Patchwork [1/3] block: add resize monitor command

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Submitter Christoph Hellwig
Date Jan. 19, 2011, 5:02 p.m.
Message ID <20110119170248.GA9819@lst.de>
Download mbox | patch
Permalink /patch/79496/
State New
Headers show

Comments

Christoph Hellwig - Jan. 19, 2011, 5:02 p.m.
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 <hch@lst.de>
Stefan Hajnoczi - Jan. 20, 2011, 8:56 a.m.
On Wed, Jan 19, 2011 at 06:02:48PM +0100, Christoph Hellwig wrote:
> Index: qemu/hmp-commands.hx
> ===================================================================
> --- qemu.orig/hmp-commands.hx	2011-01-19 17:47:10.444004409 +0100
> +++ qemu/hmp-commands.hx	2011-01-19 17:49:51.673254095 +0100
> @@ -53,6 +53,25 @@ Quit the emulator.
>  ETEXI
>  
>      {
> +        .name       = "resize",
> +        .args_type  = "id:s,size:o",
> +        .params     = "device size",
> +        .help       = "resize a block image",
> +        .user_print = monitor_user_noop,
> +        .mhandler.cmd_new = do_resize,
> +    },
> +
> +STEXI
> +@item resize
> +@findex 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/qmp-commands.hx
> ===================================================================
> --- qemu.orig/qmp-commands.hx	2011-01-19 17:47:10.478012371 +0100
> +++ qemu/qmp-commands.hx	2011-01-19 17:50:07.406016841 +0100
> @@ -601,6 +601,34 @@ Example:
>  -> { "execute": "netdev_del", "arguments": { "id": "netdev1" } }
>  <- { "return": {} }
>  
> +
> +EQMP
> +
> +    {
> +        .name       = "block_resize",
> +        .args_type  = "id:s,size:o",
> +        .params     = "id size",
> +        .help       = "resize a block image",
> +        .user_print = monitor_user_noop,
> +        .mhandler.cmd_new = do_resize,
> +    },
> +
> +SQMP
> +block_resize
> +------------
> +
> +Resize a block image while a guest is running.
> +
> +Arguments:
> +
> +- "id": the device's ID, must be unique (json-string)
> +- "size": new size
> +
> +Example:
> +
> +-> { "execute": "block_resize", "arguments": { "id": "scratch", "size": 1073741824 } }
> +<- { "return": {} }
> +
>  EQMP

eject, change, block_passwd, and others call the device name argument
"device" instead of "id".  In the interest of a consistent external API
it would be nice to use "device" for the block_resize command too.

Stefan
Christoph Hellwig - Jan. 20, 2011, 9:43 a.m.
On Thu, Jan 20, 2011 at 08:56:07AM +0000, Stefan Hajnoczi wrote:
> eject, change, block_passwd, and others call the device name argument
> "device" instead of "id".  In the interest of a consistent external API
> it would be nice to use "device" for the block_resize command too.

Sure, I can do that with the next respin.

Patch

Index: qemu/hmp-commands.hx
===================================================================
--- qemu.orig/hmp-commands.hx	2011-01-19 17:47:10.444004409 +0100
+++ qemu/hmp-commands.hx	2011-01-19 17:49:51.673254095 +0100
@@ -53,6 +53,25 @@  Quit the emulator.
 ETEXI
 
     {
+        .name       = "resize",
+        .args_type  = "id:s,size:o",
+        .params     = "device size",
+        .help       = "resize a block image",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_resize,
+    },
+
+STEXI
+@item resize
+@findex 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	2011-01-19 17:47:10.455004828 +0100
+++ qemu/blockdev.c	2011-01-19 17:49:51.674253955 +0100
@@ -706,3 +706,33 @@  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_resize(Monitor *mon, const QDict *qdict, QObject **ret_data)
+{
+    const char *id = qdict_get_str(qdict, "id");
+    int64_t size = qdict_get_int(qdict, "size");
+    BlockDriverState *bs;
+
+    bs = bdrv_find(id);
+    if (!bs) {
+        qerror_report(QERR_DEVICE_NOT_FOUND, id);
+        return -1;
+    }
+
+    if (size < 0) {
+        qerror_report(QERR_UNDEFINED_ERROR);
+        return -1;
+    }
+
+    if (bdrv_truncate(bs, size)) {
+        qerror_report(QERR_UNDEFINED_ERROR);
+        return -1;
+    }
+
+    return 0;
+}
Index: qemu/blockdev.h
===================================================================
--- qemu.orig/blockdev.h	2011-01-19 17:47:10.464012091 +0100
+++ qemu/blockdev.h	2011-01-19 17:49:51.677282590 +0100
@@ -53,5 +53,6 @@  int do_change_block(Monitor *mon, const
                     const char *filename, const char *fmt);
 int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data);
 int do_snapshot_blkdev(Monitor *mon, const QDict *qdict, QObject **ret_data);
+int do_resize(Monitor *mon, const QDict *qdict, QObject **ret_data);
 
 #endif
Index: qemu/qmp-commands.hx
===================================================================
--- qemu.orig/qmp-commands.hx	2011-01-19 17:47:10.478012371 +0100
+++ qemu/qmp-commands.hx	2011-01-19 17:50:07.406016841 +0100
@@ -601,6 +601,34 @@  Example:
 -> { "execute": "netdev_del", "arguments": { "id": "netdev1" } }
 <- { "return": {} }
 
+
+EQMP
+
+    {
+        .name       = "block_resize",
+        .args_type  = "id:s,size:o",
+        .params     = "id size",
+        .help       = "resize a block image",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_resize,
+    },
+
+SQMP
+block_resize
+------------
+
+Resize a block image while a guest is running.
+
+Arguments:
+
+- "id": the device's ID, must be unique (json-string)
+- "size": new size
+
+Example:
+
+-> { "execute": "block_resize", "arguments": { "id": "scratch", "size": 1073741824 } }
+<- { "return": {} }
+
 EQMP
 
     {