Pramfs: Persistent and protected ram filesystem

This is a second attempt at mainlining Pramfs. The first attempt was back in early 2004 by MontaVista. Since then the kernel code has almost been completely rewritten. So my first item on the list was porting the code on a recent kernel version. After that I added the XIP support.

Now some FAQs:

What is the goal of this filesystem?

Many embedded systems have a block of non-volatile RAM separate from normal system memory, i.e. of which the kernel maintains no memory page descriptors. For such systems it would be beneficial to mount a fast read/write filesystem over this "I/O memory", for storing frequently accessed data that must survive system reboots and power cycles. An example usage might be system logs under /var/log, or a user address book in a cell phone or PDA.

Why this kind of filesystem should be "mainlined"?

Linux traditionally had no support for a persistent, non-volatile RAM-based filesystem, persistent meaning the filesystem survives a system reboot or power cycle intact. The RAM-based filesystems such as tmpfs and ramfs have no actual backing store but exist entirely in the page and buffer caches, hence the filesystem disappears after a system reboot or power cycle.

Are there any pending patents on this code?

NO, there aren't patents pending on this code. MontaVista had a pending patent application but now it has abandoned this way. Daniel Walker can confirm that.

Marco