[PATCH] s390_hypfs filesystem

On zSeries machines there exists an interface which allows the operating
system to retrieve LPAR hypervisor accounting data.  For example, it is
possible to get usage data for physical and virtual cpus.  In order to
provide this information to user space programs, I implemented a new
virtual Linux file system named 's390_hypfs' using the Linux 2.6 libfs
framework.  The name 's390_hypfs' stands for 'S390 Hypervisor Filesystem'.
All the accounting information is put into different virtual files which
can be accessed from user space.  All data is represented as ASCII strings.

When the file system is mounted the accounting information is retrieved and
a file system tree is created with the attribute files containing the cpu
information.  The content of the files remains unchanged until a new update
is made.  An update can be triggered from user space through writing
'something' into a special purpose update file.

We create the following directory structure:

<mount-point>/
        update
        cpus/
                <cpu-id>
                        type
                        mgmtime
                <cpu-id>
                        ...
        hyp/
                type
        systems/
                <lpar-name>
                        cpus/
                                <cpu-id>
                                        type
                                        mgmtime
                                        cputime
                                        onlinetime
                                <cpu-id>
                                        ...
                <lpar-name>
                        cpus/
                                ...

- update: File to trigger update
- cpus/: Directory for all physical cpus
- cpus/<cpu-id>/: Directory for one physical cpu.
- cpus/<cpu-id>/type: Type name of physical zSeries cpu.
- cpus/<cpu-id>/mgmtime: Physical-LPAR-management time in microseconds.
- hyp/: Directory for hypervisor information
- hyp/type: Typ of hypervisor (currently only 'LPAR Hypervisor')
- systems/: Directory for all LPARs
- systems/<lpar-name>/: Directory for one LPAR.
- systems/<lpar-name>/cpus/<cpu-id>/: Directory for the virtual cpus
- systems/<lpar-name>/cpus/<cpu-id>/type: Typ of cpu.
- systems/<lpar-name>/cpus/<cpu-id>/mgmtime:
Accumulated number of microseconds during which a physical
CPU was assigned to the logical cpu and the cpu time was
consumed by the hypervisor and was not provided to
the LPAR (LPAR overhead).

- systems/<lpar-name>/cpus/<cpu-id>/cputime:
Accumulated number of microseconds during which a physical CPU
was assigned to the logical cpu and the cpu time was consumed
by the LPAR.

- systems/<lpar-name>/cpus/<cpu-id>/onlinetime:
Accumulated number of microseconds during which the logical CPU
has been online.

As mount point for the filesystem /sys/hypervisor/s390 is created.

The update process is triggered when writing 'something' into the
'update' file at the top level hypfs directory. You can do this e.g.
with 'echo 1 > update'. During the update the whole directory structure
is deleted and built up again.

Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Ingo Oeser <ioe-lkml@rameria.de>
Cc: Joern Engel <joern@wohnheim.fh-wedel.de>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/s390/Kconfig

@@ -446,6 +446,14 @@ config NO_IDLE_HZ_INIT
 	  The HZ timer is switched off in idle by default. That means the
 	  HZ timer is already disabled at boot time.
 
+config S390_HYPFS_FS
+	bool "s390 hypervisor file system support"
+	select SYS_HYPERVISOR
+	default y
+	help
+	  This is a virtual file system intended to provide accounting
+	  information in an s390 hypervisor environment.
+
 config KEXEC
 	bool "kexec system call (EXPERIMENTAL)"
 	depends on EXPERIMENTAL

arch/s390/Makefile

@@ -76,7 +76,7 @@ LDFLAGS_vmlinux := -e start
 head-y		:= arch/$(ARCH)/kernel/head.o arch/$(ARCH)/kernel/init_task.o
 
 core-y		+= arch/$(ARCH)/mm/ arch/$(ARCH)/kernel/ arch/$(ARCH)/crypto/ \
-		   arch/$(ARCH)/appldata/
+		   arch/$(ARCH)/appldata/ arch/$(ARCH)/hypfs/
 libs-y		+= arch/$(ARCH)/lib/
 drivers-y	+= drivers/s390/
 drivers-$(CONFIG_MATHEMU) += arch/$(ARCH)/math-emu/

arch/s390/hypfs/Makefile

+#
+# Makefile for the linux hypfs filesystem routines.
+#
+
+obj-$(CONFIG_S390_HYPFS_FS) += s390_hypfs.o
+
+s390_hypfs-objs := inode.o hypfs_diag.o

arch/s390/hypfs/hypfs.h

+/*
+ *  fs/hypfs/hypfs.h
+ *    Hypervisor filesystem for Linux on s390.
+ *
+ *    Copyright (C) IBM Corp. 2006
+ *    Author(s): Michael Holzheu <holzheu@de.ibm.com>
+ */
+
+#ifndef _HYPFS_H_
+#define _HYPFS_H_
+
+#include <linux/fs.h>
+#include <linux/types.h>
+
+#define REG_FILE_MODE    0440
+#define UPDATE_FILE_MODE 0220
+#define DIR_MODE         0550
+
+extern struct dentry *hypfs_mkdir(struct super_block *sb, struct dentry *parent,
+				  const char *name);
+
+extern struct dentry *hypfs_create_u64(struct super_block *sb,
+				       struct dentry *dir, const char *name,
+				       __u64 value);
+
+extern struct dentry *hypfs_create_str(struct super_block *sb,
+				       struct dentry *dir, const char *name,
+				       char *string);
+
+#endif /* _HYPFS_H_ */

arch/s390/hypfs/hypfs_diag.h

+/*
+ *  fs/hypfs/hypfs_diag.h
+ *    Hypervisor filesystem for Linux on s390.
+ *
+ *    Copyright (C) IBM Corp. 2006
+ *    Author(s): Michael Holzheu <holzheu@de.ibm.com>
+ */
+
+#ifndef _HYPFS_DIAG_H_
+#define _HYPFS_DIAG_H_
+
+extern int hypfs_diag_init(void);
+extern void hypfs_diag_exit(void);
+extern int hypfs_diag_create_files(struct super_block *sb, struct dentry *root);
+
+#endif /* _HYPFS_DIAG_H_ */