Changed the question to be more specific, in the hope it will be reopened.
On Ubuntu, how does one apply a patch (using the patch command) to apply a patch to a kernel (this patch, to get btrfs to accept my replacement disk, of all things). I found on the web and here some instructions (Ubuntu's BuildYourOwnKernel), but not the full recipe I am looking for. With this question, I hope someone will provide an easy recipe for all to follow. Following is what is needed:
How to fetch the source of the currently running kernel.
How to apply the patch on it.
How to compile it using the configuration which is usually used for my distribution.
How to change the version of the kernel, so I can install it without replacing the current official kernel. Adding '-tmp' or some initials to differentiate it from the official one, if possible.
How to get grub recognize the newly built kernel and have it shown in its menu, but not having it loading it by default; previous official kernel should be loaded by default. I want to select explicitely my custom kernel.
How to reboot the system such as upon reboot, grub allows one to select the kernel to boot from.
Once my usage for the kernel finished, how to remove all traces of it from the filesystem and grub.