[RFC 1/3] include/linux.h: Factor out generic platform_test_fs_fd() helper

[Ojaswin Mujoo]

Factor our the generic code to detect the FS type out of
platform_test_fs_fd(). This can then be used to detect different file
systems types based on magic number.

Also, add a helper to detect if the fd is from an ext4 filesystem.

Signed-off-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
---
 include/linux.h | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/include/linux.h b/include/linux.h
index e9eb7bfb26a1..52c64014c57f 100644
--- a/include/linux.h
+++ b/include/linux.h
@@ -43,13 +43,7 @@ static __inline__ int xfsctl(const char *path, int fd, int cmd, void *p)
 	return ioctl(fd, cmd, p);
 }
 
-/*
- * platform_test_xfs_*() implies that xfsctl will succeed on the file;
- * on Linux, at least, special files don't get xfs file ops,
- * so return 0 for those
- */
-
-static __inline__ int platform_test_xfs_fd(int fd)
+static __inline__ int platform_test_fs_fd(int fd, long type)
 {
 	struct statfs statfsbuf;
 	struct stat statbuf;
@@ -60,7 +54,22 @@ static __inline__ int platform_test_xfs_fd(int fd)
 		return 0;
 	if (!S_ISREG(statbuf.st_mode) && !S_ISDIR(statbuf.st_mode))
 		return 0;
-	return (statfsbuf.f_type == 0x58465342);	/* XFSB */
+	return (statfsbuf.f_type == type);
+}
+
+/*
+ * platform_test_xfs_*() implies that xfsctl will succeed on the file;
+ * on Linux, at least, special files don't get xfs file ops,
+ * so return 0 for those
+ */
+static __inline__ int platform_test_xfs_fd(int fd)
+{
+	return platform_test_fs_fd(fd, 0x58465342); /* XFSB */
+}
+
+static __inline__ int platform_test_ext4_fd(int fd)
+{
+	return platform_test_fs_fd(fd, 0xef53); /* EXT4 magic number */
 }
 
 static __inline__ int platform_test_xfs_path(const char *path)
-- 
2.43.5