Re: [Qemu-devel] [PATCH v2 00/11] block: Fix some things about bdrv_has_zero_init()

[Max Reitz]

On 24.07.19 19:12, Max Reitz wrote:
> Hi,
> 
> See the previous cover letter for the reason for patches 6 through 9:
> https://lists.nongnu.org/archive/html/qemu-block/2019-07/msg00563.html
> 
> But no only some bdrv_has_zero_init() implementations are wrong, some
> callers also use it the wrong way.
> 
> First, qemu-img and mirror use it for pre-existing images, where it
> doesn’t have any meaning.  Both should consider pre-existing images to
> always be non-zero and not look at bdrv_has-zero_init() (patches 1, 2,
> and the tests in 10 and 11).
> 
> Second, vhdx and parallels call bdrv_has_zero_init() when they do not
> really care about an image’s post-create state but only about what
> happens when you grow an image.  That is a bit ugly, and also overly
> safe when growing preallocated images without preallocating the new
> areas.  So this series adds a new function bdrv_has_zero_init_truncate()
> that is more suited to vhdx's and parallel's needs (patches 3 through
> 5).

Thanks for the reviews, I took a part of this last paragraph, added it
as patch 5’s commit message, and applied the series to my block-next branch.

Max

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