Commit c0469496 authored by Eyal Moscovici's avatar Eyal Moscovici Committed by Eric Blake
Browse files

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: default avatarEric Blake <eblake@redhat.com>
Acked-by: default avatarMark Kanda <mark.kanda@oracle.com>
Co-developed-by: default avatarYoav Elnekave <yoav.elnekave@oracle.com>
Signed-off-by: default avatarYoav Elnekave <yoav.elnekave@oracle.com>
Signed-off-by: default avatarEyal Moscovici <eyal.moscovici@oracle.com>
Message-Id: <20200513133629.18508-5-eyal.moscovici@oracle.com>
Signed-off-by: default avatarEric Blake <eblake@redhat.com>
parent e46c0b18

docs/tools/qemu-img.rst

+1 −1
Original line number Diff line number Diff line
@@ -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

qemu-img-cmds.hx

+2 −2
Original line number Diff line number Diff line
@@ -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,

qemu-img.c

+21 −1
Original line number Diff line number Diff line
@@ -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;