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From: Oliver Neukum <oliver@neukum.name>
To: Xuan Baldauf <xuan--reiserfs@baldauf.org>
Subject: Re: Heuristic readahead for filesystems
Date: Wed, 11 Sep 2002 21:04:41 +0200
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Cc: Rik van Riel <riel@conectiva.com.br>, linux-kernel@vger.kernel.org
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Am Mittwoch, 11. September 2002 20:43 schrieb Xuan Baldauf:

> > Please correct me, if I am wrong, but wouldn't read() block ?
>
> AFAIK, "man open" tells
>
> [...]
>       int open(const char *pathname, int flags);
> [...]
>        O_NONBLOCK or O_NDELAY
>                The file is opened in non-blocking mode. Neither the open
> nor any __subsequent__ operations  on  the  file  descriptor
>                which is returned will cause the calling process to wait.
> [...]
>
> So read won't block if the file has been opened with O_NONBLOCK.

Well, so the man page tells you. The kernel sources tell otherwise, unless
I am badly mistaken.

> > Aio should be able to do it. But even that want help you with the stat
> > data.
>
> Aio would help me announcing stat() usage for the future?

No, it won't. But it would solve the issue of reading ahead.
Stating needs a kernel implementation of 'stat ahead'
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