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qemu-img: Specify backing file for commit

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Introduce a new parameter for qemu-img commit which may be used to
explicitly specify the backing file into which an image should be
committed if the backing chain has more than a single layer.

[Applied Eric Blake's qemu-img.texi documentation rewording
--Stefan]

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 1414159063-25977-12-git-send-email-mreitz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Max Reitz 2014-10-24 15:57:40 +02:00 committed by Stefan Hajnoczi
parent 687fa1d830
commit 1b22bffd82
3 changed files with 36 additions and 12 deletions
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4
qemu-img-cmds.hx
View File

@ -22,9 +22,9 @@ STEXI
ETEXI
DEF("commit", img_commit,
"commit [-q] [-f fmt] [-t cache] [-d] [-p] filename")
"commit [-q] [-f fmt] [-t cache] [-b base] [-d] [-p] filename")
STEXI
@item commit [-q] [-f @var{fmt}] [-t @var{cache}] [-d] [-p] @var{filename}
@item commit [-q] [-f @var{fmt}] [-t @var{cache}] [-b @var{base}] [-d] [-p] @var{filename}
ETEXI
DEF("compare", img_compare,

32
qemu-img.c
View File

@ -759,7 +759,7 @@ static void run_block_job(BlockJob *job, Error **errp)
static int img_commit(int argc, char **argv)
{
int c, ret, flags;
const char *filename, *fmt, *cache;
const char *filename, *fmt, *cache, *base;
BlockBackend *blk;
BlockDriverState *bs, *base_bs;
bool progress = false, quiet = false, drop = false;
@ -768,8 +768,9 @@ static int img_commit(int argc, char **argv)
fmt = NULL;
cache = BDRV_DEFAULT_CACHE;
base = NULL;
for(;;) {
c = getopt(argc, argv, "f:ht:dpq");
c = getopt(argc, argv, "f:ht:b:dpq");
if (c == -1) {
break;
}
@ -784,6 +785,11 @@ static int img_commit(int argc, char **argv)
case 't':
cache = optarg;
break;
case 'b':
base = optarg;
/* -b implies -d */
drop = true;
break;
case 'd':
drop = true;
break;
@ -822,13 +828,21 @@ static int img_commit(int argc, char **argv)
qemu_progress_init(progress, 1.f);
qemu_progress_print(0.f, 100);
/* This is different from QMP, which by default uses the deepest file in the
* backing chain (i.e., the very base); however, the traditional behavior of
* qemu-img commit is using the immediate backing file. */
base_bs = bs->backing_hd;
if (!base_bs) {
error_setg(&local_err, "Image does not have a backing file");
goto done;
if (base) {
base_bs = bdrv_find_backing_image(bs, base);
if (!base_bs) {
error_set(&local_err, QERR_BASE_NOT_FOUND, base);
goto done;
}
} else {
/* This is different from QMP, which by default uses the deepest file in
* the backing chain (i.e., the very base); however, the traditional
* behavior of qemu-img commit is using the immediate backing file. */
base_bs = bs->backing_hd;
if (!base_bs) {
error_setg(&local_err, "Image does not have a backing file");
goto done;
}
}
cbi = (CommonBlockJobCBInfo){

12
qemu-img.texi
View File

@ -167,7 +167,7 @@ this case. @var{backing_file} will never be modified unless you use the
The size can also be specified using the @var{size} option with @code{-o},
it doesn't need to be specified separately in this case.
@item commit [-q] [-f @var{fmt}] [-t @var{cache}] [-d] [-p] @var{filename}
@item commit [-q] [-f @var{fmt}] [-t @var{cache}] [-b @var{base}] [-d] [-p] @var{filename}
Commit the changes recorded in @var{filename} in its base image or backing file.
If the backing file is smaller than the snapshot, then the backing file will be
@ -180,6 +180,16 @@ The image @var{filename} is emptied after the operation has succeeded. If you do
not need @var{filename} afterwards and intend to drop it, you may skip emptying
@var{filename} by specifying the @code{-d} flag.
If the backing chain of the given image file @var{filename} has more than one
layer, the backing file into which the changes will be committed may be
specified as @var{base} (which has to be part of @var{filename}'s backing
chain). If @var{base} is not specified, the immediate backing file of the top
image (which is @var{filename}) will be used. For reasons of consistency,
explicitly specifying @var{base} will always imply @code{-d} (since emptying an
image after committing to an indirect backing file would lead to different data
being read from the image due to content in the intermediate backing chain
overruling the commit target).
@item compare [-f @var{fmt}] [-F @var{fmt}] [-T @var{src_cache}] [-p] [-s] [-q] @var{filename1} @var{filename2}
Check if two images have the same content. You can compare images with