On 08/17/2017 05:15 AM, Pavel Butsykin wrote: > This patch add shrinking of the image file for qcow2. As a result, this allows > us to reduce the virtual image size and free up space on the disk without > copying the image. Image can be fragmented and shrink is done by punching > holes > in the image file. > > # ./qemu-img create -f qcow2 image.qcow2 4G > Formatting 'image.qcow2', fmt=qcow2 size=4294967296 encryption=off > cluster_size=65536 lazy_refcounts=off refcount_bits=16 > > # ./qemu-io -c "write -P 0x22 0 1G" image.qcow2 > wrote 1073741824/1073741824 bytes at offset 0 > 1 GiB, 1 ops; 0:00:04.59 (222.886 MiB/sec and 0.2177 ops/sec) > > # ./qemu-img resize image.qcow2 512M > warning: qemu-img: Shrinking an image will delete all data beyond the > shrunken image's end. Before performing such an operation, make sure there is > no important data there. > error: qemu-img: Use the --shrink option to perform a shrink operation. > > # ./qemu-img resize --shrink image.qcow2 128M > Image resized. > > # ./qemu-img info image.qcow2 > image: image.qcow2 > file format: qcow2 > virtual size: 128M (134217728 bytes) > disk size: 128M > cluster_size: 65536 > Format specific information: > compat: 1.1 > lazy refcounts: false > refcount bits: 16 > corrupt: false > > # du -h image.qcow2 > 129M image.qcow2 >
It looks sane to me, and already has a full set of R-Bs from Max. Are we waiting for Kevin? It looks like in Vladimir's series we sidestepped the problem of what happens if we resize with persistent bitmaps: we deny the operation, regardless of if we are shrinking, growing, or have bitmaps that are read-only, frozen, or what-have-you. It shouldn't be too hard to add soon, but this is fine for now. (I think for adding it we just need to make sure the bitmaps aren't frozen and are not read-only, and the implementation bitmap structure can already handle truncation in either direction just fine.) Anyway; Reviewed-by: John Snow <js...@redhat.com> > Changes from v1: > - add --shrink flag for qemu-img resize > - add qcow2_cache_discard > - simplify qcow2_shrink_l1_table() to reduce the likelihood of image > corruption > - add new qemu-iotests for shrinking images > > Changes from v2: > - replace qprintf() on error_report() (1) > - rewrite warning messages (1) > - enforce --shrink flag for all formats except raw (1) > - split qcow2_cache_discard() (2) > - minor fixes according to comments (3) > - rewrite the last part of qcow2_shrink_reftable() to avoid > qcow2_free_clusters() calls inside (3) > - improve test for shrinking image (4) > > Changes from v3: > - rebase on "Implement a warning_report function" Alistair's patch-set (1) > - spelling fixes (1) > - the man page fix according to the discussion (1) > - add call qcow2_signal_corruption() in case of image corruption (3) > > Changes from v4: > - rebase on https://github.com/XanClic/qemu/commits/block Max's block branch > > Changes from v5: > - the condition refcount == 0 should be enough to evict the l2/refcount > cluster > from the cache (2) > - overwrite the l1/refcount table in memory with zeros, even if overwriting > the > l1/refcount table on disk has failed (3) > - replace g_try_malloc() on g_malloc() for allocation reftable_tmp (3) > > Changes from v6: > - rebase on master 1f29673387 > > Pavel Butsykin (4): > qemu-img: add --shrink flag for resize > qcow2: add qcow2_cache_discard > qcow2: add shrink image support > qemu-iotests: add shrinking image test > > block/qcow2-cache.c | 26 +++++++ > block/qcow2-cluster.c | 50 +++++++++++++ > block/qcow2-refcount.c | 140 ++++++++++++++++++++++++++++++++++++- > block/qcow2.c | 43 +++++++++--- > block/qcow2.h | 17 +++++ > qapi/block-core.json | 3 +- > qemu-img-cmds.hx | 4 +- > qemu-img.c | 23 ++++++ > qemu-img.texi | 6 +- > tests/qemu-iotests/102 | 4 +- > tests/qemu-iotests/163 | 170 > +++++++++++++++++++++++++++++++++++++++++++++ > tests/qemu-iotests/163.out | 5 ++ > tests/qemu-iotests/group | 1 + > 13 files changed, 475 insertions(+), 17 deletions(-) > create mode 100644 tests/qemu-iotests/163 > create mode 100644 tests/qemu-iotests/163.out >
