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a900d150e4
Existing messaging intarface for thin-pool has a few 'weak' points: * Message were posted with each 'resume' operation, thus not allowing activation of thin-pool with the existing state. * Acceleration skipped suspend step has not worked in cluster, since clvmd resumes only nodes which are suspended (have proper lock state). * Resume may fail and code is not really designed to 'fail' in this phase (generic rule here is resume DOES NOT fail unless something serious is wrong and lvm2 tool usually doesn't handle recovery path in this case.) * Full thin-pool suspend happened, when taken a thin-volume snapshot. With this patch the new method relocates message passing into suspend state. This has a few drawbacks with current API, but overal it performs better and gives are more posibilities to deal with errors. Patch introduces a new logic for 'origin-only' suspend of thin-pool and this also relates to thin-volume when taking snapshot. When suspend_origin_only operation is invoked on a pool with queued messages then only those messages are posted to thin-pool and actual suspend of thin pool and data and metadata volume is skipped. This makes taking a snapshot of thin-volume lighter operation and avoids blocking of other unrelated active thin volumes. Also fail now happens in 'suspend' state where the 'Fail' is more expected and it is better handled through error paths. Activation of thin-pool is now not sending any message and leaves upto a tool to decided later how to finish unfinished double-commit transaction. Problem which needs some API improvements relates to the lvm2 tree construction. For the suspend tree we do not add target table line into the tree, but only a device is inserted into a tree. Current mechanism to attach messages for thin-pool requires the libdm to know about thin-pool target, so lvm2 currently takes assumption, node is really a thin-pool and fills in the table line for this node (which should be ensured by the PRELOAD phase, but it's a misuse of internal API) we would possibly need to be able to attach message to 'any' node. Other thing to notice - current messaging interface in thin-pool target requires to suspend thin volume origin first and then send a create message, but this could not have any 'nice' solution on lvm2 side and IMHO we should introduce something like 'create_after_resume' message. Patch also changes the moment, where lvm2 transaction id is increased. Now it happens only after successful finish of kernel transaction id change. This change was needed to handle properly activation of pool, which is in the middle of unfinished transaction, and also this corrects usage of thin-pool by external apps like Docker. |
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| .. | ||
| activate.c | ||
| activate.h | ||
| dev_manager.c | ||
| dev_manager.h | ||
| fs.c | ||
| fs.h | ||
| targets.h | ||