kernel: Add functionality to allow external inodes (such as sockets) to acquire an inode number from a file system

This is only implemented in tmpfs.

kernel/src/fs/VFS.h

@@ -35,6 +35,11 @@ namespace VFS
 
         virtual Result<SharedPtr<Inode>> create_symlink_inode(StringView link) = 0;
 
+        virtual Result<u64> allocate_inode_number()
+        {
+            return err(ENOTSUP);
+        }
+
         virtual Result<void> set_mount_dir(SharedPtr<Inode> parent) = 0;
 
         virtual Result<void> reset_mount_dir() = 0;

kernel/src/fs/tmpfs/FileSystem.cpp

@@ -16,6 +16,11 @@ namespace TmpFS
         return (SharedPtr<VFS::FileSystem>)fs;
     }
 
+    Result<u64> FileSystem::allocate_inode_number()
+    {
+        return m_next_inode_number++;
+    }
+
     Result<SharedPtr<VFS::Inode>> FileSystem::create_file_inode()
     {
         SharedPtr<FileInode> inode = TRY(make_shared<FileInode>());

kernel/src/fs/tmpfs/FileSystem.h

@@ -18,6 +18,8 @@ namespace TmpFS
         Result<SharedPtr<VFS::Inode>> create_device_inode(u32 major, u32 minor) override;
         Result<SharedPtr<VFS::Inode>> create_symlink_inode(StringView link) override;
 
+        Result<u64> allocate_inode_number() override;
+
         Result<void> set_mount_dir(SharedPtr<VFS::Inode> parent) override;
 
         Result<void> reset_mount_dir() override;