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Date: Thu, 26 Jul 2001 16:04:13 -0400 (EDT)
From: Richard A Nelson <cowboy@vnet.ibm.com>
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To: Linus Torvalds <torvalds@transmeta.com>
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Subject: Re: ext3-2.4-0.9.4
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On Thu, 26 Jul 2001, Linus Torvalds wrote:

> > 	1) Does fsync() of a directory work on most/all current FS?
>
> Modulo bugs, yes.

Great, that was a big concern

> Now, there's another issue, of course: if you have an important mail-spool
> on some of the less tested filesystems, I would consider you crazy
> regardless of fsync() working ;). I don't think anybody has ever verified
> that fsync() (or much anything else wrt writing) does the right thing on
> NTFS, for example.

Caveat Emptor ;-)

> > 	2) Does it work on 2.2.x as well as 2.4.x?
>
> Yes. However, there may be performance issues. As with just about
> anything, we didn't start optimizing things until it became a real issue,
> and in some cases at least historically the filesystems fell back on just
> doing a whole "fsync_dev()" if they had nothing better to do.
>
> I think later 2.2.x kernels (ie the ones past the point where Alan took
> over) probably have the fsync() optimizations at least for ext2.

That should be recent enough - I push 2.2.19 for shm support and security
reasons anyway - though I see alot of folk on 2.2.16/17.

Are the optimizations more than writing out only changed blocks?
Has anyone any information on the performance differences between
optimized vs non-optimized?

Thanks, I'm feeling much better about getting this support added
-- 
Rick Nelson
Life'll kill ya                         -- Warren Zevon
Then you'll be dead                     -- Life'll kill ya