Messages in this thread | | | Date | Sat, 30 Dec 2000 18:57:43 -0500 (EST) | From | Alexander Viro <> | Subject | Re: PROBLEM: multiple mount of devices possible 2.4.0-test1 - 2.4.0-test13-pre4 |
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On Sat, 30 Dec 2000, Ton Hospel wrote:
> It should still need a special flag or something, since it's > impossible for userspace to check this atomically.
To check _what_? Having the same tree mounted in several places is allowed. End of story. Atomicity of any kind is a non-issue - if you have processes that do not cooperate and do random mounts you are getting exactly what you are asking for.
BTW, mount(2) is outside of POSIX scope. Ditto for SuS, so references to standards are not likely to work. Not allowing multiple mounts of the same fs was an artifact of original namei() implementation. At some point (late 80s) it had been fixed by Bell Labs folks in their branch. In Linux it had been fixed during the last spring. That's it. You were never promised that multiple mounts will not work. Moreover, in special cases they did work since long - e.g. Linux procfs could be mounted in several places since '94, if not earlier. AFAIK NFS implementations allowed the same thing since mid-80s...
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