diff --git a/libc/include/sys/statvfs.h b/libc/include/sys/statvfs.h
index e60cadc..93fa3d7 100644
--- a/libc/include/sys/statvfs.h
+++ b/libc/include/sys/statvfs.h
@@ -14,8 +14,12 @@
  * limitations under the License.
  */
 
-#ifndef _SYS_STATVFS_H_
-#define _SYS_STATVFS_H_
+#pragma once
+
+/**
+ * @file sys/statvfs.h
+ * @brief Filesystem statistics.
+ */
 
 #include <stdint.h>
 #include <sys/cdefs.h>
@@ -23,47 +27,123 @@
 
 __BEGIN_DECLS
 
-#ifdef __LP64__
-#define __STATVFS64_RESERVED uint32_t __f_reserved[6];
-#else
-#define __STATVFS64_RESERVED
+struct statvfs {
+  /** Block size. */
+  unsigned long f_bsize;
+  /** Fragment size. */
+  unsigned long f_frsize;
+  /** Total size of filesystem in `f_frsize` blocks. */
+  fsblkcnt_t f_blocks;
+  /** Number of free blocks. */
+  fsblkcnt_t f_bfree;
+  /** Number of free blocks for non-root. */
+  fsblkcnt_t f_bavail;
+  /** Number of inodes. */
+  fsfilcnt_t f_files;
+  /** Number of free inodes. */
+  fsfilcnt_t f_ffree;
+  /** Number of free inodes for non-root. */
+  fsfilcnt_t f_favail;
+  /** Filesystem id. */
+  unsigned long f_fsid;
+  /** Mount flags. (See `ST_` constants.) */
+  unsigned long f_flag;
+  /** Maximum filename length. */
+  unsigned long f_namemax;
+
+#if defined(__LP64__)
+  uint32_t __f_reserved[6];
 #endif
+};
 
-#define __STATVFS64_BODY \
-  unsigned long f_bsize; \
-  unsigned long f_frsize; \
-  fsblkcnt_t    f_blocks; \
-  fsblkcnt_t    f_bfree; \
-  fsblkcnt_t    f_bavail; \
-  fsfilcnt_t    f_files; \
-  fsfilcnt_t    f_ffree; \
-  fsfilcnt_t    f_favail; \
-  unsigned long f_fsid; \
-  unsigned long f_flag; \
-  unsigned long f_namemax; \
-  __STATVFS64_RESERVED
+struct statvfs64 {
+  /** Block size. */
+  unsigned long f_bsize;
+  /** Fragment size. */
+  unsigned long f_frsize;
+  /** Total size of filesystem in `f_frsize` blocks. */
+  fsblkcnt_t f_blocks;
+  /** Number of free blocks. */
+  fsblkcnt_t f_bfree;
+  /** Number of free blocks for non-root. */
+  fsblkcnt_t f_bavail;
+  /** Number of inodes. */
+  fsfilcnt_t f_files;
+  /** Number of free inodes. */
+  fsfilcnt_t f_ffree;
+  /** Number of free inodes for non-root. */
+  fsfilcnt_t f_favail;
+  /** Filesystem id. */
+  unsigned long f_fsid;
+  /** Mount flags. (See `ST_` constants.) */
+  unsigned long f_flag;
+  /** Maximum filename length. */
+  unsigned long f_namemax;
 
-struct statvfs { __STATVFS64_BODY };
-struct statvfs64 { __STATVFS64_BODY };
+#if defined(__LP64__)
+  uint32_t __f_reserved[6];
+#endif
+};
 
-#undef __STATVFS64_BODY
-#undef __STATVFS64_RESERVED
-
+/** Flag for `f_flag` in `struct statvfs`: mounted read-only. */
 #define ST_RDONLY      0x0001
+
+/** Flag for `f_flag` in `struct statvfs`: setuid/setgid ignored. */
 #define ST_NOSUID      0x0002
+
+/** Flag for `f_flag` in `struct statvfs`: access to device files disallowed. */
 #define ST_NODEV       0x0004
+
+/** Flag for `f_flag` in `struct statvfs`: execution disallowed. */
 #define ST_NOEXEC      0x0008
+
+/** Flag for `f_flag` in `struct statvfs`: writes synced immediately. */
 #define ST_SYNCHRONOUS 0x0010
+
+/** Flag for `f_flag` in `struct statvfs`: mandatory locking permitted. */
 #define ST_MANDLOCK    0x0040
+
+/** Flag for `f_flag` in `struct statvfs`: access times not updated. */
 #define ST_NOATIME     0x0400
+
+/** Flag for `f_flag` in `struct statvfs`: directory access times not updated. */
 #define ST_NODIRATIME  0x0800
+
+/** Flag for `f_flag` in `struct statvfs`: see `MS_RELATIME`. */
 #define ST_RELATIME    0x1000
 
+#if __ANDROID_API__ >= 19
+// These functions are implemented as static inlines before API level 19.
+
+/**
+ * [statvfs(3)](http://man7.org/linux/man-pages/man3/statvfs.3.html)
+ * queries filesystem statistics for the given path.
+ *
+ * Returns 0 on success, and returns -1 and sets `errno` on failure.
+ */
 int statvfs(const char* __path, struct statvfs* __buf) __INTRODUCED_IN(19);
-int statvfs64(const char* __path, struct statvfs64* __buf) __INTRODUCED_IN(21);
+
+/**
+ * [fstatvfs(3)](http://man7.org/linux/man-pages/man3/fstatvfs.3.html)
+ * queries filesystem statistics for the given file descriptor.
+ *
+ * Returns 0 on success, and returns -1 and sets `errno` on failure.
+ */
 int fstatvfs(int __fd, struct statvfs* __buf) __INTRODUCED_IN(19);
+
+#endif
+
+#if __ANDROID_API__ >= 21
+// These functions are implemented as static inlines before API level 21.
+
+/** Equivalent to statvfs(). */
+int statvfs64(const char* __path, struct statvfs64* __buf) __INTRODUCED_IN(21);
+
+/** Equivalent to fstatvfs(). */
 int fstatvfs64(int __fd, struct statvfs64* __buf) __INTRODUCED_IN(21);
 
+#endif
+
 __END_DECLS
 
-#endif
+#include <android/legacy_sys_statvfs_inlines.h>