From: Matthew Wilcox <willy@debian.org>
To: Mark B <mark@lemna.hr>
Cc: linux-fsdevel@vger.kernel.org
Subject: Re: same page access
Date: Wed, 22 Oct 2003 12:21:28 +0100 [thread overview]
Message-ID: <20031022112128.GN18370@parcelfarce.linux.theplanet.co.uk> (raw)
In-Reply-To: <200310221015.17946.mark@lemna.hr>
On Wed, Oct 22, 2003 at 10:15:17AM +0200, Mark B wrote:
> I usually dig around kernel code to find answers, but I think this would take
> alot more time to dig than to explain from someone.
>
> Process 1 opens a file x, and does a read on the first few bytes, which in
> turn causes kernel to load the first page from the file (if the filesystem is
> using address_space_operations for all of it's access to files)
> Now a process 2 opens the same file and overwrites a few first bytes.
>
> Now, how does the kernel update the Process 1's page if it is already loaded?
It doesn't. A subsequent write() to a file doesn't affect any previous
read()s by this or any other process. The situation is diferent if
you're talking about mmap(), but as far as I can tell, you aren't.
--
"It's not Hollywood. War is real, war is primarily not about defeat or
victory, it is about death. I've seen thousands and thousands of dead bodies.
Do you think I want to have an academic debate on this subject?" -- Robert Fisk
next prev parent reply other threads:[~2003-10-22 11:21 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-10-07 19:02 zeroes read back more often than appended Pat LaVarre
2003-10-07 20:54 ` Pat LaVarre
2003-10-08 3:49 ` Ben Fennema
2003-10-08 16:41 ` Pat LaVarre
2003-10-08 16:47 ` editable udf metadata Pat LaVarre
2003-10-08 17:51 ` Pat LaVarre
2003-10-08 18:09 ` big-endian udfct_1_0r2 Pat LaVarre
2003-10-08 18:30 ` Matthew Wilcox
[not found] ` <3F8472FE.9040403@lougher.demon.co.uk>
2003-10-08 19:49 ` Matthew Wilcox
2003-10-08 20:43 ` Phillip Lougher
2003-10-21 21:54 ` editable udf metadata Pat LaVarre
2003-10-21 23:17 ` Pat LaVarre
2003-10-23 16:06 ` Pat LaVarre
2003-10-24 21:40 ` Pat LaVarre
2003-10-22 8:15 ` same page access Mark B
2003-10-22 11:21 ` Matthew Wilcox [this message]
2003-10-22 17:09 ` Mark B
2003-10-22 17:10 ` Matthew Wilcox
2003-10-08 17:02 ` zeroes read back more often than appended Pat LaVarre
2003-10-08 17:06 ` toggling smp clears x86_mce_p4thermal of make xconfig Pat LaVarre
2003-10-08 17:21 ` zeroes read back more often than appended Pat LaVarre
2003-10-08 16:46 ` soft trace of read/write of drivers/block/loop.c Pat LaVarre
2003-10-08 20:32 ` zeroes read back more often than appended Pat LaVarre
2003-10-09 20:54 ` Pat LaVarre
2003-10-10 0:52 ` Pat LaVarre
2003-10-10 16:39 ` Pat LaVarre
2003-10-10 18:15 ` Pat LaVarre
2003-10-14 0:38 ` Pat LaVarre
2003-10-14 1:48 ` Pat LaVarre
2003-10-20 23:20 ` Pat LaVarre
2003-10-21 14:47 ` Pat LaVarre
2003-10-21 16:46 ` Pat LaVarre
2003-10-21 18:44 ` Pat LaVarre
2003-10-23 18:52 ` Pat LaVarre
2003-10-27 21:55 ` Pat LaVarre
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