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[Qemu-block] [PATCH v4 1/4] qemu-img: add --shrink flag for resize
From: |
Pavel Butsykin |
Subject: |
[Qemu-block] [PATCH v4 1/4] qemu-img: add --shrink flag for resize |
Date: |
Tue, 11 Jul 2017 15:40:21 +0300 |
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 <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
---
qemu-img-cmds.hx | 4 ++--
qemu-img.c | 23 +++++++++++++++++++++++
qemu-img.texi | 6 +++++-
tests/qemu-iotests/102 | 4 ++--
4 files changed, 32 insertions(+), 5 deletions(-)
diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index a39fcdba71..3b2eab9d20 100644
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -76,9 +76,9 @@ STEXI
ETEXI
DEF("resize", img_resize,
- "resize [--object objectdef] [--image-opts] [-q] filename [+ | -]size")
+ "resize [--object objectdef] [--image-opts] [-q] [--shrink] filename [+ |
-]size")
STEXI
address@hidden resize [--object @var{objectdef}] [--image-opts] [-q]
@var{filename} [+ | address@hidden
address@hidden resize [--object @var{objectdef}] [--image-opts] [-q] [--shrink]
@var{filename} [+ | address@hidden
ETEXI
DEF("amend", img_amend,
diff --git a/qemu-img.c b/qemu-img.c
index 91ad6bebbf..6c28dc439d 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -61,6 +61,7 @@ enum {
OPTION_FLUSH_INTERVAL = 261,
OPTION_NO_DRAIN = 262,
OPTION_TARGET_IMAGE_OPTS = 263,
+ OPTION_SHRINK = 264,
};
typedef enum OutputFormat {
@@ -3458,6 +3459,7 @@ static int img_resize(int argc, char **argv)
},
};
bool image_opts = false;
+ bool shrink = false;
/* Remove size from argv manually so that negative numbers are not treated
* as options by getopt. */
@@ -3475,6 +3477,7 @@ static int img_resize(int argc, char **argv)
{"help", no_argument, 0, 'h'},
{"object", required_argument, 0, OPTION_OBJECT},
{"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+ {"shrink", no_argument, 0, OPTION_SHRINK},
{0, 0, 0, 0}
};
c = getopt_long(argc, argv, ":f:hq",
@@ -3509,6 +3512,9 @@ static int img_resize(int argc, char **argv)
case OPTION_IMAGE_OPTS:
image_opts = true;
break;
+ case OPTION_SHRINK:
+ shrink = true;
+ break;
}
}
if (optind != argc - 1) {
@@ -3568,6 +3574,23 @@ static int img_resize(int argc, char **argv)
goto out;
}
+ if (total_size < blk_getlength(blk) && !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, &err);
if (!ret) {
qprintf(quiet, "Image resized.\n");
diff --git a/qemu-img.texi b/qemu-img.texi
index 5b925ecf41..79ba802481 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -499,7 +499,7 @@ qemu-img rebase -b base.img diff.qcow2
At this point, @code{modified.img} can be discarded, since
@code{base.img + diff.qcow2} contains the same information.
address@hidden resize @var{filename} [+ | address@hidden
address@hidden resize [--shrink] @var{filename} [+ | address@hidden
Change the disk image as if it had been created with @var{size}.
@@ -507,6 +507,10 @@ Before using this command to shrink a disk image, you MUST
use file system and
partitioning tools inside the VM to reduce allocated file systems and partition
sizes accordingly. Failure to do so will result in data loss!
+When shrinking images, the @code{--shrink} option must be given. This informs
+qemu-img that the user acknowledges all loss of data beyond the truncated
+image's end.
+
After using this command to grow a disk image, you must use file system and
partitioning tools inside the VM to actually begin using the new space on the
device.
diff --git a/tests/qemu-iotests/102 b/tests/qemu-iotests/102
index 87db1bb1bf..d7ad8d9840 100755
--- a/tests/qemu-iotests/102
+++ b/tests/qemu-iotests/102
@@ -54,7 +54,7 @@ _make_test_img $IMG_SIZE
$QEMU_IO -c 'write 0 64k' "$TEST_IMG" | _filter_qemu_io
# Remove data cluster from image (first cluster: image header, second:
reftable,
# third: refblock, fourth: L1 table, fifth: L2 table)
-$QEMU_IMG resize -f raw "$TEST_IMG" $((5 * 64 * 1024))
+$QEMU_IMG resize -f raw --shrink "$TEST_IMG" $((5 * 64 * 1024))
$QEMU_IO -c map "$TEST_IMG"
$QEMU_IMG map "$TEST_IMG"
@@ -69,7 +69,7 @@ $QEMU_IO -c 'write 0 64k' "$TEST_IMG" | _filter_qemu_io
qemu_comm_method=monitor _launch_qemu -drive if=none,file="$TEST_IMG",id=drv0
-$QEMU_IMG resize -f raw "$TEST_IMG" $((5 * 64 * 1024))
+$QEMU_IMG resize -f raw --shrink "$TEST_IMG" $((5 * 64 * 1024))
_send_qemu_cmd $QEMU_HANDLE 'qemu-io drv0 map' 'allocated' \
| sed -e 's/^(qemu).*qemu-io drv0 map...$/(qemu) qemu-io drv0 map/'
--
2.13.0
- [Qemu-block] [PATCH v4 0/4] Add shrink image for qcow2, Pavel Butsykin, 2017/07/11
- [Qemu-block] [PATCH v4 3/4] qcow2: add shrink image support, Pavel Butsykin, 2017/07/11
- [Qemu-block] [PATCH v4 1/4] qemu-img: add --shrink flag for resize,
Pavel Butsykin <=
- [Qemu-block] [PATCH v4 2/4] qcow2: add qcow2_cache_discard, Pavel Butsykin, 2017/07/11
- [Qemu-block] [PATCH v4 4/4] qemu-iotests: add shrinking image test, Pavel Butsykin, 2017/07/11
- Re: [Qemu-block] [Qemu-devel] [PATCH v4 0/4] Add shrink image for qcow2, no-reply, 2017/07/11
- Re: [Qemu-block] [Qemu-devel] [PATCH v4 0/4] Add shrink image for qcow2, no-reply, 2017/07/11
- Re: [Qemu-block] [PATCH v4 0/4] Add shrink image for qcow2, Max Reitz, 2017/07/11