CP-11936: Automatically plug block-based RAW VDIs via blkback #251
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franciozzy
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This patch causes block-based (LV) RAW VDIs to be automatically plugged by blkback. This is achieved as follows: During VDI.attach, we detect that the SR handles LVM and that the VDI driver is 'aio'. In that case, we write 'backend-kind: vbd' to xenstore_data, which causes the toolstack to use the /local/domain/0/backend/vbd/ path instead of .../vbd3/. This is the preferred method following CP-11511. By writing to .../vbd/, blkback wakes up instead of tapback. During VDI.activate, we create the /dev/sm/backend/ node using the maj/min numbers of the actual VDI (LV) instead of those of the blktap2 device. This causes the udev hotplug scripts to write the /physical-device/ entry with information of the LV, creating the blkfront-blkback-vdi datapath without blktap2 or tapdisk3 in the middle. Note that a tapdisk3 and a blktap2 will still exist in dom0, providing all necessary backend infrastructure resources for other operations. Signed-off-by: Felipe Franciosi <felipe@paradoxo.org>
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Reviewed and tested. Looks good to merge @franciozzy |
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Placed in the PQ. |
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This patch causes block-based (LV) RAW VDIs to be automatically plugged by
blkback. This is achieved as follows:
During VDI.attach, we detect that the SR handles LVM and that the VDI driver
is 'aio'. In that case, we write 'backend-kind: vbd' to xenstore_data, which
causes the toolstack to use the /local/domain/0/backend/vbd/ path instead of
.../vbd3/. This is the preferred method following CP-11511. By writing to
.../vbd/, blkback wakes up instead of tapback.
During VDI.activate, we create the /dev/sm/backend/ node using the maj/min
numbers of the actual VDI (LV) instead of those of the blktap2 device. This
causes the udev hotplug scripts to write the /physical-device/ entry with
information of the LV, creating the blkfront-blkback-vdi datapath without
blktap2 or tapdisk3 in the middle.
Note that a tapdisk3 and a blktap2 will still exist in dom0, providing all
necessary backend infrastructure resources for other operations.
Signed-off-by: Felipe Franciosi felipe@paradoxo.org