Re: [Qemu-devel] [Qemu-block] [PATCH v3] LUKS: support preallocation

[Maxim Levitsky <mlevitsk@redhat.com>]

On Thu, 2019-07-11 at 18:27 +0200, Stefano Garzarella wrote:
> On Thu, Jul 11, 2019 at 06:09:40PM +0300, Maxim Levitsky wrote:
> > preallocation=off and preallocation=metadata
> > both allocate luks header only, and preallocation=falloc/full
> > is passed to underlying file.
> > 
> > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1534951
> > 
> > Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> > 
> > ---
> > 
> > Note that QMP support was only compile tested, since I am still learning
> > on how to use it.
> > 
> > If there is some library/script/etc which makes it more high level,
> > I would more that glad to hear about it. So far I used the qmp-shell
> > 
> > Also can I use qmp's blockdev-create outside a vm running?
> > 
> >  block/crypto.c       | 29 ++++++++++++++++++++++++++---
> >  qapi/block-core.json |  5 ++++-
> >  2 files changed, 30 insertions(+), 4 deletions(-)
> > 
> > diff --git a/block/crypto.c b/block/crypto.c
> > index 8237424ae6..034a645652 100644
> > --- a/block/crypto.c
> > +++ b/block/crypto.c
> > @@ -74,6 +74,7 @@ static ssize_t block_crypto_read_func(QCryptoBlock *block,
> >  struct BlockCryptoCreateData {
> >      BlockBackend *blk;
> >      uint64_t size;
> > +    PreallocMode prealloc;
> >  };
> >  
> >  
> > @@ -112,7 +113,7 @@ static ssize_t block_crypto_init_func(QCryptoBlock *block,
> >       * available to the guest, so we must take account of that
> >       * which will be used by the crypto header
> >       */
> > -    return blk_truncate(data->blk, data->size + headerlen, PREALLOC_MODE_OFF,
> > +    return blk_truncate(data->blk, data->size + headerlen, data->prealloc,
> >                          errp);
> >  }
> >  
> > @@ -251,6 +252,7 @@ static int block_crypto_open_generic(QCryptoBlockFormat format,
> >  static int block_crypto_co_create_generic(BlockDriverState *bs,
> >                                            int64_t size,
> >                                            QCryptoBlockCreateOptions *opts,
> > +                                          PreallocMode prealloc,
> >                                            Error **errp)
> >  {
> >      int ret;
> > @@ -266,9 +268,14 @@ static int block_crypto_co_create_generic(BlockDriverState *bs,
> >          goto cleanup;
> >      }
> >  
> > +    if (prealloc == PREALLOC_MODE_METADATA) {
> > +        prealloc = PREALLOC_MODE_OFF;
> > +    }
> > +
> >      data = (struct BlockCryptoCreateData) {
> >          .blk = blk,
> >          .size = size,
> > +        .prealloc = prealloc,
> >      };
> >  
> >      crypto = qcrypto_block_create(opts, NULL,
> > @@ -500,6 +507,7 @@ block_crypto_co_create_luks(BlockdevCreateOptions *create_options, Error **errp)
> >      BlockdevCreateOptionsLUKS *luks_opts;
> >      BlockDriverState *bs = NULL;
> >      QCryptoBlockCreateOptions create_opts;
> > +    PreallocMode preallocation = PREALLOC_MODE_OFF;
> >      int ret;
> >  
> >      assert(create_options->driver == BLOCKDEV_DRIVER_LUKS);
> > @@ -515,8 +523,11 @@ block_crypto_co_create_luks(BlockdevCreateOptions *create_options, Error **errp)
> >          .u.luks = *qapi_BlockdevCreateOptionsLUKS_base(luks_opts),
> >      };
> >  
> > +    if (luks_opts->has_preallocation)
> > +        preallocation = luks_opts->preallocation;
> > +
> >      ret = block_crypto_co_create_generic(bs, luks_opts->size, &create_opts,
> > -                                         errp);
> > +                                         preallocation, errp);
> >      if (ret < 0) {
> >          goto fail;
> >      }
> > @@ -534,12 +545,24 @@ static int coroutine_fn block_crypto_co_create_opts_luks(const char *filename,
> >      QCryptoBlockCreateOptions *create_opts = NULL;
> >      BlockDriverState *bs = NULL;
> >      QDict *cryptoopts;
> > +    PreallocMode prealloc;
> > +    char *buf = NULL;
> >      int64_t size;
> >      int ret;
> > +    Error *local_err = NULL;
> >  
> >      /* Parse options */
> >      size = qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0);
> >  
> > +    buf = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC);
> > +    prealloc = qapi_enum_parse(&PreallocMode_lookup, buf,
> > +                               PREALLOC_MODE_OFF, &local_err);
> > +    g_free(buf);
> > +    if (local_err) {
> > +        error_propagate(errp, local_err);
> > +        return -EINVAL;
> > +    }
> > +
> >      cryptoopts = qemu_opts_to_qdict_filtered(opts, NULL,
> >                                               &block_crypto_create_opts_luks,
> >                                               true);
> > @@ -565,7 +588,7 @@ static int coroutine_fn block_crypto_co_create_opts_luks(const char *filename,
> >      }
> >  
> >      /* Create format layer */
> > -    ret = block_crypto_co_create_generic(bs, size, create_opts, errp);
> > +    ret = block_crypto_co_create_generic(bs, size, create_opts, prealloc, errp);
> >      if (ret < 0) {
> >          goto fail;
> >      }
> > diff --git a/qapi/block-core.json b/qapi/block-core.json
> > index 0d43d4f37c..ebcfc9f903 100644
> > --- a/qapi/block-core.json
> > +++ b/qapi/block-core.json
> > @@ -4205,13 +4205,16 @@
> >  #
> >  # @file             Node to create the image format on
> >  # @size             Size of the virtual disk in bytes
> > +# @preallocation    Preallocation mode for the new image (default: off;
> > +#                   allowed values: off/falloc/full
> 
> Should we add also "metadata" to allowed values? and "since: 4.2"?
> I'd like to have (just to have similar documentation with others
> preallocation parameters):

It it support but preallocation=off is the same as preallocation=metadata in luks,
as luks only metadata is the header which is created anyway.
In some sense I should throw a error for preallocation=off, but I suspect that
that will break userspace api.
What do you think?

I forgot to add 'since: 4.2', will do in the next revision of that patch series.

> 
>   # @preallocation    Preallocation mode for the new image (default: off;
>   #                   allowed values: off, falloc, full, metadata; since: 4.2)
> 
> 
> Thanks,
> Stefano


Best regards,
	Maxim Levitsky