[Qemu-devel] [PATCH v6 02/16] block: check bdrv_in_use() before blockdev operations

[Stefan Hajnoczi]

Long-running block operations like block migration and image streaming
must have continual access to their block device.  It is not safe to
perform operations like hotplug, eject, change, resize, commit, or
external snapshot while a long-running operation is in progress.

This patch adds the missing bdrv_in_use() checks so that block migration
and image streaming never have the rug pulled out from underneath them.

Signed-off-by: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
---
 block.c    |    4 ++++
 blockdev.c |   16 +++++++++++++++-
 2 files changed, 19 insertions(+), 1 deletions(-)

diff --git a/block.c b/block.c
index 3f072f6..43f6484 100644
--- a/block.c
+++ b/block.c
@@ -1020,6 +1020,10 @@ int bdrv_commit(BlockDriverState *bs)
         return -EACCES;
     }
 
+    if (bdrv_in_use(bs) || bdrv_in_use(bs->backing_hd)) {
+        return -EBUSY;
+    }
+
     backing_drv = bs->backing_hd->drv;
     ro = bs->backing_hd->read_only;
     strncpy(filename, bs->backing_hd->filename, sizeof(filename));
diff --git a/blockdev.c b/blockdev.c
index c832782..6d78b36 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -592,12 +592,18 @@ void do_commit(Monitor *mon, const QDict *qdict)
     if (!strcmp(device, "all")) {
         bdrv_commit_all();
     } else {
+        int ret;
+
         bs = bdrv_find(device);
         if (!bs) {
             qerror_report(QERR_DEVICE_NOT_FOUND, device);
             return;
         }
-        bdrv_commit(bs);
+        ret = bdrv_commit(bs);
+        if (ret == -EBUSY) {
+            qerror_report(QERR_DEVICE_IN_USE, device);
+            return;
+        }
     }
 }
 
@@ -616,6 +622,10 @@ void qmp_blockdev_snapshot_sync(const char *device, const 
char *snapshot_file,
         error_set(errp, QERR_DEVICE_NOT_FOUND, device);
         return;
     }
+    if (bdrv_in_use(bs)) {
+        error_set(errp, QERR_DEVICE_IN_USE, device);
+        return;
+    }
 
     pstrcpy(old_filename, sizeof(old_filename), bs->filename);
 
@@ -667,6 +677,10 @@ void qmp_blockdev_snapshot_sync(const char *device, const 
char *snapshot_file,
 
 static int eject_device(Monitor *mon, BlockDriverState *bs, int force)
 {
+    if (bdrv_in_use(bs)) {
+        qerror_report(QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
+        return -1;
+    }
     if (!bdrv_dev_has_removable_media(bs)) {
         qerror_report(QERR_DEVICE_NOT_REMOVABLE, bdrv_get_device_name(bs));
         return -1;
-- 
1.7.8.3