From a5675f390116a927e320984f02f473a6affc9fcd Mon Sep 17 00:00:00 2001 From: Alberto Garcia Date: Wed, 17 Jun 2020 16:00:36 +0200 Subject: [PATCH] qcow2: Fix preallocation on images with unaligned sizes When resizing an image with qcow2_co_truncate() using the falloc or full preallocation modes the code assumes that both the old and new sizes are cluster-aligned. There are two problems with this: 1) The calculation of how many clusters are involved does not always get the right result. Example: creating a 60KB image and resizing it (with preallocation=full) to 80KB won't allocate the second cluster. 2) No copy-on-write is performed, so in the previous example if there is a backing file then the first 60KB of the first cluster won't be filled with data from the backing file. This patch fixes both issues. Signed-off-by: Alberto Garcia Message-Id: <20200617140036.20311-1-berto@igalia.com> Reviewed-by: Eric Blake Signed-off-by: Max Reitz --- block/qcow2.c | 17 ++++++++++++++--- tests/qemu-iotests/125 | 24 ++++++++++++++++++++++++ tests/qemu-iotests/125.out | 9 +++++++++ 3 files changed, 47 insertions(+), 3 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index 0cd2e6757e..e20590c3b7 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -4239,8 +4239,8 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset, old_file_size = ROUND_UP(old_file_size, s->cluster_size); } - nb_new_data_clusters = DIV_ROUND_UP(offset - old_length, - s->cluster_size); + nb_new_data_clusters = (ROUND_UP(offset, s->cluster_size) - + start_of_cluster(s, old_length)) >> s->cluster_bits; /* This is an overestimation; we will not actually allocate space for * these in the file but just make sure the new refcount structures are @@ -4317,10 +4317,21 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset, int64_t nb_clusters = MIN( nb_new_data_clusters, s->l2_slice_size - offset_to_l2_slice_index(s, guest_offset)); - QCowL2Meta allocation = { + unsigned cow_start_length = offset_into_cluster(s, guest_offset); + QCowL2Meta allocation; + guest_offset = start_of_cluster(s, guest_offset); + allocation = (QCowL2Meta) { .offset = guest_offset, .alloc_offset = host_offset, .nb_clusters = nb_clusters, + .cow_start = { + .offset = 0, + .nb_bytes = cow_start_length, + }, + .cow_end = { + .offset = nb_clusters << s->cluster_bits, + .nb_bytes = 0, + }, }; qemu_co_queue_init(&allocation.dependent_requests); diff --git a/tests/qemu-iotests/125 b/tests/qemu-iotests/125 index d510984045..7cb1c19730 100755 --- a/tests/qemu-iotests/125 +++ b/tests/qemu-iotests/125 @@ -164,6 +164,30 @@ for GROWTH_SIZE in 16 48 80; do done done +# Test image resizing using preallocation and unaligned offsets +$QEMU_IMG create -f raw "$TEST_IMG.base" 128k | _filter_img_create +$QEMU_IO -c 'write -q -P 1 0 128k' -f raw "$TEST_IMG.base" +for orig_size in 31k 33k; do + echo "--- Resizing image from $orig_size to 96k ---" + _make_test_img -F raw -b "$TEST_IMG.base" -o cluster_size=64k "$orig_size" + $QEMU_IMG resize -f "$IMGFMT" --preallocation=full "$TEST_IMG" 96k + # The first part of the image should contain data from the backing file + $QEMU_IO -c "read -q -P 1 0 ${orig_size}" "$TEST_IMG" + # The resized part of the image should contain zeroes + $QEMU_IO -c "read -q -P 0 ${orig_size} 63k" "$TEST_IMG" + # If the image does not have an external data file we can also verify its + # actual size. The resized image should have 7 clusters: + # header, L1 table, L2 table, refcount table, refcount block, 2 data clusters + if ! _get_data_file "$TEST_IMG" > /dev/null; then + expected_file_length=$((65536 * 7)) + file_length=$(stat -c '%s' "$TEST_IMG_FILE") + if [ "$file_length" != "$expected_file_length" ]; then + echo "ERROR: file length $file_length (expected $expected_file_length)" + fi + fi + echo +done + # success, all done echo '*** done' rm -f $seq.full diff --git a/tests/qemu-iotests/125.out b/tests/qemu-iotests/125.out index 596905f533..7f76f7af20 100644 --- a/tests/qemu-iotests/125.out +++ b/tests/qemu-iotests/125.out @@ -767,4 +767,13 @@ wrote 2048000/2048000 bytes at offset 0 wrote 81920/81920 bytes at offset 2048000 80 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) +Formatting 'TEST_DIR/t.IMGFMT.base', fmt=raw size=131072 +--- Resizing image from 31k to 96k --- +Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=31744 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=raw +Image resized. + +--- Resizing image from 33k to 96k --- +Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33792 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=raw +Image resized. + *** done