Re: [PATCH v8 1/3] block: introduce compress filter driver

[Vladimir Sementsov-Ogievskiy]

18.11.2019 8:49, 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 <address@hidden>
> Signed-off-by: Andrey Shinkevich <address@hidden>
> ---
>   block/Makefile.objs     |   1 +
>   block/filter-compress.c | 201 
> ++++++++++++++++++++++++++++++++++++++++++++++++
>   qapi/block-core.json    |  10 ++-
>   3 files changed, 208 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..522d6c3
> --- /dev/null
> +++ b/block/filter-compress.c
> @@ -0,0 +1,201 @@
> +/*
> + * Compress filter block driver
> + *
> + * Copyright (c) 2019 Virtuozzo International GmbH
> + *
> + * Author:
> + *   Andrey Shinkevich <address@hidden>
> + *   (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"
> +
> +
> +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;
> +    }

Let's check here compression support in bs->file and if it isn't, return error.

> +
> +    bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
> +        BDRV_REQ_WRITE_COMPRESSED |

Not sure that we want this flag, but it doesn't hurt

> +        (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.
> +     */

I don't know why we need this logic, but it's just a copy from COR filter..

> +    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_truncate(BlockDriverState *bs,
> +                                             int64_t offset, bool exact,
> +                                             PreallocMode prealloc,
> +                                             Error **errp)
> +{
> +    return bdrv_co_truncate(bs->file, offset, exact, prealloc, errp);
> +}

COR don't have this handler.. Do we need it?

I see, bdrv_co_truncate has own filter recursion, so we don't need it.

> +
> +
> +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);
> +}

OK, that's the main thing)

> +
> +
> +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 int compress_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
> +{
> +    return bdrv_get_info(bs->file->bs, bdi);
> +}

COR don't have this handler, do we need it?

Look at bdrv_get_info, it has own filter recursion, so, we don't need it.


> +
> +
> +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;
> +}

OK, this is significant.

> +
> +
> +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_truncate                   = compress_co_truncate,
> +
> +    .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_get_info                      = compress_get_info,
> +    .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',
> 


-- 
Best regards,
Vladimir