NetBSD Problem Report #28673
From dyoung@netbsd.org Wed Dec 15 23:23:19 2004
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Date: Wed, 15 Dec 2004 23:23:19 +0000 (UTC)
From: dyoung@netbsd.org
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To: gnats-bugs@netbsd.org
Subject: pages allocated by genfs_getpages() prematurely written to disk
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>Number: 28673
>Category: kern
>Synopsis: pages allocated by genfs_getpages() prematurely written to disk
>Confidential: no
>Severity: serious
>Priority: high
>Responsible: kern-bug-people
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Wed Dec 15 23:24:00 +0000 2004
>Originator: David Young
>Release: NetBSD 2.0
>Organization:
NetBSD
>Environment:
>Description:
According to Charles Hannum, genfs_getpages() may allow pages to be written
out before there is data in them. He says on icb,
genfs_getpages() is used to allocate new blocks. Note it clears PG_CLEAN
*and may unlock the pages, allowing them to be written out before there is
actual data in them*.
Further, Charles says,
This is probably why Dan (Carosone) sees zeroed blocks instead of data.
Even worse, there is a systematic problem with the Unified Buffer Cache (UBC),
... there are too many places where PG_CLEAN is maintained, and often far
from where a page is actually modified ... That's part of the problem
with genfs_getpages().
>How-To-Repeat:
Code inspection.
>Fix:
(Contact us)
$NetBSD: query-full-pr,v 1.39 2013/11/01 18:47:49 spz Exp $
$NetBSD: gnats_config.sh,v 1.8 2006/05/07 09:23:38 tsutsui Exp $
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