On 04/04/2018 04:13 AM, Peter Krempa wrote:
> The disk cache mode translates to various frontend and backend
> attributes for the qemu block layer. For the frontend device the
> 'writeback' parameter is used and provided as 'write-cache'. Implement
> this so that we can later switch to using -blockdev where we will not
> pass the cachemode directly any more.
>
> Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx>
> ---
> src/qemu/qemu_command.c | 27 +++++++++++++++++++++++++++
> 1 file changed, 27 insertions(+)
>
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index bbd3cd0a7d..83e263e9f9 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -1882,6 +1882,30 @@ qemuCheckIOThreads(const virDomainDef *def,
> }
>
>
> +static int
> +qemuBuildDriveDevCacheStr(virDomainDiskDefPtr disk,
> + virBufferPtr buf,
> + virQEMUCapsPtr qemuCaps)
> +{
> + bool wb;
> +
> + if (disk->cachemode == VIR_DOMAIN_DISK_CACHE_DEFAULT)
> + return 0;
> +
> + if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_DISK_WRITE_CACHE))
> + return 0;
As I noted in patch 4 - this is checking a bit that's defined in QEMU
2.7 on some arches, but the test in patch 6 (probably should be in this
patch) would seem to indicate QEMU 2.12 is required.
> +
> + if (qemuDomainDiskCachemodeFlags(disk->cachemode, &wb, NULL, NULL) < 0)
> + return -1;
Wouldn't bother with -1 since we already know that cachemode will be
valid (e.g. from my comments in patch 4).
John
> +
> + virBufferStrcat(buf, ",write-cache=",
> + virTristateSwitchTypeToString(virTristateSwitchFromBool(wb)),
> + NULL);
> +
> + return 0;
> +}
> +
> +
> char *
> qemuBuildDriveDevStr(const virDomainDef *def,
> virDomainDiskDefPtr disk,
> @@ -2194,6 +2218,9 @@ qemuBuildDriveDevStr(const virDomainDef *def,
> }
> }
>
> + if (qemuBuildDriveDevCacheStr(disk, &opt, qemuCaps) < 0)
> + goto error;
> +
> if (virBufferCheckError(&opt) < 0)
> goto error;
>
--
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