[Qemu-devel] [PATCH v1 0/6]: block: Add I/O status support

[Qemu-devel] [PATCH v1 0/6]: block: Add I/O status support

[Luiz Capitulino]

This series adds support to the block layer to keep track of devices'
I/O status. That information is also made available in QMP and HMP.

The goal here is to allow management applications that miss the
BLOCK_IO_ERROR event to able to query the VM to determine if any device has
caused the VM to stop and which device caused it.

Please, note that this series depends on the following series:

 o [PATCH v3 0/8]: Introduce the RunState type
 o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00118.html

And to be able to properly test it you'll also need:

 o [PATCH 0/3] qcow2/coroutine fixes
 o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00074.html

Here's an HMP example:

  (qemu) info status 
  VM status: paused (io-error)
  (qemu) info block
  ide0-hd0: removable=0 io-status=ok file=disks/test2.img ro=0 drv=qcow2 encrypted=0
  ide0-hd1: removable=0 io-status=nospace file=/dev/vg_doriath/kvmtest ro=0 drv=qcow2 encrypted=0
  ide1-cd0: removable=1 locked=0 io-status=ok [not inserted]
  floppy0: removable=1 locked=0 [not inserted]
  sd0: removable=1 locked=0 [not inserted]

The "info status" command shows that the VM is stopped due to an I/O error.
By issuing "info block" it's possible to determine that the 'ide0-hd1' device
caused the error, which turns out to be due to no space.

 block.c         |   51 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 block.h         |    9 +++++++++
 block_int.h     |    1 +
 hw/ide/core.c   |    2 ++
 hw/scsi-disk.c  |    2 ++
 hw/virtio-blk.c |    2 ++
 monitor.c       |    6 ++++++
 qmp-commands.hx |    5 +++++
 8 files changed, 77 insertions(+), 1 deletions(-)

[Qemu-devel] [PATCH 1/6] block: Keep track of devices' I/O status

[Luiz Capitulino]

This commit adds support to the BlockDriverState type to keep track
of the devices' I/O status.

There are three possible status: BDRV_IOS_OK (no error so far),
BDRV_IOS_ENOSPC (no space error) and BDRV_IOS_FAILED (any other error).
The distinction between no space and other errors is important because
a management application may want to watch for no space in order to
extend the host's underline device and put the VM to run again.

Qemu devices supporting the I/O status feature have to enable it
explicitly by calling bdrv_iostatus_enable() _and_ have to be
configured to stop the VM on errors (ie. werror=stop|enospc or
rerror=stop).

In case of multiple errors being triggered in sequence only the first
one is stored. The I/O status is set back to BDRV_IOS_OK when the
'cont' command is issued.

Next commits will add support to some devices and extend the
query-block/info block commands with the I/O status information.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 block.c     |   32 ++++++++++++++++++++++++++++++++
 block.h     |    9 +++++++++
 block_int.h |    1 +
 monitor.c   |    6 ++++++
 4 files changed, 48 insertions(+), 0 deletions(-)

diff --git a/block.c b/block.c
index 03a21d8..c54caf2 100644
--- a/block.c
+++ b/block.c
@@ -220,6 +220,7 @@ BlockDriverState *bdrv_new(const char *device_name)
     if (device_name[0] != '\0') {
         QTAILQ_INSERT_TAIL(&bdrv_states, bs, list);
     }
+    bs->iostatus = BDRV_IOS_INVAL;
     return bs;
 }
 
@@ -3165,6 +3166,37 @@ int bdrv_in_use(BlockDriverState *bs)
     return bs->in_use;
 }
 
+void bdrv_iostatus_enable(BlockDriverState *bs)
+{
+    assert(bs->iostatus == BDRV_IOS_INVAL);
+    bs->iostatus = BDRV_IOS_OK;
+}
+
+/* The I/O status is only enabled if the drive explicitly
+ * enables it _and_ the VM is configured to stop on errors */
+bool bdrv_iostatus_is_enabled(const BlockDriverState *bs)
+{
+    return (bs->iostatus != BDRV_IOS_INVAL &&
+           (bs->on_write_error == BLOCK_ERR_STOP_ENOSPC ||
+            bs->on_write_error == BLOCK_ERR_STOP_ANY    ||
+            bs->on_read_error == BLOCK_ERR_STOP_ANY));
+}
+
+void bdrv_iostatus_reset(BlockDriverState *bs)
+{
+    if (bdrv_iostatus_is_enabled(bs)) {
+        bs->iostatus = BDRV_IOS_OK;
+    }
+}
+
+void bdrv_iostatus_update(BlockDriverState *bs, int error)
+{
+    if (bdrv_iostatus_is_enabled(bs) && bs->iostatus == BDRV_IOS_OK) {
+        bs->iostatus = (abs(error) == ENOSPC) ? BDRV_IOS_ENOSPC :
+                                                BDRV_IOS_FAILED;
+    }
+}
+
 void
 bdrv_acct_start(BlockDriverState *bs, BlockAcctCookie *cookie, int64_t bytes,
         enum BlockAcctType type)
diff --git a/block.h b/block.h
index 3ac0b94..24914e0 100644
--- a/block.h
+++ b/block.h
@@ -51,6 +51,15 @@ typedef enum {
     BDRV_ACTION_REPORT, BDRV_ACTION_IGNORE, BDRV_ACTION_STOP
 } BlockMonEventAction;
 
+typedef enum {
+    BDRV_IOS_INVAL, BDRV_IOS_OK, BDRV_IOS_FAILED, BDRV_IOS_ENOSPC,
+    BDRV_IOS_MAX
+} BlockIOStatus;
+
+void bdrv_iostatus_enable(BlockDriverState *bs);
+void bdrv_iostatus_reset(BlockDriverState *bs);
+bool bdrv_iostatus_is_enabled(const BlockDriverState *bs);
+void bdrv_iostatus_update(BlockDriverState *bs, int error);
 void bdrv_mon_event(const BlockDriverState *bdrv,
                     BlockMonEventAction action, int is_read);
 void bdrv_info_print(Monitor *mon, const QObject *data);
diff --git a/block_int.h b/block_int.h
index 8a72b80..600801d 100644
--- a/block_int.h
+++ b/block_int.h
@@ -203,6 +203,7 @@ struct BlockDriverState {
        drivers. They are not used by the block driver */
     int cyls, heads, secs, translation;
     BlockErrorAction on_read_error, on_write_error;
+    BlockIOStatus iostatus;
     char device_name[32];
     unsigned long *dirty_bitmap;
     int64_t dirty_count;
diff --git a/monitor.c b/monitor.c
index 9807005..69f1b3c 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1302,6 +1302,11 @@ struct bdrv_iterate_context {
     int err;
 };
 
+static void iostatus_bdrv_it(void *opaque, BlockDriverState *bs)
+{
+    bdrv_iostatus_reset(bs);
+}
+
 /**
  * do_cont(): Resume emulation.
  */
@@ -1318,6 +1323,7 @@ static int do_cont(Monitor *mon, const QDict *qdict, QObject **ret_data)
         return -1;
     }
 
+    bdrv_iterate(iostatus_bdrv_it, NULL);
     bdrv_iterate(encrypted_bdrv_it, &context);
     /* only resume the vm if all keys are set and valid */
     if (!context.err) {
-- 
1.7.7.rc0.72.g4b5ea

[Qemu-devel] [PATCH 2/6] virtio: Support I/O status

[Luiz Capitulino]

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 hw/virtio-blk.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index 8a33720..bd81586 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -78,6 +78,7 @@ static int virtio_blk_handle_rw_error(VirtIOBlockReq *req, int error,
         s->rq = req;
         bdrv_mon_event(s->bs, BDRV_ACTION_STOP, is_read);
         vm_stop(RSTATE_IO_ERROR);
+        bdrv_iostatus_update(s->bs, error);
     } else {
         virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
         bdrv_acct_done(s->bs, &req->acct);
@@ -602,6 +603,7 @@ VirtIODevice *virtio_blk_init(DeviceState *dev, BlockConf *conf,
     bdrv_set_change_cb(s->bs, virtio_blk_change_cb, s);
     s->bs->buffer_alignment = conf->logical_block_size;
 
+    bdrv_iostatus_enable(s->bs);
     add_boot_device_path(conf->bootindex, dev, "/disk@0,0");
 
     return &s->vdev;
-- 
1.7.7.rc0.72.g4b5ea

[Qemu-devel] [PATCH 3/6] ide: Support I/O status

[Luiz Capitulino]

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 hw/ide/core.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/hw/ide/core.c b/hw/ide/core.c
index 41f2679..16b422f 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -527,6 +527,7 @@ static int ide_handle_rw_error(IDEState *s, int error, int op)
         s->bus->error_status = op;
         bdrv_mon_event(s->bs, BDRV_ACTION_STOP, is_read);
         vm_stop(RSTATE_IO_ERROR);
+        bdrv_iostatus_update(s->bs, error);
     } else {
         if (op & BM_STATUS_DMA_RETRY) {
             dma_buf_commit(s, 0);
@@ -1801,6 +1802,7 @@ int ide_init_drive(IDEState *s, BlockDriverState *bs, IDEDriveKind kind,
     }
 
     ide_reset(s);
+    bdrv_iostatus_enable(bs);
     bdrv_set_removable(bs, s->drive_kind == IDE_CD);
     return 0;
 }
-- 
1.7.7.rc0.72.g4b5ea

[Qemu-devel] [PATCH 4/6] scsi: Support I/O status

[Luiz Capitulino]

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 hw/scsi-disk.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index 9f451bc..85b1ce0 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -193,6 +193,7 @@ static int scsi_handle_rw_error(SCSIDiskReq *r, int error, int type)
 
         bdrv_mon_event(s->bs, BDRV_ACTION_STOP, is_read);
         vm_stop(RSTATE_IO_ERROR);
+        bdrv_iostatus_update(s->bs, error);
     } else {
         switch (error) {
         case ENOMEM:
@@ -1168,6 +1169,7 @@ static int scsi_initfn(SCSIDevice *dev, uint8_t scsi_type)
 
     s->qdev.type = scsi_type;
     qemu_add_vm_change_state_handler(scsi_dma_restart_cb, s);
+    bdrv_iostatus_enable(s->bs);
     bdrv_set_removable(s->bs, scsi_type == TYPE_ROM);
     add_boot_device_path(s->qdev.conf.bootindex, &dev->qdev, ",0");
     return 0;
-- 
1.7.7.rc0.72.g4b5ea

[Qemu-devel] [PATCH 5/6] QMP: query-status: Add 'io-status' key

[Luiz Capitulino]

Contains the I/O status for the given device. The key is only present
if the device supports it and the VM is configured to stop on errors.

Please, check the documentation being added in this commit for more
information.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 block.c         |   15 ++++++++++++++-
 qmp-commands.hx |    5 +++++
 2 files changed, 19 insertions(+), 1 deletions(-)

diff --git a/block.c b/block.c
index c54caf2..77579b6 100644
--- a/block.c
+++ b/block.c
@@ -1865,6 +1865,12 @@ void bdrv_info_print(Monitor *mon, const QObject *data)
     qlist_iter(qobject_to_qlist(data), bdrv_print_dict, mon);
 }
 
+static const char *const io_status_name[BDRV_IOS_MAX] = {
+    [BDRV_IOS_OK] = "ok",
+    [BDRV_IOS_FAILED] = "failed",
+    [BDRV_IOS_ENOSPC] = "nospace",
+};
+
 void bdrv_info(Monitor *mon, QObject **ret_data)
 {
     QList *bs_list;
@@ -1874,15 +1880,16 @@ void bdrv_info(Monitor *mon, QObject **ret_data)
 
     QTAILQ_FOREACH(bs, &bdrv_states, list) {
         QObject *bs_obj;
+        QDict *bs_dict;
 
         bs_obj = qobject_from_jsonf("{ 'device': %s, 'type': 'unknown', "
                                     "'removable': %i, 'locked': %i }",
                                     bs->device_name, bs->removable,
                                     bs->locked);
+        bs_dict = qobject_to_qdict(bs_obj);
 
         if (bs->drv) {
             QObject *obj;
-            QDict *bs_dict = qobject_to_qdict(bs_obj);
 
             obj = qobject_from_jsonf("{ 'file': %s, 'ro': %i, 'drv': %s, "
                                      "'encrypted': %i }",
@@ -1897,6 +1904,12 @@ void bdrv_info(Monitor *mon, QObject **ret_data)
 
             qdict_put_obj(bs_dict, "inserted", obj);
         }
+
+        if (bdrv_iostatus_is_enabled(bs)) {
+            qdict_put(bs_dict, "io-status",
+                      qstring_from_str(io_status_name[bs->iostatus]));
+        }
+
         qlist_append_obj(bs_list, bs_obj);
     }
 
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 1fbda8c..c045043 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1143,6 +1143,9 @@ Each json-object contain the following:
                                 "tftp", "vdi", "vmdk", "vpc", "vvfat"
          - "backing_file": backing file name (json-string, optional)
          - "encrypted": true if encrypted, false otherwise (json-bool)
+- "io-status": I/O operation status, only present if the device supports it
+               and the VM is configured to stop on errors (json_string,optional)
+             - Possible values: "ok", "failed", "nospace"
 
 Example:
 
@@ -1150,6 +1153,7 @@ Example:
 <- {
       "return":[
          {
+            "io-status": "ok",
             "device":"ide0-hd0",
             "locked":false,
             "removable":false,
@@ -1162,6 +1166,7 @@ Example:
             "type":"unknown"
          },
          {
+            "io-status": "ok",
             "device":"ide1-cd0",
             "locked":false,
             "removable":true,
-- 
1.7.7.rc0.72.g4b5ea

[Qemu-devel] [PATCH 6/6] HMP: Print 'io-status' information

[Luiz Capitulino]

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 block.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/block.c b/block.c
index 77579b6..ac9e913 100644
--- a/block.c
+++ b/block.c
@@ -1840,6 +1840,10 @@ static void bdrv_print_dict(QObject *obj, void *opaque)
         monitor_printf(mon, " locked=%d", qdict_get_bool(bs_dict, "locked"));
     }
 
+    if (qdict_haskey(bs_dict, "io-status")) {
+        monitor_printf(mon, " io-status=%s", qdict_get_str(bs_dict, "io-status"));
+    }
+
     if (qdict_haskey(bs_dict, "inserted")) {
         QDict *qdict = qobject_to_qdict(qdict_get(bs_dict, "inserted"));
 
-- 
1.7.7.rc0.72.g4b5ea

Re: [Qemu-devel] [PATCH v1 0/6]: block: Add I/O status support

[Luiz Capitulino]

On Thu,  1 Sep 2011 15:37:49 -0300
Luiz Capitulino <lcapitulino@redhat.com> wrote:

> This series adds support to the block layer to keep track of devices'
> I/O status. That information is also made available in QMP and HMP.

ping?

I'll have to rebase it anyway, but I'd like to know if the general approach
is acceptable.

Re: [Qemu-devel] [PATCH v1 0/6]: block: Add I/O status support

[Kevin Wolf]

Am 01.09.2011 20:37, schrieb Luiz Capitulino:
> This series adds support to the block layer to keep track of devices'
> I/O status. That information is also made available in QMP and HMP.
> 
> The goal here is to allow management applications that miss the
> BLOCK_IO_ERROR event to able to query the VM to determine if any device has
> caused the VM to stop and which device caused it.
> 
> Please, note that this series depends on the following series:
> 
>  o [PATCH v3 0/8]: Introduce the RunState type
>  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00118.html
> 
> And to be able to properly test it you'll also need:
> 
>  o [PATCH 0/3] qcow2/coroutine fixes
>  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00074.html
> 
> Here's an HMP example:
> 
>   (qemu) info status 
>   VM status: paused (io-error)
>   (qemu) info block
>   ide0-hd0: removable=0 io-status=ok file=disks/test2.img ro=0 drv=qcow2 encrypted=0
>   ide0-hd1: removable=0 io-status=nospace file=/dev/vg_doriath/kvmtest ro=0 drv=qcow2 encrypted=0
>   ide1-cd0: removable=1 locked=0 io-status=ok [not inserted]
>   floppy0: removable=1 locked=0 [not inserted]
>   sd0: removable=1 locked=0 [not inserted]
> 
> The "info status" command shows that the VM is stopped due to an I/O error.
> By issuing "info block" it's possible to determine that the 'ide0-hd1' device
> caused the error, which turns out to be due to no space.

Looks like I didn't reply here yet?

I still don't quite like that the devices are involved, but their part
is minimal and it makes the implementation much easier, so for me that's
acceptable.

Kevin

Re: [Qemu-devel] [PATCH v1 0/6]: block: Add I/O status support

[Luiz Capitulino]

On Mon, 19 Sep 2011 15:40:06 +0200
Kevin Wolf <kwolf@redhat.com> wrote:

> Am 01.09.2011 20:37, schrieb Luiz Capitulino:
> > This series adds support to the block layer to keep track of devices'
> > I/O status. That information is also made available in QMP and HMP.
> > 
> > The goal here is to allow management applications that miss the
> > BLOCK_IO_ERROR event to able to query the VM to determine if any device has
> > caused the VM to stop and which device caused it.
> > 
> > Please, note that this series depends on the following series:
> > 
> >  o [PATCH v3 0/8]: Introduce the RunState type
> >  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00118.html
> > 
> > And to be able to properly test it you'll also need:
> > 
> >  o [PATCH 0/3] qcow2/coroutine fixes
> >  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00074.html
> > 
> > Here's an HMP example:
> > 
> >   (qemu) info status 
> >   VM status: paused (io-error)
> >   (qemu) info block
> >   ide0-hd0: removable=0 io-status=ok file=disks/test2.img ro=0 drv=qcow2 encrypted=0
> >   ide0-hd1: removable=0 io-status=nospace file=/dev/vg_doriath/kvmtest ro=0 drv=qcow2 encrypted=0
> >   ide1-cd0: removable=1 locked=0 io-status=ok [not inserted]
> >   floppy0: removable=1 locked=0 [not inserted]
> >   sd0: removable=1 locked=0 [not inserted]
> > 
> > The "info status" command shows that the VM is stopped due to an I/O error.
> > By issuing "info block" it's possible to determine that the 'ide0-hd1' device
> > caused the error, which turns out to be due to no space.
> 
> Looks like I didn't reply here yet?

No, you didn't.

> I still don't quite like that the devices are involved, but their part
> is minimal and it makes the implementation much easier, so for me that's
> acceptable.

Suggestions on better ways of implementing this are welcome! :)

Re: [Qemu-devel] [PATCH v1 0/6]: block: Add I/O status support

[Kevin Wolf]

Am 19.09.2011 16:09, schrieb Luiz Capitulino:
> On Mon, 19 Sep 2011 15:40:06 +0200
> Kevin Wolf <kwolf@redhat.com> wrote:
> 
>> Am 01.09.2011 20:37, schrieb Luiz Capitulino:
>>> This series adds support to the block layer to keep track of devices'
>>> I/O status. That information is also made available in QMP and HMP.
>>>
>>> The goal here is to allow management applications that miss the
>>> BLOCK_IO_ERROR event to able to query the VM to determine if any device has
>>> caused the VM to stop and which device caused it.
>>>
>>> Please, note that this series depends on the following series:
>>>
>>>  o [PATCH v3 0/8]: Introduce the RunState type
>>>  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00118.html
>>>
>>> And to be able to properly test it you'll also need:
>>>
>>>  o [PATCH 0/3] qcow2/coroutine fixes
>>>  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00074.html
>>>
>>> Here's an HMP example:
>>>
>>>   (qemu) info status 
>>>   VM status: paused (io-error)
>>>   (qemu) info block
>>>   ide0-hd0: removable=0 io-status=ok file=disks/test2.img ro=0 drv=qcow2 encrypted=0
>>>   ide0-hd1: removable=0 io-status=nospace file=/dev/vg_doriath/kvmtest ro=0 drv=qcow2 encrypted=0
>>>   ide1-cd0: removable=1 locked=0 io-status=ok [not inserted]
>>>   floppy0: removable=1 locked=0 [not inserted]
>>>   sd0: removable=1 locked=0 [not inserted]
>>>
>>> The "info status" command shows that the VM is stopped due to an I/O error.
>>> By issuing "info block" it's possible to determine that the 'ide0-hd1' device
>>> caused the error, which turns out to be due to no space.
>>
>> Looks like I didn't reply here yet?
> 
> No, you didn't.
> 
>> I still don't quite like that the devices are involved, but their part
>> is minimal and it makes the implementation much easier, so for me that's
>> acceptable.
> 
> Suggestions on better ways of implementing this are welcome! :)

I don't have one. :-)

Surely it would be possible to do everything in block.c, but I see that
this would make things much more complicated (would need to get an AIO
callback added to the chain that can save the error code). It's not
worth the trouble.

Kevin

Re: [Qemu-devel] [PATCH v1 0/6]: block: Add I/O status support

[Markus Armbruster]

Kevin Wolf <kwolf@redhat.com> writes:

> Am 19.09.2011 16:09, schrieb Luiz Capitulino:
>> On Mon, 19 Sep 2011 15:40:06 +0200
>> Kevin Wolf <kwolf@redhat.com> wrote:
>> 
>>> Am 01.09.2011 20:37, schrieb Luiz Capitulino:
>>>> This series adds support to the block layer to keep track of devices'
>>>> I/O status. That information is also made available in QMP and HMP.
>>>>
>>>> The goal here is to allow management applications that miss the
>>>> BLOCK_IO_ERROR event to able to query the VM to determine if any device has
>>>> caused the VM to stop and which device caused it.
>>>>
>>>> Please, note that this series depends on the following series:
>>>>
>>>>  o [PATCH v3 0/8]: Introduce the RunState type
>>>>  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00118.html
>>>>
>>>> And to be able to properly test it you'll also need:
>>>>
>>>>  o [PATCH 0/3] qcow2/coroutine fixes
>>>>  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00074.html
>>>>
>>>> Here's an HMP example:
>>>>
>>>>   (qemu) info status 
>>>>   VM status: paused (io-error)
>>>>   (qemu) info block
>>>>   ide0-hd0: removable=0 io-status=ok file=disks/test2.img ro=0 drv=qcow2 encrypted=0
>>>>   ide0-hd1: removable=0 io-status=nospace file=/dev/vg_doriath/kvmtest ro=0 drv=qcow2 encrypted=0
>>>>   ide1-cd0: removable=1 locked=0 io-status=ok [not inserted]
>>>>   floppy0: removable=1 locked=0 [not inserted]
>>>>   sd0: removable=1 locked=0 [not inserted]
>>>>
>>>> The "info status" command shows that the VM is stopped due to an I/O error.
>>>> By issuing "info block" it's possible to determine that the 'ide0-hd1' device
>>>> caused the error, which turns out to be due to no space.
>>>
>>> Looks like I didn't reply here yet?
>> 
>> No, you didn't.
>> 
>>> I still don't quite like that the devices are involved, but their part
>>> is minimal and it makes the implementation much easier, so for me that's
>>> acceptable.
>> 
>> Suggestions on better ways of implementing this are welcome! :)
>
> I don't have one. :-)
>
> Surely it would be possible to do everything in block.c, but I see that
> this would make things much more complicated (would need to get an AIO
> callback added to the chain that can save the error code). It's not
> worth the trouble.

The block layer necessarily detects errors in a huge number of places.

It also has a rich and complex interface to device models, with error
reporting in many places.

virtio-blk, ide and scsi-disk each have a single error handler to handle
block layer errors.

For better or worse, these are the only block layer error "chokepoints"
we have now, and therefore the only easy places to set BDS I/O status.
But they're still wrong.

The block layer shouldn't require device models to tell it what it
already knows.

Now, I don't want to block your series just because it adds this wart.
But the wart should be documented in the code.

Also document that any device model implementing werror=stop|enospc or
rerror=stop must update I/O status.  Extra points if you find a way to
enforce it instead.

Apropos enforcing.  Currently, -drive accepts any werror and rerror
action with if={ide,virtio,scsi,none}.  We rely on device models not
implementing an action to check and fail during initialization.
scsi-generic and the floppy devices do.  All the other qdevified devices
don't, and that's broken.

Are werror and rerror really host state?

Re: [Qemu-devel] [PATCH v1 0/6]: block: Add I/O status support

[Kevin Wolf]

Am 23.09.2011 10:55, schrieb Markus Armbruster:
> Kevin Wolf <kwolf@redhat.com> writes:
> 
>> Am 19.09.2011 16:09, schrieb Luiz Capitulino:
>>> On Mon, 19 Sep 2011 15:40:06 +0200
>>> Kevin Wolf <kwolf@redhat.com> wrote:
>>>
>>>> Am 01.09.2011 20:37, schrieb Luiz Capitulino:
>>>>> This series adds support to the block layer to keep track of devices'
>>>>> I/O status. That information is also made available in QMP and HMP.
>>>>>
>>>>> The goal here is to allow management applications that miss the
>>>>> BLOCK_IO_ERROR event to able to query the VM to determine if any device has
>>>>> caused the VM to stop and which device caused it.
>>>>>
>>>>> Please, note that this series depends on the following series:
>>>>>
>>>>>  o [PATCH v3 0/8]: Introduce the RunState type
>>>>>  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00118.html
>>>>>
>>>>> And to be able to properly test it you'll also need:
>>>>>
>>>>>  o [PATCH 0/3] qcow2/coroutine fixes
>>>>>  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00074.html
>>>>>
>>>>> Here's an HMP example:
>>>>>
>>>>>   (qemu) info status 
>>>>>   VM status: paused (io-error)
>>>>>   (qemu) info block
>>>>>   ide0-hd0: removable=0 io-status=ok file=disks/test2.img ro=0 drv=qcow2 encrypted=0
>>>>>   ide0-hd1: removable=0 io-status=nospace file=/dev/vg_doriath/kvmtest ro=0 drv=qcow2 encrypted=0
>>>>>   ide1-cd0: removable=1 locked=0 io-status=ok [not inserted]
>>>>>   floppy0: removable=1 locked=0 [not inserted]
>>>>>   sd0: removable=1 locked=0 [not inserted]
>>>>>
>>>>> The "info status" command shows that the VM is stopped due to an I/O error.
>>>>> By issuing "info block" it's possible to determine that the 'ide0-hd1' device
>>>>> caused the error, which turns out to be due to no space.
>>>>
>>>> Looks like I didn't reply here yet?
>>>
>>> No, you didn't.
>>>
>>>> I still don't quite like that the devices are involved, but their part
>>>> is minimal and it makes the implementation much easier, so for me that's
>>>> acceptable.
>>>
>>> Suggestions on better ways of implementing this are welcome! :)
>>
>> I don't have one. :-)
>>
>> Surely it would be possible to do everything in block.c, but I see that
>> this would make things much more complicated (would need to get an AIO
>> callback added to the chain that can save the error code). It's not
>> worth the trouble.
> 
> The block layer necessarily detects errors in a huge number of places.
> 
> It also has a rich and complex interface to device models, with error
> reporting in many places.
> 
> virtio-blk, ide and scsi-disk each have a single error handler to handle
> block layer errors.
> 
> For better or worse, these are the only block layer error "chokepoints"
> we have now, and therefore the only easy places to set BDS I/O status.
> But they're still wrong.
> 
> The block layer shouldn't require device models to tell it what it
> already knows.
> 
> Now, I don't want to block your series just because it adds this wart.
> But the wart should be documented in the code.
> 
> Also document that any device model implementing werror=stop|enospc or
> rerror=stop must update I/O status.  Extra points if you find a way to
> enforce it instead.
> 
> Apropos enforcing.  Currently, -drive accepts any werror and rerror
> action with if={ide,virtio,scsi,none}.  We rely on device models not
> implementing an action to check and fail during initialization.
> scsi-generic and the floppy devices do.  All the other qdevified devices
> don't, and that's broken.
> 
> Are werror and rerror really host state?

If you want to convince me of the opposite, show me the real device that
implements them.

In fact, for the implementation of rerror/werror the very same thing is
true as you say about I/O status updates. Other than being easy to
implement, there is really no reason to do it in the devices. The block
layer could just as well stop the VM and queue the requests for
resubmission when the VM is restarted. Of course, you can't keep
migration compatibility when doing such a fundamental change to the
design, but if you take the host state thing serious, this is what you
should do.

Kevin

Re: [Qemu-devel] [PATCH v1 0/6]: block: Add I/O status support

[Markus Armbruster]

Kevin Wolf <kwolf@redhat.com> writes:

> Am 23.09.2011 10:55, schrieb Markus Armbruster:
[...]
>> Apropos enforcing.  Currently, -drive accepts any werror and rerror
>> action with if={ide,virtio,scsi,none}.  We rely on device models not
>> implementing an action to check and fail during initialization.
>> scsi-generic and the floppy devices do.  All the other qdevified devices
>> don't, and that's broken.
>> 
>> Are werror and rerror really host state?
>
> If you want to convince me of the opposite, show me the real device that
> implements them.

It's an honest question.

> In fact, for the implementation of rerror/werror the very same thing is
> true as you say about I/O status updates. Other than being easy to
> implement, there is really no reason to do it in the devices. The block
> layer could just as well stop the VM and queue the requests for
> resubmission when the VM is restarted. Of course, you can't keep
> migration compatibility when doing such a fundamental change to the
> design, but if you take the host state thing serious, this is what you
> should do.

Good answer.  I'd love to have it spelled out in the code.

Re: [Qemu-devel] [PATCH v1 0/6]: block: Add I/O status support

[Luiz Capitulino]

On Fri, 23 Sep 2011 10:55:39 +0200
Markus Armbruster <armbru@redhat.com> wrote:

> Kevin Wolf <kwolf@redhat.com> writes:
> 
> > Am 19.09.2011 16:09, schrieb Luiz Capitulino:
> >> On Mon, 19 Sep 2011 15:40:06 +0200
> >> Kevin Wolf <kwolf@redhat.com> wrote:
> >> 
> >>> Am 01.09.2011 20:37, schrieb Luiz Capitulino:
> >>>> This series adds support to the block layer to keep track of devices'
> >>>> I/O status. That information is also made available in QMP and HMP.
> >>>>
> >>>> The goal here is to allow management applications that miss the
> >>>> BLOCK_IO_ERROR event to able to query the VM to determine if any device has
> >>>> caused the VM to stop and which device caused it.
> >>>>
> >>>> Please, note that this series depends on the following series:
> >>>>
> >>>>  o [PATCH v3 0/8]: Introduce the RunState type
> >>>>  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00118.html
> >>>>
> >>>> And to be able to properly test it you'll also need:
> >>>>
> >>>>  o [PATCH 0/3] qcow2/coroutine fixes
> >>>>  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00074.html
> >>>>
> >>>> Here's an HMP example:
> >>>>
> >>>>   (qemu) info status 
> >>>>   VM status: paused (io-error)
> >>>>   (qemu) info block
> >>>>   ide0-hd0: removable=0 io-status=ok file=disks/test2.img ro=0 drv=qcow2 encrypted=0
> >>>>   ide0-hd1: removable=0 io-status=nospace file=/dev/vg_doriath/kvmtest ro=0 drv=qcow2 encrypted=0
> >>>>   ide1-cd0: removable=1 locked=0 io-status=ok [not inserted]
> >>>>   floppy0: removable=1 locked=0 [not inserted]
> >>>>   sd0: removable=1 locked=0 [not inserted]
> >>>>
> >>>> The "info status" command shows that the VM is stopped due to an I/O error.
> >>>> By issuing "info block" it's possible to determine that the 'ide0-hd1' device
> >>>> caused the error, which turns out to be due to no space.
> >>>
> >>> Looks like I didn't reply here yet?
> >> 
> >> No, you didn't.
> >> 
> >>> I still don't quite like that the devices are involved, but their part
> >>> is minimal and it makes the implementation much easier, so for me that's
> >>> acceptable.
> >> 
> >> Suggestions on better ways of implementing this are welcome! :)
> >
> > I don't have one. :-)
> >
> > Surely it would be possible to do everything in block.c, but I see that
> > this would make things much more complicated (would need to get an AIO
> > callback added to the chain that can save the error code). It's not
> > worth the trouble.
> 
> The block layer necessarily detects errors in a huge number of places.
> 
> It also has a rich and complex interface to device models, with error
> reporting in many places.
> 
> virtio-blk, ide and scsi-disk each have a single error handler to handle
> block layer errors.
> 
> For better or worse, these are the only block layer error "chokepoints"
> we have now, and therefore the only easy places to set BDS I/O status.
> But they're still wrong.
> 
> The block layer shouldn't require device models to tell it what it
> already knows.
> 
> Now, I don't want to block your series just because it adds this wart.
> But the wart should be documented in the code.

Is something like:

 /* XXX: this should be implemented in the block layer */

good enough?

> Also document that any device model implementing werror=stop|enospc or
> rerror=stop must update I/O status.  Extra points if you find a way to
> enforce it instead.

Why? It's probably a nice thing because we can know which device caused
the VM to stop, but I don't see it as a must have (it's probably a
no brainer to update the I/O status though).

> 
> Apropos enforcing.  Currently, -drive accepts any werror and rerror
> action with if={ide,virtio,scsi,none}.  We rely on device models not
> implementing an action to check and fail during initialization.
> scsi-generic and the floppy devices do.  All the other qdevified devices
> don't, and that's broken.

I think I can fix that, but this series doesn't depend on that, right?
(in the meaning that we could merge this before getting that problem fixed).

> 
> Are werror and rerror really host state?
> 

Re: [Qemu-devel] [PATCH v1 0/6]: block: Add I/O status support

[Markus Armbruster]

Luiz Capitulino <lcapitulino@redhat.com> writes:

> On Fri, 23 Sep 2011 10:55:39 +0200
> Markus Armbruster <armbru@redhat.com> wrote:
>
>> Kevin Wolf <kwolf@redhat.com> writes:
>> 
>> > Am 19.09.2011 16:09, schrieb Luiz Capitulino:
>> >> On Mon, 19 Sep 2011 15:40:06 +0200
>> >> Kevin Wolf <kwolf@redhat.com> wrote:
>> >> 
>> >>> Am 01.09.2011 20:37, schrieb Luiz Capitulino:
>> >>>> This series adds support to the block layer to keep track of devices'
>> >>>> I/O status. That information is also made available in QMP and HMP.
>> >>>>
>> >>>> The goal here is to allow management applications that miss the
>> >>>> BLOCK_IO_ERROR event to able to query the VM to determine if any device has
>> >>>> caused the VM to stop and which device caused it.
>> >>>>
>> >>>> Please, note that this series depends on the following series:
>> >>>>
>> >>>>  o [PATCH v3 0/8]: Introduce the RunState type
>> >>>>  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00118.html
>> >>>>
>> >>>> And to be able to properly test it you'll also need:
>> >>>>
>> >>>>  o [PATCH 0/3] qcow2/coroutine fixes
>> >>>>  o http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00074.html
>> >>>>
>> >>>> Here's an HMP example:
>> >>>>
>> >>>>   (qemu) info status 
>> >>>>   VM status: paused (io-error)
>> >>>>   (qemu) info block
>> >>>>   ide0-hd0: removable=0 io-status=ok file=disks/test2.img ro=0 drv=qcow2 encrypted=0
>> >>>>   ide0-hd1: removable=0 io-status=nospace file=/dev/vg_doriath/kvmtest ro=0 drv=qcow2 encrypted=0
>> >>>>   ide1-cd0: removable=1 locked=0 io-status=ok [not inserted]
>> >>>>   floppy0: removable=1 locked=0 [not inserted]
>> >>>>   sd0: removable=1 locked=0 [not inserted]
>> >>>>
>> >>>> The "info status" command shows that the VM is stopped due to an I/O error.
>> >>>> By issuing "info block" it's possible to determine that the 'ide0-hd1' device
>> >>>> caused the error, which turns out to be due to no space.
>> >>>
>> >>> Looks like I didn't reply here yet?
>> >> 
>> >> No, you didn't.
>> >> 
>> >>> I still don't quite like that the devices are involved, but their part
>> >>> is minimal and it makes the implementation much easier, so for me that's
>> >>> acceptable.
>> >> 
>> >> Suggestions on better ways of implementing this are welcome! :)
>> >
>> > I don't have one. :-)
>> >
>> > Surely it would be possible to do everything in block.c, but I see that
>> > this would make things much more complicated (would need to get an AIO
>> > callback added to the chain that can save the error code). It's not
>> > worth the trouble.
>> 
>> The block layer necessarily detects errors in a huge number of places.
>> 
>> It also has a rich and complex interface to device models, with error
>> reporting in many places.
>> 
>> virtio-blk, ide and scsi-disk each have a single error handler to handle
>> block layer errors.
>> 
>> For better or worse, these are the only block layer error "chokepoints"
>> we have now, and therefore the only easy places to set BDS I/O status.
>> But they're still wrong.
>> 
>> The block layer shouldn't require device models to tell it what it
>> already knows.
>> 
>> Now, I don't want to block your series just because it adds this wart.
>> But the wart should be documented in the code.
>
> Is something like:
>
>  /* XXX: this should be implemented in the block layer */
>
> good enough?

Add a brief "why", and it's perfect.

>> Also document that any device model implementing werror=stop|enospc or
>> rerror=stop must update I/O status.  Extra points if you find a way to
>> enforce it instead.
>
> Why? It's probably a nice thing because we can know which device caused
> the VM to stop, but I don't see it as a must have (it's probably a
> no brainer to update the I/O status though).

I misread and thought it would lie in that case, but it's actually
silent then (bdrv_iostatus_is_enabled() returns false).  Thus, it's not
a must.

I'd still be tempted to make it one, so clients can rely on io-status
after error stop.  Can't see why anyone would want to do stop on error
in a device model without also setting I/O status.  But use your own
judgement.

>> Apropos enforcing.  Currently, -drive accepts any werror and rerror
>> action with if={ide,virtio,scsi,none}.  We rely on device models not
>> implementing an action to check and fail during initialization.
>> scsi-generic and the floppy devices do.  All the other qdevified devices
>> don't, and that's broken.
>
> I think I can fix that, but this series doesn't depend on that, right?
> (in the meaning that we could merge this before getting that problem fixed).

Right.

[...]

[Qemu-devel] [PATCH 4/6] scsi: Support I/O status

[Luiz Capitulino]

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 hw/scsi-disk.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index e843f71..a980a53 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -228,6 +228,7 @@ static int scsi_handle_rw_error(SCSIDiskReq *r, int error, int type)
 
         bdrv_mon_event(s->bs, BDRV_ACTION_STOP, is_read);
         vm_stop(RSTATE_IO_ERROR);
+        bdrv_iostatus_set_err(s->bs, error);
     } else {
         switch (error) {
         case ENOMEM:
@@ -1260,6 +1261,7 @@ static int scsi_initfn(SCSIDevice *dev, uint8_t scsi_type)
 
     s->qdev.type = scsi_type;
     qemu_add_vm_change_state_handler(scsi_dma_restart_cb, s);
+    bdrv_iostatus_enable(s->bs);
     add_boot_device_path(s->qdev.conf.bootindex, &dev->qdev, ",0");
     return 0;
 }
-- 
1.7.7.rc0.72.g4b5ea

[Qemu-devel] [PATCH 4/6] scsi: Support I/O status

[Luiz Capitulino]

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 hw/scsi-disk.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index e843f71..a980a53 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -228,6 +228,7 @@ static int scsi_handle_rw_error(SCSIDiskReq *r, int error, int type)
 
         bdrv_mon_event(s->bs, BDRV_ACTION_STOP, is_read);
         vm_stop(RSTATE_IO_ERROR);
+        bdrv_iostatus_set_err(s->bs, error);
     } else {
         switch (error) {
         case ENOMEM:
@@ -1260,6 +1261,7 @@ static int scsi_initfn(SCSIDevice *dev, uint8_t scsi_type)
 
     s->qdev.type = scsi_type;
     qemu_add_vm_change_state_handler(scsi_dma_restart_cb, s);
+    bdrv_iostatus_enable(s->bs);
     add_boot_device_path(s->qdev.conf.bootindex, &dev->qdev, ",0");
     return 0;
 }
-- 
1.7.7.rc0.72.g4b5ea