A new device-mapper thin provisioning target together with supporting block-manager, btree, space-map and transaction-manager infrastructure is online at https://github.com/jthornber/linux-2.6 for review. We are interested in correctness and performance test results and senseful coding related change requests. Please find more details below and provide any feedback through dm-devel@xxxxxxxxxxx Heinz and Joe. --- The thin provisioning target is on branch "thin-provisioning" including its respective infrastructure: drivers/md/dm-thin-prov.c (target) drivers/md/thinp-metadata.[ch] (infrastructure wrappers) drivers/md/persistent-data/* (infrastructure; see below) This target allows for creation of thin provisioned mapped devices with housekeeping persistent metadata on a backing store device separate from the data device holding provisioned blocks. The block size is selectable on thin provisioned device creation and the data device is extensible. Each thin provisioned device has its own pair of metadata and data devices. Instructions how to use the target follow further down. --- The supporting infrastructure itself, which we intend to utilize with other functionality (eg. snapshots), is on branch "persistent-data" in directory drivers/md/persistent-data/: block-manager.c Kconfig space-map-dummy.c block-manager.h Makefile space-map.h block-manager-test.c pd-module.c space-map-staged.c btree.c space-map-staged.h btree.h space-map-core.c space-map-test.c btree-internal.h space-map-core.h transaction-manager.c btree-spine.c space-map-disk.c transaction-manager.h btree-test.c space-map-disk.h block-manager*; a low level block pool creation and (locked) block io API. btree*: hierarchical b+-tree with arbitrary values API space-map*: API to keep record of how many times a block-manager block is being referenced transaction-manager*: 2 phase commit API to allow for consistent multi-block updates pd-module.c: tiny kernel module helper --- Using the thin provisioning target Table line syntax (also see thinp_ctr() in dm-thin-prov.c): <start> <len> thin-prov \ <data_dev> <meta_dev> <data_block_size> <low_water_mark> * data_dev: device holding thin provisioned data blocks * meta_dev: device keeping track of provisioned blocks * data_block_size: provisioning unit size in sectors * low_water_mark: block low water mark to throw a dm event for userpace to resize E.g.: 0 16777216 thin-prov \ /dev/tst/thin-prov-data /dev/tst/thin-prov-meta 32786 16 defines an 8GB thin provisioned mapped device using logical volumes tst/thin-prov-meta and tst/thin-prov-data for metadata and data backing stores respectively with a block size of 16MB and a low water mark of 16 blocks. Support to resize the data device is implemented but the metadata device should be large enough. Use the following formula to do the calculation: sz[4KB blocks] = \ 1 + ceiling(device size / block size / 255) * 3 metadata_dev_size[KB] = (sz > 100 ? sz : 100) * 4KB So, for the above example, assuming a data device size of 1GB, this results in:: 1 + ceiling(2097152 / 32768 / 255) * 3 = 4 4 is smaller than 100 so we'll go by 400KB. The metadata logical volume has 1 extent allocated, thus there's typically at least 4MB space available, which would allow for more than 87000 blocks. I.e. a thin provisioned device capacity larger than 1.32TB. Create the mapped device: dmsetup create --table \ "0 16777216 thin-prov \ /dev/tst/thin-prov-data /dev/tst/thin-prov-meta 32786 16" thin-dev Access /dev/mapper/thin-dev for arbitrary use (mkfs, mount, ...). Resize the data device: #!/bin/sh # Assuming data device size was smaller than 4GB dmsetup wait thin-dev lvextend -L4G tst/thin-prov-data echo "0 16777216 thin-prov \ /dev/tst/thin-prov-data /dev/tst/thin-prov-meta 32786 16"| \ dmsetup load dmsetup suspend --noflush thin-dev dmsetup resume thin-dev Resize the thin provisioned device to 16GB: echo "0 33554432 thin-prov \ /dev/tst/thin-prov-data /dev/tst/thin-prov-meta 32786 16"| \ dmsetup load dmsetup suspend --noflush thin-dev dmsetup resume thin-dev Remove the idle (e.g. unmounted) mapped device: dmsetup remove thin-dev -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
