Re: [PATCH v2 3/6] qemu-nbd: add compression flag support

[Roman Kagan]

On Wed, Oct 02, 2019 at 05:22:43PM +0300, Andrey Shinkevich wrote:
> Added possibility to write compressed data by using the
> blk_write_compressed. This action has the limitations of the format
> driver. For example we can't write compressed data over other.
> 
> $ ./qemu-img create -f qcow2 -o size=10G ./image.qcow2
> $ sudo ./qemu-nbd -c /dev/nbd0 ./image.qcow2
> $ sudo dd if=/dev/sda1 of=/dev/nbd0 bs=10M count=10
> 10+0 records in
> 10+0 records out
> 104857600 bytes (105 MB) copied, 0,0890581 s, 1,2 GB/s
> $ sudo ./qemu-nbd -d /dev/nbd0
> $ du -sh ./image.qcow2
> 101M    ./image.qcow2
> 
> $ ./qemu-img create -f qcow2 -o size=10G ./image.qcow2
> $ sudo ./qemu-nbd -C -c /dev/nbd0 ./image.qcow2
> $ sudo dd if=/dev/sda1 of=/dev/nbd0 bs=10M count=10
> 10+0 records in
> 10+0 records out
> 104857600 bytes (105 MB) copied, 0,076046 s, 1,4 GB/s
> $ sudo ./qemu-nbd -d /dev/nbd0
> $ du -sh ./image.qcow2
> 5,3M    ./image.qcow2
> 
> Signed-off-by: Pavel Butsykin <address@hidden>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> Signed-off-by: Denis V. Lunev <address@hidden>
> Signed-off-by: Andrey Shinkevich <address@hidden>
> ---
>  blockdev-nbd.c      |  8 ++++++--
>  include/block/nbd.h | 11 +++++++++--
>  nbd/server.c        | 14 ++++++++++----
>  qemu-nbd.c          | 30 ++++++++++++++++++++++++++----
>  qemu-nbd.texi       |  2 ++
>  5 files changed, 53 insertions(+), 12 deletions(-)
> 
> diff --git a/blockdev-nbd.c b/blockdev-nbd.c
> index 6a8b206..e83036b 100644
> --- a/blockdev-nbd.c
> +++ b/blockdev-nbd.c
> @@ -151,6 +151,7 @@ void qmp_nbd_server_add(const char *device, bool 
> has_name, const char *name,
>      BlockBackend *on_eject_blk;
>      NBDExport *exp;
>      int64_t len;
> +    uint32_t iflags = 0;
>      AioContext *aio_context;
>  
>      if (!nbd_server) {
> @@ -189,9 +190,12 @@ void qmp_nbd_server_add(const char *device, bool 
> has_name, const char *name,
>      if (bdrv_is_read_only(bs)) {
>          writable = false;
>      }
> +    if (!writable) {
> +        iflags = NBD_INTERNAL_FLAG_READONLY | NBD_INTERNAL_FLAG_SHARED;
> +    }
>  
> -    exp = nbd_export_new(bs, 0, len, name, NULL, bitmap, !writable, 
> !writable,
> -                         NULL, false, on_eject_blk, errp);
> +    exp = nbd_export_new(bs, 0, len, name, NULL, bitmap, iflags, NULL,
> +                         on_eject_blk, errp);
>      if (!exp) {
>          goto out;
>      }
> diff --git a/include/block/nbd.h b/include/block/nbd.h
> index 316fd70..80be9d5 100644
> --- a/include/block/nbd.h
> +++ b/include/block/nbd.h
> @@ -25,6 +25,13 @@
>  #include "crypto/tlscreds.h"
>  #include "qapi/error.h"
>  
> +enum {
> +    NBD_INTERNAL_FLAG_READONLY     = 1 << 0, /* Device is read-only */
> +    NBD_INTERNAL_FLAG_SHARED       = 1 << 1, /* Device can be shared */
> +    NBD_INTERNAL_FLAG_WRITETHROUGH = 1 << 2, /* Enable write cache */
> +    NBD_INTERNAL_FLAG_COMPRESS     = 1 << 3, /* Use compressed write */
> +};
> +
>  /* Handshake phase structs - this struct is passed on the wire */
>  
>  struct NBDOption {
> @@ -330,8 +337,8 @@ typedef struct NBDClient NBDClient;
>  
>  NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
>                            uint64_t size, const char *name, const char *desc,
> -                          const char *bitmap, bool readonly, bool shared,
> -                          void (*close)(NBDExport *), bool writethrough,
> +                          const char *bitmap, uint32_t iflags,
> +                          void (*close)(NBDExport *),
>                            BlockBackend *on_eject_blk, Error **errp);
>  void nbd_export_close(NBDExport *exp);
>  void nbd_export_remove(NBDExport *exp, NbdServerRemoveMode mode, Error 
> **errp);
> diff --git a/nbd/server.c b/nbd/server.c
> index d8d1e62..cf3b75d 100644
> --- a/nbd/server.c
> +++ b/nbd/server.c
> @@ -91,6 +91,7 @@ struct NBDExport {
>      uint16_t nbdflags;
>      QTAILQ_HEAD(, NBDClient) clients;
>      QTAILQ_ENTRY(NBDExport) next;
> +    uint32_t iflags;
>  
>      AioContext *ctx;
>  
> @@ -1471,13 +1472,14 @@ static void nbd_eject_notifier(Notifier *n, void 
> *data)
>  
>  NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
>                            uint64_t size, const char *name, const char *desc,
> -                          const char *bitmap, bool readonly, bool shared,
> -                          void (*close)(NBDExport *), bool writethrough,
> +                          const char *bitmap, uint32_t iflags,
> +                          void (*close)(NBDExport *),
>                            BlockBackend *on_eject_blk, Error **errp)
>  {
>      AioContext *ctx;
>      BlockBackend *blk;
>      NBDExport *exp = g_new0(NBDExport, 1);
> +    bool readonly = iflags & NBD_INTERNAL_FLAG_READONLY;
>      uint64_t perm;
>      int ret;
>  
> @@ -1504,7 +1506,7 @@ NBDExport *nbd_export_new(BlockDriverState *bs, 
> uint64_t dev_offset,
>      if (ret < 0) {
>          goto fail;
>      }
> -    blk_set_enable_write_cache(blk, !writethrough);
> +    blk_set_enable_write_cache(blk, !(iflags & 
> NBD_INTERNAL_FLAG_WRITETHROUGH));
>      blk_set_allow_aio_context_change(blk, true);
>  
>      exp->refcount = 1;
> @@ -1518,13 +1520,14 @@ NBDExport *nbd_export_new(BlockDriverState *bs, 
> uint64_t dev_offset,
>                       NBD_FLAG_SEND_FUA | NBD_FLAG_SEND_CACHE);
>      if (readonly) {
>          exp->nbdflags |= NBD_FLAG_READ_ONLY;
> -        if (shared) {
> +        if (iflags & NBD_INTERNAL_FLAG_SHARED) {
>              exp->nbdflags |= NBD_FLAG_CAN_MULTI_CONN;
>          }
>      } else {
>          exp->nbdflags |= (NBD_FLAG_SEND_TRIM | NBD_FLAG_SEND_WRITE_ZEROES |
>                            NBD_FLAG_SEND_FAST_ZERO);
>      }
> +    exp->iflags = iflags;
>      assert(size <= INT64_MAX - dev_offset);
>      exp->size = QEMU_ALIGN_DOWN(size, BDRV_SECTOR_SIZE);
>  
> @@ -2312,6 +2315,9 @@ static coroutine_fn int nbd_handle_request(NBDClient 
> *client,
>          if (request->flags & NBD_CMD_FLAG_FUA) {
>              flags |= BDRV_REQ_FUA;
>          }
> +        if (exp->iflags & NBD_INTERNAL_FLAG_COMPRESS) {
> +            flags |= BDRV_REQ_WRITE_COMPRESSED;
> +        }
>          ret = blk_pwrite(exp->blk, request->from + exp->dev_offset,
>                           data, request->len, flags);
>          return nbd_send_generic_reply(client, request->handle, ret,
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index 9032b6d..4163135 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -139,6 +139,7 @@ static void usage(const char *name)
>  "      --discard=MODE        set discard mode (ignore, unmap)\n"
>  "      --detect-zeroes=MODE  set detect-zeroes mode (off, on, unmap)\n"
>  "      --image-opts          treat FILE as a full set of image options\n"
> +"  -C, --compress            use data compression (if the target format 
> supports it)\n"
>  "\n"
>  QEMU_HELP_BOTTOM "\n"
>      , name, name, NBD_DEFAULT_PORT, "DEVICE");
> @@ -602,6 +603,7 @@ int main(int argc, char **argv)
>      BlockDriverState *bs;
>      uint64_t dev_offset = 0;
>      bool readonly = false;
> +    uint32_t iflags = 0;
>      bool disconnect = false;
>      const char *bindto = NULL;
>      const char *port = NULL;
> @@ -610,7 +612,7 @@ int main(int argc, char **argv)
>      int64_t fd_size;
>      QemuOpts *sn_opts = NULL;
>      const char *sn_id_or_name = NULL;
> -    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:x:T:D:B:L";
> +    const char *sopt = "hVb:o:p:rsnCP:c:dvk:e:f:tl:x:T:D:B:L";
>      struct option lopt[] = {
>          { "help", no_argument, NULL, 'h' },
>          { "version", no_argument, NULL, 'V' },
> @@ -619,6 +621,7 @@ int main(int argc, char **argv)
>          { "socket", required_argument, NULL, 'k' },
>          { "offset", required_argument, NULL, 'o' },
>          { "read-only", no_argument, NULL, 'r' },
> +        { "compress", no_argument, NULL, 'C'},
>          { "partition", required_argument, NULL, 'P' },
>          { "bitmap", required_argument, NULL, 'B' },
>          { "connect", required_argument, NULL, 'c' },
> @@ -786,6 +789,9 @@ int main(int argc, char **argv)
>              readonly = true;
>              flags &= ~BDRV_O_RDWR;
>              break;
> +        case 'C':
> +            iflags |= NBD_INTERNAL_FLAG_COMPRESS;
> +            break;
>          case 'P':
>              warn_report("The '-P' option is deprecated; use --image-opts 
> with "
>                          "a raw device wrapper for subset exports instead");
> @@ -1117,6 +1123,14 @@ int main(int argc, char **argv)
>  
>      blk_set_enable_write_cache(blk, !writethrough);
>  
> +    if ((iflags & NBD_INTERNAL_FLAG_COMPRESS) &&
> +        !(bs->drv && bs->drv->bdrv_co_pwritev_compressed_part))
> +    {
> +        error_report("Compression not supported for this file format %s",
> +                     argv[optind]);
> +        exit(EXIT_FAILURE);
> +    }
> +
>      if (sn_opts) {
>          ret = bdrv_snapshot_load_tmp(bs,
>                                       qemu_opt_get(sn_opts, SNAPSHOT_OPT_ID),
> @@ -1173,10 +1187,18 @@ int main(int argc, char **argv)
>          fd_size = limit;
>      }
>  
> +    if (writethrough) {
> +        iflags |= NBD_INTERNAL_FLAG_WRITETHROUGH;
> +    }
> +    if (readonly) {
> +        iflags |= NBD_INTERNAL_FLAG_READONLY;
> +    }
> +    if (shared > 1) {
> +        iflags |= NBD_INTERNAL_FLAG_SHARED;
> +    }
>      export = nbd_export_new(bs, dev_offset, fd_size, export_name,
> -                            export_description, bitmap, readonly, shared > 1,
> -                            nbd_export_closed, writethrough, NULL,
> -                            &error_fatal);
> +                            export_description, bitmap, iflags,
> +                            nbd_export_closed, NULL, &error_fatal);
>  
>      if (device) {
>  #if HAVE_NBD_DEVICE
> diff --git a/qemu-nbd.texi b/qemu-nbd.texi
> index 7f55657..26ea1ec 100644
> --- a/qemu-nbd.texi
> +++ b/qemu-nbd.texi
> @@ -55,6 +55,8 @@ Force the use of the block driver for format @var{fmt} 
> instead of
>  auto-detecting.
>  @item -r, --read-only
>  Export the disk as read-only.
> +@item -C, --compress
> +Use data compression (if the target format supports it)
>  @item -P, --partition=@var{num}
>  Deprecated: Only expose MBR partition @var{num}.  Understands physical
>  partitions 1-4 and logical partition 5. New code should instead use

I wonder if we're better off adding a generic blockdev option instead,
so that all tools can benefit from it?

Roman.