[PATCH] 32-bit dev_t: internal use

Starting the conversion:
	* internal dev_t made 32bit.
	* new helpers - new_encode_dev(), new_decode_dev(), huge_encode_dev(),
huge_decode_dev(), new_valid_dev().  They do encoding/decoding of 32bit and
64bit values; for now huge_... are aliases for new_... and new_valid_dev()
is always true.  We do 12:20 for 32bit; representation is compatible with
16bit one - we have major in bits 19--8 and minor in 31--20,7--0.  That's
what the userland sees; internally we have (major << 20)|minor, of course.
	* MKDEV(), MAJOR() and MINOR() updated.
	* several places used to handle Missed'em'V dev_t (14:18 split)
manually; that stuff had been taken into common helpers.
	Now we can start replacing old_... with new_... and huge_..., depending
on the width available.  MKDEV() callers should (for now) make sure that major
and minor are within 12:20.  That's what the next chunk will do.

4 files changed, 74 insertions, 11 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 20a7b18b0841..b3a714c094d2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1392,9 +1392,6 @@ struct tree_descr { char *name; struct file_operations *ops; int mode; };
 extern int simple_fill_super(struct super_block *, int, struct tree_descr *);
 extern int simple_pin_fs(char *name, struct vfsmount **mount, int *count);
 extern void simple_release_fs(struct vfsmount **mount, int *count);
-extern int old_valid_dev(dev_t);
-extern u16 old_encode_dev(dev_t);
-extern dev_t old_decode_dev(u16);
 
 extern int inode_change_ok(struct inode *, struct iattr *);
 extern int inode_setattr(struct inode *, struct iattr *);
diff --git a/include/linux/kdev_t.h b/include/linux/kdev_t.h
index f60508da024d..bceea527dd37 100644
--- a/include/linux/kdev_t.h
+++ b/include/linux/kdev_t.h
@@ -1,8 +1,7 @@
 #ifndef _LINUX_KDEV_T_H
 #define _LINUX_KDEV_T_H
 #ifdef __KERNEL__
-/* These are for user-level "dev_t" */
-#define MINORBITS	8
+#define MINORBITS	20
 #define MINORMASK	((1U << MINORBITS) - 1)
 
 #define MAJOR(dev)	((unsigned int) ((dev) >> MINORBITS))
@@ -18,6 +17,77 @@
 		buffer;							\
 	})
 
+/* acceptable for old filesystems */
+static inline int old_valid_dev(dev_t dev)
+{
+	return MAJOR(dev) < 256 && MINOR(dev) < 256;
+}
+
+static inline u16 old_encode_dev(dev_t dev)
+{
+	return (MAJOR(dev) << 8) | MINOR(dev);
+}
+
+static inline dev_t old_decode_dev(u16 val)
+{
+	return MKDEV((val >> 8) & 255, val & 255);
+}
+
+static inline int new_valid_dev(dev_t dev)
+{
+	return 1;
+}
+
+static inline u32 new_encode_dev(dev_t dev)
+{
+	unsigned major = MAJOR(dev);
+	unsigned minor = MINOR(dev);
+	return (minor & 0xff) | (major << 8) | ((minor & ~0xff) << 12);
+}
+
+static inline dev_t new_decode_dev(u32 dev)
+{
+	unsigned major = (dev & 0xfff00) >> 8;
+	unsigned minor = (dev & 0xff) | ((dev >> 12) & 0xfff00);
+	return MKDEV(major, minor);
+}
+
+static inline int huge_valid_dev(dev_t dev)
+{
+	return 1;
+}
+
+static inline u64 huge_encode_dev(dev_t dev)
+{
+	return new_encode_dev(dev);
+}
+
+static inline dev_t huge_decode_dev(u64 dev)
+{
+	return new_decode_dev(dev);
+}
+
+static inline int sysv_valid_dev(dev_t dev)
+{
+	return MAJOR(dev) < (1<<14) && MINOR(dev) < (1<<18);
+}
+
+static inline u32 sysv_encode_dev(dev_t dev)
+{
+	return MINOR(dev) | (MAJOR(dev) << 18);
+}
+
+static inline unsigned sysv_major(u32 dev)
+{
+	return (dev >> 18) & 0x3fff;
+}
+
+static inline unsigned sysv_minor(u32 dev)
+{
+	return dev & 0x3ffff;
+}
+
+
 #else /* __KERNEL__ */
 
 /*
diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 70c5d117da8d..c9466321a2b2 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -64,11 +64,7 @@ static inline int level_to_pers (int level)
 typedef struct mddev_s mddev_t;
 typedef struct mdk_rdev_s mdk_rdev_t;
 
-#if (MINORBITS != 8)
-#error MD does not handle bigger kdev yet
-#endif
-
-#define MAX_MD_DEVS  (1<<MINORBITS)	/* Max number of md dev */
+#define MAX_MD_DEVS  256	/* Max number of md dev */
 
 /*
  * options passed in raidrun:
diff --git a/include/linux/types.h b/include/linux/types.h
index e3a3d8b1b6bb..3b407b06b48f 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -17,7 +17,7 @@
 
 #ifndef __KERNEL_STRICT_NAMES
 
-typedef __u16 __kernel_dev_t;
+typedef __u32 __kernel_dev_t;
 
 typedef __kernel_fd_set		fd_set;
 typedef __kernel_dev_t		dev_t;