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qemu-img: Expose PreallocMode for resizing 

Add a --preallocation command line option to qemu-img resize which can
be used to set the PreallocMode parameter of blk_truncate().

While touching this code, fix the fact that we did not handle errors
returned by blk_getlength().

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20170613202107.10125-5-mreitz@redhat.com
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Max Reitz 2017-06-13 22:20:55 +02:00
parent 3a691c50f1
commit dc5f690b97
2 changed files with 36 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
qemu-img.c
View File

@ -24,6 +24,7 @@
#include "qemu/osdep.h"
#include "qemu-version.h"
#include "qapi/error.h"
#include "qapi/util.h"
#include "qapi-visit.h"
#include "qapi/qobject-output-visitor.h"
#include "qapi/qmp/qerror.h"
@ -62,6 +63,7 @@ enum {
OPTION_NO_DRAIN = 262,
OPTION_TARGET_IMAGE_OPTS = 263,
OPTION_SIZE = 264,
OPTION_PREALLOCATION = 265,
};
typedef enum OutputFormat {
@ -3408,9 +3410,10 @@ static int img_resize(int argc, char **argv)
Error *err = NULL;
int c, ret, relative;
const char *filename, *fmt, *size;
int64_t n, total_size;
int64_t n, total_size, current_size;
bool quiet = false;
BlockBackend *blk = NULL;
PreallocMode prealloc = PREALLOC_MODE_OFF;
QemuOpts *param;
static QemuOptsList resize_options = {
@ -3444,6 +3447,7 @@ 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},
{"preallocation", required_argument, 0, OPTION_PREALLOCATION},
{0, 0, 0, 0}
};
c = getopt_long(argc, argv, ":f:hq",
@ -3478,6 +3482,15 @@ static int img_resize(int argc, char **argv)
case OPTION_IMAGE_OPTS:
image_opts = true;
break;
case OPTION_PREALLOCATION:
prealloc = qapi_enum_parse(PreallocMode_lookup, optarg,
PREALLOC_MODE__MAX, PREALLOC_MODE__MAX,
NULL);
if (prealloc == PREALLOC_MODE__MAX) {
error_report("Invalid preallocation mode '%s'", optarg);
return 1;
}
break;
}
}
if (optind != argc - 1) {
@ -3526,8 +3539,16 @@ static int img_resize(int argc, char **argv)
goto out;
}
current_size = blk_getlength(blk);
if (current_size < 0) {
error_report("Failed to inquire current image length: %s",
strerror(-current_size));
ret = -1;
goto out;
}
if (relative) {
total_size = blk_getlength(blk) + n * relative;
total_size = current_size + n * relative;
} else {
total_size = n;
}
@ -3537,7 +3558,13 @@ static int img_resize(int argc, char **argv)
goto out;
}
ret = blk_truncate(blk, total_size, PREALLOC_MODE_OFF, &err);
if (total_size <= current_size && prealloc != PREALLOC_MODE_OFF) {
error_report("Preallocation can only be used for growing images");
ret = -1;
goto out;
}
ret = blk_truncate(blk, total_size, prealloc, &err);
if (!ret) {
qprintf(quiet, "Image resized.\n");
} else {

7
qemu-img.texi
View File

@ -529,7 +529,7 @@ 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.
@item resize @var{filename} [+ | -]@var{size}
@item resize [--preallocation=@var{prealloc}] @var{filename} [+ | -]@var{size}
Change the disk image as if it had been created with @var{size}.
@ -541,6 +541,11 @@ 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.
When growing an image, the @code{--preallocation} option may be used to specify
how the additional image area should be allocated on the host. See the format
description in the @code{NOTES} section which values are allowed. Using this
option may result in slightly more data being allocated than necessary.
@item amend [-p] [-f @var{fmt}] [-t @var{cache}] -o @var{options} @var{filename}
Amends the image format specific @var{options} for the image file