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[[!meta copyright="Copyright © 2008, 2009 Free Software Foundation, Inc."]]
[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
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document under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with no Invariant
Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license
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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: ?
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.
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