Kernel: Make F11 drop disk cache

This can be useful to detect memory leaks or something

kernel/include/kernel/FS/DevFS/FileSystem.h

@@ -22,6 +22,7 @@ namespace Kernel
 
 		void add_inode(BAN::StringView path, BAN::RefPtr<TmpInode>);
 
+		void initiate_disk_cache_drop();
 		void initiate_sync(bool should_block);
 
 	private:
@@ -37,6 +38,10 @@ namespace Kernel
 		ThreadBlocker m_sync_done;
 		ThreadBlocker m_sync_thread_blocker;
 		volatile bool m_should_sync { false };
+
+		SpinLock m_disk_cache_lock;
+		ThreadBlocker m_disk_cache_thread_blocker;
+		BAN::Atomic<bool> m_should_drop_disk_cache { false };
 	};
 
 }

kernel/include/kernel/Storage/StorageDevice.h

@@ -33,6 +33,7 @@ namespace Kernel
 		BAN::Vector<BAN::RefPtr<Partition>>& partitions() { return m_partitions; }
 		const BAN::Vector<BAN::RefPtr<Partition>>& partitions() const { return m_partitions; }
 
+		size_t drop_disk_cache();
 		BAN::ErrorOr<void> sync_disk_cache();
 		virtual bool is_storage_device() const override { return true; }