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Re: [Qemu-devel] [PATCH v3 13/19] qemu-img: add a "map" subcommand
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH v3 13/19] qemu-img: add a "map" subcommand |
Date: |
Tue, 30 Jul 2013 17:13:53 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Am 25.07.2013 um 16:23 hat Paolo Bonzini geschrieben:
> This command dumps the metadata of an entire chain, in either tabular or JSON
> format.
>
> Signed-off-by: Paolo Bonzini <address@hidden>
Hm, we have a 'map' command in qemu-io, which isn't exactly the same,
but then not much different either.
Depending on the use cases, should we move this to qemu-io, should we
remove the old function from qemu-io, or should we really keep both?
> diff --git a/qemu-img.c b/qemu-img.c
> index c5c8ebc..b28d388 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -1768,6 +1768,192 @@ 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;
> +} 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("%"PRId64" %"PRId64" %d %"PRId64"\n",
> + e->start, e->length, e->depth, e->offset);
Is this really human-readable output?
> + }
> + /* 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");
Correct JSON uses double quotes.
> + if (e->flags & BDRV_BLOCK_OFFSET_VALID) {
> + printf(", 'offset': %"PRId64"", e->offset);
> + }
> + putchar('}');
> +
> + if (!next) {
> + printf("]\n");
> + }
> + break;
> + }
> +}
> +
> +static int64_t get_block_status(BlockDriverState *bs, int64_t sector_num,
> + int *nb_sectors, int *depth)
> +{
> + int64_t ret;
> +
> + /* 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 (;;) {
> + int orig_nb_sectors = *nb_sectors;
> +
> + ret = bdrv_get_block_status(bs, sector_num, *nb_sectors, nb_sectors);
> + if (ret < 0) {
> + return ret;
> + }
> + if (ret & (BDRV_BLOCK_ZERO|BDRV_BLOCK_DATA)) {
> + return ret;
> + }
> + if (!*nb_sectors) {
> + /* Beyond the end of this image. The extra data is read as
> zeroes.
> + * We're in the range of the BlockDriverState above this one, so
> + * adjust depth.
> + */
> + *nb_sectors = orig_nb_sectors;
> + (*depth)--;
> + return BDRV_BLOCK_ZERO;
If you implement my suggestion that bdrv_co_get_block_status() returns
BDRV_BLOCK_ZERO instead of 0 if the image has no backing file, it might
also make sense to put this check there and return BDRV_BLOCK_ZERO even
if it has a backing file, but we're after its end.
> + }
> +
> + bs = bs->backing_hd;
> + if (bs == NULL) {
> + return 0;
> + }
> +
> + (*depth)++;
> + }
> +}
> +
> +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;
> +
> + 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;
> + }
> +
> + length = bdrv_getlength(bs);
bdrv_getlength() can fail.
> + while (curr.start + curr.length < length) {
> + int64_t nsectors_left, ret;
> + int64_t sector_num;
> + int n, depth, flags;
> +
> + /* Probe up to 1 G at a time. */
> + sector_num = (curr.start + curr.length) >> BDRV_SECTOR_BITS;
> + 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, &depth);
> +
> + if (ret < 0) {
> + error_report("Could not read file metadata: %s", strerror(-ret));
> + return 1;
This leaks bs.
> + }
> +
> + flags = ret & ~BDRV_BLOCK_OFFSET_MASK;
> + ret &= BDRV_BLOCK_OFFSET_MASK;
> + if (curr.length == 0 || curr.flags != flags || curr.depth != depth ||
> + ((curr.flags & BDRV_BLOCK_OFFSET_VALID) &&
> + curr.offset + curr.length != ret)) {
> + next.flags = flags;
> + next.depth = depth;
> + next.start = sector_num << BDRV_SECTOR_BITS;
> + next.offset = ret;
> + next.length = 0;
> + if (curr.length > 0) {
> + dump_map_entry(output_format, &curr, &next);
> + }
> + curr = next;
> + }
> + curr.length += n << BDRV_SECTOR_BITS;
> + }
> +
> + dump_map_entry(output_format, &curr, NULL);
> + return 0;
> +}
> +
> #define SNAPSHOT_LIST 1
> #define SNAPSHOT_CREATE 2
> #define SNAPSHOT_APPLY 3
Kevin
[Qemu-devel] [PATCH v3 13/19] qemu-img: add a "map" subcommand, Paolo Bonzini, 2013/07/25
- Re: [Qemu-devel] [PATCH v3 13/19] qemu-img: add a "map" subcommand,
Kevin Wolf <=
- Re: [Qemu-devel] [PATCH v3 13/19] qemu-img: add a "map" subcommand, Paolo Bonzini, 2013/07/30
- Re: [Qemu-devel] [PATCH v3 13/19] qemu-img: add a "map" subcommand, Kevin Wolf, 2013/07/30
- Re: [Qemu-devel] [PATCH v3 13/19] qemu-img: add a "map" subcommand, Kevin Wolf, 2013/07/31
- Re: [Qemu-devel] [PATCH v3 13/19] qemu-img: add a "map" subcommand, Paolo Bonzini, 2013/07/31
- Re: [Qemu-devel] [PATCH v3 13/19] qemu-img: add a "map" subcommand, Kevin Wolf, 2013/07/31
[Qemu-devel] [PATCH v3 14/19] docs, qapi: document qemu-img map, Paolo Bonzini, 2013/07/25
[Qemu-devel] [PATCH v3 15/19] block: use bdrv_has_zero_init to return BDRV_BLOCK_ZERO, Paolo Bonzini, 2013/07/25