On 06/15/2012 02:47 PM, Supriya Kannery wrote: > New command "block_set_hostcache" added for dynamically changing > host pagecache setting of a block device. > > Usage: > block_set_hostcache <device> <option> > <device> = block device > <option> = on/off > > Example: > (qemu) block_set_hostcache ide0-hd0 off > > Signed-off-by: Supriya Kannery <supri...@linux.vnet.ibm.com> > > --- > block.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > block.h | 2 ++ > blockdev.c | 26 ++++++++++++++++++++++++++ > blockdev.h | 2 ++ > hmp-commands.hx | 14 ++++++++++++++ > qmp-commands.hx | 27 +++++++++++++++++++++++++++ > 6 files changed, 125 insertions(+)
Doesn't this also need to touch qapi-schema.json?
[/me reads full patch]
Oh, you did - but your diffstat is stale. It might be worth figuring
out what in your workflow leads to stale diffstats.
>
> Index: qemu/block.c
> ===================================================================
> --- qemu.orig/block.c
> +++ qemu/block.c
> @@ -858,6 +858,35 @@ unlink_and_fail:
> return ret;
> }
>
> +int bdrv_reopen(BlockDriverState *bs, int bdrv_flags)
> +{
> + BlockDriver *drv = bs->drv;
> + int ret = 0, open_flags;
> +
> + /* Quiesce IO for the given block device */
> + qemu_aio_flush();
> + ret = bdrv_flush(bs);
> + if (ret != 0) {
> + qerror_report(QERR_DATA_SYNC_FAILED, bs->device_name);
> + return ret;
> + }
> + open_flags = bs->open_flags;
> + bdrv_close(bs);
> +
> + ret = bdrv_open(bs, bs->filename, bdrv_flags, drv);
Yuck. This is bad, and why 'transaction' was invented. Any time you
close() before open() you risk completely losing the file...
> + if (ret < 0) {
> + /* Reopen failed. Try to open with original flags */
> + qerror_report(QERR_OPEN_FILE_FAILED, bs->filename);
> + ret = bdrv_open(bs, bs->filename, open_flags, drv);
> + if (ret < 0) {
> + /* Reopen failed with orig and modified flags */
> + abort();
and an abort() is not a nice reaction to that.
I think we should rebase the series to do the safe reopen prior to
adding this command (at least, just judging by the title of 4/10), to
avoid intermediate bad code.
> @@ -808,7 +808,6 @@ ETEXI
> .mhandler.cmd = hmp_migrate,
> },
>
> -
> STEXI
Spurious whitespace change.
> +
> +SQMP
> +block_set_hostcache
QMP commands favor '-' over '_'; this should be 'block-set-hostcache'.
> Index: qemu/qapi-schema.json
> ===================================================================
> --- qemu.orig/qapi-schema.json
> +++ qemu/qapi-schema.json
> @@ -1598,6 +1598,22 @@
> { 'command': 'block_set_io_throttle',
> 'data': { 'device': 'str', 'bps': 'int', 'bps_rd': 'int', 'bps_wr': 'int',
> 'iops': 'int', 'iops_rd': 'int', 'iops_wr': 'int' } }
> +##
> +# @block_set_hostcache:
> +#
> +# Change host pagecache setting of a block device
> +#
> +# @device: name of the block device
> +#
> +# @option: hostcache setting (true/false)
> +#
> +# Returns: Nothing on success
> +# If @device is not a valid block device, DeviceNotFound
What happens if the device is valid, but the setting cannot be changed
(perhaps because reopen has not been implemented for that driver)?
--
Eric Blake ebl...@redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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