simplefs - a ridiculosly simple file system from the scratch

[Rajat Sharma]

Hey buddy, its a good work. You never know how many people you end up
helping with this code. I would definitely recommend this as a
starter.

One recommendation: add support for page-cache. Start with read-cache
only, and then mmap support, you need that to allow binary execution.

-Rajat

On Tue, Aug 6, 2013 at 12:27 AM, Sankar P <sankar.curiosity at gmail.com> wrote:
> Hi,
>
> For learning purposes, I thought I would implement a filesystem from
> the scratch. It has reached a state where I can do a 1.0 release.
>
> The sources are at: https://github.com/psankar/simplefs
>
> The layout is simple. The first (zeroth) block is the superblock and
> contains information like fs magic, number of inodes, freeblock map
> etc. The next block is the inode store. Creation of files and
> directories is supported. Nested directories are supported. A file can
> grow up to one block only. The data blocks for a directory contain the
> filename and inode number of its children. For files, it will
> obviously contain the actual data of the file. There are three
> rudimentary locks to make sure the accesses are thread safe.
>
> The 1.0 version is filled with a lot of TODOs and memory leaks. Also
> while implementing this, I realized that it is a bad idea to maintain
> the superblock and the freeblock store together in a block. So I am
> planning to change the on-disk layout in the next version.
>
> Apart from moving the super block to minimize locks, I am planning to
> implement support for extents in the next version, and journalling in
> the next-to-next version. The next version will take some time to
> come, though. But if someone wants to try filesystems from the
> scratch, I thought it may be useful if I share the link now itself.
>
> Also, I take this moment to thank the kernelnewbies list, especially
> the regular people like Mulyadi Santosa, Valdis Kletnieks, Rajat
> Sharma, Greg Freemyer etc. Also I would like to thank Neha Naik,
> Manish Katiyar who helped me with some queries during this particular
> implementation. I saw that Manish Katiyar has also done a similar
> from-the-scratch implementation and it motivated me to pursue further.
>
> Any feedback on the code is welcome. Although, I want to inform that I
> plan to change the locking until after I decide on a good on-disk
> layout for the next version, which will by-design minimize the locking
> needs, by splitting out freestore from superblock, keep track of
> children inode in a better way etc. Also I have been resisting the
> urge to look at ext or any other filesystem's design so as to not skew
> my thoughts and go with a fresh state of mind and get my own design :)
>
> Thanks.
>
> --
> Sankar P
> http://psankar.blogspot.com
>
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