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authorMike Snitzer <snitzer@redhat.com>2009-12-10 23:52:24 +0000
committerAlasdair G Kergon <agk@redhat.com>2009-12-10 23:52:24 +0000
commitc1f0c183f6acc6d32c5a1d0249ec68bf783af7b1 (patch)
treef8e8e88e5403a9dbbebff14dc4afd6d475d1c03a /drivers/ata/ahci.c
parent042d2a9bcd80fe12d4b0871706aa9dd2231e8238 (diff)
downloadop-kernel-dev-c1f0c183f6acc6d32c5a1d0249ec68bf783af7b1.zip
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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 <snitzer@redhat.com> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
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