On Mon, Jan 24, 2011 at 01:32:33PM +0100, Christoph Hellwig wrote:
> Add a monitor command that allows resizing of block devices while
> qemu is running. It uses the existing bdrv_truncate method already
> used by qemu-img to do it's work. Compared to qemu-img the size
> parsing is very simplicistic, but I think having a properly numering
> object is more useful for non-humand monitor users than having
> the units and relative resize parsing.
>
> For SCSI devices the new size can be updated in Linux guests by
> doing the following shell command:
>
> echo > /sys/class/scsi_device/0:0:0:0/device/rescan
>
> For ATA devices I don't know of a way to update the block device
> size in Linux system, and for virtio-blk the next two patches
> will provide an automatic update of the size when this command
> is issued on the host.
>
> Signed-off-by: Christoph Hellwig <h...@lst.de>
>
> Index: qemu/hmp-commands.hx
> ===================================================================
> --- qemu.orig/hmp-commands.hx 2011-01-24 11:55:36.744254374 +0100
> +++ qemu/hmp-commands.hx 2011-01-24 11:56:23.619254094 +0100
> @@ -53,6 +53,25 @@ Quit the emulator.
> ETEXI
>
> {
> + .name = "block_resize",
> + .args_type = "device:B,size:o",
> + .params = "device size",
> + .help = "resize a block image",
> + .user_print = monitor_user_noop,
> + .mhandler.cmd_new = do_block_resize,
> + },
> +
> +STEXI
> +@item block_resize
> +@findex block_resize
> +Resize a block image while a guest is running. Usually requires guest
> +action to see the updated size. Resize to a lower size is supported,
> +but should be used with extreme caution. Note that this command only
> +resizes image files, it can not resize block devices like LVM volumes.
> +ETEXI
> +
> +
> + {
> .name = "eject",
> .args_type = "force:-f,device:B",
> .params = "[-f] device",
> Index: qemu/blockdev.c
> ===================================================================
> --- qemu.orig/blockdev.c 2011-01-24 11:56:20.903004129 +0100
> +++ qemu/blockdev.c 2011-01-24 11:56:38.391254165 +0100
> @@ -705,3 +705,33 @@ int do_drive_del(Monitor *mon, const QDi
>
> return 0;
> }
> +
> +/*
> + * XXX: replace the QERR_UNDEFINED_ERROR errors with real values once the
> + * existing QERR_ macro mess is cleaned up. A good example for better
> + * error reports can be found in the qemu-img resize code.
> + */
> +int do_block_resize(Monitor *mon, const QDict *qdict, QObject **ret_data)
> +{
> + const char *device = qdict_get_str(qdict, "device");
> + int64_t size = qdict_get_int(qdict, "size");
> + BlockDriverState *bs;
> +
> + bs = bdrv_find(device);
> + if (!bs) {
> + qerror_report(QERR_DEVICE_NOT_FOUND, device);
> + return -1;
> + }
> +
> + if (size < 0) {
> + qerror_report(QERR_UNDEFINED_ERROR);
> + return -1;
> + }
> +
> + if (bdrv_truncate(bs, size)) {
> + qerror_report(QERR_UNDEFINED_ERROR);
> + return -1;
> + }
Can't resize if block migration is in progress. Don't see a problem
with simply disallowing resize in that case.
