Skip the OFD locks tests on OverlayFS and musl

OFD lock functions don't work as expected on overlayfs, which is a type
of union file system.  And OVERLAYFS_SUPER_MAGIC isn't defined on musl,
at least not yet.

Cargo.toml

@@ -17,7 +17,7 @@ exclude     = [
 ]
 
 [dependencies]
-libc = { git = "https://github.com/rust-lang/libc/", features = [ "extra_traits" ] }
+libc = { git = "https://github.com/rust-lang/libc/", rev = "fdc5cf4a1ba362aec989bd3dc7ec88bcd371a23a", features = [ "extra_traits" ] }
 bitflags = "1.1"
 cfg-if = "0.1.10"
 

src/sys/statfs.rs

@@ -72,6 +72,8 @@ pub const NFS_SUPER_MAGIC: FsType = FsType(libc::NFS_SUPER_MAGIC);
 #[cfg(all(target_os = "linux", not(target_env = "musl"), not(target_arch = "s390x")))]
 pub const OPENPROM_SUPER_MAGIC: FsType = FsType(libc::OPENPROM_SUPER_MAGIC);
 #[cfg(all(target_os = "linux", not(target_env = "musl"), not(target_arch = "s390x")))]
+pub const OVERLAYFS_SUPER_MAGIC: FsType = FsType(libc::OVERLAYFS_SUPER_MAGIC);
+#[cfg(all(target_os = "linux", not(target_env = "musl"), not(target_arch = "s390x")))]
 pub const PROC_SUPER_MAGIC: FsType = FsType(libc::PROC_SUPER_MAGIC);
 #[cfg(all(target_os = "linux", not(target_env = "musl"), not(target_arch = "s390x")))]
 pub const QNX4_SUPER_MAGIC: FsType = FsType(libc::QNX4_SUPER_MAGIC);

test/test_fcntl.rs

@@ -228,11 +228,19 @@ mod linux_android {
                   target_arch = "mips64",
                   target_arch = "mips64el",
                   target_arch = "powerpc64",
-                  target_arch = "powerpc64le")))]
+                  target_arch = "powerpc64le",
+                  target_env = "musl")))]
     fn test_ofd_write_lock() {
         let tmp = NamedTempFile::new().unwrap();
 
         let fd = tmp.as_raw_fd();
+        let statfs = nix::sys::statfs::fstatfs(&tmp).unwrap();
+        if statfs.filesystem_type() == nix::sys::statfs::OVERLAYFS_SUPER_MAGIC {
+            // OverlayFS is a union file system.  It returns one inode value in
+            // stat(2), but a different one shows up in /proc/locks.  So we must
+            // skip the test.
+            skip!("/proc/locks does not work on overlayfs");
+        }
         let inode = fstat(fd).expect("fstat failed").st_ino as usize;
 
         let mut flock = libc::flock {
@@ -262,11 +270,19 @@ mod linux_android {
                   target_arch = "mips64",
                   target_arch = "mips64el",
                   target_arch = "powerpc64",
-                  target_arch = "powerpc64le")))]
+                  target_arch = "powerpc64le",
+                  target_env = "musl")))]
     fn test_ofd_read_lock() {
         let tmp = NamedTempFile::new().unwrap();
 
         let fd = tmp.as_raw_fd();
+        let statfs = nix::sys::statfs::fstatfs(&tmp).unwrap();
+        if statfs.filesystem_type() == nix::sys::statfs::OVERLAYFS_SUPER_MAGIC {
+            // OverlayFS is a union file system.  It returns one inode value in
+            // stat(2), but a different one shows up in /proc/locks.  So we must
+            // skip the test.
+            skip!("/proc/locks does not work on overlayfs");
+        }
         let inode = fstat(fd).expect("fstat failed").st_ino as usize;
 
         let mut flock = libc::flock {