Re: [Qemu-devel] [PATCH 1/9] block: Create bdrv_fill_options()

["Benoît Canet" <benoit.canet@irqsave.net>]

The Monday 23 Jun 2014 à 17:30:45 (+0200), Kevin Wolf wrote :
> Am 12.06.2014 um 14:08 hat Benoît Canet geschrieben:
> > The Wednesday 11 Jun 2014 à 16:04:55 (+0200), Kevin Wolf wrote :
> > > The idea of bdrv_fill_options() is to convert every parameter for
> > > opening images, in particular the filename and flags, to entries in the
> > > options QDict.
> > > 
> > > This patch starts with moving the filename parsing and driver probing
> > > part from bdrv_file_open() to the new function.
> > > 
> > > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > > ---
> > >  block.c | 116 ++++++++++++++++++++++++++++++++++++++++------------------------
> > >  1 file changed, 73 insertions(+), 43 deletions(-)
> > > 
> > > diff --git a/block.c b/block.c
> > > index 17f763d..c5707e8 100644
> > > --- a/block.c
> > > +++ b/block.c
> > > @@ -1007,77 +1007,107 @@ free_and_fail:
> > >  }
> > >  
> > >  /*
> > > - * Opens a file using a protocol (file, host_device, nbd, ...)
> > > - *
> > > - * options is an indirect pointer to a QDict of options to pass to the block
> > > - * drivers, or pointer to NULL for an empty set of options. If this function
> > > - * takes ownership of the QDict reference, it will set *options to NULL;
> > > - * otherwise, it will contain unused/unrecognized options after this function
> > > - * returns. Then, the caller is responsible for freeing it. If it intends to
> > > - * reuse the QDict, QINCREF() should be called beforehand.
> > > + * Fills in default options for opening images and converts the legacy
> > > + * filename/flags pair to option QDict entries.
> > >   */
> > > -static int bdrv_file_open(BlockDriverState *bs, const char *filename,
> > > -                          QDict **options, int flags, Error **errp)
> > > +static int bdrv_fill_options(QDict **options, const char *filename,
> > > +                             Error **errp)
> > >  {
> > > -    BlockDriver *drv;
> > >      const char *drvname;
> > >      bool parse_filename = false;
> > >      Error *local_err = NULL;
> > > -    int ret;
> > > +    BlockDriver *drv;
> > >  
> > >      /* Fetch the file name from the options QDict if necessary */
> > > -    if (!filename) {
> > > -        filename = qdict_get_try_str(*options, "filename");
> > > -    } else if (filename && !qdict_haskey(*options, "filename")) {
> > > -        qdict_put(*options, "filename", qstring_from_str(filename));
> > > -        parse_filename = true;
> > > -    } else {
> > > -        error_setg(errp, "Can't specify 'file' and 'filename' options at the "
> > > -                   "same time");
> > > -        ret = -EINVAL;
> > > -        goto fail;
> > > +    if (filename) {
> > > +        if (filename && !qdict_haskey(*options, "filename")) {
> > 
> > The inner filename testing is redundant.
> 
> Will fix.
> 
> > > +            qdict_put(*options, "filename", qstring_from_str(filename));
> > > +            parse_filename = true;
> > > +        } else {
> > > +            error_setg(errp, "Can't specify 'file' and 'filename' options at "
> > > +                             "the same time");
> > > +            return -EINVAL;
> > > +        }
> > >      }
> > >  
> > >      /* Find the right block driver */
> > > +    filename = qdict_get_try_str(*options, "filename");
> > >      drvname = qdict_get_try_str(*options, "driver");
> > > -    if (drvname) {
> > > -        drv = bdrv_find_format(drvname);
> > > -        if (!drv) {
> > > -            error_setg(errp, "Unknown driver '%s'", drvname);
> > > -        }
> > > -        qdict_del(*options, "driver");
> > > -    } else if (filename) {
> > > -        drv = bdrv_find_protocol(filename, parse_filename);
> > > -        if (!drv) {
> > > -            error_setg(errp, "Unknown protocol");
> > > +
> > > +    if (!drvname) {
> > > +        if (filename) {
> > > +            drv = bdrv_find_protocol(filename, parse_filename);
> > > +            if (!drv) {
> > > +                error_setg(errp, "Unknown protocol");
> > > +                return -EINVAL;
> > > +            }
> > > +
> > > +            drvname = drv->format_name;
> > > +            qdict_put(*options, "driver", qstring_from_str(drvname));
> > > +        } else {
> > > +            error_setg(errp, "Must specify either driver or file");
> > 
> > Isn't it "Must specify either driver or _filename_ ?
> 
> This is only code motion, but changing it in a separate patch would make
> sense, I guess.
> 
> > > +            return -EINVAL;
> > >          }
> > > -    } else {
> > > -        error_setg(errp, "Must specify either driver or file");
> > > -        drv = NULL;
> > >      }
> > >  
> > > +    drv = bdrv_find_format(drvname);
> > >      if (!drv) {
> > > -        /* errp has been set already */
> > > -        ret = -ENOENT;
> > > -        goto fail;
> > > +        error_setg(errp, "Unknown driver '%s'", drvname);
> > > +        return -ENOENT;
> > >      }
> > >  
> > > -    /* Parse the filename and open it */
> > > +    /* Driver-specific filename parsing */
> > >      if (drv->bdrv_parse_filename && parse_filename) {
> > >          drv->bdrv_parse_filename(filename, *options, &local_err);
> > >          if (local_err) {
> > >              error_propagate(errp, local_err);
> > > -            ret = -EINVAL;
> > > -            goto fail;
> > > +            return -EINVAL;
> > >          }
> > >  
> > >          if (!drv->bdrv_needs_filename) {
> > >              qdict_del(*options, "filename");
> > > -        } else {
> > > -            filename = qdict_get_str(*options, "filename");
> > >          }
> > >      }
> > >  
> > > +    return 0;
> > > +}
> > > +
> > > +/*
> > > + * Opens a file using a protocol (file, host_device, nbd, ...)
> > > + *
> > > + * options is an indirect pointer to a QDict of options to pass to the block
> > > + * drivers, or pointer to NULL for an empty set of options. If this function
> > > + * takes ownership of the QDict reference, it will set *options to NULL;
> > > + * otherwise, it will contain unused/unrecognized options after this function
> > > + * returns. Then, the caller is responsible for freeing it. If it intends to
> > > + * reuse the QDict, QINCREF() should be called beforehand.
> > > + */
> > > +static int bdrv_file_open(BlockDriverState *bs, const char *filename,
> > > +                          QDict **options, int flags, Error **errp)
> > > +{
> > > +    BlockDriver *drv;
> > > +    const char *drvname;
> > > +    Error *local_err = NULL;
> > > +    int ret;
> > > +
> > > +    ret = bdrv_fill_options(options, filename, &local_err);
> > > +    if (local_err) {
> > > +        error_propagate(errp, local_err);
> > > +        return ret;
> > Why not goto fail for consistency with the rest of the function ?
> 
> Okay. Rather pointless and the function will be gone at the end of the
> series, but more consistent indeed.
> 
> > > +    }
> > > +
> > > +    filename = qdict_get_try_str(*options, "filename");
> > > +    drvname = qdict_get_str(*options, "driver");
> > > +
> > > +    drv = bdrv_find_format(drvname);
> > > +    if (!drv) {
> > > +        error_setg(errp, "Unknown driver '%s'", drvname);
> > > +        ret = -ENOENT;
> > > +        goto fail;
> > > +    }
> > > +    qdict_del(*options, "driver");
> > > +
> > > +    /* Open the file */
> > >      if (!drv->bdrv_file_open) {
> > 
> > Don't we need:
> >            qdict_del(*options, "filename");
> > Here so bdrv_open don't see an extra filename option ?
> 
> I think it doesn't matter because bdrv_open() would put it back again.
> Do you have an example where it makes a difference?
No, I don't understand the code that much.
I was just thinking outloud betting it would point to something. It's not :)
> 
> > >          ret = bdrv_open(&bs, filename, NULL, *options, flags, drv, &local_err);
> > >          *options = NULL;
> 
> Kevin