[Qemu-devel] [RFC PATCH 13/36] block: introduce block job error

[Paolo Bonzini <pbonzini@redhat.com>]

The following behaviors are possible:

'report': The behavior is the same as in 1.1.  An I/O error,
respectively during a read or a write, will complete the job immediately
with an error code.

'ignore': An I/O error, respectively during a read or a write, will be
ignored.  For streaming, the job will complete with an error and the
backing file will be left in place.  For mirroring, the sector will be
marked again as dirty and re-examined later.

'stop': The job will be paused and the job iostatus will be set to
failed or nospace, while the VM will keep running.  This can only be
specified if the block device has rerror=stop and werror=stop or enospc.

'enospc': Behaves as 'stop' for ENOSPC errors, 'report' for others.

In all cases, even for 'report', the I/O error is reported as a QMP
event BLOCK_JOB_ERROR, with the same arguments as BLOCK_IO_ERROR.

It is possible that while stopping the VM a BLOCK_IO_ERROR event will be
reported and will clobber the event from BLOCK_JOB_ERROR, or vice versa.
This is not really avoidable since stopping the VM completes all pending
I/O requests.  In fact, it is already possible now that a series of
BLOCK_IO_ERROR events are reported with rerror=stop, because vm_stop
calls bdrv_drain_all and this can generate further errors.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 QMP/qmp-events.txt |   27 +++++++++++++++++++++++
 block.c            |    9 ++++----
 block_int.h        |    4 ++++
 blockjob.c         |   62 +++++++++++++++++++++++++++++++++++++++++++++++-----
 blockjob.h         |   17 ++++++++++++++
 monitor.c          |    1 +
 monitor.h          |    1 +
 qapi-schema.json   |    5 ++++-
 8 files changed, 115 insertions(+), 11 deletions(-)

diff --git a/QMP/qmp-events.txt b/QMP/qmp-events.txt
index 9286af5..6e09ee6 100644
--- a/QMP/qmp-events.txt
+++ b/QMP/qmp-events.txt
@@ -335,3 +335,30 @@ Example:
                "len": 10737418240, "offset": 134217728,
                "speed": 0 },
      "timestamp": { "seconds": 1267061043, "microseconds": 959568 } }
+
+
+BLOCK_JOB_ERROR
+---------------
+
+Emitted when a block job encounters an error.
+
+Data:
+
+- "device": device name (json-string)
+- "operation": I/O operation (json-string, "read" or "write")
+- "action": action that has been taken, it's one of the following (json-string):
+    "ignore": error has been ignored, the job may fail later
+    "report": error will be reported and the job canceled
+    "stop": error caused job to be paused
+
+Example:
+
+{ "event": "BLOCK_JOB_ERROR",
+    "data": { "device": "ide0-hd1",
+              "operation": "write",
+              "action": "stop" },
+    "timestamp": { "seconds": 1265044230, "microseconds": 450486 } }
+
+Note: If action is "stop", a STOP event will eventually follow the
+BLOCK_JOB_ERROR event.  If action is "report", a BLOCK_JOB_CANCELLED
+event will eventually follow the BLOCK_JOB_ERROR event.
diff --git a/block.c b/block.c
index 2f6384a..4b580b5 100644
--- a/block.c
+++ b/block.c
@@ -1159,8 +1159,9 @@ void bdrv_set_dev_ops(BlockDriverState *bs, const BlockDevOps *ops,
     }
 }
 
-static void bdrv_emit_qmp_error_event(const BlockDriverState *bdrv,
-                                      BlockErrorAction action, int is_read)
+void bdrv_emit_qmp_error_event(const BlockDriverState *bdrv,
+                               enum MonitorEvent ev,
+                               BlockErrorAction action, int is_read)
 {
     QObject *data;
     const char *action_str;
@@ -1183,7 +1184,7 @@ static void bdrv_emit_qmp_error_event(const BlockDriverState *bdrv,
                               bdrv->device_name,
                               action_str,
                               is_read ? "read" : "write");
-    monitor_protocol_event(QEVENT_BLOCK_IO_ERROR, data);
+    monitor_protocol_event(ev, data);
 
     qobject_decref(data);
 }
@@ -2424,7 +2425,7 @@ void bdrv_error_action(BlockDriverState *bs, BlockErrorAction action,
                        int is_read, int error)
 {
     assert(error >= 0);
-    bdrv_emit_qmp_error_event(bs, action, is_read);
+    bdrv_emit_qmp_error_event(bs, QEVENT_BLOCK_IO_ERROR, action, is_read);
     if (action == BDRV_ACTION_STOP) {
         vm_stop(RUN_STATE_IO_ERROR);
         bdrv_iostatus_set_err(bs, error);
diff --git a/block_int.h b/block_int.h
index afe3dd1..53fec71 100644
--- a/block_int.h
+++ b/block_int.h
@@ -30,6 +30,7 @@
 #include "qemu-coroutine.h"
 #include "qemu-timer.h"
 #include "qapi-types.h"
+#include "monitor.h"
 
 #define BLOCK_FLAG_ENCRYPT	1
 #define BLOCK_FLAG_COMPAT6	4
@@ -277,6 +278,9 @@ void bdrv_set_io_limits(BlockDriverState *bs,
 #ifdef _WIN32
 int is_windows_drive(const char *filename);
 #endif
+void bdrv_emit_qmp_error_event(const BlockDriverState *bdrv,
+                               enum MonitorEvent ev,
+                               BlockErrorAction action, int is_read);
 
 /**
  * stream_start:
diff --git a/blockjob.c b/blockjob.c
index a18da3f..562e0b5 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -112,6 +112,7 @@ bool block_job_is_paused(BlockJob *job)
 void block_job_resume(BlockJob *job)
 {
     job->paused = false;
+    job->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
     if (job->co && !job->busy) {
         qemu_coroutine_enter(job->co, NULL);
     }
@@ -189,11 +190,60 @@ void block_job_sleep_ns(BlockJob *job, QEMUClock *clock, int64_t ns)
 BlockJobInfo *block_job_query(BlockJob *job)
 {
     BlockJobInfo *info = g_new(BlockJobInfo, 1);
-    info->type   = g_strdup(job->job_type->job_type);
-    info->device = g_strdup(bdrv_get_device_name(job->bs));
-    info->len    = job->len;
-    info->paused = job->paused;
-    info->offset = job->offset;
-    info->speed  = job->speed;
+    info->type      = g_strdup(job->job_type->job_type);
+    info->device    = g_strdup(bdrv_get_device_name(job->bs));
+    info->len       = job->len;
+    info->paused    = job->paused;
+    info->offset    = job->offset;
+    info->speed     = job->speed;
+    info->io_status = job->iostatus;
     return info;
 }
+
+static void block_job_iostatus_set_err(BlockJob *job, int error)
+{
+    BlockDeviceIoStatus new_status =
+        (error == ENOSPC ? BLOCK_DEVICE_IO_STATUS_NOSPACE :
+                           BLOCK_DEVICE_IO_STATUS_FAILED);
+
+    /* iostatus values are sorted from less severe to most severe
+     * (ok, nospace, failed).  */
+    if (job->iostatus < new_status) {
+        job->iostatus = new_status;
+    }
+}
+
+
+BlockErrorAction block_job_error_action(BlockJob *job, BlockDriverState *bs,
+                                        BlockdevOnError on_err,
+                                        int is_read, int error)
+{
+    BlockErrorAction action;
+
+    switch (on_err) {
+    case BLOCKDEV_ON_ERROR_ENOSPC:
+        action = (error == ENOSPC) ? BDRV_ACTION_STOP : BDRV_ACTION_REPORT;
+        break;
+    case BLOCKDEV_ON_ERROR_STOP:
+        action = BDRV_ACTION_STOP;
+        break;
+    case BLOCKDEV_ON_ERROR_REPORT:
+        action = BDRV_ACTION_REPORT;
+        break;
+    case BLOCKDEV_ON_ERROR_IGNORE:
+        action = BDRV_ACTION_IGNORE;
+        break;
+    default:
+        abort();
+    }
+    bdrv_emit_qmp_error_event(job->bs, QEVENT_BLOCK_JOB_ERROR, action, is_read);
+    if (action == BDRV_ACTION_STOP) {
+        block_job_pause(job);
+        if (bs == job->bs) {
+            block_job_iostatus_set_err(job, error);
+        } else {
+            bdrv_iostatus_set_err(bs, error);
+        }
+    }
+    return action;
+}
diff --git a/blockjob.h b/blockjob.h
index 58e1b56..8f0b93b 100644
--- a/blockjob.h
+++ b/blockjob.h
@@ -84,6 +84,9 @@ struct BlockJob {
      */
     bool busy;
 
+    /** Status that is published by the query-block-jobs QMP API */
+    BlockDeviceIoStatus iostatus;
+
     /** Offset that is published by the query-block-jobs QMP API */
     int64_t offset;
 
@@ -218,5 +221,19 @@ bool block_job_is_paused(BlockJob *job);
  */
 int block_job_cancel_sync(BlockJob *job);
 
+/**
+ * block_job_error_action:
+ * @job: The job to signal an error for.
+ * @bs: The block device on which to set an I/O error.
+ * @on_err: The error action setting.
+ * @is_read: Whether the operation was a read.
+ * @error: The error that was reported.
+ *
+ * Report an I/O error for a block job and possibly stop the VM.  Return the
+ * action that was selected based on @on_err and @error.
+ */
+BlockErrorAction block_job_error_action(BlockJob *job, BlockDriverState *bs,
+                                        BlockdevOnError on_err,
+                                        int is_read, int error);
 #endif
 
diff --git a/monitor.c b/monitor.c
index a3bc2c7..b6d67f0 100644
--- a/monitor.c
+++ b/monitor.c
@@ -440,6 +440,7 @@ static const char *monitor_event_names[] = {
     [QEVENT_SPICE_DISCONNECTED] = "SPICE_DISCONNECTED",
     [QEVENT_BLOCK_JOB_COMPLETED] = "BLOCK_JOB_COMPLETED",
     [QEVENT_BLOCK_JOB_CANCELLED] = "BLOCK_JOB_CANCELLED",
+    [QEVENT_BLOCK_JOB_ERROR] = "BLOCK_JOB_ERROR",
     [QEVENT_DEVICE_TRAY_MOVED] = "DEVICE_TRAY_MOVED",
     [QEVENT_SUSPEND] = "SUSPEND",
     [QEVENT_WAKEUP] = "WAKEUP",
diff --git a/monitor.h b/monitor.h
index cd1d878..5931636 100644
--- a/monitor.h
+++ b/monitor.h
@@ -38,6 +38,7 @@ typedef enum MonitorEvent {
     QEVENT_SPICE_DISCONNECTED,
     QEVENT_BLOCK_JOB_COMPLETED,
     QEVENT_BLOCK_JOB_CANCELLED,
+    QEVENT_BLOCK_JOB_ERROR,
     QEVENT_DEVICE_TRAY_MOVED,
     QEVENT_SUSPEND,
     QEVENT_WAKEUP,
diff --git a/qapi-schema.json b/qapi-schema.json
index d09d267..0a1a35b 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -935,11 +935,14 @@
 #
 # @speed: the rate limit, bytes per second
 #
+# @io-status: the status of the job
+#
 # Since: 1.1
 ##
 { 'type': 'BlockJobInfo',
   'data': {'type': 'str', 'device': 'str', 'len': 'int',
-           'offset': 'int', 'paused': 'bool', 'speed': 'int'} }
+           'offset': 'int', 'paused': 'bool', 'speed': 'int',
+           'io-status': 'BlockDeviceIoStatus'} }
 
 ##
 # @query-block-jobs:
-- 
1.7.10.2