Date: Tue, 23 Dec 1997 03:36:23 +0300 From: Dmitrij Tejblum <dima@tejblum.dnttm.rssi.ru> To: luoqi@watermarkgroup.com (Luoqi Chen) Cc: hackers@freebsd.org Subject: Re: msdosfs win95 long file name support Message-ID: <199712230036.DAA01959@tejblum.dnttm.rssi.ru> In-Reply-To: Your message of "Mon, 22 Dec 1997 10:54:45 EST." <9712221554.AA11732@watermarkgroup.com>
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Luoqi Chen wrote:
> Actually I looked at NetBSD's code before I started.
To be honest, i didn't looked at it. I only merged it.
> But its lookup code is
> somehow not very efficient: directory entry found is stored as directory
> relative offset, as opposed to file system relative offset as in our code.
^^^^^^^^^
You mean "old NetBSD code"? :)
> This results in extra pcbmap() calls in subsequent vnops (this problem is
> somewhat alleviated by the usage of fat cache, though).
Hmm. I see, you store begin and end cluster of dir entry in denode. Don't you
assume that dir entry can only be in 2 clusters, by a chance? Probably, very
long names cannot happen, but it wouldn't look as a good design.
>
> Their long file name support is not very well designed too. For instance,
> if we are to create a file with long file name, we need to find a unique
> 8.3 name. The logical place is to do that is in the lookup code, where we
> traverse the whole directory. NetBSD's code instead does that in vnops code,
> which means that you need to go through the directory TWICE. This is a
> Bad Thing(TM) if the directory is very large (say, windows/system :)
Oh, indeed, your way seems much better than the NetBSD's. Congratulations.
> > - NetBSD support FAT32 (I haven't tested it)
> This would be nice to have in our code. I don't know how hard that would be.
> I remember read in the mailing-list archive, someone said it was a completely
> different beast than FAT16/12.
I don't think so. From looking at the NetBSD code, the only differences is
that FAT entry is 32-bit, and the root directory has a FAT chain as every
other file. There are some new fields in the BPB also.
>
> > - NetBSD support such things as access time of a file.
> Yes, they support creation/access time. But they didn't try hard to set them
> correctly. If I've read their code correctly, both creation and access time
> are always set to equal to the modification time.
No, I think, they set access time if denode has DE_ACCESS flag, and
modification time if denode has DE_UPDATE flag. At least, the times seems to be
different on my computer.
> After all, it is trivial
> to add support for them.
Sure.
Dima
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