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Date: Thu, 1 Aug 2002 15:40:56 -0700 (PDT)
From: Linus Torvalds <torvalds@transmeta.com>
To: David Woodhouse <dwmw2@infradead.org>
cc: Roman Zippel <zippel@linux-m68k.org>, David Howells <dhowells@redhat.com>,
       <alan@redhat.com>, <linux-kernel@vger.kernel.org>
Subject: Re: manipulating sigmask from filesystems and drivers 
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On Thu, 1 Aug 2002, David Woodhouse wrote:
> 
> torvalds@transmeta.com said:
> >  Any regular file IO is supposed to give you the full result. 
> 
> read(2) is permitted to return -EINTR.

It is _not_ allowed to do that for regular UNIX filesystems.

It is allowed to return it for things like pipes, sockets, etc, and for 
filesystems that do not have UNIX behaviour.

> Regular file I/O through the page cache is inherently restartable, anyway, 
> as long as you're careful about fpos.

It's not the kernel side that is not restartable. It's the _user_ side. 
There is 30 _years_ of history on this, and there are programs that have 
been programmed to follow the existing documentation.

And the existing documentation says that if you return a partial read from 
a normal file, that means EOF for that file.

You may not like it, but that doesn't make it less so. Linux has UNIX 
semantics for read(). Linux is not a research project where we change 
fundamental semantics just because we don't like it. That's final.

		Linus

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