Re: [PATCH v2 2/6] block: truncate: Don't make backing file data visible

From: Alberto Garcia <berto@igalia.com>
To: Kevin Wolf <kwolf@redhat.com>, Max Reitz <mreitz@redhat.com>
Cc: vsementsov@virtuozzo.com, qemu-block@nongnu.org,
	stefanha@redhat.com, qemu-devel@nongnu.org
Subject: Re: [PATCH v2 2/6] block: truncate: Don't make backing file data visible
Date: Fri, 22 Nov 2019 15:07:52 +0100	[thread overview]
Message-ID: <w51h82w0zt3.fsf@maestria.local.igalia.com> (raw)
In-Reply-To: <20191121143331.GG6007@linux.fritz.box>

On Thu 21 Nov 2019 03:33:31 PM CET, Kevin Wolf wrote:
> For commit it's an image corruptor. For resize, I'll admit that it's
> just wrong behaviour that is probably harmless in most cases, but it's
> still wrong behaviour. It would be a corruptor in the same way as
> commit if it allowed resizing intermediate nodes, but I _think_ the
> old-style op blockers still forbid this. We'd have to double-check
> this if we leave things broken for block_resize.

I tried but cannot make block_resize touch an intermediate image:

    if (!bdrv_is_first_non_filter(bs)) {
        error_setg(errp, QERR_FEATURE_DISABLED, "resize");
        goto out;
    }

Berto