Re: [uml-devel] A quick humfs HOWTO

[Nuno Silva <nuno.silva@vgertech.com>]

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Jeff Dike wrote:

[..]

|
| The root contains two directories :
| 	data - which contains the files
| 	metadata - which shadows "data" and whose files contain ownership
| 		information
| and one file
| 	superblock - which contains information about the filesystem as a
| 		whole

Great news, compiling right now! :-)

In the meanwhile I'm thinking about this system and it seems that this
will eat lots of inodes because every file will be present twice in the
[host] filesystem with the metadata version using only a few bytes. Also
every "ls -la" (if it's not cached) in UML will generate a read in the
file's metafile file (say this 3 times quickly! eheheh). With 1000 files
in a directory thats lot's of fopen()s.

Wouldn't it be better to add support for a simple DB, like sleepycat or
CMU cyrus' project skiplist or even something lighter? This way we can
have only 2 files in the humfs "root", the superblock and the metadataDB.

This can save inodes and improve performance because you have only one
file that's indexed! :-)

The downsides:
- - another linker requirement at build time;
- - can't inspect and/or easily modify permissions with emacs. :-)

Any thoughts?

Regards,
Nuno Silva
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