[Qemu-devel] [PATCH 1/3] FVD: Added support for 'qemu-img update'

[Chunqiang Tang <ctang@us.ibm.com>]

This patch is part of the Fast Virtual Disk (FVD) proposal. See the related
discussions at
http://lists.gnu.org/archive/html/qemu-devel/2011-01/msg00426.html.

This patch adds the 'update' command to qemu-img. FVD stores various
image-specific configurable parameters in the image header. A user can use
'qemu-img update' to modify those parameters and accordingly controls FVD's
runtime behavior. This command may also be leveraged by other block device
drivers, e.g., to set the size of the in-memory metadata cache. Currently
those parameters are hard-coded in a one-size-fit-all manner.

Signed-off-by: Chunqiang Tang <ctang@us.ibm.com>
---
 block_int.h      |    1 +
 qemu-img-cmds.hx |    6 ++++++
 qemu-img.c       |   43 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+), 0 deletions(-)

diff --git a/block_int.h b/block_int.h
index 12663e8..e98872a 100644
--- a/block_int.h
+++ b/block_int.h
@@ -98,6 +98,7 @@ struct BlockDriver {
     int (*bdrv_snapshot_load_tmp)(BlockDriverState *bs,
                                   const char *snapshot_name);
     int (*bdrv_get_info)(BlockDriverState *bs, BlockDriverInfo *bdi);
+    int (*bdrv_update)(BlockDriverState *bs, int argc, char **argv);
 
     int (*bdrv_save_vmstate)(BlockDriverState *bs, const uint8_t *buf,
                              int64_t pos, int size);
diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index 6c7176f..1ad378b 100644
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -39,6 +39,12 @@ STEXI
 @item info [-f @var{fmt}] @var{filename}
 ETEXI
 
+DEF("update", img_update,
+    "update [-f fmt] filename [attr1=val1 attr2=val2 ...]")
+STEXI
+@item update [-f @var{fmt}] @var{filename} [@var{attr1=val1 attr2=val2 ...}]")
+ETEXI
+
 DEF("snapshot", img_snapshot,
     "snapshot [-l | -a snapshot | -c snapshot | -d snapshot] filename")
 STEXI
diff --git a/qemu-img.c b/qemu-img.c
index afd9ed2..5f35c4d 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1054,6 +1054,49 @@ static int img_info(int argc, char **argv)
     return 0;
 }
 
+static int img_update(int argc, char **argv)
+{
+    int c;
+    const char *filename, *fmt;
+    BlockDriverState *bs;
+
+    fmt = NULL;
+    for(;;) {
+        c = getopt(argc, argv, "f:h");
+        if (c == -1)
+            break;
+        switch(c) {
+        case 'h':
+            help();
+            break;
+        case 'f':
+            fmt = optarg;
+            break;
+        }
+    }
+    if (optind >= argc)
+        help();
+    filename = argv[optind++];
+    bs = bdrv_new_open(filename, fmt, BDRV_O_FLAGS | BDRV_O_NO_BACKING
+                       | BDRV_O_RDWR);
+    if (!bs) {
+        return 1;
+    }
+
+    if (bs->drv->bdrv_update) {
+        bs->drv->bdrv_update(bs, argc-optind, &argv[optind]);
+    }
+    else {
+        char fmt_name[128];
+        bdrv_get_format(bs, fmt_name, sizeof(fmt_name));
+        error_report ("The 'update' command is not supported for "
+                      "the '%s' image format.", fmt_name);
+    }
+
+    bdrv_delete(bs);
+    return 0;
+}
+
 #define SNAPSHOT_LIST   1
 #define SNAPSHOT_CREATE 2
 #define SNAPSHOT_APPLY  3
-- 
1.7.0.4