linux-kernel - Re: [RFC] readdir mess

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Message-ID: <alpine.LFD.1.10.0808121316570.3462@nehalem.linux-foundation.org>
Date:	Tue, 12 Aug 2008 13:21:56 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...IV.linux.org.uk>
cc:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] readdir mess

On Tue, 12 Aug 2008, Al Viro wrote:
> 
> you've just lost e.g. -EIO for getdents().  And if you bail out on
> non-zero return value from vfs_readdir(), you are back to -EINVAL
> on full buffer.

Btw, this whole sentence, and the one from your next email seems to really 
show a fundamental misunderstanding of the whole readdir() error handling:

> PS: we might get away with both, if we used _positive_ values as well.
> E.g. have getdents() filldir return 1 if we are out of buffer *and*
> have ->previous != NULL (and -EINVAL if we are out of buffer on the
> first call)...  And have some other positive constant for "->readdir()
> didn't feel like going all the way to the end of directory".

We *must* handle partial returns by returning "success". And we do, 
except for our _confusion_ about ->readdir() returning error and that 
somehow "overriding" the fact that it already returned non-errors earlier 
through the callback.

All your blathering about "positive values as well" seems to ttoally 
misunderstand how readdir() works. We absolutely do *not* need positive 
return values, because the fact is, the only positive return value we ever 
need is the "we already filled _earlier_ buffers". And that's the one 
that we already do.

The fact is, NO ERROR VALUE CAN POSSIBLY MATTER if we already returned one 
or more entries to getdents/readdir(). We should return a success value.

			Linus
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