[PATCH v9 0/3] qcow2: advanced compression options

[PATCH v9 0/3] qcow2: advanced compression options

[Andrey Shinkevich]

The compression filter driver is introduced as suggested by Max.
A sample usage of the filter can be found in the test #214.
Now, multiple clusters can be written compressed.
It is useful for the backup job.

v9: The filter functions unrelated to the 'file' child were removed.
    The check for compression support in bs->file is checked in the
    compress_open().

  Discussed in the email thread with the message ID
  <1574056144-625164-1-git-send-email-andrey.shinkevich@virtuozzo.com>

Andrey Shinkevich (3):
  block: introduce compress filter driver
  qcow2: Allow writing compressed data of multiple clusters
  tests/qemu-iotests: add case to write compressed data of multiple
    clusters

 block/Makefile.objs        |   1 +
 block/filter-compress.c    | 190 +++++++++++++++++++++++++++++++++++++++++++++
 block/qcow2.c              | 102 +++++++++++++++++-------
 qapi/block-core.json       |  10 ++-
 tests/qemu-iotests/214     |  43 ++++++++++
 tests/qemu-iotests/214.out |  14 ++++
 6 files changed, 329 insertions(+), 31 deletions(-)
 create mode 100644 block/filter-compress.c

-- 
1.8.3.1

[PATCH v9 1/3] block: introduce compress filter driver

[Andrey Shinkevich]

Allow writing all the data compressed through the filter driver.
The written data will be aligned by the cluster size.
Based on the QEMU current implementation, that data can be written to
unallocated clusters only. May be used for a backup job.

Suggested-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
 block/Makefile.objs     |   1 +
 block/filter-compress.c | 190 ++++++++++++++++++++++++++++++++++++++++++++++++
 qapi/block-core.json    |  10 ++-
 3 files changed, 197 insertions(+), 4 deletions(-)
 create mode 100644 block/filter-compress.c

diff --git a/block/Makefile.objs b/block/Makefile.objs
index e394fe0..330529b 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -43,6 +43,7 @@ block-obj-y += crypto.o
 
 block-obj-y += aio_task.o
 block-obj-y += backup-top.o
+block-obj-y += filter-compress.o
 
 common-obj-y += stream.o
 
diff --git a/block/filter-compress.c b/block/filter-compress.c
new file mode 100644
index 0000000..ef4b12b
--- /dev/null
+++ b/block/filter-compress.c
@@ -0,0 +1,190 @@
+/*
+ * Compress filter block driver
+ *
+ * Copyright (c) 2019 Virtuozzo International GmbH
+ *
+ * Author:
+ *   Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
+ *   (based on block/copy-on-read.c by Max Reitz)
+ *
+ * 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 the Free Software Foundation; either version 2 or
+ * (at your option) any later version of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "block/block_int.h"
+#include "qemu/module.h"
+#include "qapi/error.h"
+
+
+static int compress_open(BlockDriverState *bs, QDict *options, int flags,
+                         Error **errp)
+{
+    bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file, false,
+                               errp);
+    if (!bs->file) {
+        return -EINVAL;
+    }
+
+    if (!bs->file->bs->drv || !block_driver_can_compress(bs->file->bs->drv)) {
+        error_setg(errp, "Compression is not supported with this drive %s",
+                   bdrv_get_device_name(bs->file->bs));
+        return -ENOTSUP;
+    }
+
+    bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
+        (BDRV_REQ_FUA & bs->file->bs->supported_write_flags);
+
+    bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
+        ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
+            bs->file->bs->supported_zero_flags);
+
+    return 0;
+}
+
+
+#define PERM_PASSTHROUGH (BLK_PERM_CONSISTENT_READ \
+                          | BLK_PERM_WRITE \
+                          | BLK_PERM_RESIZE)
+#define PERM_UNCHANGED (BLK_PERM_ALL & ~PERM_PASSTHROUGH)
+
+static void compress_child_perm(BlockDriverState *bs, BdrvChild *c,
+                                const BdrvChildRole *role,
+                                BlockReopenQueue *reopen_queue,
+                                uint64_t perm, uint64_t shared,
+                                uint64_t *nperm, uint64_t *nshared)
+{
+    *nperm = perm & PERM_PASSTHROUGH;
+    *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED;
+
+    /*
+     * We must not request write permissions for an inactive node, the child
+     * cannot provide it.
+     */
+    if (!(bs->open_flags & BDRV_O_INACTIVE)) {
+        *nperm |= BLK_PERM_WRITE_UNCHANGED;
+    }
+}
+
+
+static int64_t compress_getlength(BlockDriverState *bs)
+{
+    return bdrv_getlength(bs->file->bs);
+}
+
+
+static int coroutine_fn compress_co_preadv_part(BlockDriverState *bs,
+                                                uint64_t offset, uint64_t bytes,
+                                                QEMUIOVector *qiov,
+                                                size_t qiov_offset,
+                                                int flags)
+{
+    return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset,
+                               flags);
+}
+
+
+static int coroutine_fn compress_co_pwritev_part(BlockDriverState *bs,
+                                                 uint64_t offset,
+                                                 uint64_t bytes,
+                                                 QEMUIOVector *qiov,
+                                                 size_t qiov_offset, int flags)
+{
+    return bdrv_co_pwritev_part(bs->file, offset, bytes, qiov, qiov_offset,
+                                flags | BDRV_REQ_WRITE_COMPRESSED);
+}
+
+
+static int coroutine_fn compress_co_pwrite_zeroes(BlockDriverState *bs,
+                                                  int64_t offset, int bytes,
+                                                  BdrvRequestFlags flags)
+{
+    return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
+}
+
+
+static int coroutine_fn compress_co_pdiscard(BlockDriverState *bs,
+                                             int64_t offset, int bytes)
+{
+    return bdrv_co_pdiscard(bs->file, offset, bytes);
+}
+
+
+static void compress_refresh_limits(BlockDriverState *bs, Error **errp)
+{
+    BlockDriverInfo bdi;
+    int ret;
+
+    if (!bs->file) {
+        return;
+    }
+
+    ret = bdrv_get_info(bs->file->bs, &bdi);
+    if (ret < 0 || bdi.cluster_size == 0) {
+        return;
+    }
+
+    bs->bl.request_alignment = bdi.cluster_size;
+}
+
+
+static void compress_eject(BlockDriverState *bs, bool eject_flag)
+{
+    bdrv_eject(bs->file->bs, eject_flag);
+}
+
+
+static void compress_lock_medium(BlockDriverState *bs, bool locked)
+{
+    bdrv_lock_medium(bs->file->bs, locked);
+}
+
+
+static bool compress_recurse_is_first_non_filter(BlockDriverState *bs,
+                                                 BlockDriverState *candidate)
+{
+    return bdrv_recurse_is_first_non_filter(bs->file->bs, candidate);
+}
+
+
+static BlockDriver bdrv_compress = {
+    .format_name                        = "compress",
+
+    .bdrv_open                          = compress_open,
+    .bdrv_child_perm                    = compress_child_perm,
+
+    .bdrv_getlength                     = compress_getlength,
+
+    .bdrv_co_preadv_part                = compress_co_preadv_part,
+    .bdrv_co_pwritev_part               = compress_co_pwritev_part,
+    .bdrv_co_pwrite_zeroes              = compress_co_pwrite_zeroes,
+    .bdrv_co_pdiscard                   = compress_co_pdiscard,
+    .bdrv_refresh_limits                = compress_refresh_limits,
+
+    .bdrv_eject                         = compress_eject,
+    .bdrv_lock_medium                   = compress_lock_medium,
+
+    .bdrv_co_block_status               = bdrv_co_block_status_from_backing,
+
+    .bdrv_recurse_is_first_non_filter   = compress_recurse_is_first_non_filter,
+
+    .has_variable_length                = true,
+    .is_filter                          = true,
+};
+
+static void bdrv_compress_init(void)
+{
+    bdrv_register(&bdrv_compress);
+}
+
+block_init(bdrv_compress_init);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index aa97ee2..2f34703 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -2884,15 +2884,16 @@
 # @copy-on-read: Since 3.0
 # @blklogwrites: Since 3.0
 # @blkreplay: Since 4.2
+# @compress: Since 5.0
 #
 # Since: 2.9
 ##
 { 'enum': 'BlockdevDriver',
   'data': [ 'blkdebug', 'blklogwrites', 'blkreplay', 'blkverify', 'bochs',
-            'cloop', 'copy-on-read', 'dmg', 'file', 'ftp', 'ftps', 'gluster',
-            'host_cdrom', 'host_device', 'http', 'https', 'iscsi', 'luks',
-            'nbd', 'nfs', 'null-aio', 'null-co', 'nvme', 'parallels', 'qcow',
-            'qcow2', 'qed', 'quorum', 'raw', 'rbd',
+            'cloop', 'copy-on-read', 'compress', 'dmg', 'file', 'ftp', 'ftps',
+            'gluster', 'host_cdrom', 'host_device', 'http', 'https', 'iscsi',
+            'luks', 'nbd', 'nfs', 'null-aio', 'null-co', 'nvme', 'parallels',
+            'qcow', 'qcow2', 'qed', 'quorum', 'raw', 'rbd',
             { 'name': 'replication', 'if': 'defined(CONFIG_REPLICATION)' },
             'sheepdog',
             'ssh', 'throttle', 'vdi', 'vhdx', 'vmdk', 'vpc', 'vvfat', 'vxhs' ] }
@@ -4045,6 +4046,7 @@
       'bochs':      'BlockdevOptionsGenericFormat',
       'cloop':      'BlockdevOptionsGenericFormat',
       'copy-on-read':'BlockdevOptionsGenericFormat',
+      'compress':   'BlockdevOptionsGenericFormat',
       'dmg':        'BlockdevOptionsGenericFormat',
       'file':       'BlockdevOptionsFile',
       'ftp':        'BlockdevOptionsCurlFtp',
-- 
1.8.3.1

[PATCH v9 2/3] qcow2: Allow writing compressed data of multiple clusters

[Andrey Shinkevich]

QEMU currently supports writing compressed data of the size equal to
one cluster. This patch allows writing QCOW2 compressed data that
exceed one cluster. Now, we split buffered data into separate clusters
and write them compressed using the block/aio_task API.

Suggested-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/qcow2.c | 102 ++++++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 75 insertions(+), 27 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index 7c18721..0e03a1a 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -4222,10 +4222,8 @@ fail:
     return ret;
 }
 
-/* XXX: put compressed sectors first, then all the cluster aligned
-   tables to avoid losing bytes in alignment */
 static coroutine_fn int
-qcow2_co_pwritev_compressed_part(BlockDriverState *bs,
+qcow2_co_pwritev_compressed_task(BlockDriverState *bs,
                                  uint64_t offset, uint64_t bytes,
                                  QEMUIOVector *qiov, size_t qiov_offset)
 {
@@ -4235,32 +4233,11 @@ qcow2_co_pwritev_compressed_part(BlockDriverState *bs,
     uint8_t *buf, *out_buf;
     uint64_t cluster_offset;
 
-    if (has_data_file(bs)) {
-        return -ENOTSUP;
-    }
-
-    if (bytes == 0) {
-        /* align end of file to a sector boundary to ease reading with
-           sector based I/Os */
-        int64_t len = bdrv_getlength(bs->file->bs);
-        if (len < 0) {
-            return len;
-        }
-        return bdrv_co_truncate(bs->file, len, false, PREALLOC_MODE_OFF, NULL);
-    }
-
-    if (offset_into_cluster(s, offset)) {
-        return -EINVAL;
-    }
+    assert(bytes == s->cluster_size || (bytes < s->cluster_size &&
+           (offset + bytes == bs->total_sectors << BDRV_SECTOR_BITS)));
 
     buf = qemu_blockalign(bs, s->cluster_size);
-    if (bytes != s->cluster_size) {
-        if (bytes > s->cluster_size ||
-            offset + bytes != bs->total_sectors << BDRV_SECTOR_BITS)
-        {
-            qemu_vfree(buf);
-            return -EINVAL;
-        }
+    if (bytes < s->cluster_size) {
         /* Zero-pad last write if image size is not cluster aligned */
         memset(buf + bytes, 0, s->cluster_size - bytes);
     }
@@ -4309,6 +4286,77 @@ fail:
     return ret;
 }
 
+static coroutine_fn int qcow2_co_pwritev_compressed_task_entry(AioTask *task)
+{
+    Qcow2AioTask *t = container_of(task, Qcow2AioTask, task);
+
+    assert(!t->cluster_type && !t->l2meta);
+
+    return qcow2_co_pwritev_compressed_task(t->bs, t->offset, t->bytes, t->qiov,
+                                            t->qiov_offset);
+}
+
+/*
+ * XXX: put compressed sectors first, then all the cluster aligned
+ * tables to avoid losing bytes in alignment
+ */
+static coroutine_fn int
+qcow2_co_pwritev_compressed_part(BlockDriverState *bs,
+                                 uint64_t offset, uint64_t bytes,
+                                 QEMUIOVector *qiov, size_t qiov_offset)
+{
+    BDRVQcow2State *s = bs->opaque;
+    AioTaskPool *aio = NULL;
+    int ret = 0;
+
+    if (has_data_file(bs)) {
+        return -ENOTSUP;
+    }
+
+    if (bytes == 0) {
+        /*
+         * align end of file to a sector boundary to ease reading with
+         * sector based I/Os
+         */
+        int64_t len = bdrv_getlength(bs->file->bs);
+        if (len < 0) {
+            return len;
+        }
+        return bdrv_co_truncate(bs->file, len, false, PREALLOC_MODE_OFF, NULL);
+    }
+
+    if (offset_into_cluster(s, offset)) {
+        return -EINVAL;
+    }
+
+    while (bytes && aio_task_pool_status(aio) == 0) {
+        uint64_t chunk_size = MIN(bytes, s->cluster_size);
+
+        if (!aio && chunk_size != bytes) {
+            aio = aio_task_pool_new(QCOW2_MAX_WORKERS);
+        }
+
+        ret = qcow2_add_task(bs, aio, qcow2_co_pwritev_compressed_task_entry,
+                             0, 0, offset, chunk_size, qiov, qiov_offset, NULL);
+        if (ret < 0) {
+            break;
+        }
+        qiov_offset += chunk_size;
+        offset += chunk_size;
+        bytes -= chunk_size;
+    }
+
+    if (aio) {
+        aio_task_pool_wait_all(aio);
+        if (ret == 0) {
+            ret = aio_task_pool_status(aio);
+        }
+        g_free(aio);
+    }
+
+    return ret;
+}
+
 static int coroutine_fn
 qcow2_co_preadv_compressed(BlockDriverState *bs,
                            uint64_t file_cluster_offset,
-- 
1.8.3.1

[PATCH v9 3/3] tests/qemu-iotests: add case to write compressed data of multiple clusters

[Andrey Shinkevich]

Add the case to the iotest #214 that checks possibility of writing
compressed data of more than one cluster size. The test case involves
the compress filter driver showing a sample usage of that.

Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 tests/qemu-iotests/214     | 43 +++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/214.out | 14 ++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/tests/qemu-iotests/214 b/tests/qemu-iotests/214
index 21ec8a2..aacf66f 100755
--- a/tests/qemu-iotests/214
+++ b/tests/qemu-iotests/214
@@ -89,6 +89,49 @@ _check_test_img -r all
 $QEMU_IO -c "read  -P 0x11  0 4M" "$TEST_IMG" 2>&1 | _filter_qemu_io | _filter_testdir
 $QEMU_IO -c "read  -P 0x22 4M 4M" "$TEST_IMG" 2>&1 | _filter_qemu_io | _filter_testdir
 
+echo
+echo "=== Write compressed data of multiple clusters ==="
+echo
+cluster_size=0x10000
+_make_test_img 2M -o cluster_size=$cluster_size
+
+echo "Write uncompressed data:"
+let data_size="8 * $cluster_size"
+$QEMU_IO -c "write -P 0xaa 0 $data_size" "$TEST_IMG" \
+         2>&1 | _filter_qemu_io | _filter_testdir
+sizeA=$($QEMU_IMG info --output=json "$TEST_IMG" |
+        sed -n '/"actual-size":/ s/[^0-9]//gp')
+
+_make_test_img 2M -o cluster_size=$cluster_size
+echo "Write compressed data:"
+let data_size="3 * $cluster_size + $cluster_size / 2"
+# Set compress on. That will align the written data
+# by the cluster size and will write them compressed.
+QEMU_IO_OPTIONS=$QEMU_IO_OPTIONS_NO_FMT \
+$QEMU_IO -c "write -P 0xbb 0 $data_size" --image-opts \
+         "driver=compress,file.driver=$IMGFMT,file.file.driver=file,file.file.filename=$TEST_IMG" \
+         2>&1 | _filter_qemu_io | _filter_testdir
+
+let offset="4 * $cluster_size + $cluster_size / 4"
+QEMU_IO_OPTIONS=$QEMU_IO_OPTIONS_NO_FMT \
+$QEMU_IO -c "write -P 0xcc $offset $data_size" "json:{\
+    'driver': 'compress',
+    'file': {'driver': '$IMGFMT',
+             'file': {'driver': 'file',
+                      'filename': '$TEST_IMG'}}}" | \
+                          _filter_qemu_io | _filter_testdir
+
+sizeB=$($QEMU_IMG info --output=json "$TEST_IMG" |
+        sed -n '/"actual-size":/ s/[^0-9]//gp')
+
+if [ $sizeA -le $sizeB ]
+then
+    echo "Compression ERROR"
+fi
+
+$QEMU_IMG check --output=json "$TEST_IMG" |
+          sed -n 's/,$//; /"compressed-clusters":/ s/^ *//p'
+
 # success, all done
 echo '*** done'
 rm -f $seq.full
diff --git a/tests/qemu-iotests/214.out b/tests/qemu-iotests/214.out
index 0fcd8dc..9fc6728 100644
--- a/tests/qemu-iotests/214.out
+++ b/tests/qemu-iotests/214.out
@@ -32,4 +32,18 @@ read 4194304/4194304 bytes at offset 0
 4 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 4194304/4194304 bytes at offset 4194304
 4 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+=== Write compressed data of multiple clusters ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2097152
+Write uncompressed data:
+wrote 524288/524288 bytes at offset 0
+512 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2097152
+Write compressed data:
+wrote 229376/229376 bytes at offset 0
+224 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 229376/229376 bytes at offset 278528
+224 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+"compressed-clusters": 8
 *** done
-- 
1.8.3.1

Re: [PATCH v9 1/3] block: introduce compress filter driver

[Eric Blake]

On 11/26/19 8:43 AM, Andrey Shinkevich wrote:
> Allow writing all the data compressed through the filter driver.
> The written data will be aligned by the cluster size.
> Based on the QEMU current implementation, that data can be written to
> unallocated clusters only. May be used for a backup job.
> 
> Suggested-by: Max Reitz <mreitz@redhat.com>
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---

> +++ b/qapi/block-core.json
> @@ -2884,15 +2884,16 @@
>   # @copy-on-read: Since 3.0
>   # @blklogwrites: Since 3.0
>   # @blkreplay: Since 4.2
> +# @compress: Since 5.0
>   #
>   # Since: 2.9
>   ##
>   { 'enum': 'BlockdevDriver',
>     'data': [ 'blkdebug', 'blklogwrites', 'blkreplay', 'blkverify', 'bochs',
> -            'cloop', 'copy-on-read', 'dmg', 'file', 'ftp', 'ftps', 'gluster',
> -            'host_cdrom', 'host_device', 'http', 'https', 'iscsi', 'luks',
> -            'nbd', 'nfs', 'null-aio', 'null-co', 'nvme', 'parallels', 'qcow',
> -            'qcow2', 'qed', 'quorum', 'raw', 'rbd',
> +            'cloop', 'copy-on-read', 'compress', 'dmg', 'file', 'ftp', 'ftps',

Nit: Preserving alphabetical ordering means 'compress' comes before 
'copy-on-read'.

> +            'gluster', 'host_cdrom', 'host_device', 'http', 'https', 'iscsi',
> +            'luks', 'nbd', 'nfs', 'null-aio', 'null-co', 'nvme', 'parallels',
> +            'qcow', 'qcow2', 'qed', 'quorum', 'raw', 'rbd',
>               { 'name': 'replication', 'if': 'defined(CONFIG_REPLICATION)' },
>               'sheepdog',
>               'ssh', 'throttle', 'vdi', 'vhdx', 'vmdk', 'vpc', 'vvfat', 'vxhs' ] }
> @@ -4045,6 +4046,7 @@
>         'bochs':      'BlockdevOptionsGenericFormat',
>         'cloop':      'BlockdevOptionsGenericFormat',
>         'copy-on-read':'BlockdevOptionsGenericFormat',
> +      'compress':   'BlockdevOptionsGenericFormat',

and again

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

Re: [PATCH v9 1/3] block: introduce compress filter driver

[Max Reitz]

[-- Attachment #1.1: Type: text/plain, Size: 2085 bytes --]

On 26.11.19 15:43, Andrey Shinkevich wrote:
> Allow writing all the data compressed through the filter driver.
> The written data will be aligned by the cluster size.
> Based on the QEMU current implementation, that data can be written to
> unallocated clusters only. May be used for a backup job.
> 
> Suggested-by: Max Reitz <mreitz@redhat.com>
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
>  block/Makefile.objs     |   1 +
>  block/filter-compress.c | 190 ++++++++++++++++++++++++++++++++++++++++++++++++
>  qapi/block-core.json    |  10 ++-
>  3 files changed, 197 insertions(+), 4 deletions(-)
>  create mode 100644 block/filter-compress.c

[...]

> diff --git a/block/filter-compress.c b/block/filter-compress.c
> new file mode 100644
> index 0000000..ef4b12b
> --- /dev/null
> +++ b/block/filter-compress.c

[...]

> +#define PERM_PASSTHROUGH (BLK_PERM_CONSISTENT_READ \
> +                          | BLK_PERM_WRITE \
> +                          | BLK_PERM_RESIZE)
> +#define PERM_UNCHANGED (BLK_PERM_ALL & ~PERM_PASSTHROUGH)
> +
> +static void compress_child_perm(BlockDriverState *bs, BdrvChild *c,
> +                                const BdrvChildRole *role,
> +                                BlockReopenQueue *reopen_queue,
> +                                uint64_t perm, uint64_t shared,
> +                                uint64_t *nperm, uint64_t *nshared)
> +{
> +    *nperm = perm & PERM_PASSTHROUGH;
> +    *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED;
> +
> +    /*
> +     * We must not request write permissions for an inactive node, the child
> +     * cannot provide it.
> +     */
> +    if (!(bs->open_flags & BDRV_O_INACTIVE)) {
> +        *nperm |= BLK_PERM_WRITE_UNCHANGED;
> +    }

The copy-on-read filter has to take the WRITE_UNCHANGED permission
because it will do such writes for every read, but I don’t think this
driver ever needs to take this permission.  Therefore it should be
enough to use bdrv_filter_default_perms for .bdrv_child_perm.

Max


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Re: [PATCH v9 2/3] qcow2: Allow writing compressed data of multiple clusters

[Max Reitz]

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On 26.11.19 15:43, Andrey Shinkevich wrote:
> QEMU currently supports writing compressed data of the size equal to
> one cluster. This patch allows writing QCOW2 compressed data that
> exceed one cluster. Now, we split buffered data into separate clusters
> and write them compressed using the block/aio_task API.
> 
> Suggested-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
> Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/qcow2.c | 102 ++++++++++++++++++++++++++++++++++++++++++----------------
>  1 file changed, 75 insertions(+), 27 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>


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Re: [PATCH v9 3/3] tests/qemu-iotests: add case to write compressed data of multiple clusters

[Max Reitz]

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On 26.11.19 15:43, Andrey Shinkevich wrote:
> Add the case to the iotest #214 that checks possibility of writing
> compressed data of more than one cluster size. The test case involves
> the compress filter driver showing a sample usage of that.
> 
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  tests/qemu-iotests/214     | 43 +++++++++++++++++++++++++++++++++++++++++++
>  tests/qemu-iotests/214.out | 14 ++++++++++++++
>  2 files changed, 57 insertions(+)

Reviewed-by: Max Reitz <mreitz@redhat.com>


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