Commit 4c93a13b authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Stefan Hajnoczi
Browse files

qemu-img: add a "map" subcommand 



This command dumps the metadata of an entire chain, in either tabular or JSON
format.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent f0ad5712

qemu-img-cmds.hx

+6 −0
Original line number Diff line number Diff line
@@ -45,6 +45,12 @@ STEXI 
@item info [-f @var{fmt}] [--output=@var{ofmt}] [--backing-chain] @var{filename}

ETEXI



DEF("map", img_map,

    "map [-f fmt] [--output=ofmt] filename")

STEXI

@item map [-f @var{fmt}] [--output=@var{ofmt}] @var{filename}

ETEXI



DEF("snapshot", img_snapshot,

    "snapshot [-q] [-l | -a snapshot | -c snapshot | -d snapshot] filename")

STEXI

qemu-img.c

+191 −0
Original line number Diff line number Diff line
@@ -1801,6 +1801,197 @@ static int img_info(int argc, char **argv) 
    return 0;

}





typedef struct MapEntry {

    int flags;

    int depth;

    int64_t start;

    int64_t length;

    int64_t offset;

    BlockDriverState *bs;

} MapEntry;



static void dump_map_entry(OutputFormat output_format, MapEntry *e,

                           MapEntry *next)

{

    switch (output_format) {

    case OFORMAT_HUMAN:

        if ((e->flags & BDRV_BLOCK_DATA) &&

            !(e->flags & BDRV_BLOCK_OFFSET_VALID)) {

            error_report("File contains external, encrypted or compressed clusters.");

            exit(1);

        }

        if ((e->flags & (BDRV_BLOCK_DATA|BDRV_BLOCK_ZERO)) == BDRV_BLOCK_DATA) {

            printf("%#-16"PRIx64"%#-16"PRIx64"%#-16"PRIx64"%s\n",

                   e->start, e->length, e->offset, e->bs->filename);

        }

        /* This format ignores the distinction between 0, ZERO and ZERO|DATA.

         * Modify the flags here to allow more coalescing.

         */

        if (next &&

            (next->flags & (BDRV_BLOCK_DATA|BDRV_BLOCK_ZERO)) != BDRV_BLOCK_DATA) {

            next->flags &= ~BDRV_BLOCK_DATA;

            next->flags |= BDRV_BLOCK_ZERO;

        }

        break;

    case OFORMAT_JSON:

        printf("%s{ \"start\": %"PRId64", \"length\": %"PRId64", \"depth\": %d,"

               " \"zero\": %s, \"data\": %s",

               (e->start == 0 ? "[" : ",\n"),

               e->start, e->length, e->depth,

               (e->flags & BDRV_BLOCK_ZERO) ? "true" : "false",

               (e->flags & BDRV_BLOCK_DATA) ? "true" : "false");

        if (e->flags & BDRV_BLOCK_OFFSET_VALID) {

            printf(", 'offset': %"PRId64"", e->offset);

        }

        putchar('}');



        if (!next) {

            printf("]\n");

        }

        break;

    }

}



static int get_block_status(BlockDriverState *bs, int64_t sector_num,

                            int nb_sectors, MapEntry *e)

{

    int64_t ret;

    int depth;



    /* As an optimization, we could cache the current range of unallocated

     * clusters in each file of the chain, and avoid querying the same

     * range repeatedly.

     */



    depth = 0;

    for (;;) {

        ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &nb_sectors);

        if (ret < 0) {

            return ret;

        }

        assert(nb_sectors);

        if (ret & (BDRV_BLOCK_ZERO|BDRV_BLOCK_DATA)) {

            break;

        }

        bs = bs->backing_hd;

        if (bs == NULL) {

            ret = 0;

            break;

        }



        depth++;

    }



    e->start = sector_num * BDRV_SECTOR_SIZE;

    e->length = nb_sectors * BDRV_SECTOR_SIZE;

    e->flags = ret & ~BDRV_BLOCK_OFFSET_MASK;

    e->offset = ret & BDRV_BLOCK_OFFSET_MASK;

    e->depth = depth;

    e->bs = bs;

    return 0;

}



static int img_map(int argc, char **argv)

{

    int c;

    OutputFormat output_format = OFORMAT_HUMAN;

    BlockDriverState *bs;

    const char *filename, *fmt, *output;

    int64_t length;

    MapEntry curr = { .length = 0 }, next;

    int ret = 0;



    fmt = NULL;

    output = NULL;

    for (;;) {

        int option_index = 0;

        static const struct option long_options[] = {

            {"help", no_argument, 0, 'h'},

            {"format", required_argument, 0, 'f'},

            {"output", required_argument, 0, OPTION_OUTPUT},

            {0, 0, 0, 0}

        };

        c = getopt_long(argc, argv, "f:h",

                        long_options, &option_index);

        if (c == -1) {

            break;

        }

        switch (c) {

        case '?':

        case 'h':

            help();

            break;

        case 'f':

            fmt = optarg;

            break;

        case OPTION_OUTPUT:

            output = optarg;

            break;

        }

    }

    if (optind >= argc) {

        help();

    }

    filename = argv[optind++];



    if (output && !strcmp(output, "json")) {

        output_format = OFORMAT_JSON;

    } else if (output && !strcmp(output, "human")) {

        output_format = OFORMAT_HUMAN;

    } else if (output) {

        error_report("--output must be used with human or json as argument.");

        return 1;

    }



    bs = bdrv_new_open(filename, fmt, BDRV_O_FLAGS, true, false);

    if (!bs) {

        return 1;

    }



    if (output_format == OFORMAT_HUMAN) {

        printf("%-16s%-16s%-16s%s\n", "Offset", "Length", "Mapped to", "File");

    }



    length = bdrv_getlength(bs);

    while (curr.start + curr.length < length) {

        int64_t nsectors_left;

        int64_t sector_num;

        int n;



        sector_num = (curr.start + curr.length) >> BDRV_SECTOR_BITS;



        /* Probe up to 1 GiB at a time.  */

        nsectors_left = DIV_ROUND_UP(length, BDRV_SECTOR_SIZE) - sector_num;

        n = MIN(1 << (30 - BDRV_SECTOR_BITS), nsectors_left);

        ret = get_block_status(bs, sector_num, n, &next);



        if (ret < 0) {

            error_report("Could not read file metadata: %s", strerror(-ret));

            goto out;

        }



        if (curr.length != 0 && curr.flags == next.flags &&

            curr.depth == next.depth &&

            ((curr.flags & BDRV_BLOCK_OFFSET_VALID) == 0 ||

             curr.offset + curr.length == next.offset)) {

            curr.length += next.length;

            continue;

        }



        if (curr.length > 0) {

            dump_map_entry(output_format, &curr, &next);

        }

        curr = next;

    }



    dump_map_entry(output_format, &curr, NULL);



out:

    bdrv_unref(bs);

    return ret < 0;

}



#define SNAPSHOT_LIST   1

#define SNAPSHOT_CREATE 2

#define SNAPSHOT_APPLY  3