From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=40156 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PhhYd-0008TB-41 for qemu-devel@nongnu.org; Tue, 25 Jan 2011 06:59:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PhhYb-0003F1-ND for qemu-devel@nongnu.org; Tue, 25 Jan 2011 06:59:35 -0500 Received: from mx1.redhat.com ([209.132.183.28]:30530) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PhhYb-0003Eh-Fn for qemu-devel@nongnu.org; Tue, 25 Jan 2011 06:59:33 -0500 Message-ID: <4D3EBB80.1000107@redhat.com> Date: Tue, 25 Jan 2011 13:01:04 +0100 From: Kevin Wolf MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 1/3] block: add block_resize monitor command References: <20110124123223.GA16558@lst.de> <20110124123233.GA16613@lst.de> <20110124174416.GA6178@amt.cnet> In-Reply-To: <20110124174416.GA6178@amt.cnet> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Marcelo Tosatti Cc: Christoph Hellwig , qemu-devel@nongnu.org Am 24.01.2011 18:44, schrieb Marcelo Tosatti: > 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 >> >> 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. Then we should add a check to bdrv_truncate. Kevin