From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [10.33.0.40] (breeves.fab.redhat.com [10.33.0.40]) by pobox.fab.redhat.com (8.13.1/8.13.1) with ESMTP id m1TJFDgo014136 for ; Fri, 29 Feb 2008 14:15:13 -0500 Message-ID: <47C8589A.7000309@redhat.com> Date: Fri, 29 Feb 2008 19:10:18 +0000 From: "Bryn M. Reeves" MIME-Version: 1.0 Subject: Re: [linux-lvm] Page cache corruption when creating a snapshot References: <200802291732.m1THWfD7013248@outgoing.mit.edu> <20080229183148.GI1788@agk.fab.redhat.com> <1204312265.5850.7.camel@error-messages.mit.edu> In-Reply-To: <1204312265.5850.7.camel@error-messages.mit.edu> 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 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 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. (I > could churn the page cache into oblivion with a bazillion reads of > different files, but I'd have no way of knowing when I had succeeded in > reusing the corrupted cache page.) You should be able to achieve that via the /proc/sys/vm/drop_caches sysctl: Documentation/filesystems/proc.txt: drop_caches - ----------- Writing to this will cause the kernel to drop clean caches, dentries and inodes from memory, causing that memory to become free. To free pagecache: echo 1 > /proc/sys/vm/drop_caches To free dentries and inodes: echo 2 > /proc/sys/vm/drop_caches To free pagecache, dentries and inodes: echo 3 > /proc/sys/vm/drop_caches I guess a 1 would be a good first try & if that doesn't clear it, a 3 should force the entire inode to be re-read from disk. Regards, Bryn. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iD8DBQFHyFia6YSQoMYUY94RArInAJ9dRVLCGYXcllL4RDz4pei4qGnUVQCg4LL1 d22/7jgF5zxsGnFPeCfpkwA= =v99d -----END PGP SIGNATURE-----