Hi all! Here is a filter, which does preallocation on write.
In Virtuozzo we have to deal with some custom distributed storage solution, where allocation is relatively expensive operation. We have to workaround it in Qemu, so here is a new filter. Patches 1-10 introduces the new filter and suggested to be merged to master. Patches 11,12 are here just to show how we are going to use the feature. I don't know can they be somehow generally useful, ideas are welcome. Difference from v1: 1-6 are new and substitutes bdrv_co_range_try_lock mechanism used in v1 07: add note to docs/system/qemu-block-drivers.rst.inc add open options rebase on new BDRV_REQ_NO_WAIT flag drop bs->file check in _co_flush() add active logic, to make it possible to insert filter dynamically 08,09: new 10: - use new iotests.verify_o_direct() 10: - add qemu-img check call 11,12: not for commit Vladimir Sementsov-Ogievskiy (12): block: simplify comment to BDRV_REQ_SERIALISING block/io.c: drop assertion on double waiting for request serialisation block/io: split out bdrv_find_conflicting_request block/io: bdrv_wait_serialising_requests_locked: drop extra bs arg block: bdrv_mark_request_serialising: split non-waiting function block: introduce BDRV_REQ_NO_WAIT flag block: introduce preallocate filter iotests.py: add verify_o_direct helper iotests.py: add filter_img_check iotests: add 298 to test new preallocate filter driver block: add bdrv_is_file_on_fuse helper block/qcow2: automatically insert preallocate filter when on FUSE docs/system/qemu-block-drivers.rst.inc | 26 +++ qapi/block-core.json | 20 +- include/block/block.h | 22 +- include/block/block_int.h | 3 +- block/file-posix.c | 23 +- block/io.c | 131 ++++++----- block/preallocate.c | 291 +++++++++++++++++++++++++ block/qcow2.c | 38 ++++ block/Makefile.objs | 1 + tests/qemu-iotests/298 | 50 +++++ tests/qemu-iotests/298.out | 6 + tests/qemu-iotests/group | 1 + tests/qemu-iotests/iotests.py | 10 + 13 files changed, 554 insertions(+), 68 deletions(-) create mode 100644 block/preallocate.c create mode 100644 tests/qemu-iotests/298 create mode 100644 tests/qemu-iotests/298.out -- 2.18.0