New API: resize2fs-size to allow shrinking ext2 filesystems (RHBZ#585221).

daemon/ext2.c

@@ -20,6 +20,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <inttypes.h>
 #include <string.h>
 #include <unistd.h>
 
@@ -300,6 +301,41 @@ do_resize2fs (const char *device)
   return 0;
 }
 
+int
+do_resize2fs_size (const char *device, int64_t size)
+{
+  char *err;
+  int r;
+
+  char prog[] = "resize2fs";
+  if (e2prog (prog) == -1)
+    return -1;
+
+  /* resize2fs itself may impose additional limits.  Since we are
+   * going to use the 'K' suffix however we can only work with whole
+   * kilobytes.
+   */
+  if (size & 1023) {
+    reply_with_error ("%" PRIi64 ": size must be a round number of kilobytes",
+                      size);
+    return -1;
+  }
+  size /= 1024;
+
+  char buf[32];
+  snprintf (buf, sizeof buf, "%" PRIi64 "K", size);
+
+  r = command (NULL, &err, prog, device, buf, NULL);
+  if (r == -1) {
+    reply_with_error ("%s", err);
+    free (err);
+    return -1;
+  }
+
+  free (err);
+  return 0;
+}
+
 int
 do_e2fsck_f (const char *device)
 {

src/generator.ml

@@ -4686,6 +4686,13 @@ unlikely for regular files in ordinary circumstances.
 
 See also C<guestfs_pread>.");
 
+  ("resize2fs_size", (RErr, [Device "device"; Int64 "size"]), 248, [],
+   [],
+   "resize an ext2/ext3 filesystem (with size)",
+   "\
+This command is the same as C<guestfs_resize2fs> except that it
+allows you to specify the new size (in bytes) explicitly.");
+
 ]
 
 let all_functions = non_daemon_functions @ daemon_functions