s390,alpha: switch to 64-bit ino_t

s390 and alpha are the only 64 bit architectures with a 32-bit ino_t.
Since this is quite unusual this causes bugs from time to time.

See e.g. commit ebce3eb2 ("ceph: fix inode number handling on
arches with 32-bit ino_t") for an example.

This (obviously) also prevents s390 and alpha to use 64-bit ino_t for
tmpfs. See commit b85a7a8b ("tmpfs: disallow CONFIG_TMPFS_INODE64
on s390").

Therefore switch both s390 and alpha to 64-bit ino_t. This should only
have an effect on the ustat system call. To prevent ABI breakage
define struct ustat compatible to the old layout and change
sys_ustat() accordingly.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/Kconfig

@@ -327,6 +327,10 @@ config ARCH_32BIT_OFF_T
 	  still support 32-bit off_t. This option is enabled for all such
 	  architectures explicitly.
 
+# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
+config ARCH_32BIT_USTAT_F_TINODE
+	bool
+
 config HAVE_ASM_MODVERSIONS
 	bool
 	help

arch/alpha/Kconfig

@@ -2,6 +2,7 @@
 config ALPHA
 	bool
 	default y
+	select ARCH_32BIT_USTAT_F_TINODE
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_MIGHT_HAVE_PC_SERIO
 	select ARCH_NO_PREEMPT

arch/s390/Kconfig

@@ -58,6 +58,7 @@ config S390
 	# Note: keep this list sorted alphabetically
 	#
 	imply IMA_SECURE_AND_OR_TRUSTED_BOOT
+	select ARCH_32BIT_USTAT_F_TINODE
 	select ARCH_BINFMT_ELF_STATE
 	select ARCH_HAS_DEBUG_VM_PGTABLE
 	select ARCH_HAS_DEBUG_WX

fs/statfs.c

@@ -255,7 +255,10 @@ SYSCALL_DEFINE2(ustat, unsigned, dev, struct ustat __user *, ubuf)
 
 	memset(&tmp,0,sizeof(struct ustat));
 	tmp.f_tfree = sbuf.f_bfree;
-	tmp.f_tinode = sbuf.f_ffree;
+	if (IS_ENABLED(CONFIG_ARCH_32BIT_USTAT_F_TINODE))
+		tmp.f_tinode = min_t(u64, sbuf.f_ffree, UINT_MAX);
+	else
+		tmp.f_tinode = sbuf.f_ffree;
 
 	return copy_to_user(ubuf, &tmp, sizeof(struct ustat)) ? -EFAULT : 0;
 }

include/linux/types.h

@@ -14,7 +14,7 @@ typedef u32 __kernel_dev_t;
 
 typedef __kernel_fd_set		fd_set;
 typedef __kernel_dev_t		dev_t;
-typedef __kernel_ino_t		ino_t;
+typedef __kernel_ulong_t	ino_t;
 typedef __kernel_mode_t		mode_t;
 typedef unsigned short		umode_t;
 typedef u32			nlink_t;
@@ -189,7 +189,11 @@ struct hlist_node {
 
 struct ustat {
 	__kernel_daddr_t	f_tfree;
-	__kernel_ino_t		f_tinode;
+#ifdef CONFIG_ARCH_32BIT_USTAT_F_TINODE
+	unsigned int		f_tinode;
+#else
+	unsigned long		f_tinode;
+#endif
 	char			f_fname[6];
 	char			f_fpack[6];
 };