For block replication, we have such backing chain:
secondary disk <-- hidden disk <-- active disk
secondary disk is top BDS (use bacing reference), so it can be opened in
read-write mode. But hidden disk is read only, and we need to write to
hidden disk (backup job will write data to it).
TODO: support opening backing file in read-write mode if the BDS is
created by QMP command blockdev-add.
Signed-off-by: Wen Congyang <we...@cn.fujitsu.com>
Signed-off-by: zhanghailiang <zhang.zhanghaili...@huawei.com>
Signed-off-by: Gonglei <arei.gong...@huawei.com>
---
block.c | 41 ++++++++++++++++++++++++++++++++++++++++-
1 file changed, 40 insertions(+), 1 deletion(-)
diff --git a/block.c b/block.c
index 52a91ad..32ed776 100644
--- a/block.c
+++ b/block.c
@@ -737,6 +737,15 @@ static const BdrvChildRole child_backing = {
.inherit_flags = bdrv_backing_flags,
};
+static int bdrv_backing_rw_flags(int flags)
+{
+ return bdrv_backing_flags(flags) | BDRV_O_RDWR;
+}
+
+static const BdrvChildRole child_backing_rw = {
+ .inherit_flags = bdrv_backing_rw_flags,
+};
+
static int bdrv_open_flags(BlockDriverState *bs, int flags)
{
int open_flags = flags | BDRV_O_CACHE_WB;
@@ -1184,6 +1193,20 @@ out:
bdrv_refresh_limits(bs, NULL);
}
+#define ALLOW_WRITE_BACKING_FILE "allow-write-backing-file"
+static QemuOptsList backing_file_opts = {
+ .name = "backing_file",
+ .head = QTAILQ_HEAD_INITIALIZER(backing_file_opts.head),
+ .desc = {
+ {
+ .name = ALLOW_WRITE_BACKING_FILE,
+ .type = QEMU_OPT_BOOL,
+ .help = "allow writes to backing file",
+ },
+ { /* end of list */ }
+ },
+};
+
/*
* Opens the backing file for a BlockDriverState if not yet open
*
@@ -1198,6 +1221,9 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict
*options, Error **errp)
int ret = 0;
BlockDriverState *backing_hd;
Error *local_err = NULL;
+ QemuOpts *opts = NULL;
+ bool child_rw = false;
+ const BdrvChildRole *child_role = NULL;
if (bs->backing != NULL) {
QDECREF(options);
@@ -1210,6 +1236,18 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict
*options, Error **errp)
}
bs->open_flags &= ~BDRV_O_NO_BACKING;
+
+ opts = qemu_opts_create(&backing_file_opts, NULL, 0, &error_abort);
+ qemu_opts_absorb_qdict(opts, options, &local_err);
+ if (local_err) {
+ ret = -EINVAL;
+ error_propagate(errp, local_err);
+ QDECREF(options);
+ goto free_exit;
+ }
+ child_rw = qemu_opt_get_bool(opts, ALLOW_WRITE_BACKING_FILE, false);
+ child_role = child_rw ? &child_backing_rw : &child_backing;
+
if (qdict_haskey(options, "file.filename")) {
backing_filename[0] = '\0';
} else if (bs->backing_file[0] == '\0' && qdict_size(options) == 0) {
@@ -1242,7 +1280,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict
*options, Error **errp)
assert(bs->backing == NULL);
ret = bdrv_open_inherit(&backing_hd,
*backing_filename ? backing_filename : NULL,
- NULL, options, 0, bs, &child_backing, &local_err);
+ NULL, options, 0, bs, child_role, &local_err);
if (ret < 0) {
bdrv_unref(backing_hd);
backing_hd = NULL;
@@ -1259,6 +1297,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict
*options, Error **errp)
bdrv_unref(backing_hd);
free_exit:
+ qemu_opts_del(opts);
g_free(backing_filename);
return ret;
}
--
2.4.3
