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qemu-img: Add --start-offset and --max-length to map 

The mapping operation of large disks especially ones stored over a
long chain of QCOW2 files can take a long time to finish.
Additionally when mapping fails there was no way recover by
restarting the mapping from the failed location.

The new options, --start-offset and --max-length allows the user to
divide these type of map operations into shorter independent tasks.

Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Mark Kanda <mark.kanda@oracle.com>
Co-developed-by: Yoav Elnekave <yoav.elnekave@oracle.com>
Signed-off-by: Yoav Elnekave <yoav.elnekave@oracle.com>
Signed-off-by: Eyal Moscovici <eyal.moscovici@oracle.com>
Message-Id: <20200513133629.18508-5-eyal.moscovici@oracle.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Eyal Moscovici 2020-05-13 16:36:29 +03:00 committed by Eric Blake
parent e46c0b18cf
commit c0469496b3
3 changed files with 24 additions and 4 deletions
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2
docs/tools/qemu-img.rst
View File

@ -519,7 +519,7 @@ Command description:
``ImageInfoSpecific*`` QAPI object (e.g. ``ImageInfoSpecificQCow2``
for qcow2 images).
.. option:: map [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [-U] FILENAME
.. option:: map [--object OBJECTDEF] [--image-opts] [-f FMT] [--start-offset=OFFSET] [--max-length=LEN] [--output=OFMT] [-U] FILENAME
Dump the metadata of image *FILENAME* and its backing file chain.
In particular, this commands dumps the allocation state of every sector

4
qemu-img-cmds.hx
View File

@ -63,9 +63,9 @@ SRST
ERST
DEF("map", img_map,
"map [--object objectdef] [--image-opts] [-f fmt] [--output=ofmt] [-U] filename")
"map [--object objectdef] [--image-opts] [-f fmt] [--start-offset=offset] [--max-length=len] [--output=ofmt] [-U] filename")
SRST
.. option:: map [--object OBJECTDEF] [--image-opts] [-f FMT] [--output=OFMT] [-U] FILENAME
.. option:: map [--object OBJECTDEF] [--image-opts] [-f FMT] [--start-offset=OFFSET] [--max-length=LEN] [--output=OFMT] [-U] FILENAME
ERST
DEF("measure", img_measure,

22
qemu-img.c
View File

@ -3009,6 +3009,8 @@ static int img_map(int argc, char **argv)
int ret = 0;
bool image_opts = false;
bool force_share = false;
int64_t start_offset = 0;
int64_t max_length = -1;
fmt = NULL;
output = NULL;
@ -3021,9 +3023,11 @@ static int img_map(int argc, char **argv)
{"object", required_argument, 0, OPTION_OBJECT},
{"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
{"force-share", no_argument, 0, 'U'},
{"start-offset", required_argument, 0, 's'},
{"max-length", required_argument, 0, 'l'},
{0, 0, 0, 0}
};
c = getopt_long(argc, argv, ":f:hU",
c = getopt_long(argc, argv, ":f:s:l:hU",
long_options, &option_index);
if (c == -1) {
break;
@ -3047,6 +3051,18 @@ static int img_map(int argc, char **argv)
case OPTION_OUTPUT:
output = optarg;
break;
case 's':
start_offset = cvtnum("start offset", optarg);
if (start_offset < 0) {
return 1;
}
break;
case 'l':
max_length = cvtnum("max length", optarg);
if (max_length < 0) {
return 1;
}
break;
case OPTION_OBJECT: {
QemuOpts *opts;
opts = qemu_opts_parse_noisily(&qemu_object_opts,
@ -3097,7 +3113,11 @@ static int img_map(int argc, char **argv)
error_report("Failed to get size for '%s'", filename);
return 1;
}
if (max_length != -1) {
length = MIN(start_offset + max_length, length);
}
curr.start = start_offset;
while (curr.start + curr.length < length) {
int64_t offset = curr.start + curr.length;
int64_t n;