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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1739203875; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=x5zLuQrHVGbOmvU8jjmcpxMxUJDwC9esChLaBL+yZwE=; b=DbnG8cp7+mW6WDO2YSINpf4ImYmVu1OrIvOMEStqpITJJ8l4JhADw1FgPSs9KO8RRECfPz 7LPf3B+GuS/DIebIu0PDFMNFl8RPwY+WiBQw2Gwld84G0QZjPRIweXf+cUrdVGgCfcIRkZ YsH5zQwnLBZa+nmUR6TI7tJm3kqIhJY= X-MC-Unique: YkR4w-KaM3aiEJS_fRlHqw-1 X-Mimecast-MFC-AGG-ID: YkR4w-KaM3aiEJS_fRlHqw From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [PULL 11/25] block: Inactivate external snapshot overlays when necessary Date: Mon, 10 Feb 2025 17:10:20 +0100 Message-ID: <20250210161034.76494-12-kwolf@redhat.com> In-Reply-To: <20250210161034.76494-1-kwolf@redhat.com> References: <20250210161034.76494-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; 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charset="utf-8" Putting an active block node on top of an inactive one is strictly speaking an invalid configuration and the next patch will turn it into a hard error. However, taking a snapshot while disk images are inactive after completing migration has an important use case: After migrating to a file, taking an external snapshot is what is needed to take a full VM snapshot. In order for this to keep working after the later patches, change creating a snapshot such that it automatically inactivates an overlay that is added on top of an already inactive node. Signed-off-by: Kevin Wolf Acked-by: Fabiano Rosas Reviewed-by: Eric Blake Reviewed-by: Stefan Hajnoczi Message-ID: <20250204211407.381505-4-kwolf@redhat.com> Signed-off-by: Kevin Wolf --- blockdev.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/blockdev.c b/blockdev.c index 218024497b..eb2517f1dd 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1497,6 +1497,22 @@ static void external_snapshot_action(TransactionActi= on *action, return; } =20 + /* + * Older QEMU versions have allowed adding an active parent node to an + * inactive child node. This is unsafe in the general case, but there = is an + * important use case, which is taking a VM snapshot with migration to= file + * and then adding an external snapshot while the VM is still stopped = and + * images are inactive. Requiring the user to explicitly create the ov= erlay + * as inactive would break compatibility, so just do it automatically = here + * to keep this working. + */ + if (bdrv_is_inactive(state->old_bs) && !bdrv_is_inactive(state->new_bs= )) { + ret =3D bdrv_inactivate(state->new_bs, errp); + if (ret < 0) { + return; + } + } + ret =3D bdrv_append(state->new_bs, state->old_bs, errp); if (ret < 0) { return; --=20 2.48.1