[qemu-xen staging] sheepdog: Add trivial backing_fmt support

[patchbot@xxxxxxx]

commit 80fa43e7df5d68d60a2662036b7d3d95ca8b68f3
Author:     Eric Blake <eblake@xxxxxxxxxx>
AuthorDate: Mon Jul 6 15:39:47 2020 -0500
Commit:     Kevin Wolf <kwolf@xxxxxxxxxx>
CommitDate: Tue Jul 14 15:18:59 2020 +0200

    sheepdog: Add trivial backing_fmt support
    
    Sheepdog already requires that if backing_file is present, that it be
    another sheepdog image (see sd_co_create).  Meanwhile, we want to move
    towards always being explicit about the backing format for other
    drivers where it matters.  So for convenience, make qemu-img create -F
    sheepdog work, while rejecting all other explicit formats (note that
    this is only for QemuOpts usage; there is no change to the QAPI to
    allow a format through -blockdev).
    
    Signed-off-by: Eric Blake <eblake@xxxxxxxxxx>
    Message-Id: <20200706203954.341758-4-eblake@xxxxxxxxxx>
    Signed-off-by: Kevin Wolf <kwolf@xxxxxxxxxx>
---
 block/sheepdog.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/block/sheepdog.c b/block/sheepdog.c
index 6c487c8322..cbbebc1aaf 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -2151,13 +2151,21 @@ static int coroutine_fn sd_co_create_opts(BlockDriver 
*drv,
                                           Error **errp)
 {
     BlockdevCreateOptions *create_options = NULL;
-    QDict *qdict, *location_qdict;
+    QDict *qdict = NULL, *location_qdict;
     Visitor *v;
-    char *redundancy;
+    char *redundancy = NULL;
     Error *local_err = NULL;
     int ret;
+    char *backing_fmt = NULL;
 
     redundancy = qemu_opt_get_del(opts, BLOCK_OPT_REDUNDANCY);
+    backing_fmt = qemu_opt_get_del(opts, BLOCK_OPT_BACKING_FMT);
+
+    if (backing_fmt && strcmp(backing_fmt, "sheepdog") != 0) {
+        error_setg(errp, "backing_file must be a sheepdog image");
+        ret = -EINVAL;
+        goto fail;
+    }
 
     qdict = qemu_opts_to_qdict(opts, NULL);
     qdict_put_str(qdict, "driver", "sheepdog");
@@ -2220,6 +2228,7 @@ fail:
     qapi_free_BlockdevCreateOptions(create_options);
     qobject_unref(qdict);
     g_free(redundancy);
+    g_free(backing_fmt);
     return ret;
 }
 
@@ -3177,6 +3186,11 @@ static QemuOptsList sd_create_opts = {
             .type = QEMU_OPT_STRING,
             .help = "File name of a base image"
         },
+        {
+            .name = BLOCK_OPT_BACKING_FMT,
+            .type = QEMU_OPT_STRING,
+            .help = "Must be 'sheepdog' if present",
+        },
         {
             .name = BLOCK_OPT_PREALLOC,
             .type = QEMU_OPT_STRING,
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#staging