Implement StatFS for various VFS2 filesystems.

This mainly involved enabling kernfs' client filesystems to provide a
StatFS implementation.

Fixes #3411, #3515.

PiperOrigin-RevId: 329009864

5 files changed, 54 insertions, 6 deletions

diff --git a/test/syscalls/BUILD b/test/syscalls/BUILD
index 65e8299c3..f949bc0e3 100644
--- a/test/syscalls/BUILD
+++ b/test/syscalls/BUILD
@@ -803,6 +803,7 @@ syscall_test(
 syscall_test(
     add_overlay = True,
     test = "//test/syscalls/linux:statfs_test",
+    use_tmpfs = True,  # Test specifically relies on TEST_TMPDIR to be tmpfs.
 )
 
 syscall_test(
diff --git a/test/syscalls/linux/pipe.cc b/test/syscalls/linux/pipe.cc
index 34291850d..c097c9187 100644
--- a/test/syscalls/linux/pipe.cc
+++ b/test/syscalls/linux/pipe.cc
@@ -13,7 +13,9 @@
 // limitations under the License.
 
 #include <fcntl.h> /* Obtain O_* constant definitions */
+#include <linux/magic.h>
 #include <sys/ioctl.h>
+#include <sys/statfs.h>
 #include <sys/uio.h>
 #include <unistd.h>
 
@@ -198,6 +200,16 @@ TEST_P(PipeTest, NonBlocking) {
               SyscallFailsWithErrno(EWOULDBLOCK));
 }
 
+TEST(PipeTest, StatFS) {
+  int fds[2];
+  ASSERT_THAT(pipe(fds), SyscallSucceeds());
+  struct statfs st;
+  EXPECT_THAT(fstatfs(fds[0], &st), SyscallSucceeds());
+  EXPECT_EQ(st.f_type, PIPEFS_MAGIC);
+  EXPECT_EQ(st.f_bsize, getpagesize());
+  EXPECT_EQ(st.f_namelen, NAME_MAX);
+}
+
 TEST(Pipe2Test, CloExec) {
   int fds[2];
   ASSERT_THAT(pipe2(fds, O_CLOEXEC), SyscallSucceeds());
diff --git a/test/syscalls/linux/proc.cc b/test/syscalls/linux/proc.cc
index d6b875dbf..b73189e55 100644
--- a/test/syscalls/linux/proc.cc
+++ b/test/syscalls/linux/proc.cc
@@ -16,6 +16,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
+#include <linux/magic.h>
 #include <sched.h>
 #include <signal.h>
 #include <stddef.h>
@@ -26,6 +27,7 @@
 #include <sys/mman.h>
 #include <sys/prctl.h>
 #include <sys/stat.h>
+#include <sys/statfs.h>
 #include <sys/utsname.h>
 #include <syscall.h>
 #include <unistd.h>
@@ -2159,6 +2161,18 @@ TEST(Proc, PidTidIOAccounting) {
   noop.Join();
 }
 
+TEST(Proc, Statfs) {
+  struct statfs st;
+  EXPECT_THAT(statfs("/proc", &st), SyscallSucceeds());
+  if (IsRunningWithVFS1()) {
+    EXPECT_EQ(st.f_type, ANON_INODE_FS_MAGIC);
+  } else {
+    EXPECT_EQ(st.f_type, PROC_SUPER_MAGIC);
+  }
+  EXPECT_EQ(st.f_bsize, getpagesize());
+  EXPECT_EQ(st.f_namelen, NAME_MAX);
+}
+
 }  // namespace
 }  // namespace testing
 }  // namespace gvisor
diff --git a/test/syscalls/linux/socket.cc b/test/syscalls/linux/socket.cc
index c20cd3fcc..e680d3dd7 100644
--- a/test/syscalls/linux/socket.cc
+++ b/test/syscalls/linux/socket.cc
@@ -14,6 +14,7 @@
 
 #include <sys/socket.h>
 #include <sys/stat.h>
+#include <sys/statfs.h>
 #include <sys/types.h>
 #include <unistd.h>
 
@@ -26,6 +27,9 @@
 namespace gvisor {
 namespace testing {
 
+// From linux/magic.h, but we can't depend on linux headers here.
+#define SOCKFS_MAGIC 0x534F434B
+
 TEST(SocketTest, UnixSocketPairProtocol) {
   int socks[2];
   ASSERT_THAT(socketpair(AF_UNIX, SOCK_STREAM, PF_UNIX, socks),
@@ -94,6 +98,19 @@ TEST(SocketTest, UnixSocketStat) {
   }
 }
 
+TEST(SocketTest, UnixSocketStatFS) {
+  SKIP_IF(IsRunningWithVFS1());
+
+  FileDescriptor bound =
+      ASSERT_NO_ERRNO_AND_VALUE(Socket(AF_UNIX, SOCK_STREAM, PF_UNIX));
+
+  struct statfs st;
+  EXPECT_THAT(fstatfs(bound.get(), &st), SyscallSucceeds());
+  EXPECT_EQ(st.f_type, SOCKFS_MAGIC);
+  EXPECT_EQ(st.f_bsize, getpagesize());
+  EXPECT_EQ(st.f_namelen, NAME_MAX);
+}
+
 using SocketOpenTest = ::testing::TestWithParam<int>;
 
 // UDS cannot be opened.
diff --git a/test/syscalls/linux/statfs.cc b/test/syscalls/linux/statfs.cc
index aca51d30f..49f2f156c 100644
--- a/test/syscalls/linux/statfs.cc
+++ b/test/syscalls/linux/statfs.cc
@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include <fcntl.h>
+#include <linux/magic.h>
 #include <sys/statfs.h>
 #include <unistd.h>
 
@@ -26,6 +27,10 @@ namespace testing {
 
 namespace {
 
+// From linux/magic.h. For some reason, not defined in the headers for some
+// build environments.
+#define OVERLAYFS_SUPER_MAGIC 0x794c7630
+
 TEST(StatfsTest, CannotStatBadPath) {
   auto temp_file = NewTempAbsPathInDir("/tmp");
 
@@ -38,19 +43,18 @@ TEST(StatfsTest, InternalTmpfs) {
 
   struct statfs st;
   EXPECT_THAT(statfs(temp_file.path().c_str(), &st), SyscallSucceeds());
+  // Note: We could be an overlay or goferfs on some configurations.
+  EXPECT_TRUE(st.f_type == TMPFS_MAGIC || st.f_type == OVERLAYFS_SUPER_MAGIC ||
+              st.f_type == V9FS_MAGIC);
 }
 
 TEST(StatfsTest, InternalDevShm) {
   struct statfs st;
   EXPECT_THAT(statfs("/dev/shm", &st), SyscallSucceeds());
-}
-
-TEST(StatfsTest, NameLen) {
-  struct statfs st;
-  EXPECT_THAT(statfs("/dev/shm", &st), SyscallSucceeds());
 
   // This assumes that /dev/shm is tmpfs.
-  EXPECT_EQ(st.f_namelen, NAME_MAX);
+  // Note: We could be an overlay on some configurations.
+  EXPECT_TRUE(st.f_type == TMPFS_MAGIC || st.f_type == OVERLAYFS_SUPER_MAGIC);
 }
 
 TEST(FstatfsTest, CannotStatBadFd) {