From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx3.redhat.com (mx3.redhat.com [172.16.48.32]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id m1TJZfaf025619 for ; Fri, 29 Feb 2008 14:35:41 -0500 Received: from biscayne-one-station.mit.edu (BISCAYNE-ONE-STATION.MIT.EDU [18.7.7.80]) by mx3.redhat.com (8.13.8/8.13.8) with ESMTP id m1TJZ93k015180 for ; Fri, 29 Feb 2008 14:35:09 -0500 Received: from outgoing.mit.edu (OUTGOING-AUTH.MIT.EDU [18.7.22.103]) by biscayne-one-station.mit.edu (8.13.6/8.9.2) with ESMTP id m1TJZ3ZK024762 for ; Fri, 29 Feb 2008 14:35:03 -0500 (EST) Received: from [10.0.0.102] (c-65-96-107-158.hsd1.ma.comcast.net [65.96.107.158]) (authenticated bits=0) (User authenticated as ghudson@ATHENA.MIT.EDU) by outgoing.mit.edu (8.13.6/8.12.4) with ESMTP id m1TJZ2tc007873 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT) for ; Fri, 29 Feb 2008 14:35:03 -0500 (EST) Subject: Re: [linux-lvm] Page cache corruption when creating a snapshot From: Greg Hudson In-Reply-To: <47C8589A.7000309@redhat.com> References: <200802291732.m1THWfD7013248@outgoing.mit.edu> <20080229183148.GI1788@agk.fab.redhat.com> <1204312265.5850.7.camel@error-messages.mit.edu> <47C8589A.7000309@redhat.com> Date: Fri, 29 Feb 2008 14:35:16 -0500 Message-Id: <1204313716.5850.12.camel@error-messages.mit.edu> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii" To: LVM general discussion and development On Fri, 2008-02-29 at 19:10 +0000, Bryn M. Reeves wrote: > Greg Hudson wrote: > > Nope, that never made it go away. I'm not sure in what situations > > flushing write buffers would have any effect. If I had a way to throw > > away the read-only page cache and force a file reload from disk, I would > > expect that to eliminate the visible effect of the corruption; at the > > moment the only reliable way I know how to do that is to reboot. > To free pagecache: > echo 1 > /proc/sys/vm/drop_caches Thank you! Verified that freeing the page cache causes the apparently-corrupted file's md5sum to revert to the correct value: [Abbreviated diff output:] --- /tmp/sum.pre 2008-02-29 14:30:29.000000000 -0500 +++ /tmp/sum.post 2008-02-29 14:30:32.000000000 -0500 -3e497fef20ce899c5621dcfbcbfec9a3 /tmp/test/krb5-1.6.dfsg/src/windows/cns/kerbnet.hlp +e9725c38b630515dc304a26bde28fa51 /tmp/test/krb5-1.6.dfsg/src/windows/cns/kerbnet.hlp root@linux-build-10:~# md5sum /tmp/test/krb5-1.6.dfsg/src/windows/cns/kerbnet.hlp e9725c38b630515dc304a26bde28fa51 /tmp/test/krb5-1.6.dfsg/src/windows/cns/kerbnet.hlp root@linux-build-10:~# echo 1 > /proc/sys/vm/drop_caches root@linux-build-10:~# md5sum /tmp/test/krb5-1.6.dfsg/src/windows/cns/kerbnet.hlp 3e497fef20ce899c5621dcfbcbfec9a3 /tmp/test/krb5-1.6.dfsg/src/windows/cns/kerbnet.hlp