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Message-ID: <4ED4B174.80300@nexen.alterway.fr> Date: Tue, 29 Nov 2011 11:18:28 +0100 From: Vivien Bernet-Rollande <vivien.bernet-rollande@...en.alterway.fr> To: linux-kernel@...r.kernel.org Subject: Flushing block-level read cache for a single (shared) device. Hi list. I have two Xen hypervisors. Virtual machines use raw ISCSI devices for storage. I ran into a cache coherency issue with live migration. Let's say VM "a" runs on hypervisor "x1", and I want to move it to "x2". This works fine. Now, I let "a" do some file system operations on "x2". The problem arises when I move "a" back to "x1". What happens is x1 still has it's old caches for the iscsi LUN. After a few minutes, the filesystem of the VM gets heavily corrupted, and is basically unrecoverable. I'm currently working around this issue by running something like "sync; echo 3 > /proc/sys/vm/drop_caches" on the destination before any migration. This works, and I no longer have any data corruption. However I feel dropping all caches is not a satisfying solution. I'm looking for a way to invalidate the cache for a single block device. I know of BLKFLSBUF to flush write buffers, but I couldn't find anything related to read caches. -- Vivien Bernet-Rollande Systems& Networking Engineer Alter Way Hosting -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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