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

[Kevin Wolf]

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 <address@hidden>
> > ---
> >  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?

> >          ret = bdrv_open(&bs, filename, NULL, *options, flags, drv, 
> > &local_err);
> >          *options = NULL;

Kevin