From: Mike Snitzer Date: Thu, 10 Dec 2009 23:52:24 +0000 (+0000) Subject: dm snapshot: allow live exception store handover between tables X-Git-Tag: v2.6.33-rc1~75^2~21 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c1f0c183f6acc6d32c5a1d0249ec68bf783af7b1;p=pandora-kernel.git dm snapshot: allow live exception store handover between tables Permit in-use snapshot exception data to be 'handed over' from one snapshot instance to another. This is a pre-requisite for patches that allow the changes made in a snapshot device to be merged back into its origin device and also allows device resizing. The basic call sequence is: dmsetup load new_snapshot (referencing the existing in-use cow device) - the ctr code detects that the cow is already in use and allows the two snapshot target instances to be linked together dmsetup suspend original_snapshot dmsetup resume new_snapshot - the new_snapshot becomes live, and if anything now tries to access the original one it will receive -EIO dmsetup remove original_snapshot (There can only be two snapshot targets referencing the same cow device simultaneously.) Signed-off-by: Mike Snitzer Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon --- Reading git-diff-tree failed