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[[!meta title="Fix tmpfs"]]

In some situations it is desirable to have a file system that is not backed by
actual disk storage, but only by anonymous memory, i.e. lives in the RAM (and
possibly swap space).

A simplistic way to implement such a memory filesystem is literally creating a
ramdisk, i.e. simply allocating a big chunck of RAM (called a memory store in
Hurd terminology), and create a normal filesystem like ext2 on that.  However,
this is not very efficient, and not very convenient either (the filesystem
needs to be recreated each time the ramdisk is invoked).  A nicer solution is
having a real [[hurd/translator/tmpfs]], which creates all filesystem
structures directly in RAM, allocating memory on demand.

The Hurd has had such a tmpfs for a long time.  However, the existing
implementation doesn't work anymore -- it got broken by changes in other parts
of the Hurd design.

There are several issues.  The most serious known problem seems to be that for
technical reasons it receives [[microkernel/mach/RPC]]s from two different
sources on one [[microkernel/mach/port]], and gets mixed up with them.  Fixing
this is non-trivial, and requires a good understanding of the involved
mechanisms.

The goal of this project is to get a fully working, full featured tmpfs
implementation.  It requires digging into some parts of the Hurd, including the
[[pager_interface|hurd/libpager]] and [[hurd/translator]] programming.  This
task probably doesn't require any design work, only good debugging skills.

Possible mentors: Carl Fredrik Hammar (cfhammar)

Exercise: Take a look at tmpfs and try to fix one of the existing issues. Some
of them are probably not too tricky; or you might discover something else you
could improve while working on it. If you don't find anything obvious, contact
us about a different exercise task.