exec/util: add blkid API to query block devices based on FSTYPE

This change adds a building block to query block devices based on
the particular filesystem.

internal/exec/util/blkid.c

@@ -19,6 +19,12 @@
 static inline void _free_probe(blkid_probe *pr) { if (pr) blkid_free_probe(*pr); }
 #define _cleanup_probe_ __attribute__((cleanup(_free_probe)))
 
+static inline void _free_cache(blkid_cache *gcache) { blkid_put_cache(*gcache); }
+#define _cleanup_cache_ __attribute__((cleanup(_free_cache)))
+
+static inline void _free_iterator(blkid_dev_iterate *iter) { blkid_dev_iterate_end(*iter); }
+#define _cleanup_iterator_ __attribute__((cleanup(_free_iterator)))
+
 static result_t extract_part_info(blkid_partition part, struct partition_info *info, long sector_divisor);
 
 static result_t checked_copy(char *dest, const char *src, size_t len);
@@ -248,3 +254,39 @@ static result_t extract_part_info(blkid_partition part, struct partition_info *i
 
 	return RESULT_OK;
 }
+
+// blkid_get_block_devices fetches block devices with the given FSTYPE
+result_t blkid_get_block_devices(const char *fstype, struct block_device_list *device) {
+	blkid_dev_iterate iter _cleanup_iterator_ = NULL;
+	blkid_dev dev;
+	blkid_cache cache _cleanup_cache_ = NULL;
+	int err, count = 0;
+	const char *ctmp = NULL;
+
+	 if (blkid_get_cache(&cache, "/dev/null") != 0)
+	    return RESULT_GET_CACHE_FAILED;
+
+	 if (blkid_probe_all(cache) != 0)
+        return RESULT_PROBE_FAILED;
+
+	iter = blkid_dev_iterate_begin(cache);
+
+	blkid_dev_set_search(iter, "TYPE", fstype);
+
+	while (blkid_dev_next(iter, &dev) == 0) {
+	    dev = blkid_verify(cache, dev);
+	    if (!dev)
+		continue;
+	    ctmp = blkid_dev_devname(dev);
+		if (count > MAX_BLOCK_DEVICES)
+	       return RESULT_MAX_BLOCK_DEVICES;
+	    err = checked_copy(device->path[count], ctmp, MAX_BLOCK_DEVICE_PATH_LEN);
+	    if (err)
+	       return err;
+	    count++;
+	}
+	blkid_dev_iterate_end(iter);
+
+	device->count = count;
+	return RESULT_OK;
+}

internal/exec/util/blkid.go

@@ -110,6 +110,8 @@ func cResultToErr(res C.result_t) error {
 		return errors.New("bad partition index specified")
 	case C.RESULT_GET_PARTLIST_FAILED:
 		return errors.New("failed to get list of partitions")
+	case C.RESULT_GET_CACHE_FAILED:
+		return fmt.Errorf("failed to retrieve cache")
 	case C.RESULT_DISK_HAS_NO_TYPE:
 		return errors.New("disk has no type string, despite having a partition table")
 	case C.RESULT_DISK_NOT_GPT:
@@ -118,6 +120,8 @@ func cResultToErr(res C.result_t) error {
 		return errors.New("bad parameters passed")
 	case C.RESULT_OVERFLOW:
 		return errors.New("return value doesn't fit in buffer")
+	case C.RESULT_MAX_BLOCK_DEVICES:
+		return fmt.Errorf("found too many filesystems of the specified type")
 	case C.RESULT_NO_TOPO:
 		return errors.New("failed to get topology information")
 	case C.RESULT_NO_SECTOR_SIZE:
@@ -190,3 +194,20 @@ func filesystemLookup(device string, allowAmbivalent bool, fieldName string) (st
 	}
 	return string(buf[:bytes.IndexByte(buf[:], 0)]), nil
 }
+
+// GetBlockDevices returns a slice of block devices with the given filesystem
+func GetBlockDevices(fstype string) ([]string, error) {
+	var dev C.struct_block_device_list
+	res := C.blkid_get_block_devices(C.CString(fstype), &dev)
+
+	if res != C.RESULT_OK {
+		return nil, cResultToErr(res)
+	}
+
+	length := int(dev.count)
+	blkDeviceList := make([]string, length)
+	for i := 0; i < length; i++ {
+		blkDeviceList[i] = C.GoString(&dev.path[i][0])
+	}
+	return blkDeviceList, nil
+}

internal/exec/util/blkid.h

@@ -27,10 +27,12 @@ typedef enum {
 	RESULT_NO_PARTITION_TABLE,
 	RESULT_BAD_INDEX,
 	RESULT_GET_PARTLIST_FAILED,
+	RESULT_GET_CACHE_FAILED,
 	RESULT_DISK_HAS_NO_TYPE,
 	RESULT_DISK_NOT_GPT,
 	RESULT_BAD_PARAMS,
 	RESULT_OVERFLOW,
+	RESULT_MAX_BLOCK_DEVICES,
 	RESULT_NO_TOPO,
 	RESULT_NO_SECTOR_SIZE,
 	RESULT_BAD_SECTOR_SIZE,
@@ -48,6 +50,14 @@ struct partition_info {
 	int number;
 };
 
+#define MAX_BLOCK_DEVICES 10
+#define MAX_BLOCK_DEVICE_PATH_LEN 50
+
+struct block_device_list {
+	char path[MAX_BLOCK_DEVICES][MAX_BLOCK_DEVICE_PATH_LEN];
+	int count;
+};
+
 result_t blkid_lookup(const char *device, bool allow_ambivalent, const char *field_name, char buf[], size_t buf_len);
 
 result_t blkid_get_num_partitions(const char *device, int *ret);
@@ -57,5 +67,6 @@ result_t blkid_get_logical_sector_size(const char *device, int *ret_sector_size)
 // WARNING part_num may not be what you expect. see the .c file's comment for why
 result_t blkid_get_partition(const char *device, int part_num, struct partition_info *info);
 
-#endif // _BLKID_H_
+result_t blkid_get_block_devices(const char *fstype, struct block_device_list *device);
 
+#endif // _BLKID_H_