Subject: Re: The Joys of Linux

From: Werner Almesberger <[email-masked]>
Date: Tue, 20 Oct 1998 03:26:57 +0200 (MET DST)

[ Oops, Cc to the list was wrong in the 1st try ... ]

Russell King - ARM Linux Admin wrote:
> About the only thing that I can think of doing to make ADFS writable under
> Linux is to ensure that when you have an inode in use which belongs to a
> directory to *lock the directory against any changes* until all inodes in
> that directory /and/ their cached versions have been unused/flushed.

Hmm, if I got that right, why can't you write-through cache the per-directory
inode associations in memory until the directory is released ? That way, you
only run into problems when the directory runs out of potential inodes or
when pages get re-assigned to different directories. The former can be
partially solved by occasionally trying to reclaim old "virtual" inode
numbers, the latter by either locking directories in place until all
references are gone or by maintaining a list of all "open" directories and
checking against it before growing directories.

If your FS structure allows to grow directories without filling them with
content, you can also simply growe the directory to avoid running out of
virtual inodes. Maximum physical size = real entries + deleted but still
open entries.

Not very nice and potentially wasteful in terms of memory (although for
non-pathological usage patterns, it's probably quite okay), but probably
better than read-only.

- Werner

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