Writing to the same qcow2 file from two QEMU processes at the same time
will never work correctly, so disable it even when the caller specifies
BDRV_O_RDWR.
Other formats are less vulnerable because they don't have internal
snapshots thus qemu-img is less often misused to create live snapshot.
Signed-off-by: Fam Zheng <f...@redhat.com>
---
block/qcow2.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/block/qcow2.c b/block/qcow2.c
index 96fb8a8..879361a 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1177,6 +1177,17 @@ static int qcow2_open(BlockDriverState *bs, QDict
*options, int flags,
}
}
+ if ((flags & BDRV_O_SHARE_RW) && (flags & BDRV_O_RDWR)) {
+ /* Shared write is never a good idea for qcow2, override it.
+ * XXX: Use permission propagation and masking mechanism in op blockers
+ * API once it's there. */
+ ret = bdrv_reopen(bs->file->bs, flags & ~BDRV_O_SHARE_RW, &local_err);
+ if (ret) {
+ error_propagate(errp, local_err);
+ goto fail;
+ }
+ }
+
#ifdef DEBUG_ALLOC
{
BdrvCheckResult result = {0};
--
2.9.3
