qemu-img: add --shrink flag for resize
The flag is additional precaution against data loss. Perhaps in the future the
operation shrink without this flag will be blocked for all formats, but for now
we need to maintain compatibility with raw.
Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20170918124230.8152-2-pbutsykin@virtuozzo.com
[mreitz: Added a missing space to a warning]
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/qemu-img.c b/qemu-img.c
index df984b1..d6007b2 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -64,6 +64,7 @@
OPTION_TARGET_IMAGE_OPTS = 263,
OPTION_SIZE = 264,
OPTION_PREALLOCATION = 265,
+ OPTION_SHRINK = 266,
};
typedef enum OutputFormat {
@@ -3436,6 +3437,7 @@
},
};
bool image_opts = false;
+ bool shrink = false;
/* Remove size from argv manually so that negative numbers are not treated
* as options by getopt. */
@@ -3454,6 +3456,7 @@
{"object", required_argument, 0, OPTION_OBJECT},
{"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
{"preallocation", required_argument, 0, OPTION_PREALLOCATION},
+ {"shrink", no_argument, 0, OPTION_SHRINK},
{0, 0, 0, 0}
};
c = getopt_long(argc, argv, ":f:hq",
@@ -3496,6 +3499,9 @@
return 1;
}
break;
+ case OPTION_SHRINK:
+ shrink = true;
+ break;
}
}
if (optind != argc - 1) {
@@ -3569,6 +3575,23 @@
goto out;
}
+ if (total_size < current_size && !shrink) {
+ warn_report("Shrinking an image will delete all data beyond the "
+ "shrunken image's end. Before performing such an "
+ "operation, make sure there is no important data there.");
+
+ if (g_strcmp0(bdrv_get_format_name(blk_bs(blk)), "raw") != 0) {
+ error_report(
+ "Use the --shrink option to perform a shrink operation.");
+ ret = -1;
+ goto out;
+ } else {
+ warn_report("Using the --shrink option will suppress this message. "
+ "Note that future versions of qemu-img may refuse to "
+ "shrink images without this option.");
+ }
+ }
+
ret = blk_truncate(blk, total_size, prealloc, &err);
if (!ret) {
qprintf(quiet, "Image resized.\n");