Messages in this thread | | | Date | Sat, 5 Feb 2000 23:02:54 +0000 (GMT) | From | Riley Williams <> | Subject | Re: kernel read/write question |
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Hi Christopher.
> I would like to thank Stephen, Laslo and Andreas for the links > and info about e2compr, but I already knew about the patch.
> If I understand the patch correcly, it works by setting a > permission bit to determine if a file is to be compressed, and > if the file is a directory, then all new files are compressed > (if I'm wrong, let me know).
I use the patch in question, and can confirm that it does far more than that. What basically happens is that the user runs, for example...
chattr -R -V +c /usr/src
...which causes the `chattr` command to recursively descend from /usr/src/ telling the kernel to set the +c attribute on every file and directory it finds, and verbosely tells you what it's doing whilst it's at it.
Each time the kernel is asked to set the +c attribute on a file that doesn't already have that attribute set, it promptly compresses it using the currently specified compression method, and blocks until the compression is finished.
Likewise, if you specify -c instead of +c then as the kernel clears the said flag, it also decompresses the file.
> My intention is to mount a filesystem where everything is > compressed, except for the files already compressed.
I'm not even sure what you mean by that, so can hardly comment thereon.
> An example would be a directory or file move and having it > already compressed without having to set additional bits...
If the target directory has the +c attribute set, that happens automatically, even if it wasn't compressed in the directory it's being moved from.
> ...or remembering to set the compression bit each time I mount a > disk.
You don't have to do that now - once set, it remains set across mount/umount/reboot until somebody explicitly clears it.
> I'm not sure if that helps any.
I would suspect that you haven't even tried the patch, and would suggest you do so, and then clarify your comments if I've misunderstood them...
Best wishes from Riley.
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