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authorJoe Thornber <ejt@redhat.com>2012-03-28 18:41:28 +0100
committerAlasdair G Kergon <agk@redhat.com>2012-03-28 18:41:28 +0100
commit2dd9c257fbc243aa76ee6db0bb8371f9f74fad2d (patch)
tree51c82de6e41b4f53f9d41dfe1211c4feba55dc6d /drivers/md/dm-io.c
parentc4a69ecdb463a901b4645230613961e134e897cd (diff)
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dm thin: support read only external snapshot origins
Support the use of an external _read only_ device as an origin for a thin device. Any read to an unprovisioned area of the thin device will be passed through to the origin. Writes trigger allocation of new blocks as usual. One possible use case for this would be VM hosts that want to run guests on thinly-provisioned volumes but have the base image on another device (possibly shared between many VMs). Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md/dm-io.c')
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