On Wed, 4 Nov 2015 20:19:32 +0300
"Denis V. Lunev" <address@hidden> wrote:
The patch enforces proper locking for this operation.
Signed-off-by: Denis V. Lunev <address@hidden>
CC: Juan Quintela <address@hidden>
CC: Stefan Hajnoczi <address@hidden>
CC: Kevin Wolf <address@hidden>
---
block/snapshot.c | 27 +++++++++++++++++++++++++++
include/block/snapshot.h | 9 +++++++++
migration/savevm.c | 17 ++++-------------
3 files changed, 40 insertions(+), 13 deletions(-)
diff --git a/block/snapshot.c b/block/snapshot.c
index 89500f2..2ef4545 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -356,3 +356,30 @@ int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState
*bs,
return ret;
}
+
+
+/* Group operations. All block drivers are involved.
+ * These functions will properly handle dataplace (take aio_context_acquire
s/dataplace/dataplane
+ * when appropriate for appropriate block drivers
Missing ) and anyway the "(take aio_context_acquire..." part more or less
quotes the code and is not needed.
+ *
+ * Returned block driver will be always locked.
+ */
+
+bool bdrv_all_can_snapshot(BlockDriverState **first_bad_bs)
Juan suggested bdrv_snapshot_is_possible() and FWIW you already emphasize
that it involves all block drivers in the above comment.
+{
+ bool ok = true;
+ BlockDriverState *bs = NULL;
+
+ while ((bs = bdrv_next(bs)) && ok) {
+ AioContext *ctx = bdrv_get_aio_context(bs);
+
+ aio_context_acquire(ctx);
+ if (bdrv_is_inserted(bs) && !bdrv_is_read_only(bs)) {
+ ok = bdrv_can_snapshot(bs);
+ }
+ aio_context_release(ctx);
+ }
+
+ *first_bad_bs = bs;
+ return ok;
+}
diff --git a/include/block/snapshot.h b/include/block/snapshot.h
index 770d9bb..0a3cf0d 100644
--- a/include/block/snapshot.h
+++ b/include/block/snapshot.h
@@ -75,4 +75,13 @@ int bdrv_snapshot_load_tmp(BlockDriverState *bs,
int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs,
const char *id_or_name,
Error **errp);
+
+
+/* Group operations. All block drivers are involved.
+ * These functions will properly handle dataplace (take aio_context_acquire
+ * when appropriate for appropriate block drivers
+ *
+ */
This comment is not needed here, already in block/snapshot.c
+bool bdrv_all_can_snapshot(BlockDriverState **first_bad_bs);
+
#endif
diff --git a/migration/savevm.c b/migration/savevm.c
index dbcc39a..3ac3f07 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1290,19 +1290,10 @@ void hmp_savevm(Monitor *mon, const QDict *qdict)
const char *name = qdict_get_try_str(qdict, "name");
Error *local_err = NULL;
- /* Verify if there is a device that doesn't support snapshots and is
writable */
- bs = NULL;
- while ((bs = bdrv_next(bs))) {
-
- if (!bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
- continue;
- }
-
- if (!bdrv_can_snapshot(bs)) {
- monitor_printf(mon, "Device '%s' is writable but does not support
snapshots.\n",
- bdrv_get_device_name(bs));
- return;
- }
+ if (!bdrv_all_can_snapshot(&bs)) {
+ monitor_printf(mon, "Device '%s' is writable but does not "
+ "support snapshots.\n", bdrv_get_device_name(bs));
+ return;
}
bs = find_vmstate_bs();
Reviewed-by: Greg Kurz <address@hidden>