On 11/14/2014 06:06 AM, Max Reitz wrote: > Add a test for conversion between different refcount widths and errors > specific to certain widths (i.e. snapshots with refcount_width=1). > > Signed-off-by: Max Reitz <mre...@redhat.com> > --- > tests/qemu-iotests/112 | 252 > +++++++++++++++++++++++++++++++++++++++++++++ > tests/qemu-iotests/112.out | 131 +++++++++++++++++++++++ > tests/qemu-iotests/group | 1 + > 3 files changed, 384 insertions(+) > create mode 100755 tests/qemu-iotests/112 > create mode 100644 tests/qemu-iotests/112.out > > +echo > +echo '=== Testing too many references for check ===' > +echo > + > +IMGOPTS="$IMGOPTS,refcount_width=1" _make_test_img 64M > +print_refcount_width > + > +# This cluster should be created at 0x50000 > +$QEMU_IO -c 'write 0 64k' "$TEST_IMG" | _filter_qemu_io > +# Now make the second L2 entry (the L2 table should be at 0x40000) point to > that > +# cluster, so we have two references > +poke_file "$TEST_IMG" $((0x40008)) "\x80\x00\x00\x00\x00\x05\x00\x00" > + > +# This should say "please use amend" > +_check_test_img -r all > + > +# So we do that > +$QEMU_IMG amend -o refcount_width=2 "$TEST_IMG" > +print_refcount_width > + > +# And try again > +_check_test_img -r all
I think this section also deserves a test that fuzzes an image with width=64 to intentionally set the most significant bit of one of the refcounts, and make sure that we gracefully diagnose it as invalid. > + > +echo > +echo '=== Multiple walks necessary during amend ===' > +echo > + > +IMGOPTS="$IMGOPTS,refcount_width=1,cluster_size=512" _make_test_img 64k > + > +# Cluster 0 is the image header, clusters 1 to 4 are used by the L1 table, a > +# single L2 table, the reftable and a single refblock. This creates 58 data > +# clusters (actually, the L2 table is created here, too), so in total there > are > +# then 63 used clusters in the image. With a refcount width of 64, one > refblock > +# describes 64 clusters (512 bytes / 64 bits/entry = 64 entries), so this > will > +# make the first target refblock have exactly one free entry. > +$QEMU_IO -c "write 0 $((58 * 512))" "$TEST_IMG" | _filter_qemu_io > + > +# Now change the refcount width; since the first target refblock has exactly > one > +# free entry, that entry will be used to store its own reference. No other > +# refblocks are needed, so then the new reftable will be allocated; since the > +# first target refblock is completely filled up, this will require a new > +# refblock which is why the refcount width changing function will need to run > +# through everything one more time until the allocations are stable. > +$QEMU_IMG amend -o refcount_width=64 "$TEST_IMG" > +print_refcount_width Umm, that sounds backwards from what you document. It's a good test of the _new_ reftable needing a second round of allocations. So keep it with corrected comments. But I think you _intended_ to write a test that starts with a refcount_width=64 image and resize to a refcount_width=1, where the _old_ reftable then suffers a reallocation as part of allocating refblocks for the new table. It may even help if you add a tracepoint for every iteration through the walk function callback, to prove we are indeed executing it 3 times instead of the usual 2, for these test cases. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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