Add a --thinpool argument to lxc-create, to use thin pool backed lvm when creating the container. When cloning a container backed by a thin pool, the clone will default to the same thin pool.

src/lxc/arguments.h

@@ -80,7 +80,7 @@ struct lxc_arguments {
 	char *bdevtype, *configfile, *template;
 	char *fstype;
 	unsigned long fssize;
-	char *lvname, *vgname;
+	char *lvname, *vgname, *thinpool;
 	char *zfsroot, *lowerdir, *dir;
 
 	/* remaining arguments */

src/lxc/bdev.c

@@ -816,7 +816,7 @@ static int lvm_umount(struct bdev *bdev)
  * not yet exist.  This function will attempt to create /dev/$vg/$lv of
  * size $size.
  */
-static int do_lvm_create(const char *path, unsigned long size)
+static int do_lvm_create(const char *path, unsigned long size, const char *thinpool)
 {
 	int ret, pid;
 	char sz[24], *pathdup, *vg, *lv;
@@ -848,11 +848,61 @@ static int do_lvm_create(const char *path, unsigned long size)
 	if (!vg)
 		exit(1);
 	vg++;
-	execlp("lvcreate", "lvcreate", "-L", sz, vg, "-n", lv, (char *)NULL);
+	if (!thinpool) {
+	    execlp("lvcreate", "lvcreate", "-L", sz, vg, "-n", lv, (char *)NULL);
+	} else {
+	    execlp("lvcreate", "lvcreate", "--thinpool", thinpool, "-V", sz, vg, "-n", lv, (char *)NULL);
+	}
 	free(pathdup);
 	exit(1);
 }
 
+static int lvm_is_thin_volume(const char *path)
+{
+	FILE *f;
+	int ret, len, start=0;
+	char *cmd, output[12];
+	const char *lvscmd = "lvs --unbuffered --noheadings -o lv_attr %s 2>/dev/null";
+
+	len = strlen(lvscmd) + strlen(path) - 1;
+	cmd = malloc(len);
+	if (!cmd)
+		return -1;
+
+	ret = snprintf(cmd, len, lvscmd, path);
+	if (ret < 0 || ret >= len)
+		return -1;
+
+	process_lock();
+	f = popen(cmd, "r");
+	process_unlock();
+
+	if (f == NULL) {
+		SYSERROR("popen failed");
+		return -1;
+	}
+
+	if (fgets(output, 12, f) == NULL)
+		return -1;
+
+	process_lock();
+	ret = pclose(f);
+	process_unlock();
+
+	if (!WIFEXITED(ret)) {
+		SYSERROR("error executing lvs");
+		return -1;
+	}
+
+	len = strlen(output);
+	while(start < len && output[start] == ' ') start++;
+
+	if (start + 6 < len && output[start + 6] == 't')
+		return 1;
+
+	return 0;
+}
+
 static int lvm_snapshot(const char *orig, const char *path, unsigned long size)
 {
 	int ret, pid;
@@ -882,7 +932,18 @@ static int lvm_snapshot(const char *orig, const char *path, unsigned long size)
 	*lv = '\0';
 	lv++;
 
-	ret = execlp("lvcreate", "lvcreate", "-s", "-L", sz, "-n", lv, orig, (char *)NULL);
+	// check if the original lv is backed by a thin pool, in which case we
+	// cannot specify a size that's different from the original size.
+	ret = lvm_is_thin_volume(orig);
+	if (ret == -1)
+		return -1;
+
+	if (!ret) {
+		ret = execlp("lvcreate", "lvcreate", "-s", "-L", sz, "-n", lv, orig, (char *)NULL);
+	} else {
+		ret = execlp("lvcreate", "lvcreate", "-s", "-n", lv, orig, (char *)NULL);
+	}
+
 	free(pathdup);
 	exit(1);
 }
@@ -965,7 +1026,7 @@ static int lvm_clonepaths(struct bdev *orig, struct bdev *new, const char *oldna
 			return -1;
 		}
 	} else {
-		if (do_lvm_create(new->src, size) < 0) {
+		if (do_lvm_create(new->src, size, NULL) < 0) {
 			ERROR("Error creating new lvm blockdev");
 			return -1;
 		}
@@ -998,7 +1059,7 @@ static int lvm_destroy(struct bdev *orig)
 static int lvm_create(struct bdev *bdev, const char *dest, const char *n,
 			struct bdev_specs *specs)
 {
-	const char *vg, *fstype, *lv = n;
+	const char *vg, *thinpool, *fstype, *lv = n;
 	unsigned long sz;
 	int ret, len;
 
@@ -1009,6 +1070,8 @@ static int lvm_create(struct bdev *bdev, const char *dest, const char *n,
 	if (!vg)
 		vg = default_lvm_vg();
 
+	thinpool = specs->u.lvm.thinpool;
+
 	/* /dev/$vg/$lv */
 	if (specs->u.lvm.lv)
 		lv = specs->u.lvm.lv;
@@ -1027,7 +1090,7 @@ static int lvm_create(struct bdev *bdev, const char *dest, const char *n,
 		sz = DEFAULT_FS_SIZE;
 
 	INFO("Error creating new lvm blockdev %s size %lu", bdev->src, sz);
-	if (do_lvm_create(bdev->src, sz) < 0) {
+	if (do_lvm_create(bdev->src, sz, thinpool) < 0) {
 		ERROR("Error creating new lvm blockdev %s size %lu", bdev->src, sz);
 		return -1;
 	}

src/lxc/bdev.h

@@ -46,6 +46,7 @@ struct bdev_specs {
 			char *lv;
 			char *fstype;
 			unsigned long fssize;  // fs size in bytes
+			char *thinpool; // lvm thin pool to use, if any
 		} lvm;
 		struct {
 			char *fstype;

src/lxc/lxc_config.c

@@ -31,6 +31,7 @@ struct lxc_config_items items[] =
 {
 	{ .name = "lxcpath", .fn = &lxc_get_default_config_path, },
 	{ .name = "lvm_vg", .fn = &lxc_get_default_lvm_vg, },
+	{ .name = "lvm_thin_pool", .fn = &lxc_get_default_lvm_thin_pool, },
 	{ .name = "zfsroot", .fn = &lxc_get_default_zfs_root, },
 	{ .name = NULL, },
 };

src/lxc/lxc_create.c

@@ -64,10 +64,11 @@ static int my_parser(struct lxc_arguments* args, int c, char* arg)
 	case 't': args->template = arg; break;
 	case '0': args->lvname = arg; break;
 	case '1': args->vgname = arg; break;
-	case '2': args->fstype = arg; break;
+	case '2': args->thinpool = arg; break;
-	case '3': args->fssize = get_fssize(arg); break;
+	case '3': args->fstype = arg; break;
-	case '4': args->zfsroot = arg; break;
+	case '4': args->fssize = get_fssize(arg); break;
-	case '5': args->dir = arg; break;
+	case '5': args->zfsroot = arg; break;
+	case '6': args->dir = arg; break;
 	}
 	return 0;
 }
@@ -78,10 +79,11 @@ static const struct option my_longopts[] = {
 	{"template", required_argument, 0, 't'},
 	{"lvname", required_argument, 0, '0'},
 	{"vgname", required_argument, 0, '1'},
-	{"fstype", required_argument, 0, '2'},
+	{"thinpool", required_argument, 0, '2'},
-	{"fssize", required_argument, 0, '3'},
+	{"fstype", required_argument, 0, '3'},
-	{"zfsroot", required_argument, 0, '4'},
+	{"fssize", required_argument, 0, '4'},
-	{"dir", required_argument, 0, '5'},
+	{"zfsroot", required_argument, 0, '5'},
+	{"dir", required_argument, 0, '6'},
 	LXC_COMMON_OPTIONS
 };
 
@@ -129,6 +131,8 @@ Options :\n\
                      (Default: container name)\n\
   --vgname=VG        Use LVM vg called VG\n\
                      (Default: lxc))\n\
+  --thinpool=TP      Use LVM thin pool called TP\n\
+                     (Default: none))\n\
   --fstype=TYPE      Create fstype TYPE\n\
                      (Default: ext3))\n\
   --fssize=SIZE      Create filesystem of size SIZE\n\
@@ -151,8 +155,8 @@ bool validate_bdev_args(struct lxc_arguments *a)
 		}
 	}
 	if (strcmp(a->bdevtype, "lvm") != 0) {
-		if (a->lvname || a->vgname) {
+		if (a->lvname || a->vgname || a->thinpool) {
-			fprintf(stderr, "--lvname and --vgname are only valid with -B lvm\n");
+			fprintf(stderr, "--lvname, --vgname and --thinpool are only valid with -B lvm\n");
 			return false;
 		}
 	}
@@ -221,6 +225,8 @@ int main(int argc, char *argv[])
 			spec.u.lvm.lv = my_args.lvname;
 		if (my_args.vgname)
 			spec.u.lvm.vg = my_args.vgname;
+		if (my_args.thinpool)
+			spec.u.lvm.thinpool = my_args.thinpool;
 		if (my_args.fstype)
 			spec.u.lvm.fstype = my_args.fstype;
 		if (my_args.fssize)

src/lxc/lxccontainer.c

@@ -1807,6 +1807,11 @@ const char *lxc_get_default_lvm_vg(void)
 	return default_lvm_vg();
 }
 
+const char *lxc_get_default_lvm_thin_pool(void)
+{
+	return default_lvm_thin_pool();
+}
+
 const char *lxc_get_default_zfs_root(void)
 {
 	return default_zfs_root();

src/lxc/lxccontainer.h

@@ -245,6 +245,7 @@ int lxc_container_put(struct lxc_container *c);
 int lxc_get_wait_states(const char **states);
 const char *lxc_get_default_config_path(void);
 const char *lxc_get_default_lvm_vg(void);
+const char *lxc_get_default_lvm_thin_pool(void);
 const char *lxc_get_default_zfs_root(void);
 const char *lxc_get_version(void);
 

src/lxc/utils.c

@@ -243,6 +243,7 @@ const char *lxc_global_config_value(const char *option_name)
 {
 	static const char *options[][2] = {
 		{ "lvm_vg",          DEFAULT_VG      },
+		{ "lvm_thin_pool",   NULL            },
 		{ "zfsroot",         DEFAULT_ZFSROOT },
 		{ "lxcpath",         LXCPATH         },
 		{ "cgroup.pattern",  DEFAULT_CGROUP_PATTERN },
@@ -326,6 +327,11 @@ const char *default_lvm_vg(void)
 	return lxc_global_config_value("lvm_vg");
 }
 
+const char *default_lvm_thin_pool(void)
+{
+	return lxc_global_config_value("lvm_thin_pool");
+}
+
 const char *default_zfs_root(void)
 {
 	return lxc_global_config_value("zfsroot");

src/lxc/utils.h

@@ -48,6 +48,7 @@ extern const char *lxc_global_config_value(const char *option_name);
 extern const char *default_lxc_path(void);
 extern const char *default_zfs_root(void);
 extern const char *default_lvm_vg(void);
+extern const char *default_lvm_thin_pool(void);
 
 /* Define getline() if missing from the C library */
 #ifndef HAVE_GETLINE