache_flushed_alert
+		// with custom data (client_data_t) to be associated with this operation.
 		//
 		// Note that by the time you get the alert, libtorrent may have cached
 		// more data for the torrent, but you are guaranteed that whatever cached
 		// data libtorrent had by the time you called
-		// ``torrent_handle::flush_cache()`` has been written to disk.
-		void flush_cache() const;
+		// ``torrent_handle::flush_cache(client_data_t)`` with the provided client_data_t
+		// has been written to disk.
+		void flush_cache(client_data_t userdata = {}) const;
 
 		// ``force_recheck`` puts the torrent back in a state where it assumes to
 		// have no resume data. All peers will be disconnected and the torrent
diff --git a/src/alert.cpp b/src/alert.cpp
index e0853ea9b3a..c18a0af97b2 100644
--- a/src/alert.cpp
+++ b/src/alert.cpp
@@ -1561,8 +1561,9 @@ namespace {
 #endif // TORRENT_ABI_VERSION
 
 	cache_flushed_alert::cache_flushed_alert(aux::stack_allocator& alloc
-		, torrent_handle const& h)
-		: torrent_alert(alloc, h) {}
+		, torrent_handle const& h, client_data_t u)
+		: torrent_alert(alloc, h)
+		, userdata(u) {}
 
 #if TORRENT_ABI_VERSION == 1
 	anonymous_mode_alert::anonymous_mode_alert(aux::stack_allocator& alloc
diff --git a/src/torrent.cpp b/src/torrent.cpp
index 43e2cddea18..ed10c0939c2 100644
--- a/src/torrent.cpp
+++ b/src/torrent.cpp
@@ -18,7 +18,7 @@ Copyright (c) 2018, airium
 Copyright (c) 2018, d-komarov
 Copyright (c) 2020, Paul-Louis Ageneau
 Copyright (c) 2021, AdvenT
-Copyright (c) 2021, Joris CARRIER
+Copyright (c) 2021, 2023, Joris CARRIER
 Copyright (c) 2021, thrnz
 All rights reserved.
 
@@ -8397,7 +8397,7 @@ namespace {
 		{
 			// we need to keep the object alive during this operation
 			m_ses.disk_thread().async_release_files(m_storage
-				, std::bind(&torrent::on_cache_flushed, shared_from_this(), false));
+				, std::bind(&torrent::on_cache_flushed, shared_from_this(), false, client_data_t()));
 			m_ses.deferred_submit_jobs();
 		}
 
@@ -9462,7 +9462,7 @@ namespace {
 			&& !m_session_paused;
 	}
 
-	void torrent::flush_cache()
+	void torrent::flush_cache(client_data_t userdata)
 	{
 		TORRENT_ASSERT(is_single_thread());
 
@@ -9473,18 +9473,18 @@ namespace {
 			return;
 		}
 		m_ses.disk_thread().async_release_files(m_storage
-			, std::bind(&torrent::on_cache_flushed, shared_from_this(), true));
+			, std::bind(&torrent::on_cache_flushed, shared_from_this(), true, userdata));
 		m_ses.deferred_submit_jobs();
 	}
 
-	void torrent::on_cache_flushed(bool const manually_triggered) try
+	void torrent::on_cache_flushed(bool const manually_triggered, client_data_t userdata) try
 	{
 		TORRENT_ASSERT(is_single_thread());
 
 		if (m_ses.is_aborted()) return;
 
 		if (manually_triggered || alerts().should_post<cache_flushed_alert>())
-			alerts().emplace_alert<cache_flushed_alert>(get_handle());
+			alerts().emplace_alert<cache_flushed_alert>(get_handle(), userdata);
 	}
 	catch (...) { handle_exception(); }
 
diff --git a/src/torrent_handle.cpp b/src/torrent_handle.cpp
index c255e7a7282..ac9e464e4e2 100644
--- a/src/torrent_handle.cpp
+++ b/src/torrent_handle.cpp
@@ -8,6 +8,7 @@ Copyright (c) 2017, Falcosc
 Copyright (c) 2018, Steven Siloti
 Copyright (c) 2019, Andrei Kurushin
 Copyright (c) 2019, ghbplayer
+Copyright (c) 2023, Joris Carrier
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
@@ -356,9 +357,9 @@ namespace libtorrent {
 	{ async_call(&torrent::set_sequential_download, sd); }
 #endif
 
-	void torrent_handle::flush_cache() const
+	void torrent_handle::flush_cache(client_data_t userdata) const
 	{
-		async_call(&torrent::flush_cache);
+		async_call(&torrent::flush_cache, userdata);
 	}
 
 	void torrent_handle::set_ssl_certificate(