Re: [Qemu-devel] [RFC] Using BlockdevRef in the block layer

[Kevin Wolf <kwolf@redhat.com>]

Am 05.12.2013 um 19:35 hat Max Reitz geschrieben:
> On 05.12.2013 18:41, Max Reitz wrote:
> >[…]
> >
> >Second, if specifying a reference to an existing device should
> >really be supported, bdrv_open() should ideally not call
> >bdrv_file_open() anymore, but a function bdrv_find_ref() instead
> >which resolves a BlockdevRef structure (for simplicity, it appears
> >to be easier to use a QDict equivalent to a BlockdevRef instead of
> >the latter itself (since that results in many effectively
> >redundant conversions to and from those representations)).
> >However, bdrv_file_open() supports parsing protocol filenames,
> >which bdrv_find_ref() would not. As a result, it is probably best
> >to call bdrv_find_ref() from bdrv_file_open() instead and leave
> >bdrv_open() generally the way it is right now – yes, this is a
> >question. ;-) (“Do you agree?”)
> 
> I noticed only just now that the current design does not seem to
> allow nesting of files (i.e., driver=blkdebug-qmp,
> file.driver=qcow2, file.file.driver=file). Perhaps I do have to call
> bdrv_find_ref() in bdrv_open() and only resort to bdrv_file_open()
> if a filename that must be parsed was given...?

This is supposed to work. If it doesn't work today, it is a bug or
missing implementation rather than a design decision.

Kevin