From: David Edmondson <david.edmond...@oracle.com>
In many cases the target of a convert operation is a newly provisioned
target that the user knows is blank (reads as zero). In this situation
there is no requirement for qemu-img to wastefully zero out the entire
device.
Add a new option, --target-is-zero, allowing the user to indicate that
an existing target device will return zeros for all reads.
Signed-off-by: David Edmondson <david.edmond...@oracle.com>
Message-Id: <20200205110248.2009589-2-david.edmond...@oracle.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
Reviewed-by: Eric Blake <ebl...@redhat.com>
Signed-off-by: Max Reitz <mre...@redhat.com>
---
docs/interop/qemu-img.rst | 9 ++++++++-
qemu-img-cmds.hx | 4 ++--
qemu-img.c | 26 +++++++++++++++++++++++---
3 files changed, 33 insertions(+), 6 deletions(-)
diff --git a/docs/interop/qemu-img.rst b/docs/interop/qemu-img.rst
index 42e4451db4..5f40137c10 100644
--- a/docs/interop/qemu-img.rst
+++ b/docs/interop/qemu-img.rst
@@ -214,6 +214,13 @@ Parameters to convert subcommand:
will still be printed. Areas that cannot be read from the source will be
treated as containing only zeroes.
+.. option:: --target-is-zero
+
+ Assume that reading the destination image will always return
+ zeros. This parameter is mutually exclusive with a destination image
+ that has a backing file. It is required to also use the ``-n``
+ parameter to skip image creation.
+
Parameters to dd subcommand:
.. program:: qemu-img-dd
@@ -366,7 +373,7 @@ Command description:
4
Error on reading data
-.. option:: convert [--object OBJECTDEF] [--image-opts] [--target-image-opts]
[-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-O
OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l SNAPSHOT_PARAM] [-S SPARSE_SIZE]
[-m NUM_COROUTINES] [-W] FILENAME [FILENAME2 [...]] OUTPUT_FILENAME
+.. option:: convert [--object OBJECTDEF] [--image-opts] [--target-image-opts]
[--target-is-zero] [-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t CACHE] [-T
SRC_CACHE] [-O OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l SNAPSHOT_PARAM]
[-S SPARSE_SIZE] [-m NUM_COROUTINES] [-W] FILENAME [FILENAME2 [...]]
OUTPUT_FILENAME
Convert the disk image *FILENAME* or a snapshot *SNAPSHOT_PARAM*
to disk image *OUTPUT_FILENAME* using format *OUTPUT_FMT*. It can
diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index d7fbc6b1f4..c9c54de1df 100644
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -39,9 +39,9 @@ SRST
ERST
DEF("convert", img_convert,
- "convert [--object objectdef] [--image-opts] [--target-image-opts] [-U]
[-C] [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-T src_cache] [-O output_fmt] [-B
backing_file] [-o options] [-l snapshot_param] [-S sparse_size] [-m
num_coroutines] [-W] [--salvage] filename [filename2 [...]] output_filename")
+ "convert [--object objectdef] [--image-opts] [--target-image-opts]
[--target-is-zero] [-U] [-C] [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-T
src_cache] [-O output_fmt] [-B backing_file] [-o options] [-l snapshot_param]
[-S sparse_size] [-m num_coroutines] [-W] [--salvage] filename [filename2
[...]] output_filename")
SRST
-.. option:: convert [--object OBJECTDEF] [--image-opts] [--target-image-opts]
[-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-O
OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l SNAPSHOT_PARAM] [-S SPARSE_SIZE]
[-m NUM_COROUTINES] [-W] [--salvage] FILENAME [FILENAME2 [...]] OUTPUT_FILENAME
+.. option:: convert [--object OBJECTDEF] [--image-opts] [--target-image-opts]
[--target-is-zero] [-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t CACHE] [-T
SRC_CACHE] [-O OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l SNAPSHOT_PARAM]
[-S SPARSE_SIZE] [-m NUM_COROUTINES] [-W] [--salvage] FILENAME [FILENAME2
[...]] OUTPUT_FILENAME
ERST
DEF("create", img_create,
diff --git a/qemu-img.c b/qemu-img.c
index 2b4562b9d9..0faf2cd2f5 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -70,6 +70,7 @@ enum {
OPTION_PREALLOCATION = 265,
OPTION_SHRINK = 266,
OPTION_SALVAGE = 267,
+ OPTION_TARGET_IS_ZERO = 268,
};
typedef enum OutputFormat {
@@ -1984,10 +1985,9 @@ static int convert_do_copy(ImgConvertState *s)
int64_t sector_num = 0;
/* Check whether we have zero initialisation or can get it efficiently */
- if (s->target_is_new && s->min_sparse && !s->target_has_backing) {
+ if (!s->has_zero_init && s->target_is_new && s->min_sparse &&
+ !s->target_has_backing) {
s->has_zero_init = bdrv_has_zero_init(blk_bs(s->target));
- } else {
- s->has_zero_init = false;
}
if (!s->has_zero_init && !s->target_has_backing &&
@@ -2086,6 +2086,7 @@ static int img_convert(int argc, char **argv)
{"force-share", no_argument, 0, 'U'},
{"target-image-opts", no_argument, 0, OPTION_TARGET_IMAGE_OPTS},
{"salvage", no_argument, 0, OPTION_SALVAGE},
+ {"target-is-zero", no_argument, 0, OPTION_TARGET_IS_ZERO},
{0, 0, 0, 0}
};
c = getopt_long(argc, argv, ":hf:O:B:Cco:l:S:pt:T:qnm:WU",
@@ -2209,6 +2210,14 @@ static int img_convert(int argc, char **argv)
case OPTION_TARGET_IMAGE_OPTS:
tgt_image_opts = true;
break;
+ case OPTION_TARGET_IS_ZERO:
+ /*
+ * The user asserting that the target is blank has the
+ * same effect as the target driver supporting zero
+ * initialisation.
+ */
+ s.has_zero_init = true;
+ break;
}
}
@@ -2247,6 +2256,11 @@ static int img_convert(int argc, char **argv)
warn_report("This will become an error in future QEMU versions.");
}
+ if (s.has_zero_init && !skip_create) {
+ error_report("--target-is-zero requires use of -n flag");
+ goto fail_getopt;
+ }
+
s.src_num = argc - optind - 1;
out_filename = s.src_num >= 1 ? argv[argc - 1] : NULL;
@@ -2380,6 +2394,12 @@ static int img_convert(int argc, char **argv)
}
s.target_has_backing = (bool) out_baseimg;
+ if (s.has_zero_init && s.target_has_backing) {
+ error_report("Cannot use --target-is-zero when the destination "
+ "image has a backing file");
+ goto out;
+ }
+
if (s.src_num > 1 && out_baseimg) {
error_report("Having a backing file for the target makes no sense when
"
"concatenating multiple input images");
--
2.24.1
