On 2010-02-16 23:12, Christoph Hellwig <hch@lst.de> wrote: > On Tue, Feb 16, 2010 at 03:42:25PM -0500, Philipp Weis wrote: > > How could it end up in the page cache for this setup? There is no > > filesystem layer below the loop device. Any write that reaches the > > loop device is passed through to lvm, then md and finally the disk. > > Are you saying that there is extra caching going on at the lvm or md > > layers? > > Yes, the block device node is a cached access mode, and uses the same > pagecache as a filesystem uses. Ugh, thanks for clearing that up. Is there a way to disable the page cache for lvm and md? Or is it just not possible to have this work reliably as long as there's no write barrier support in loop? From what I understand, 2.6.33 will have full barrier support for both md and lvm. Thanks, Philipp
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