[Qemu-devel] [PATCH 0/3 v2] allow online resizing of block devices

[Qemu-devel] [PATCH 0/3 v2] allow online resizing of block devices

[Christoph Hellwig]

This patchset adds support for online resizing of block devices.

The first patch adds a new resize monitor command which call into
the existing image resize code.  This is the meat of the series
and probably needs quite a bit of review and help as I'm not sure
about how to implement the error handling for monitor commands
correctly.  Am I really supposed to add a new QERR_ definition
for each possible error?  And if yes how am I supposed to define
them?  The macros for them aren't exactly self-explaining.

The second patch adds a way to tell drivers about a resize, and the
third one adds a guest notification for config changes to virtio-blk
which allows the guest to pick it up without a rescan.  I've just sent
the corresponding Linux guest driver patch to Rusty.

Changes from version 1 to version 2:
 - also add a QMP command (block_resize)
 - use the o format for the size in the monitor command
 - fix typos
 - use QERR_UNDEFINED_ERROR for errors instead of unstructured strings
 - remove the CDROM hint check
 - add a reason argument to the change callback

[Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Christoph Hellwig]

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>

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
 
     {

[Qemu-devel] [PATCH 2/3] block: tell drivers about an image resize

[Christoph Hellwig]

Extend the change_cb callback with a reason argument, and use it
to tell drivers about size changes.

Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: qemu/block.c
===================================================================
--- qemu.orig/block.c	2011-01-18 20:54:45.246021572 +0100
+++ qemu/block.c	2011-01-18 20:56:54.117255612 +0100
@@ -645,7 +645,7 @@ int bdrv_open(BlockDriverState *bs, cons
         /* call the change callback */
         bs->media_changed = 1;
         if (bs->change_cb)
-            bs->change_cb(bs->change_opaque);
+            bs->change_cb(bs->change_opaque, CHANGE_MEDIA);
     }
 
     return 0;
@@ -684,7 +684,7 @@ void bdrv_close(BlockDriverState *bs)
         /* call the change callback */
         bs->media_changed = 1;
         if (bs->change_cb)
-            bs->change_cb(bs->change_opaque);
+            bs->change_cb(bs->change_opaque, CHANGE_MEDIA);
     }
 }
 
@@ -1135,6 +1135,8 @@ int bdrv_truncate(BlockDriverState *bs,
     ret = drv->bdrv_truncate(bs, offset);
     if (ret == 0) {
         ret = refresh_total_sectors(bs, offset >> BDRV_SECTOR_BITS);
+        if (bs->change_cb)
+            bs->change_cb(bs->change_opaque, CHANGE_SIZE);
     }
     return ret;
 }
@@ -1366,7 +1368,8 @@ int bdrv_enable_write_cache(BlockDriverS
 
 /* XXX: no longer used */
 void bdrv_set_change_cb(BlockDriverState *bs,
-                        void (*change_cb)(void *opaque), void *opaque)
+                        void (*change_cb)(void *opaque, int reason),
+                        void *opaque)
 {
     bs->change_cb = change_cb;
     bs->change_opaque = opaque;
@@ -1411,7 +1414,7 @@ int bdrv_set_key(BlockDriverState *bs, c
         /* call the change callback now, we skipped it on open */
         bs->media_changed = 1;
         if (bs->change_cb)
-            bs->change_cb(bs->change_opaque);
+            bs->change_cb(bs->change_opaque, CHANGE_MEDIA);
     }
     return ret;
 }
Index: qemu/block.h
===================================================================
--- qemu.orig/block.h	2011-01-18 20:57:00.792253448 +0100
+++ qemu/block.h	2011-01-18 20:57:09.771282850 +0100
@@ -182,7 +182,8 @@ int bdrv_is_locked(BlockDriverState *bs)
 void bdrv_set_locked(BlockDriverState *bs, int locked);
 int bdrv_eject(BlockDriverState *bs, int eject_flag);
 void bdrv_set_change_cb(BlockDriverState *bs,
-                        void (*change_cb)(void *opaque), void *opaque);
+                        void (*change_cb)(void *opaque, int reason),
+                        void *opaque);
 void bdrv_get_format(BlockDriverState *bs, char *buf, int buf_size);
 BlockDriverState *bdrv_find(const char *name);
 BlockDriverState *bdrv_next(BlockDriverState *bs);
Index: qemu/block_int.h
===================================================================
--- qemu.orig/block_int.h	2011-01-18 20:55:43.783009908 +0100
+++ qemu/block_int.h	2011-01-18 20:56:58.912004806 +0100
@@ -153,7 +153,7 @@ struct BlockDriverState {
     int valid_key; /* if true, a valid encryption key has been set */
     int sg;        /* if true, the device is a /dev/sg* */
     /* event callback when inserting/removing */
-    void (*change_cb)(void *opaque);
+    void (*change_cb)(void *opaque, int reason);
     void *change_opaque;
 
     BlockDriver *drv; /* NULL means no media */
@@ -203,6 +203,9 @@ struct BlockDriverState {
     void *private;
 };
 
+#define CHANGE_MEDIA	0x01
+#define CHANGE_SIZE	0x02
+
 struct BlockDriverAIOCB {
     AIOPool *pool;
     BlockDriverState *bs;
Index: qemu/hw/ide/core.c
===================================================================
--- qemu.orig/hw/ide/core.c	2011-01-18 20:57:17.321260780 +0100
+++ qemu/hw/ide/core.c	2011-01-18 20:59:46.242256451 +0100
@@ -1625,11 +1625,15 @@ static void ide_cfata_metadata_write(IDE
 }
 
 /* called when the inserted state of the media has changed */
-static void cdrom_change_cb(void *opaque)
+static void cdrom_change_cb(void *opaque, int reason)
 {
     IDEState *s = opaque;
     uint64_t nb_sectors;
 
+    if (!(reason & CHANGE_MEDIA)) {
+        return;
+    }
+
     bdrv_get_geometry(s->bs, &nb_sectors);
     s->nb_sectors = nb_sectors;
 
Index: qemu/hw/sd.c
===================================================================
--- qemu.orig/hw/sd.c	2011-01-18 20:57:48.978261549 +0100
+++ qemu/hw/sd.c	2011-01-18 20:59:37.000000000 +0100
@@ -422,9 +422,14 @@ static void sd_reset(SDState *sd, BlockD
     sd->pwd_len = 0;
 }
 
-static void sd_cardchange(void *opaque)
+static void sd_cardchange(void *opaque, int reason)
 {
     SDState *sd = opaque;
+
+    if (!(reason & CHANGE_MEDIA)) {
+        return;
+    }
+
     qemu_set_irq(sd->inserted_cb, bdrv_is_inserted(sd->bdrv));
     if (bdrv_is_inserted(sd->bdrv)) {
         sd_reset(sd, sd->bdrv);

[Qemu-devel] [PATCH 3/3] virtio-blk: tell the guest about size changes

[Christoph Hellwig]

Raise a config change interrupt when the size changed.  This allows
virtio-blk guest drivers to read-read the information from the
config space once it got the config chaged interrupt.

Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: qemu/hw/virtio-blk.c
===================================================================
--- qemu.orig/hw/virtio-blk.c	2011-01-19 17:47:10.335004828 +0100
+++ qemu/hw/virtio-blk.c	2011-01-19 17:50:10.748272881 +0100
@@ -504,6 +504,15 @@ static int virtio_blk_load(QEMUFile *f,
     return 0;
 }
 
+static void virtio_blk_change_cb(void *opaque, int reason)
+{
+    VirtIOBlock *s = opaque;
+
+    if (reason & CHANGE_SIZE) {
+        virtio_notify_config(&s->vdev);
+    }
+}
+
 VirtIODevice *virtio_blk_init(DeviceState *dev, BlockConf *conf)
 {
     VirtIOBlock *s;
@@ -546,6 +555,7 @@ VirtIODevice *virtio_blk_init(DeviceStat
     register_savevm(dev, "virtio-blk", virtio_blk_id++, 2,
                     virtio_blk_save, virtio_blk_load, s);
     bdrv_set_removable(s->bs, 0);
+    bdrv_set_change_cb(s->bs, virtio_blk_change_cb, s);
     s->bs->buffer_alignment = conf->logical_block_size;
 
     add_boot_device_path(conf->bootindex, dev, "/disk@0,0");

[Qemu-devel] Re: [PATCH 0/3 v2] allow online resizing of block devices

[Juan Quintela]

Christoph Hellwig <hch@lst.de> wrote:
> This patchset adds support for online resizing of block devices.
>
> The first patch adds a new resize monitor command which call into
> the existing image resize code.  This is the meat of the series
> and probably needs quite a bit of review and help as I'm not sure
> about how to implement the error handling for monitor commands
> correctly.  Am I really supposed to add a new QERR_ definition
> for each possible error?  And if yes how am I supposed to define
> them?  The macros for them aren't exactly self-explaining.
>
> The second patch adds a way to tell drivers about a resize, and the
> third one adds a guest notification for config changes to virtio-blk
> which allows the guest to pick it up without a rescan.  I've just sent
> the corresponding Linux guest driver patch to Rusty.
>
> Changes from version 1 to version 2:
>  - also add a QMP command (block_resize)
>  - use the o format for the size in the monitor command
>  - fix typos
>  - use QERR_UNDEFINED_ERROR for errors instead of unstructured strings
>  - remove the CDROM hint check
>  - add a reason argument to the change callback

Does this handle the change of the rtc data?  I can't see how/where.
(Not that I know if it is important at all until reboot).

cmos_init_hb() uses the size to guess the right geometry of the drives,
if we change the size of the drive, should we change that one?



Later, Juan.

hw/pc.c
static void pc_cmos_init_late(void *opaque)
{
    pc_cmos_init_late_arg *arg = opaque;
    ISADevice *s = arg->rtc_state;
    pint val;
    BlockDriverState *hd_table[4];
    int i;

    ide_get_bs(hd_table, arg->idebus0);
    ide_get_bs(hd_table + 2, arg->idebus1);

    rtc_set_memory(s, 0x12, (hd_table[0] ? 0xf0 : 0) | (hd_table[1] ? 0x0f : 0));
    if (hd_table[0])
        cmos_init_hd(0x19, 0x1b, hd_table[0], s);
    if (hd_table[1])
        cmos_init_hd(0x1a, 0x24, hd_table[1], s);

.....
}

static void cmos_init_hd(int type_ofs, int info_ofs, BlockDriverState *hd,
                         ISADevice *s)
{
    int cylinders, heads, sectors;
    bdrv_get_geometry_hint(hd, &cylinders, &heads, &sectors);
    rtc_set_memory(s, type_ofs, 47);
    rtc_set_memory(s, info_ofs, cylinders);
    rtc_set_memory(s, info_ofs + 1, cylinders >> 8);
    rtc_set_memory(s, info_ofs + 2, heads);
....

Re: [Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Stefan Hajnoczi]

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

Re: [Qemu-devel] [PATCH 2/3] block: tell drivers about an image resize

[Stefan Hajnoczi]

On Wed, Jan 19, 2011 at 5:02 PM, Christoph Hellwig <hch@lst.de> wrote:
> Extend the change_cb callback with a reason argument, and use it
> to tell drivers about size changes.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
>
> Index: qemu/block.c
> ===================================================================
> --- qemu.orig/block.c   2011-01-18 20:54:45.246021572 +0100
> +++ qemu/block.c        2011-01-18 20:56:54.117255612 +0100
> @@ -645,7 +645,7 @@ int bdrv_open(BlockDriverState *bs, cons
>         /* call the change callback */
>         bs->media_changed = 1;
>         if (bs->change_cb)
> -            bs->change_cb(bs->change_opaque);
> +            bs->change_cb(bs->change_opaque, CHANGE_MEDIA);

Cool, this is much nicer than stashing away state like
bs->media_changed = 1.  I just took a peek to see if we can remove
that field completely but IDE seems to use it internally.

Stefan

[Qemu-devel] Re: [PATCH 0/3 v2] allow online resizing of block devices

[Christoph Hellwig]

On Wed, Jan 19, 2011 at 06:26:49PM +0100, Juan Quintela wrote:
> Does this handle the change of the rtc data?  I can't see how/where.
> (Not that I know if it is important at all until reboot).

It doesn't.

> cmos_init_hb() uses the size to guess the right geometry of the drives,
> if we change the size of the drive, should we change that one?

I don't think changing geometry on a live system is a good idea.  But
as mentioned at least for Linux guests there's no way to find out about
the new size of an IDE disk right now.  Although I might send a patch
to allow a manual rescan, similar to SCSI.

Re: [Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Christoph Hellwig]

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.

Re: [Qemu-devel] [PATCH 2/3] block: tell drivers about an image resize

[Christoph Hellwig]

On Thu, Jan 20, 2011 at 09:14:17AM +0000, Stefan Hajnoczi wrote:
> Cool, this is much nicer than stashing away state like
> bs->media_changed = 1.  I just took a peek to see if we can remove
> that field completely but IDE seems to use it internally.

I think we could get rid of it in generic code, but let's keep this
series simple.

Re: [Qemu-devel] [PATCH 2/3] block: tell drivers about an image resize

[Kevin Wolf]

Am 19.01.2011 18:02, schrieb Christoph Hellwig:
> Extend the change_cb callback with a reason argument, and use it
> to tell drivers about size changes.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> Index: qemu/block.c
> ===================================================================
> --- qemu.orig/block.c	2011-01-18 20:54:45.246021572 +0100
> +++ qemu/block.c	2011-01-18 20:56:54.117255612 +0100
> @@ -645,7 +645,7 @@ int bdrv_open(BlockDriverState *bs, cons
>          /* call the change callback */
>          bs->media_changed = 1;
>          if (bs->change_cb)
> -            bs->change_cb(bs->change_opaque);
> +            bs->change_cb(bs->change_opaque, CHANGE_MEDIA);
>      }
>  
>      return 0;
> @@ -684,7 +684,7 @@ void bdrv_close(BlockDriverState *bs)
>          /* call the change callback */
>          bs->media_changed = 1;
>          if (bs->change_cb)
> -            bs->change_cb(bs->change_opaque);
> +            bs->change_cb(bs->change_opaque, CHANGE_MEDIA);
>      }
>  }
>  
> @@ -1135,6 +1135,8 @@ int bdrv_truncate(BlockDriverState *bs,
>      ret = drv->bdrv_truncate(bs, offset);
>      if (ret == 0) {
>          ret = refresh_total_sectors(bs, offset >> BDRV_SECTOR_BITS);
> +        if (bs->change_cb)
> +            bs->change_cb(bs->change_opaque, CHANGE_SIZE);

Braces are missing here.

Apart from that and Stefan's s/id/device/ the series looks good to me.

Kevin

Re: [Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Christoph Hellwig]

On Wed, Jan 19, 2011 at 05:01:19PM +0100, Kevin Wolf wrote:
> Oh, okay, then it makes perfect sense. We should fix 'o' then to use
> int64_t. The patch below should do it.
> 
> strtosz (which is used by 'o') has the same problem in git master.
> There's a fix by Jes, so be sure to test this on the block branch.

The larger sizes work fine on the block branch.

Re: [Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Kevin Wolf]

Am 19.01.2011 16:52, schrieb Christoph Hellwig:
> On Wed, Jan 19, 2011 at 04:49:04PM +0100, Kevin Wolf wrote:
>>> (qemu) resize scratch 2047 
>>> resize scratch 2047 
>>> (qemu) 
>>> (qemu) resize scrarch 2048
>>> resize scrarch 2048
>>> invalid size
>>>
>>> for l these worked fine.
>>
>> Hm, yeah, 'o' uses ssize_t instead of int64_t, so it's broken on a 32
>> bit host as well. Though I assume that you use a 64 bit host, and I
>> can't really see what's the problem there...
> 
> This is a test on a 32-bit host.  The target_long of "l" worked fine
> because a kvm enabled qemu always builds for an x86-64 target, even
> with a 32-bit host.

Oh, okay, then it makes perfect sense. We should fix 'o' then to use
int64_t. The patch below should do it.

strtosz (which is used by 'o') has the same problem in git master.
There's a fix by Jes, so be sure to test this on the block branch.

Kevin

diff --git a/monitor.c b/monitor.c
index d291158..0cda3da 100644
--- a/monitor.c
+++ b/monitor.c
@@ -4162,7 +4162,7 @@ static const mon_cmd_t
*monitor_parse_command(Monitor *mon,
             break;
         case 'o':
             {
-                ssize_t val;
+                int64_t val;
                 char *end;

                 while (qemu_isspace(*p)) {

Re: [Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Christoph Hellwig]

On Wed, Jan 19, 2011 at 04:49:04PM +0100, Kevin Wolf wrote:
> > (qemu) resize scratch 2047 
> > resize scratch 2047 
> > (qemu) 
> > (qemu) resize scrarch 2048
> > resize scrarch 2048
> > invalid size
> > 
> > for l these worked fine.
> 
> Hm, yeah, 'o' uses ssize_t instead of int64_t, so it's broken on a 32
> bit host as well. Though I assume that you use a 64 bit host, and I
> can't really see what's the problem there...

This is a test on a 32-bit host.  The target_long of "l" worked fine
because a kvm enabled qemu always builds for an x86-64 target, even
with a 32-bit host.

Re: [Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Kevin Wolf]

Am 19.01.2011 16:35, schrieb Christoph Hellwig:
> On Mon, Jan 17, 2011 at 06:36:15PM +0100, Kevin Wolf wrote:
>>> +        .args_type  = "id:s,size:l",
>>
>> size should be 'o' instead of 'l'. The latter may be too small on 32 bit
>> hosts and doesn't support convenient suffixes:
> 
> o actually fails for 2GB or more for me:
> 
> (qemu) resize scratch 2047 
> resize scratch 2047 
> (qemu) 
> (qemu) resize scrarch 2048
> resize scrarch 2048
> invalid size
> 
> for l these worked fine.

Hm, yeah, 'o' uses ssize_t instead of int64_t, so it's broken on a 32
bit host as well. Though I assume that you use a 64 bit host, and I
can't really see what's the problem there...

Kevin

Re: [Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Christoph Hellwig]

On Mon, Jan 17, 2011 at 06:36:15PM +0100, Kevin Wolf wrote:
> > +        .args_type  = "id:s,size:l",
> 
> size should be 'o' instead of 'l'. The latter may be too small on 32 bit
> hosts and doesn't support convenient suffixes:

o actually fails for 2GB or more for me:

(qemu) resize scratch 2047 
resize scratch 2047 
(qemu) 
(qemu) resize scrarch 2048
resize scrarch 2048
invalid size

for l these worked fine.

Re: [Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Christoph Hellwig]

On Mon, Jan 17, 2011 at 06:36:15PM +0100, Kevin Wolf wrote:
> size should be 'o' instead of 'l'. The latter may be too small on 32 bit
> hosts and doesn't support convenient suffixes:

Fixed.

> Hm, is there a real reason except that CD-ROMs are read-only? The code
> below seems to take read-only devices into account.

I've removed the CDROM check for the next version.

Re: [Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Kevin Wolf]

Am 14.01.2011 17:20, schrieb Christoph Hellwig:
> 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>
> 
> Index: qemu/hmp-commands.hx
> ===================================================================
> --- qemu.orig/hmp-commands.hx	2011-01-14 15:11:48.527004132 +0100
> +++ qemu/hmp-commands.hx	2011-01-14 15:40:14.407006506 +0100
> @@ -53,6 +53,24 @@ Quit the emulator.
>  ETEXI
>  
>      {
> +        .name       = "resize",
> +        .args_type  = "id:s,size:l",

size should be 'o' instead of 'l'. The latter may be too small on 32 bit
hosts and doesn't support convenient suffixes:

 * 'l'          target long (32 or 64 bit)

 * 'o'          octets (aka bytes)
 *              user mode accepts an optional T, t, G, g, M, m, K, k
 *              suffix, which multiplies the value by 2^40 for
 *              suffixes T and t, 2^30 for suffixes G and g, 2^20 for
 *              M and m, 2^10 for K and k

> +        .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.  Usuaully requires guest
> +action to see the updated size.  Resize to a lower size is supported,
> +but should be used with extreme caution.
> +ETEXI
> +
> +
> +    {
>          .name       = "eject",
>          .args_type  = "force:-f,device:B",
>          .params     = "[-f] device",
> Index: qemu/blockdev.c
> ===================================================================
> --- qemu.orig/blockdev.c	2011-01-14 15:11:48.539261151 +0100
> +++ qemu/blockdev.c	2011-01-14 15:50:35.604293558 +0100
> @@ -700,3 +700,41 @@ int do_drive_del(Monitor *mon, const QDi
>  
>      return 0;
>  }
> +
> +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 (bdrv_get_type_hint(bs) == BDRV_TYPE_CDROM) {
> +        error_report("Can not resize CDROM devices\n");
> +        return -1;
> +    }

Hm, is there a real reason except that CD-ROMs are read-only? The code
below seems to take read-only devices into account.

Kevin

Re: [Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Christoph Hellwig]

On Mon, Jan 17, 2011 at 11:28:47AM +0000, Stefan Hajnoczi wrote:
> > + ? ?if (bdrv_get_type_hint(bs) == BDRV_TYPE_CDROM) {
> > + ? ? ? ?error_report("Can not resize CDROM devices\n");
> > + ? ? ? ?return -1;
> > + ? ?}
> 
> Hrm...BDRV_TYPE_FLOPPY probably too?

If we want to be consistent, yes.  Or we could remove the CDROM check
and let people shoot themselves in the foot as much as they want.

Re: [Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Stefan Hajnoczi]

On Fri, Jan 14, 2011 at 4:20 PM, Christoph Hellwig <hch@lst.de> wrote:
> +STEXI
> +@item resize
> +@findex resize
> +Resize a block image while a guest is running.  Usuaully requires guest

s/Usuaully/Usually/

> +action to see the updated size.  Resize to a lower size is supported,
> +but should be used with extreme caution.

This resizes the image files.  Resizing an LVM volume is a useful case
too.  One way to integrate that feature is to implement a host_device
.bdrv_truncate() that checks the underlying device size and returns
success if it matches the new value and failure otherwise.  Or perhaps
allow the QEMU resize command without an argument to fetch the size
from the underlying device (aka refresh the size).

> +    if (bdrv_get_type_hint(bs) == BDRV_TYPE_CDROM) {
> +        error_report("Can not resize CDROM devices\n");
> +        return -1;
> +    }

Hrm...BDRV_TYPE_FLOPPY probably too?

Stefan

[Qemu-devel] [PATCH 1/3] block: add resize monitor command

[Christoph Hellwig]

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>

Index: qemu/hmp-commands.hx
===================================================================
--- qemu.orig/hmp-commands.hx	2011-01-14 15:11:48.527004132 +0100
+++ qemu/hmp-commands.hx	2011-01-14 15:40:14.407006506 +0100
@@ -53,6 +53,24 @@ Quit the emulator.
 ETEXI
 
     {
+        .name       = "resize",
+        .args_type  = "id:s,size:l",
+        .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.  Usuaully requires guest
+action to see the updated size.  Resize to a lower size is supported,
+but should be used with extreme caution.
+ETEXI
+
+
+    {
         .name       = "eject",
         .args_type  = "force:-f,device:B",
         .params     = "[-f] device",
Index: qemu/blockdev.c
===================================================================
--- qemu.orig/blockdev.c	2011-01-14 15:11:48.539261151 +0100
+++ qemu/blockdev.c	2011-01-14 15:50:35.604293558 +0100
@@ -700,3 +700,41 @@ int do_drive_del(Monitor *mon, const QDi
 
     return 0;
 }
+
+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 (bdrv_get_type_hint(bs) == BDRV_TYPE_CDROM) {
+        error_report("Can not resize CDROM devices\n");
+        return -1;
+    }
+
+    if (size < 0) {
+        error_report("Can only resize to positive sizes");
+        return -1;
+    }
+
+    switch (bdrv_truncate(bs, size)) {
+    case 0:
+        return 0;
+    case -ENOTSUP:
+        error_report("This image format does not support resize");
+        return -1;
+    case -EACCES:
+        error_report("Image is read-only");
+        return -1;
+    default:
+        error_report("Error resizing image");
+        return -1;
+    }
+}
+
Index: qemu/blockdev.h
===================================================================
--- qemu.orig/blockdev.h	2011-01-14 15:11:48.548263456 +0100
+++ qemu/blockdev.h	2011-01-14 15:12:00.965047363 +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