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Re: [bug #17877] Invalid "No such file or directory" error on filesystem
From: |
Miklos Szeredi |
Subject: |
Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers |
Date: |
Fri, 06 Oct 2006 20:03:19 +0200 |
> >> If files are identified by the path, then you can hash the
> >> path. If you use a good 64-bit hash the chance of collision
> >> is practically zero. That's good enough.
> >
> > Yes. And this solution is actually practical on pure 64bit
> > archs only. On 32bit and dual archs it's not practial, because
> > legacy apps (those compiled without largefile support)
>
> First, we're not talking about legacy apps here. The applications
> we're talking about all have largefile support, as do the vast
> majority of other applications that I use daily. So if you come up
> with a solution that works well with largefile apps, and does
> something sort-of-reasonable for legacy apps, that's fine.
>
> Second, even 32-bit hashes are pretty good. The chances of their
> screwing up in practice are quite small, if you have good hash
> functions.
For a perfect 32bit hash function the chance of a collision in a set
of 10,000 files is approx. 1%. The chance of a collision in a set of
100,000 files is approx 70%. I have 470,000 files on my root
partition, the chance of a collision within that is for all intents
and purposes 100%.
It may not matter in practice, but it would be hard to call that POSIX
conforming, which _very_ clearly states that inode numbers are
_unique_.
> > This is not a theoretical
> > possibility, I've had bug reports in this area.
>
> If it's for legacy apps, tell people to recompile with largefile
> support.
Paul, please! It is ridiculous to require end users to recompile
their applications or kernels or anything. You are living in some
dream world I think, where the users serve the programmers, and not
the other way round.
> That's much better than asking people to rewrite thousands of apps.
I think you are the only one asking for that.
> (If you're getting lots of bug reports for legacy apps, then
> improve the quality of your 32-bit hash functions. :-)
>
> > Currently I have report of exactly 1 (one) application,
> > that breaks.
>
> Sorry, that's not sufficient evidence. I'm sure lots of other apps
> will break, but people won't necessarily know where to send the bug
> reports.
I'm not holding my breath for these bug reports, sorry. Sshfs may be
a newcomer, but smbfs and fat has been around for quite some time. If
they would break applications, those bugs would have been reported
already.
> There is a standard for this, a standard that reflects longstanding
> practice.
Which is what I have been doing. Had I been using a hash function in
FUSE to get the inode number I would have been breaking long standing
practice.
> Just conform to the standard, and you'll be fine.
Neither uniqe-unstable or collinding-stable inode numbers conform to
POSIX.
Miklos
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, (continued)
- [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Paul Eggert, 2006/10/04
- [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Miklos Szeredi, 2006/10/04
- [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Paul Eggert, 2006/10/05
- [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Miklos Szeredi, 2006/10/06
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, James Youngman, 2006/10/06
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Paul Eggert, 2006/10/06
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers,
Miklos Szeredi <=
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Paul Eggert, 2006/10/06
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Miklos Szeredi, 2006/10/06
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Paul Eggert, 2006/10/06
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Miklos Szeredi, 2006/10/07
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Paul Eggert, 2006/10/07
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Miklos Szeredi, 2006/10/07
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, James Youngman, 2006/10/07
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Miklos Szeredi, 2006/10/07
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, Miklos Szeredi, 2006/10/07
- Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers, James Youngman, 2006/10/08