scsi-disk: Acquire the AioContext in scsi_*_realize()

This fixes a crash when attaching two disks with the same blockdev to
a SCSI device that is using iothreads. Test case included.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

hw/scsi/scsi-disk.c

@@ -2381,10 +2381,13 @@ static void scsi_realize(SCSIDevice *dev, Error **errp)
 static void scsi_hd_realize(SCSIDevice *dev, Error **errp)
 {
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, dev);
+    AioContext *ctx = NULL;
     /* can happen for devices without drive. The error message for missing
      * backend will be issued in scsi_realize
      */
     if (s->qdev.conf.blk) {
+        ctx = blk_get_aio_context(s->qdev.conf.blk);
+        aio_context_acquire(ctx);
         blkconf_blocksizes(&s->qdev.conf);
     }
     s->qdev.blocksize = s->qdev.conf.logical_block_size;
@@ -2393,11 +2396,15 @@ static void scsi_hd_realize(SCSIDevice *dev, Error **errp)
         s->product = g_strdup("QEMU HARDDISK");
     }
     scsi_realize(&s->qdev, errp);
+    if (ctx) {
+        aio_context_release(ctx);
+    }
 }
 
 static void scsi_cd_realize(SCSIDevice *dev, Error **errp)
 {
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, dev);
+    AioContext *ctx;
     int ret;
 
     if (!dev->conf.blk) {
@@ -2408,6 +2415,8 @@ static void scsi_cd_realize(SCSIDevice *dev, Error **errp)
         assert(ret == 0);
     }
 
+    ctx = blk_get_aio_context(dev->conf.blk);
+    aio_context_acquire(ctx);
     s->qdev.blocksize = 2048;
     s->qdev.type = TYPE_ROM;
     s->features |= 1 << SCSI_DISK_F_REMOVABLE;
@@ -2415,6 +2424,7 @@ static void scsi_cd_realize(SCSIDevice *dev, Error **errp)
         s->product = g_strdup("QEMU CD-ROM");
     }
     scsi_realize(&s->qdev, errp);
+    aio_context_release(ctx);
 }
 
 static void scsi_disk_realize(SCSIDevice *dev, Error **errp)
@@ -2553,6 +2563,7 @@ static int get_device_type(SCSIDiskState *s)
 static void scsi_block_realize(SCSIDevice *dev, Error **errp)
 {
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, dev);
+    AioContext *ctx;
     int sg_version;
     int rc;
 
@@ -2567,6 +2578,9 @@ static void scsi_block_realize(SCSIDevice *dev, Error **errp)
                           "be removed in a future version");
     }
 
+    ctx = blk_get_aio_context(s->qdev.conf.blk);
+    aio_context_acquire(ctx);
+
     /* check we are using a driver managing SG_IO (version 3 and after) */
     rc = blk_ioctl(s->qdev.conf.blk, SG_GET_VERSION_NUM, &sg_version);
     if (rc < 0) {
@@ -2574,18 +2588,18 @@ static void scsi_block_realize(SCSIDevice *dev, Error **errp)
         if (rc != -EPERM) {
             error_append_hint(errp, "Is this a SCSI device?\n");
         }
-        return;
+        goto out;
     }
     if (sg_version < 30000) {
         error_setg(errp, "scsi generic interface too old");
-        return;
+        goto out;
     }
 
     /* get device type from INQUIRY data */
     rc = get_device_type(s);
     if (rc < 0) {
         error_setg(errp, "INQUIRY failed");
-        return;
+        goto out;
     }
 
     /* Make a guess for the block size, we'll fix it when the guest sends.
@@ -2605,6 +2619,9 @@ static void scsi_block_realize(SCSIDevice *dev, Error **errp)
 
     scsi_realize(&s->qdev, errp);
     scsi_generic_read_device_inquiry(&s->qdev);
+
+out:
+    aio_context_release(ctx);
 }
 
 typedef struct SCSIBlockReq {

tests/qemu-iotests/240

@@ -83,6 +83,24 @@ run_qemu <<EOF
 { "execute": "quit"}
 EOF
 
+echo
+echo === Attach two SCSI disks using the same block device and the same iothread ===
+echo
+
+run_qemu <<EOF
+{ "execute": "qmp_capabilities" }
+{ "execute": "blockdev-add", "arguments": {"driver": "null-co", "node-name": "hd0", "read-only": true}}
+{ "execute": "object-add", "arguments": {"qom-type": "iothread", "id": "iothread0"}}
+{ "execute": "device_add", "arguments": {"id": "scsi0", "driver": "${virtio_scsi}", "iothread": "iothread0"}}
+{ "execute": "device_add", "arguments": {"id": "scsi-hd0", "driver": "scsi-hd", "drive": "hd0"}}
+{ "execute": "device_add", "arguments": {"id": "scsi-hd1", "driver": "scsi-hd", "drive": "hd0"}}
+{ "execute": "device_del", "arguments": {"id": "scsi-hd0"}}
+{ "execute": "device_del", "arguments": {"id": "scsi-hd1"}}
+{ "execute": "device_del", "arguments": {"id": "scsi0"}}
+{ "execute": "blockdev-del", "arguments": {"node-name": "hd0"}}
+{ "execute": "quit"}
+EOF
+
 # success, all done
 echo "*** done"
 rm -f $seq.full

tests/qemu-iotests/240.out

@@ -2,6 +2,22 @@ QA output created by 240
 
 === Unplug a SCSI disk and then plug it again ===
 
+Testing:
+QMP_VERSION
+{"return": {}}
+{"return": {}}
+{"return": {}}
+{"return": {}}
+{"return": {}}
+{"return": {}}
+{"return": {}}
+{"return": {}}
+{"return": {}}
+{"return": {}}
+{"return": {}}
+
+=== Attach two SCSI disks using the same block device and the same iothread ===
+
 Testing:
 QMP_VERSION
 {"return": {}}