CLONE_NAMESPACE, links for dirs and mount(2) for normal users questions
Hi,
Long long ago, (March 2000) Alexander Viro replied to Pavel Machek:
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Quoted 2 lines
Am I right that from now on each process can have completely different view of filesystem like in plan9?
Almost there ;-) And yes, the only thing we lack for proper namespaces is the union-directories (
clone()bit is trivial).
Are there any patches already?
If not, where should I start to implement them?
Probably related to the first question, what about allowing mount(2) (as a CONFIG-option) for normal user processes when they have a) rw access to the device and b) are the owner/have rw-access to the mountpoint. (There would be at least one security problem:
A normal user could mount a loopback ext2 filesystem with panic-on-error (man tune2fs) and then corrupt it)
Quoted 9 lines · Al Viro
1. We should never have more than one dentry for a writable directory.
Print it and hang it on the wall. It's a fundamental requirement. There is no way to work around it in our VFS. I tried to invent a scheme that would allow that for more than a year. And I've done most of namespace-related code in our VFS since the moment when Bill Hawes stopped working on it, so I suspect that right now I have the best working knowledge of that stuff. There is no fscking way to survive multiple dentries for writable directory without major lossage. Period.
Do I understand correctly that this means hardlinks to directories (except . and ..) are fundamentally impossible in Linux? (I'm thinking about trying to write a garbage collected filesystem with hardlinks to directories.)
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Linux 2.4.0-test11 #1 Mon Nov 20 17:19:26 CET 2000 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] Please read the FAQ at http://www.tux.org/lkml/
[Remi Turk]
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Do I understand correctly that this means hardlinks to directories (except . and ..) are fundamentally impossible in Linux?
Why do you want to be able to do that? Use symlinks or loopback mounts and stay out of trouble.
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(I'm thinking about trying to write a garbage collected filesystem with hardlinks to directories.)
Sounds like a lot of extra complexity. Is this academic or do you have a practical use for it?
Peter
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Quoted 7 lines · Peter Samuelson
[Remi Turk]
Quoted 2 lines
Do I understand correctly that this means hardlinks to directories (except . and ..) are fundamentally impossible in Linux?
Why do you want to be able to do that? Use symlinks or loopback mounts and stay out of trouble.
Probably just because I'm crazy ;-)
Of course I could use symlinks or loopback mounts, but it itn't nearly as much fun as a directory which really contains itself :-)
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(I'm thinking about trying to write a garbage collected filesystem with hardlinks to directories.)
Sounds like a lot of extra complexity. Is this academic or do you have a practical use for it?
Acedemic.
Well, I might find some practical use for it some day.
(I got inspired by an old thread about garbage collecting filesystems without a clear answer about whether it was possible to write one in Linux
(http://www.uwsg.indiana.edu/hypermail/linux/kernel/0001.1/0410.html)
and the recent thread "[BUG] Inconsistent behaviour of rmdir")
Quoted 2 lines
Peter
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Linux 2.4.0-test11-ac4 #1 Tue Nov 28 15:51:01 CET 2000 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] Please read the FAQ at http://www.tux.org/lkml/