[Qemu-devel] [PATCH V2 2/4] qemu-nbd: support internal snapshot export

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

Now it is possible to directly export an internal snapshot, which
can be used to probe the snapshot's contents without qemu-img
convert.

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
---
 qemu-nbd.c |   54 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 53 insertions(+), 1 deletions(-)

diff --git a/qemu-nbd.c b/qemu-nbd.c
index c26c98e..e450d04 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -20,6 +20,7 @@
 #include "block/block.h"
 #include "block/nbd.h"
 #include "qemu/main-loop.h"
+#include "block/snapshot.h"
 
 #include <stdarg.h>
 #include <stdio.h>
@@ -304,6 +305,23 @@ static void nbd_accept(void *opaque)
     }
 }
 
+#define SNAPSHOT_OPT_ID         "id"
+#define SNAPSHOT_OPT_NAME       "name"
+
+static QEMUOptionParameter snapshot_options[] = {
+    {
+        .name = SNAPSHOT_OPT_ID,
+        .type = OPT_STRING,
+        .help = "snapshot id"
+    },
+    {
+        .name = SNAPSHOT_OPT_NAME,
+        .type = OPT_STRING,
+        .help = "snapshot name"
+    },
+    { NULL }
+};
+
 int main(int argc, char **argv)
 {
     BlockDriverState *bs;
@@ -315,7 +333,10 @@ int main(int argc, char **argv)
     char *device = NULL;
     int port = NBD_DEFAULT_PORT;
     off_t fd_size;
-    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:t";
+    QEMUOptionParameter *sn_param = NULL;
+    const QEMUOptionParameter *sn_param_id, *sn_param_name;
+    const char *sn_id = NULL, *sn_name = NULL;
+    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:";
     struct option lopt[] = {
         { "help", 0, NULL, 'h' },
         { "version", 0, NULL, 'V' },
@@ -328,6 +349,7 @@ int main(int argc, char **argv)
         { "connect", 1, NULL, 'c' },
         { "disconnect", 0, NULL, 'd' },
         { "snapshot", 0, NULL, 's' },
+        { "snapshot-load", 1, NULL, 'l' },
         { "nocache", 0, NULL, 'n' },
         { "cache", 1, NULL, QEMU_NBD_OPT_CACHE },
 #ifdef CONFIG_LINUX_AIO
@@ -428,6 +450,14 @@ int main(int argc, char **argv)
                 errx(EXIT_FAILURE, "Offset must be positive `%s'", optarg);
             }
             break;
+        case 'l':
+            sn_param = parse_option_parameters(optarg,
+                                               snapshot_options, sn_param);
+            if (!sn_param) {
+                errx(EXIT_FAILURE,
+                     "Invalid snapshot-load options '%s'", optarg);
+            }
+            /* fall through */
         case 'r':
             nbdflags |= NBD_FLAG_READ_ONLY;
             flags &= ~BDRV_O_RDWR;
@@ -581,6 +611,24 @@ int main(int argc, char **argv)
             error_get_pretty(local_err));
     }
 
+    if (sn_param) {
+        sn_param_id = get_option_parameter(sn_param, SNAPSHOT_OPT_ID);
+        sn_param_name = get_option_parameter(sn_param, SNAPSHOT_OPT_NAME);
+        if (sn_param_id) {
+            sn_id = sn_param_id->value.s;
+        }
+        if (sn_param_name) {
+            sn_name = sn_param_name->value.s;
+        }
+        ret = bdrv_snapshot_load_tmp(bs, sn_id, sn_name, &local_err);
+        if (ret < 0) {
+            errno = -ret;
+            err(EXIT_FAILURE,
+                "Failed to load snapshot, reason:\n%s",
+                error_get_pretty(local_err));
+        }
+    }
+
     fd_size = bdrv_getlength(bs);
 
     if (partition != -1) {
@@ -641,6 +689,10 @@ int main(int argc, char **argv)
         unlink(sockpath);
     }
 
+    if (sn_param) {
+        free_option_parameters(sn_param);
+    }
+
     if (device) {
         void *ret;
         pthread_join(client_thread, &ret);
-- 
1.7.1