It's useful to know how much space can be occupied by qcow2 persistent bitmaps, even though such metadata is unrelated to the guest-visible data. Report this value as an additional QMP field, present when measuring an existing image and output format that both support bitmaps. Update iotest 178 and 190 to updated output, as well as new coverage in 190 demonstrating non-zero values made possible with the recently-added qemu-img bitmap command (see 3b51ab4b).
The new 'bitmaps size:' field is displayed automatically as part of 'qemu-img measure' any time it is present in QMP (that is, any time both the source image being measured and destination format support bitmaps, even if the measurement is 0 because there are no bitmaps present). If the field is absent, it means that no bitmaps can be copied (source, destination, or both lack bitmaps, including when measuring based on size rather than on a source image). This behavior is compatible with an upcoming patch adding 'qemu-img convert --bitmaps': that command will fail in the same situations where this patch omits the field. The addition of a new field demonstrates why we should always zero-initialize qapi C structs; while the qcow2 driver still fully populates all fields, the raw and crypto drivers had to be tweaked to avoid uninitialized data. Consideration was also given towards having a 'qemu-img measure --bitmaps' which errors out when bitmaps are not possible, and otherwise sums the bitmaps into the existing allocation totals rather than displaying as a separate field, as a potential convenience factor. But this was ultimately decided to be more complexity than necessary when the QMP interface was sufficient enough with bitmaps remaining a separate field. See also: https://bugzilla.redhat.com/1779904 Reported-by: Nir Soffer <nsof...@redhat.com> Signed-off-by: Eric Blake <ebl...@redhat.com> Message-Id: <20200521192137.1120211-3-ebl...@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> --- docs/tools/qemu-img.rst | 7 +++++ qapi/block-core.json | 16 +++++++---- block/qcow2.h | 2 ++ block/crypto.c | 2 +- block/qcow2-bitmap.c | 36 ++++++++++++++++++++++++ block/qcow2.c | 14 ++++++++-- block/raw-format.c | 2 +- qemu-img.c | 3 ++ tests/qemu-iotests/178.out.qcow2 | 16 +++++++++++ tests/qemu-iotests/190 | 47 ++++++++++++++++++++++++++++++-- tests/qemu-iotests/190.out | 27 +++++++++++++++++- 11 files changed, 159 insertions(+), 13 deletions(-) diff --git a/docs/tools/qemu-img.rst b/docs/tools/qemu-img.rst index 38d464ea3f23..320cb52b9f61 100644 --- a/docs/tools/qemu-img.rst +++ b/docs/tools/qemu-img.rst @@ -616,6 +616,7 @@ Command description: required size: 524288 fully allocated size: 1074069504 + bitmaps size: 0 The ``required size`` is the file size of the new image. It may be smaller than the virtual disk size if the image format supports compact representation. @@ -625,6 +626,12 @@ Command description: occupy with the exception of internal snapshots, dirty bitmaps, vmstate data, and other advanced image format features. + The ``bitmaps size`` is the additional size required in order to + copy bitmaps from a source image in addition to the guest-visible + data; the line is omitted if either source or destination lacks + bitmap support, or 0 if bitmaps are supported but there is nothing + to copy. + .. option:: snapshot [--object OBJECTDEF] [--image-opts] [-U] [-q] [-l | -a SNAPSHOT | -c SNAPSHOT | -d SNAPSHOT] FILENAME List, apply, create or delete snapshots in image *FILENAME*. diff --git a/qapi/block-core.json b/qapi/block-core.json index 6fbacddab2cc..0e1c6a59f228 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -636,18 +636,24 @@ # efficiently so file size may be smaller than virtual disk size. # # The values are upper bounds that are guaranteed to fit the new image file. -# Subsequent modification, such as internal snapshot or bitmap creation, may -# require additional space and is not covered here. +# Subsequent modification, such as internal snapshot or further bitmap +# creation, may require additional space and is not covered here. # -# @required: Size required for a new image file, in bytes. +# @required: Size required for a new image file, in bytes, when copying just +# allocated guest-visible contents. # # @fully-allocated: Image file size, in bytes, once data has been written -# to all sectors. +# to all sectors, when copying just guest-visible contents. +# +# @bitmaps: Additional size required if all the top-level bitmap metadata +# in the source image were to be copied to the destination, +# present only when source and destination both support +# persistent bitmaps. (since 5.1) # # Since: 2.10 ## { 'struct': 'BlockMeasureInfo', - 'data': {'required': 'int', 'fully-allocated': 'int'} } + 'data': {'required': 'int', 'fully-allocated': 'int', '*bitmaps': 'int'} } ## # @query-block: diff --git a/block/qcow2.h b/block/qcow2.h index 402e8acb1cb7..7ce2c23bdb7a 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -783,6 +783,8 @@ int qcow2_co_remove_persistent_dirty_bitmap(BlockDriverState *bs, const char *name, Error **errp); bool qcow2_supports_persistent_dirty_bitmap(BlockDriverState *bs); +uint64_t qcow2_get_persistent_dirty_bitmap_size(BlockDriverState *bs, + uint32_t cluster_size); ssize_t coroutine_fn qcow2_co_compress(BlockDriverState *bs, void *dest, size_t dest_size, diff --git a/block/crypto.c b/block/crypto.c index b216e12c3154..973b57b3eb74 100644 --- a/block/crypto.c +++ b/block/crypto.c @@ -552,7 +552,7 @@ static BlockMeasureInfo *block_crypto_measure(QemuOpts *opts, * Unallocated blocks are still encrypted so allocation status makes no * difference to the file size. */ - info = g_new(BlockMeasureInfo, 1); + info = g_new0(BlockMeasureInfo, 1); info->fully_allocated = luks_payload_size + size; info->required = luks_payload_size + size; return info; diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c index 1cf6d2ab77a3..7bf12502da8c 100644 --- a/block/qcow2-bitmap.c +++ b/block/qcow2-bitmap.c @@ -1755,3 +1755,39 @@ bool qcow2_supports_persistent_dirty_bitmap(BlockDriverState *bs) return s->qcow_version >= 3; } + +/* + * Compute the space required for bitmaps in @bs. + * + * The computation is based as if copying to a new image with the + * given @cluster_size, which may differ from the cluster size in @bs. + */ +uint64_t qcow2_get_persistent_dirty_bitmap_size(BlockDriverState *bs, + uint32_t cluster_size) +{ + uint64_t bitmaps_size = 0; + BdrvDirtyBitmap *bm; + size_t bitmap_dir_size = 0; + + FOR_EACH_DIRTY_BITMAP(bs, bm) { + if (bdrv_dirty_bitmap_get_persistence(bm)) { + const char *name = bdrv_dirty_bitmap_name(bm); + uint32_t granularity = bdrv_dirty_bitmap_granularity(bm); + uint64_t bmbytes = + get_bitmap_bytes_needed(bdrv_dirty_bitmap_size(bm), + granularity); + uint64_t bmclusters = DIV_ROUND_UP(bmbytes, cluster_size); + + /* Assume the entire bitmap is allocated */ + bitmaps_size += bmclusters * cluster_size; + /* Also reserve space for the bitmap table entries */ + bitmaps_size += ROUND_UP(bmclusters * sizeof(uint64_t), + cluster_size); + /* And space for contribution to bitmap directory size */ + bitmap_dir_size += calc_dir_entry_size(strlen(name), 0); + } + } + bitmaps_size += ROUND_UP(bitmap_dir_size, cluster_size); + + return bitmaps_size; +} diff --git a/block/qcow2.c b/block/qcow2.c index dfab8d2f6cd8..0cd2e6757e8c 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -4953,16 +4953,24 @@ static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs, required = virtual_size; } - info = g_new(BlockMeasureInfo, 1); + info = g_new0(BlockMeasureInfo, 1); info->fully_allocated = qcow2_calc_prealloc_size(virtual_size, cluster_size, ctz32(refcount_bits)) + luks_payload_size; - /* Remove data clusters that are not required. This overestimates the + /* + * Remove data clusters that are not required. This overestimates the * required size because metadata needed for the fully allocated file is - * still counted. + * still counted. Show bitmaps only if both source and destination + * would support them. */ info->required = info->fully_allocated - virtual_size + required; + info->has_bitmaps = version >= 3 && in_bs && + bdrv_supports_persistent_dirty_bitmap(in_bs); + if (info->has_bitmaps) { + info->bitmaps = qcow2_get_persistent_dirty_bitmap_size(in_bs, + cluster_size); + } return info; err: diff --git a/block/raw-format.c b/block/raw-format.c index 018441bddf27..233d019ca338 100644 --- a/block/raw-format.c +++ b/block/raw-format.c @@ -359,7 +359,7 @@ static BlockMeasureInfo *raw_measure(QemuOpts *opts, BlockDriverState *in_bs, BDRV_SECTOR_SIZE); } - info = g_new(BlockMeasureInfo, 1); + info = g_new0(BlockMeasureInfo, 1); info->required = required; /* Unallocated sectors count towards the file size in raw images */ diff --git a/qemu-img.c b/qemu-img.c index 2d30682f129f..b2311bd3f6b4 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -5302,6 +5302,9 @@ static int img_measure(int argc, char **argv) if (output_format == OFORMAT_HUMAN) { printf("required size: %" PRIu64 "\n", info->required); printf("fully allocated size: %" PRIu64 "\n", info->fully_allocated); + if (info->has_bitmaps) { + printf("bitmaps size: %" PRIu64 "\n", info->bitmaps); + } } else { dump_json_block_measure_info(info); } diff --git a/tests/qemu-iotests/178.out.qcow2 b/tests/qemu-iotests/178.out.qcow2 index 4b69524c80ee..c7997760fd6f 100644 --- a/tests/qemu-iotests/178.out.qcow2 +++ b/tests/qemu-iotests/178.out.qcow2 @@ -37,6 +37,7 @@ qemu-img: The image size is too large (try using a larger cluster size) Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=0 required size: 196608 fully allocated size: 196608 +bitmaps size: 0 converted image file size in bytes: 196608 @@ -45,6 +46,7 @@ converted image file size in bytes: 196608 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 required size: 393216 fully allocated size: 1074135040 +bitmaps size: 0 wrote 512/512 bytes at offset 512 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) wrote 65536/65536 bytes at offset 65536 @@ -53,6 +55,7 @@ wrote 64512/64512 bytes at offset 134217728 63 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) required size: 589824 fully allocated size: 1074135040 +bitmaps size: 0 converted image file size in bytes: 524288 @@ -60,6 +63,7 @@ converted image file size in bytes: 524288 required size: 524288 fully allocated size: 1074135040 +bitmaps size: 0 converted image file size in bytes: 458752 @@ -67,16 +71,19 @@ converted image file size in bytes: 458752 required size: 1074135040 fully allocated size: 1074135040 +bitmaps size: 0 == qcow2 input image and LUKS encryption == required size: 2686976 fully allocated size: 1076232192 +bitmaps size: 0 == qcow2 input image and preallocation (human) == required size: 1074135040 fully allocated size: 1074135040 +bitmaps size: 0 converted image file size in bytes: 1074135040 @@ -87,6 +94,7 @@ wrote 8388608/8388608 bytes at offset 0 8 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) required size: 8716288 fully allocated size: 8716288 +bitmaps size: 0 converted image file size in bytes: 8716288 @@ -173,6 +181,7 @@ qemu-img: The image size is too large (try using a larger cluster size) Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=0 { + "bitmaps": 0, "required": 196608, "fully-allocated": 196608 } @@ -183,6 +192,7 @@ converted image file size in bytes: 196608 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 { + "bitmaps": 0, "required": 393216, "fully-allocated": 1074135040 } @@ -193,6 +203,7 @@ wrote 65536/65536 bytes at offset 65536 wrote 64512/64512 bytes at offset 134217728 63 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) { + "bitmaps": 0, "required": 589824, "fully-allocated": 1074135040 } @@ -202,6 +213,7 @@ converted image file size in bytes: 524288 == qcow2 input image with internal snapshot (json) == { + "bitmaps": 0, "required": 524288, "fully-allocated": 1074135040 } @@ -211,6 +223,7 @@ converted image file size in bytes: 458752 == qcow2 input image and a backing file (json) == { + "bitmaps": 0, "required": 1074135040, "fully-allocated": 1074135040 } @@ -218,6 +231,7 @@ converted image file size in bytes: 458752 == qcow2 input image and LUKS encryption == { + "bitmaps": 0, "required": 2686976, "fully-allocated": 1076232192 } @@ -225,6 +239,7 @@ converted image file size in bytes: 458752 == qcow2 input image and preallocation (json) == { + "bitmaps": 0, "required": 1074135040, "fully-allocated": 1074135040 } @@ -237,6 +252,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8388608 wrote 8388608/8388608 bytes at offset 0 8 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) { + "bitmaps": 0, "required": 8716288, "fully-allocated": 8716288 } diff --git a/tests/qemu-iotests/190 b/tests/qemu-iotests/190 index 6d41650438e1..fe630918e9ad 100755 --- a/tests/qemu-iotests/190 +++ b/tests/qemu-iotests/190 @@ -2,7 +2,7 @@ # # qemu-img measure sub-command tests on huge qcow2 files # -# Copyright (C) 2017 Red Hat, Inc. +# Copyright (C) 2017-2020 Red Hat, Inc. # # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by @@ -42,7 +42,7 @@ trap "_cleanup; exit \$status" 0 1 2 3 15 _supported_fmt qcow2 _supported_proto file -echo "== Huge file ==" +echo "== Huge file without bitmaps ==" echo _make_test_img -o 'cluster_size=2M' 2T @@ -51,6 +51,49 @@ $QEMU_IMG measure -O raw -f qcow2 "$TEST_IMG" $QEMU_IMG measure -O qcow2 -o cluster_size=64k -f qcow2 "$TEST_IMG" $QEMU_IMG measure -O qcow2 -o cluster_size=2M -f qcow2 "$TEST_IMG" +echo +echo "== Huge file with bitmaps ==" +echo + +$QEMU_IMG bitmap --add --granularity 512 -f qcow2 "$TEST_IMG" b1 +$QEMU_IMG bitmap --add -g 2M -f qcow2 "$TEST_IMG" b2 + +# No bitmap without a source +$QEMU_IMG measure -O qcow2 --size 10M +# No bitmap output, since raw does not support it +$QEMU_IMG measure -O raw -f qcow2 "$TEST_IMG" +# No bitmap output, since no bitmaps on raw source. Munge required size, as +# some filesystems store the qcow2 file with less sparseness than others +$QEMU_IMG measure -O qcow2 -f raw "$TEST_IMG" | + sed '/^required size:/ s/[0-9][0-9]*/SIZE/' +# No bitmap output, since v2 does not support it +$QEMU_IMG measure -O qcow2 -o compat=0.10 -f qcow2 "$TEST_IMG" + +# Compute expected output: bitmap clusters + bitmap tables + bitmaps directory +echo +val2T=$((2*1024*1024*1024*1024)) +cluster=$((64*1024)) +b1clusters=$(( (val2T/512/8 + cluster - 1) / cluster )) +b2clusters=$(( (val2T/2/1024/1024/8 + cluster - 1) / cluster )) +echo expected bitmap $((b1clusters * cluster + + (b1clusters * 8 + cluster - 1) / cluster * cluster + + b2clusters * cluster + + (b2clusters * 8 + cluster - 1) / cluster * cluster + + cluster)) +$QEMU_IMG measure -O qcow2 -o cluster_size=64k -f qcow2 "$TEST_IMG" + +# Compute expected output: bitmap clusters + bitmap tables + bitmaps directory +echo +cluster=$((2*1024*1024)) +b1clusters=$(( (val2T/512/8 + cluster - 1) / cluster )) +b2clusters=$(( (val2T/2/1024/1024/8 + cluster - 1) / cluster )) +echo expected bitmap $((b1clusters * cluster + + (b1clusters * 8 + cluster - 1) / cluster * cluster + + b2clusters * cluster + + (b2clusters * 8 + cluster - 1) / cluster * cluster + + cluster)) +$QEMU_IMG measure --output=json -O qcow2 -o cluster_size=2M -f qcow2 "$TEST_IMG" + # success, all done echo "*** done" rm -f $seq.full diff --git a/tests/qemu-iotests/190.out b/tests/qemu-iotests/190.out index d001942002db..ed9d8214eb62 100644 --- a/tests/qemu-iotests/190.out +++ b/tests/qemu-iotests/190.out @@ -1,11 +1,36 @@ QA output created by 190 -== Huge file == +== Huge file without bitmaps == Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2199023255552 required size: 2199023255552 fully allocated size: 2199023255552 required size: 335806464 fully allocated size: 2199359062016 +bitmaps size: 0 required size: 18874368 fully allocated size: 2199042129920 +bitmaps size: 0 + +== Huge file with bitmaps == + +required size: 327680 +fully allocated size: 10813440 +required size: 2199023255552 +fully allocated size: 2199023255552 +required size: SIZE +fully allocated size: 17170432 +required size: 335806464 +fully allocated size: 2199359062016 + +expected bitmap 537198592 +required size: 335806464 +fully allocated size: 2199359062016 +bitmaps size: 537198592 + +expected bitmap 545259520 +{ + "bitmaps": 545259520, + "required": 18874368, + "fully-allocated": 2199042129920 +} *** done -- 2.26.2
