[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>

1 files changed, 492 insertions, 0 deletions

diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
new file mode 100644
index 000000000000..bab560a1357a
--- /dev/null
+++ b/arch/s390/hypfs/inode.c
@@ -0,0 +1,492 @@
+/*
+ *  fs/hypfs/inode.c
+ *    Hypervisor filesystem for Linux on s390.
+ *
+ *    Copyright (C) IBM Corp. 2006
+ *    Author(s): Michael Holzheu <holzheu@de.ibm.com>
+ */
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/vfs.h>
+#include <linux/pagemap.h>
+#include <linux/gfp.h>
+#include <linux/time.h>
+#include <linux/parser.h>
+#include <linux/sysfs.h>
+#include <linux/module.h>
+#include <asm/ebcdic.h>
+#include "hypfs.h"
+#include "hypfs_diag.h"
+
+#define HYPFS_MAGIC 0x687970    /* ASCII 'hyp' */
+#define TMP_SIZE 64             /* size of temporary buffers */
+
+static struct dentry *hypfs_create_update_file(struct super_block *sb,
+                                               struct dentry *dir);
+
+struct hypfs_sb_info {
+        uid_t uid;                      /* uid used for files and dirs */
+        gid_t gid;                      /* gid used for files and dirs */
+        struct dentry *update_file;     /* file to trigger update */
+        time_t last_update;             /* last update time in secs since 1970 */
+        struct mutex lock;              /* lock to protect update process */
+};
+
+static struct file_operations hypfs_file_ops;
+static struct file_system_type hypfs_type;
+static struct super_operations hypfs_s_ops;
+
+/* start of list of all dentries, which have to be deleted on update */
+static struct dentry *hypfs_last_dentry;
+
+static void hypfs_update_update(struct super_block *sb)
+{
+        struct hypfs_sb_info *sb_info = sb->s_fs_info;
+        struct inode *inode = sb_info->update_file->d_inode;
+
+        sb_info->last_update = get_seconds();
+        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+}
+
+/* directory tree removal functions */
+
+static void hypfs_add_dentry(struct dentry *dentry)
+{
+        dentry->d_fsdata = hypfs_last_dentry;
+        hypfs_last_dentry = dentry;
+}
+
+static void hypfs_remove(struct dentry *dentry)
+{
+        struct dentry *parent;
+
+        parent = dentry->d_parent;
+        if (S_ISDIR(dentry->d_inode->i_mode))
+                simple_rmdir(parent->d_inode, dentry);
+        else
+                simple_unlink(parent->d_inode, dentry);
+        d_delete(dentry);
+        dput(dentry);
+}
+
+static void hypfs_delete_tree(struct dentry *root)
+{
+        while (hypfs_last_dentry) {
+                struct dentry *next_dentry;
+                next_dentry = hypfs_last_dentry->d_fsdata;
+                hypfs_remove(hypfs_last_dentry);
+                hypfs_last_dentry = next_dentry;
+        }
+}
+
+static struct inode *hypfs_make_inode(struct super_block *sb, int mode)
+{
+        struct inode *ret = new_inode(sb);
+
+        if (ret) {
+                struct hypfs_sb_info *hypfs_info = sb->s_fs_info;
+                ret->i_mode = mode;
+                ret->i_uid = hypfs_info->uid;
+                ret->i_gid = hypfs_info->gid;
+                ret->i_blksize = PAGE_CACHE_SIZE;
+                ret->i_blocks = 0;
+                ret->i_atime = ret->i_mtime = ret->i_ctime = CURRENT_TIME;
+                if (mode & S_IFDIR)
+                        ret->i_nlink = 2;
+                else
+                        ret->i_nlink = 1;
+        }
+        return ret;
+}
+
+static void hypfs_drop_inode(struct inode *inode)
+{
+        kfree(inode->u.generic_ip);
+        generic_delete_inode(inode);
+}
+
+static int hypfs_open(struct inode *inode, struct file *filp)
+{
+        char *data = filp->f_dentry->d_inode->u.generic_ip;
+        struct hypfs_sb_info *fs_info;
+
+        if (filp->f_mode & FMODE_WRITE) {
+                if (!(inode->i_mode & S_IWUGO))
+                        return -EACCES;
+        }
+        if (filp->f_mode & FMODE_READ) {
+                if (!(inode->i_mode & S_IRUGO))
+                        return -EACCES;
+        }
+
+        fs_info = inode->i_sb->s_fs_info;
+        if(data) {
+                mutex_lock(&fs_info->lock);
+                filp->private_data = kstrdup(data, GFP_KERNEL);
+                if (!filp->private_data) {
+                        mutex_unlock(&fs_info->lock);
+                        return -ENOMEM;
+                }
+                mutex_unlock(&fs_info->lock);
+        }
+        return 0;
+}
+
+static ssize_t hypfs_aio_read(struct kiocb *iocb, __user char *buf,
+                              size_t count, loff_t offset)
+{
+        char *data;
+        size_t len;
+        struct file *filp = iocb->ki_filp;
+
+        data = filp->private_data;
+        len = strlen(data);
+        if (offset > len) {
+                count = 0;
+                goto out;
+        }
+        if (count > len - offset)
+                count = len - offset;
+        if (copy_to_user(buf, data + offset, count)) {
+                count = -EFAULT;
+                goto out;
+        }
+        iocb->ki_pos += count;
+        file_accessed(filp);
+out:
+        return count;
+}
+static ssize_t hypfs_aio_write(struct kiocb *iocb, const char __user *buf,
+                               size_t count, loff_t pos)
+{
+        int rc;
+        struct super_block *sb;
+        struct hypfs_sb_info *fs_info;
+
+        sb = iocb->ki_filp->f_dentry->d_inode->i_sb;
+        fs_info = sb->s_fs_info;
+        /*
+         * Currently we only allow one update per second for two reasons:
+         * 1. diag 204 is VERY expensive
+         * 2. If several processes do updates in parallel and then read the
+         *    hypfs data, the likelihood of collisions is reduced, if we restrict
+         *    the minimum update interval. A collision occurs, if during the
+         *    data gathering of one process another process triggers an update
+         *    If the first process wants to ensure consistent data, it has
+         *    to restart data collection in this case.
+         */
+        mutex_lock(&fs_info->lock);
+        if (fs_info->last_update == get_seconds()) {
+                rc = -EBUSY;
+                goto out;
+        }
+        hypfs_delete_tree(sb->s_root);
+        rc = hypfs_diag_create_files(sb, sb->s_root);
+        if (rc) {
+                printk(KERN_ERR "hypfs: Update failed\n");
+                hypfs_delete_tree(sb->s_root);
+                goto out;
+        }
+        hypfs_update_update(sb);
+        rc = count;
+out:
+        mutex_unlock(&fs_info->lock);
+        return rc;
+}
+
+static int hypfs_release(struct inode *inode, struct file *filp)
+{
+        kfree(filp->private_data);
+        return 0;
+}
+
+enum { opt_uid, opt_gid, opt_err };
+
+static match_table_t hypfs_tokens = {
+        {opt_uid, "uid=%u"},
+        {opt_gid, "gid=%u"},
+        {opt_err, NULL}
+};
+
+static int hypfs_parse_options(char *options, struct super_block *sb)
+{
+        char *str;
+        substring_t args[MAX_OPT_ARGS];
+
+        if (!options)
+                return 0;
+        while ((str = strsep(&options, ",")) != NULL) {
+                int token, option;
+                struct hypfs_sb_info *hypfs_info = sb->s_fs_info;
+
+                if (!*str)
+                        continue;
+                token = match_token(str, hypfs_tokens, args);
+                switch (token) {
+                case opt_uid:
+                        if (match_int(&args[0], &option))
+                                return -EINVAL;
+                        hypfs_info->uid = option;
+                        break;
+                case opt_gid:
+                        if (match_int(&args[0], &option))
+                                return -EINVAL;
+                        hypfs_info->gid = option;
+                        break;
+                case opt_err:
+                default:
+                        printk(KERN_ERR "hypfs: Unrecognized mount option "
+                               "\"%s\" or missing value\n", str);
+                        return -EINVAL;
+                }
+        }
+        return 0;
+}
+
+static int hypfs_fill_super(struct super_block *sb, void *data, int silent)
+{
+        struct inode *root_inode;
+        struct dentry *root_dentry;
+        int rc = 0;
+        struct hypfs_sb_info *sbi;
+
+        sbi = kzalloc(sizeof(struct hypfs_sb_info), GFP_KERNEL);
+        if (!sbi)
+                return -ENOMEM;
+        mutex_init(&sbi->lock);
+        sbi->uid = current->uid;
+        sbi->gid = current->gid;
+        sb->s_fs_info = sbi;
+        sb->s_blocksize = PAGE_CACHE_SIZE;
+        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
+        sb->s_magic = HYPFS_MAGIC;
+        sb->s_op = &hypfs_s_ops;
+        if (hypfs_parse_options(data, sb)) {
+                rc = -EINVAL;
+                goto err_alloc;
+        }
+        root_inode = hypfs_make_inode(sb, S_IFDIR | 0755);
+        if (!root_inode) {
+                rc = -ENOMEM;
+                goto err_alloc;
+        }
+        root_inode->i_op = &simple_dir_inode_operations;
+        root_inode->i_fop = &simple_dir_operations;
+        root_dentry = d_alloc_root(root_inode);
+        if (!root_dentry) {
+                iput(root_inode);
+                rc = -ENOMEM;
+                goto err_alloc;
+        }
+        rc = hypfs_diag_create_files(sb, root_dentry);
+        if (rc)
+                goto err_tree;
+        sbi->update_file = hypfs_create_update_file(sb, root_dentry);
+        if (IS_ERR(sbi->update_file)) {
+                rc = PTR_ERR(sbi->update_file);
+                goto err_tree;
+        }
+        hypfs_update_update(sb);
+        sb->s_root = root_dentry;
+        return 0;
+
+err_tree:
+        hypfs_delete_tree(root_dentry);
+        d_genocide(root_dentry);
+        dput(root_dentry);
+err_alloc:
+        kfree(sbi);
+        return rc;
+}
+
+static struct super_block *hypfs_get_super(struct file_system_type *fst,
+                                           int flags, const char *devname,
+                                           void *data)
+{
+        return get_sb_single(fst, flags, data, hypfs_fill_super);
+}
+
+static void hypfs_kill_super(struct super_block *sb)
+{
+        struct hypfs_sb_info *sb_info = sb->s_fs_info;
+
+        hypfs_delete_tree(sb->s_root);
+        hypfs_remove(sb_info->update_file);
+        kfree(sb->s_fs_info);
+        sb->s_fs_info = NULL;
+        kill_litter_super(sb);
+}
+
+static struct dentry *hypfs_create_file(struct super_block *sb,
+                                        struct dentry *parent, const char *name,
+                                        char *data, mode_t mode)
+{
+        struct dentry *dentry;
+        struct inode *inode;
+        struct qstr qname;
+
+        qname.name = name;
+        qname.len = strlen(name);
+        qname.hash = full_name_hash(name, qname.len);
+        dentry = lookup_one_len(name, parent, strlen(name));
+        if (IS_ERR(dentry))
+                return ERR_PTR(-ENOMEM);
+        inode = hypfs_make_inode(sb, mode);
+        if (!inode) {
+                dput(dentry);
+                return ERR_PTR(-ENOMEM);
+        }
+        if (mode & S_IFREG) {
+                inode->i_fop = &hypfs_file_ops;
+                if (data)
+                        inode->i_size = strlen(data);
+                else
+                        inode->i_size = 0;
+        } else if (mode & S_IFDIR) {
+                inode->i_op = &simple_dir_inode_operations;
+                inode->i_fop = &simple_dir_operations;
+                parent->d_inode->i_nlink++;
+        } else
+                BUG();
+        inode->u.generic_ip = data;
+        d_instantiate(dentry, inode);
+        dget(dentry);
+        return dentry;
+}
+
+struct dentry *hypfs_mkdir(struct super_block *sb, struct dentry *parent,
+                           const char *name)
+{
+        struct dentry *dentry;
+
+        dentry = hypfs_create_file(sb, parent, name, NULL, S_IFDIR | DIR_MODE);
+        if (IS_ERR(dentry))
+                return dentry;
+        hypfs_add_dentry(dentry);
+        parent->d_inode->i_nlink++;
+        return dentry;
+}
+
+static struct dentry *hypfs_create_update_file(struct super_block *sb,
+                                               struct dentry *dir)
+{
+        struct dentry *dentry;
+
+        dentry = hypfs_create_file(sb, dir, "update", NULL,
+                                   S_IFREG | UPDATE_FILE_MODE);
+        /*
+         * We do not put the update file on the 'delete' list with
+         * hypfs_add_dentry(), since it should not be removed when the tree
+         * is updated.
+         */
+        return dentry;
+}
+
+struct dentry *hypfs_create_u64(struct super_block *sb, struct dentry *dir,
+                                const char *name, __u64 value)
+{
+        char *buffer;
+        char tmp[TMP_SIZE];
+        struct dentry *dentry;
+
+        snprintf(tmp, TMP_SIZE, "%lld\n", (unsigned long long int)value);
+        buffer = kstrdup(tmp, GFP_KERNEL);
+        if (!buffer)
+                return ERR_PTR(-ENOMEM);
+        dentry =
+            hypfs_create_file(sb, dir, name, buffer, S_IFREG | REG_FILE_MODE);
+        if (IS_ERR(dentry)) {
+                kfree(buffer);
+                return ERR_PTR(-ENOMEM);
+        }
+        hypfs_add_dentry(dentry);
+        return dentry;
+}
+
+struct dentry *hypfs_create_str(struct super_block *sb, struct dentry *dir,
+                                const char *name, char *string)
+{
+        char *buffer;
+        struct dentry *dentry;
+
+        buffer = kmalloc(strlen(string) + 2, GFP_KERNEL);
+        if (!buffer)
+                return ERR_PTR(-ENOMEM);
+        sprintf(buffer, "%s\n", string);
+        dentry =
+            hypfs_create_file(sb, dir, name, buffer, S_IFREG | REG_FILE_MODE);
+        if (IS_ERR(dentry)) {
+                kfree(buffer);
+                return ERR_PTR(-ENOMEM);
+        }
+        hypfs_add_dentry(dentry);
+        return dentry;
+}
+
+static struct file_operations hypfs_file_ops = {
+        .open           = hypfs_open,
+        .release        = hypfs_release,
+        .read           = do_sync_read,
+        .write          = do_sync_write,
+        .aio_read       = hypfs_aio_read,
+        .aio_write      = hypfs_aio_write,
+};
+
+static struct file_system_type hypfs_type = {
+        .owner          = THIS_MODULE,
+        .name           = "s390_hypfs",
+        .get_sb         = hypfs_get_super,
+        .kill_sb        = hypfs_kill_super
+};
+
+static struct super_operations hypfs_s_ops = {
+        .statfs         = simple_statfs,
+        .drop_inode     = hypfs_drop_inode,
+};
+
+static decl_subsys(s390, NULL, NULL);
+
+static int __init hypfs_init(void)
+{
+        int rc;
+
+        if (MACHINE_IS_VM)
+                return -ENODATA;
+        if (hypfs_diag_init()) {
+                rc = -ENODATA;
+                goto fail_diag;
+        }
+        kset_set_kset_s(&s390_subsys, hypervisor_subsys);
+        rc = subsystem_register(&s390_subsys);
+        if (rc)
+                goto fail_sysfs;
+        rc = register_filesystem(&hypfs_type);
+        if (rc)
+                goto fail_filesystem;
+        return 0;
+
+fail_filesystem:
+        subsystem_unregister(&s390_subsys);
+fail_sysfs:
+        hypfs_diag_exit();
+fail_diag:
+        printk(KERN_ERR "hypfs: Initialization failed with rc = %i.\n", rc);
+        return rc;
+}
+
+static void __exit hypfs_exit(void)
+{
+        hypfs_diag_exit();
+        unregister_filesystem(&hypfs_type);
+        subsystem_unregister(&s390_subsys);
+}
+
+module_init(hypfs_init)
+module_exit(hypfs_exit)
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Michael Holzheu <holzheu@de.ibm.com>");
+MODULE_DESCRIPTION("s390 Hypervisor Filesystem");