Re: On PATH_MAX

[Michal Suchanek]

On 11/8/05, Jonathan S. Shapiro <address@hidden> wrote:
> On Tue, 2005-11-08 at 18:12 +0100, Michal Suchanek wrote:
> > On 11/8/05, Christopher Nelson <address@hidden> wrote:
> > > Eventually, some server needs to know the filename.  How else is the
> > > file mapped to its content?...
> >
> > You can just read the symbolical name and present it to the user, or
> > search for an object with the name requested by the user.
>
> Please explain how to do this when the latency of the comparison and
> copy operations is unbounded.
>
> It can be done, but the file system in question is unable to make any
> reasonable specification of latency, and we are now done with any
> consideration of even soft real time for this file system.

Even if the compare operation is bound (ie there is a limit on the
length of the filename) I do not see how the EROS solution guaratees
any  latency constraint. Searching a directory with 4G files can take
quite long.
So you can only garantee anything if you make your own directory
specifically for the purpose where you store limited number of files
with short names.

I expected that the directory server would be multithreaded. Even if
it is not the case it can still guarantee behavior no worse than the
case where the filename length is limited. It can store the long
filenames in separate files, and search only up to certain length
limit. If an application wants a long name, it receives read caps to
all matching entries (possibly into a buffer object) and can search
them as long as it likes without disrupting the short name service.
There is a slight problem with storing the names in separate files:
since the files are singlethreaded, the start of the name has to be
duplicated in the short name store for searching.

Thanks

Michal


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