Date: Mon, 17 Nov 2003 01:50:24 -0800
From: William Lee Irwin III <wli@holomorphy.com>
To: Tigran Aivazian <tigran@aivazian.fsnet.co.uk>
Cc: viro@parcelfarce.linux.theplanet.co.uk, linux-kernel@vger.kernel.org
Subject: Re: seq_file and exporting dynamically allocated data
Message-ID: <20031117095024.GD22764@holomorphy.com>
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	Tigran Aivazian <tigran@aivazian.fsnet.co.uk>,
	viro@parcelfarce.linux.theplanet.co.uk,
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On Mon, Nov 17, 2003 at 09:42:09AM +0000, Tigran Aivazian wrote:
> Here are two files: simple.c kernel module and user.c user test program.  
> If you (or anyone) believe it is possible to return more than a single
> page on a read(2) please change them accordingly and let me know.

Sorry, I needed to amend that. It's not a fixed PAGE_SIZE buffer; the
buffer is only resized up to the point it allows a single ->show()
call to succeed, and then you get short reads if you try to go beyond
the buffer size in a single read.

You could (in theory) get this to succeed > PAGE_SIZE reads by doing
the operation all in a single ->show() call, but that will have some
large overheads and will also have a retry loop where the buffer size
is doubled until the ->show() call succeeds incurred at least once
per open() at the time of the first read().


-- wli
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