dissect: enable growfs by default, but make it configurable

poettering · poettering · commit 74a54baeecfe · 2021-04-23T17:56:34.000+02:00
This adds a new --growfs=yes|no switch to systemd-dissect, defaulting to
on.
diff --git a/man/systemd-dissect.xml b/man/systemd-dissect.xml
@@ -194,6 +194,28 @@
         <option>--fsck=no</option>.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><option>--growfs=no</option></term>
+
+        <listitem><para>Turn off automatic growing of accessed file systems to their partition size, if
+        marked for that in the GPT partition table. By default when an image is accessed for writing (by
+        <option>--mount</option> or <option>--copy-to</option>) the file systems contained in the OS image
+        are automatically grown to their partition sizes, if bit 59 in the GPT partition flags is set for
+        partition types that are defined by the <ulink
+        url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions Specification</ulink>. This
+        behavior may be switched off using <option>--growfs=no</option>. File systems are grown automatically
+        on access if all of the following conditions are met:</para>
+        <orderedlist>
+          <listitem><para>The file system is mounted writable</para></listitem>
+          <listitem><para>The file system currently is smaller than the partition it is contained in (and thus can be grown)</para></listitem>
+          <listitem><para>The image contains a GPT partition table</para></listitem>
+          <listitem><para>The file system is stored on a partition defined by the Discoverable Partitions Specification</para></listitem>
+          <listitem><para>Bit 59 of the GPT partition flags for this partition is set, as per specification</para></listitem>
+          <listitem><para>The <option>--growfs=no</option> option is not passed.</para></listitem>
+        </orderedlist>
+        </listitem>
+      </varlistentry>
+
       <varlistentry>
         <term><option>--mkdir</option></term>
 
diff --git a/src/dissect/dissect.c b/src/dissect/dissect.c
@@ -49,7 +49,8 @@ static DissectImageFlags arg_flags =
         DISSECT_IMAGE_DISCARD_ON_LOOP |
         DISSECT_IMAGE_RELAX_VAR_CHECK |
         DISSECT_IMAGE_FSCK |
-        DISSECT_IMAGE_USR_NO_ROOT;
+        DISSECT_IMAGE_USR_NO_ROOT |
+        DISSECT_IMAGE_GROWFS;
 static VeritySettings arg_verity_settings = VERITY_SETTINGS_DEFAULT;
 static JsonFormatFlags arg_json_format_flags = JSON_FORMAT_OFF;
 static PagerFlags arg_pager_flags = 0;
@@ -75,6 +76,7 @@ static int help(void) {
                "     --no-legend          Do not show the headers and footers\n"
                "  -r --read-only          Mount read-only\n"
                "     --fsck=BOOL          Run fsck before mounting\n"
+               "     --growfs=BOOL        Grow file system to partition size, if marked\n"
                "     --mkdir              Make mount directory before mounting, if missing\n"
                "     --discard=MODE       Choose 'discard' mode (disabled, loop, all, crypto)\n"
                "     --root-hash=HASH     Specify root hash for verity\n"
@@ -112,6 +114,7 @@ static int parse_argv(int argc, char *argv[]) {
                 ARG_NO_LEGEND,
                 ARG_DISCARD,
                 ARG_FSCK,
+                ARG_GROWFS,
                 ARG_ROOT_HASH,
                 ARG_ROOT_HASH_SIG,
                 ARG_VERITY_DATA,
@@ -128,6 +131,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "read-only",     no_argument,       NULL, 'r'               },
                 { "discard",       required_argument, NULL, ARG_DISCARD       },
                 { "fsck",          required_argument, NULL, ARG_FSCK          },
+                { "growfs",        required_argument, NULL, ARG_GROWFS        },
                 { "root-hash",     required_argument, NULL, ARG_ROOT_HASH     },
                 { "root-hash-sig", required_argument, NULL, ARG_ROOT_HASH_SIG },
                 { "verity-data",   required_argument, NULL, ARG_VERITY_DATA   },
@@ -264,6 +268,14 @@ static int parse_argv(int argc, char *argv[]) {
                         SET_FLAG(arg_flags, DISSECT_IMAGE_FSCK, r);
                         break;
 
+                case ARG_GROWFS:
+                        r = parse_boolean(optarg);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to parse --growfs= parameter: %s", optarg);
+
+                        SET_FLAG(arg_flags, DISSECT_IMAGE_GROWFS, r);
+                        break;
+
                 case ARG_JSON:
                         r = parse_json_argument(optarg, &arg_json_format_flags);
                         if (r <= 0)
