[Qemu-devel] [RFC 3/4] qemu-img: add max-size subcommand

[Stefan Hajnoczi]

The max-size subcommand calculates the maximum size required by a new
image file.  This can be used by users or management tools that need to
allocate space on an LVM volume, SAN LUN, etc before creating or
converting an image file.

Suggested-by: Maor Lipchuk <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
 qemu-img.c       | 196 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 qemu-img-cmds.hx |   6 ++
 2 files changed, 202 insertions(+)

diff --git a/qemu-img.c b/qemu-img.c
index 98b836b..f0a5a85 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -59,6 +59,7 @@ enum {
     OPTION_PATTERN = 260,
     OPTION_FLUSH_INTERVAL = 261,
     OPTION_NO_DRAIN = 262,
+    OPTION_SIZE = 263,
 };
 
 typedef enum OutputFormat {
@@ -4287,6 +4288,201 @@ out:
     return 0;
 }
 
+static int img_max_size(int argc, char **argv)
+{
+    static const struct option long_options[] = {
+        {"help", no_argument, 0, 'h'},
+        {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+        {"object", required_argument, 0, OPTION_OBJECT},
+        {"output", required_argument, 0, OPTION_OUTPUT},
+        {"size", required_argument, 0, OPTION_SIZE},
+        {0, 0, 0, 0}
+    };
+    OutputFormat output_format = OFORMAT_HUMAN;
+    BlockBackend *in_blk = NULL;
+    BlockDriver *drv;
+    const char *filename = NULL;
+    const char *fmt = NULL;
+    const char *out_fmt = "raw";
+    char *options = NULL;
+    char *snapshot_name = NULL;
+    QemuOpts *opts = NULL;
+    QemuOpts *object_opts = NULL;
+    QemuOpts *sn_opts = NULL;
+    QemuOptsList *create_opts = NULL;
+    bool image_opts = false;
+    uint64_t img_size = ~0ULL;
+    uint64_t ret_size;
+    Error *local_err = NULL;
+    int ret = 1;
+    int c;
+
+    while ((c = getopt_long(argc, argv, "hf:O:o:l:",
+                            long_options, NULL)) != -1) {
+        switch (c) {
+        case '?':
+        case 'h':
+            help();
+            break;
+        case 'f':
+            fmt = optarg;
+            break;
+        case 'O':
+            out_fmt = optarg;
+            break;
+        case 'o':
+            if (!is_valid_option_list(optarg)) {
+                error_report("Invalid option list: %s", optarg);
+                goto fail;
+            }
+            if (!options) {
+                options = g_strdup(optarg);
+            } else {
+                char *old_options = options;
+                options = g_strdup_printf("%s,%s", options, optarg);
+                g_free(old_options);
+            }
+            break;
+        case 'l':
+            if (strstart(optarg, SNAPSHOT_OPT_BASE, NULL)) {
+                sn_opts = qemu_opts_parse_noisily(&internal_snapshot_opts,
+                                                  optarg, false);
+                if (!sn_opts) {
+                    error_report("Failed in parsing snapshot param '%s'",
+                                 optarg);
+                    goto fail;
+                }
+            } else {
+                snapshot_name = optarg;
+            }
+            break;
+        case OPTION_OBJECT:
+            object_opts = qemu_opts_parse_noisily(&qemu_object_opts,
+                                                  optarg, true);
+            if (!object_opts) {
+                goto fail;
+            }
+            break;
+        case OPTION_IMAGE_OPTS:
+            image_opts = true;
+            break;
+        case OPTION_OUTPUT:
+            if (!strcmp(optarg, "json")) {
+                output_format = OFORMAT_JSON;
+            } else if (!strcmp(optarg, "human")) {
+                output_format = OFORMAT_HUMAN;
+            } else {
+                error_report("--output must be used with human or json "
+                             "as argument.");
+                goto fail;
+            }
+            break;
+        case OPTION_SIZE:
+        {
+            int64_t sval;
+
+            sval = cvtnum(optarg);
+            if (sval < 0) {
+                if (sval == -ERANGE) {
+                    error_report("Image size must be less than 8 EiB!");
+                } else {
+                    error_report("Invalid image size specified! You may use "
+                                 "k, M, G, T, P or E suffixes for ");
+                    error_report("kilobytes, megabytes, gigabytes, terabytes, "
+                                 "petabytes and exabytes.");
+                }
+                goto fail;
+            }
+            img_size = (uint64_t)sval;
+        }
+        break;
+        }
+    }
+
+    if (qemu_opts_foreach(&qemu_object_opts,
+                          user_creatable_add_opts_foreach,
+                          NULL, NULL)) {
+        goto fail;
+    }
+
+    if (argc - optind > 1) {
+        error_report("At most one filename argument is allowed.");
+        goto fail;
+    } else if (argc - optind == 1) {
+        filename = argv[optind];
+    }
+
+    if (!filename &&
+        (object_opts || image_opts || fmt || snapshot_name || sn_opts)) {
+        error_report("--object, --image-opts, -f, and -l "
+                     "require a filename argument.");
+        goto fail;
+    }
+    if (filename && img_size != ~0ULL) {
+        error_report("--size N cannot be used together with a filename.");
+        goto fail;
+    }
+    if (!filename && img_size == ~0ULL) {
+        error_report("Either --size N or one filename must be specified.");
+        goto fail;
+    }
+
+    if (filename) {
+        in_blk = img_open(image_opts, filename, fmt, 0, false, false);
+        if (!in_blk) {
+            goto fail;
+        }
+    }
+
+    drv = bdrv_find_format(out_fmt);
+    if (!drv) {
+        error_report("Unknown file format '%s'", out_fmt);
+        goto fail;
+    }
+    if (!drv->create_opts) {
+        error_report("Format driver '%s' does not support image creation",
+                     drv->format_name);
+        goto fail;
+    }
+
+    create_opts = qemu_opts_append(create_opts, drv->create_opts);
+    opts = qemu_opts_create(create_opts, NULL, 0, &error_abort);
+    if (options) {
+        qemu_opts_do_parse(opts, options, NULL, &local_err);
+        if (local_err) {
+            error_report_err(local_err);
+            error_report("Invalid options for file format '%s'", out_fmt);
+            goto fail;
+        }
+    }
+    if (img_size != ~0ULL) {
+        qemu_opt_set_number(opts, BLOCK_OPT_SIZE, img_size, &error_abort);
+    }
+
+    ret_size = bdrv_max_size(drv, opts, in_blk ? blk_bs(in_blk) : NULL,
+                             &local_err);
+    if (local_err) {
+        error_report_err(local_err);
+        goto fail;
+    }
+
+    if (output_format == OFORMAT_HUMAN) {
+        printf("%" PRIu64 "\n", ret_size);
+    } else {
+        printf("{ \"size\": %" PRIu64 " }\n", ret_size);
+    }
+
+    ret = 0;
+
+fail:
+    qemu_opts_del(object_opts);
+    qemu_opts_del(opts);
+    qemu_opts_del(sn_opts);
+    qemu_opts_free(create_opts);
+    g_free(options);
+    blk_unref(in_blk);
+    return ret;
+}
 
 static const img_cmd_t img_cmds[] = {
 #define DEF(option, callback, arg_string)        \
diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index 9c9702c..80997f9 100644
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -87,3 +87,9 @@ STEXI
 @item amend [--object @var{objectdef}] [--image-opts] [-p] [-q] [-f @var{fmt}] 
[-t @var{cache}] -o @var{options} @var{filename}
 @end table
 ETEXI
+
+DEF("max-size", img_max_size,
+"max-size [--output=ofmt] [-O output_fmt] [-o options] [--size N | [--object 
objectdef] [--image-opts] [-f fmt] [-l snapshot_param] filename]")
+STEXI
+TODO max-size documentation
+ETEXI
-- 
2.9.3