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author | David Edmondson <david.edmondson@oracle.com> | 2020-02-05 11:02:48 +0000 |
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committer | Max Reitz <mreitz@redhat.com> | 2020-02-20 16:43:42 +0100 |
commit | 168468fe19c872d31d17581e6a6cf7b69bd105b1 (patch) | |
tree | 08c88e95d9c9797002d96c97e59bd33e9dd970da | |
parent | facda5443f5a8676fb635b82ac1046ac6b6a67ce (diff) | |
download | qemu-168468fe19c872d31d17581e6a6cf7b69bd105b1.zip qemu-168468fe19c872d31d17581e6a6cf7b69bd105b1.tar.gz qemu-168468fe19c872d31d17581e6a6cf7b69bd105b1.tar.bz2 |
qemu-img: Add --target-is-zero to convert
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.edmondson@oracle.com>
Message-Id: <20200205110248.2009589-2-david.edmondson@oracle.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
-rw-r--r-- | docs/interop/qemu-img.rst | 9 | ||||
-rw-r--r-- | qemu-img-cmds.hx | 4 | ||||
-rw-r--r-- | 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 42e4451..5f40137 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 d7fbc6b..c9c54de 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, @@ -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"); |