/*
 * linux/fs/nfs/namespace.c
 *
 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
 * - Modified by David Howells <dhowells@redhat.com>
 *
 * NFS namespace
 */

#include <linux/dcache.h>
#include <linux/gfp.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/nfs_fs.h>
#include <linux/string.h>
#include <linux/sunrpc/clnt.h>
#include <linux/vfs.h>
#include <linux/sunrpc/gss_api.h>
#include "internal.h"

#define NFSDBG_FACILITY         NFSDBG_VFS

static void nfs_expire_automounts(struct work_struct *work);

static LIST_HEAD(nfs_automount_list);
static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
int nfs_mountpoint_expiry_timeout = 500 * HZ;

static struct vfsmount *nfs_do_submount(struct dentry *dentry,
                                        struct nfs_fh *fh,
                                        struct nfs_fattr *fattr,
                                        rpc_authflavor_t authflavor);

/*
 * nfs_path - reconstruct the path given an arbitrary dentry
 * @base - used to return pointer to the end of devname part of path
 * @dentry - pointer to dentry
 * @buffer - result buffer
 * @buflen - length of buffer
 *
 * Helper function for constructing the server pathname
 * by arbitrary hashed dentry.
 *
 * This is mainly for use in figuring out the path on the
 * server side when automounting on top of an existing partition
 * and in generating /proc/mounts and friends.
 */
char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen)
{
        char *end;
        int namelen;
        unsigned seq;
        const char *base;

rename_retry:
        end = buffer+buflen;
        *--end = '\0';
        buflen--;

        seq = read_seqbegin(&rename_lock);
        rcu_read_lock();
        while (1) {
                spin_lock(&dentry->d_lock);
                if (IS_ROOT(dentry))
                        break;
                namelen = dentry->d_name.len;
                buflen -= namelen + 1;
                if (buflen < 0)
                        goto Elong_unlock;
                end -= namelen;
                memcpy(end, dentry->d_name.name, namelen);
                *--end = '/';
                spin_unlock(&dentry->d_lock);
                dentry = dentry->d_parent;
        }
        if (read_seqretry(&rename_lock, seq)) {
                spin_unlock(&dentry->d_lock);
                rcu_read_unlock();
                goto rename_retry;
        }
        if (*end != '/') {
                if (--buflen < 0) {
                        spin_unlock(&dentry->d_lock);
                        rcu_read_unlock();
                        goto Elong;
                }
                *--end = '/';
        }
        *p = end;
        base = dentry->d_fsdata;
        if (!base) {
                spin_unlock(&dentry->d_lock);
                rcu_read_unlock();
                WARN_ON(1);
                return end;
        }
        namelen = strlen(base);
        /* Strip off excess slashes in base string */
        while (namelen > 0 && base[namelen - 1] == '/')
                namelen--;
        buflen -= namelen;
        if (buflen < 0) {
                spin_unlock(&dentry->d_lock);
                rcu_read_unlock();
                goto Elong;
        }
        end -= namelen;
        memcpy(end, base, namelen);
        spin_unlock(&dentry->d_lock);
        rcu_read_unlock();
        return end;
Elong_unlock:
        spin_unlock(&dentry->d_lock);
        rcu_read_unlock();
        if (read_seqretry(&rename_lock, seq))
                goto rename_retry;
Elong:
        return ERR_PTR(-ENAMETOOLONG);
}

#ifdef CONFIG_NFS_V4
rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *flavors)
{
        struct gss_api_mech *mech;
        struct xdr_netobj oid;
        int i;
        rpc_authflavor_t pseudoflavor = RPC_AUTH_UNIX;

        for (i = 0; i < flavors->num_flavors; i++) {
                struct nfs4_secinfo_flavor *flavor;
                flavor = &flavors->flavors[i];

                if (flavor->flavor == RPC_AUTH_NULL || flavor->flavor == RPC_AUTH_UNIX) {
                        pseudoflavor = flavor->flavor;
                        break;
                } else if (flavor->flavor == RPC_AUTH_GSS) {
                        oid.len  = flavor->gss.sec_oid4.len;
                        oid.data = flavor->gss.sec_oid4.data;
                        mech = gss_mech_get_by_OID(&oid);
                        if (!mech)
                                continue;
                        pseudoflavor = gss_svc_to_pseudoflavor(mech, flavor->gss.service);
                        gss_mech_put(mech);
                        break;
                }
        }

        return pseudoflavor;
}

static struct rpc_clnt *nfs_lookup_mountpoint(struct inode *dir,
                                              struct qstr *name,
                                              struct nfs_fh *fh,
                                              struct nfs_fattr *fattr)
{
        int err;

        if (NFS_PROTO(dir)->version == 4)
                return nfs4_proc_lookup_mountpoint(dir, name, fh, fattr);

        err = NFS_PROTO(dir)->lookup(NFS_SERVER(dir)->client, dir, name, fh, fattr);
        if (err)
                return ERR_PTR(err);
        return rpc_clone_client(NFS_SERVER(dir)->client);
}
#else /* CONFIG_NFS_V4 */
static inline struct rpc_clnt *nfs_lookup_mountpoint(struct inode *dir,
                                                     struct qstr *name,
                                                     struct nfs_fh *fh,
                                                     struct nfs_fattr *fattr)
{
        int err = NFS_PROTO(dir)->lookup(NFS_SERVER(dir)->client, dir, name, fh, fattr);
        if (err)
                return ERR_PTR(err);
        return rpc_clone_client(NFS_SERVER(dir)->client);
}
#endif /* CONFIG_NFS_V4 */

/*
 * nfs_d_automount - Handle crossing a mountpoint on the server
 * @path - The mountpoint
 *
 * When we encounter a mountpoint on the server, we want to set up
 * a mountpoint on the client too, to prevent inode numbers from
 * colliding, and to allow "df" to work properly.
 * On NFSv4, we also want to allow for the fact that different
 * filesystems may be migrated to different servers in a failover
 * situation, and that different filesystems may want to use
 * different security flavours.
 */
struct vfsmount *nfs_d_automount(struct path *path)
{
        struct vfsmount *mnt;
        struct dentry *parent;
        struct nfs_fh *fh = NULL;
        struct nfs_fattr *fattr = NULL;
        struct rpc_clnt *client;

        dprintk("--> nfs_d_automount()\n");

        mnt = ERR_PTR(-ESTALE);
        if (IS_ROOT(path->dentry))
                goto out_nofree;

        mnt = ERR_PTR(-ENOMEM);
        fh = nfs_alloc_fhandle();
        fattr = nfs_alloc_fattr();
        if (fh == NULL || fattr == NULL)
                goto out;

        dprintk("%s: enter\n", __func__);

        /* Look it up again to get its attributes */
        parent = dget_parent(path->dentry);
        client = nfs_lookup_mountpoint(parent->d_inode, &path->dentry->d_name, fh, fattr);
        dput(parent);
        if (IS_ERR(client)) {
                mnt = ERR_CAST(client);
                goto out;
        }

        if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
                mnt = nfs_do_refmount(client, path->dentry);
        else
                mnt = nfs_do_submount(path->dentry, fh, fattr, client->cl_auth->au_flavor);
        rpc_shutdown_client(client);

        if (IS_ERR(mnt))
                goto out;

        dprintk("%s: done, success\n", __func__);
        mntget(mnt); /* prevent immediate expiration */
        mnt_set_expiry(mnt, &nfs_automount_list);
        schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);

out:
        nfs_free_fattr(fattr);
        nfs_free_fhandle(fh);
out_nofree:
        if (IS_ERR(mnt))
                dprintk("<-- %s(): error %ld\n", __func__, PTR_ERR(mnt));
        else
                dprintk("<-- %s() = %p\n", __func__, mnt);
        return mnt;
}

const struct inode_operations nfs_mountpoint_inode_operations = {
        .getattr        = nfs_getattr,
};

const struct inode_operations nfs_referral_inode_operations = {
};

static void nfs_expire_automounts(struct work_struct *work)
{
        struct list_head *list = &nfs_automount_list;

        mark_mounts_for_expiry(list);
        if (!list_empty(list))
                schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
}

void nfs_release_automount_timer(void)
{
        if (list_empty(&nfs_automount_list))
                cancel_delayed_work(&nfs_automount_task);
}

/*
 * Clone a mountpoint of the appropriate type
 */
static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
                                           const char *devname,
                                           struct nfs_clone_mount *mountdata)
{
#ifdef CONFIG_NFS_V4
        struct vfsmount *mnt = ERR_PTR(-EINVAL);
        switch (server->nfs_client->rpc_ops->version) {
                case 2:
                case 3:
                        mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
                        break;
                case 4:
                        mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
        }
        return mnt;
#else
        return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
#endif
}

/**
 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 * @dentry - parent directory
 * @fh - filehandle for new root dentry
 * @fattr - attributes for new root inode
 * @authflavor - security flavor to use when performing the mount
 *
 */
static struct vfsmount *nfs_do_submount(struct dentry *dentry,
                                        struct nfs_fh *fh,
                                        struct nfs_fattr *fattr,
                                        rpc_authflavor_t authflavor)
{
        struct nfs_clone_mount mountdata = {
                .sb = dentry->d_sb,
                .dentry = dentry,
                .fh = fh,
                .fattr = fattr,
                .authflavor = authflavor,
        };
        struct vfsmount *mnt = ERR_PTR(-ENOMEM);
        char *page = (char *) __get_free_page(GFP_USER);
        char *devname;

        dprintk("--> nfs_do_submount()\n");

        dprintk("%s: submounting on %s/%s\n", __func__,
                        dentry->d_parent->d_name.name,
                        dentry->d_name.name);
        if (page == NULL)
                goto out;
        devname = nfs_devname(dentry, page, PAGE_SIZE);
        mnt = (struct vfsmount *)devname;
        if (IS_ERR(devname))
                goto free_page;
        mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
free_page:
        free_page((unsigned long)page);
out:
        dprintk("%s: done\n", __func__);

        dprintk("<-- nfs_do_submount() = %p\n", mnt);
        return mnt;
}