/*
 * Copyright (c) 2012 Bryan Schumaker <bjschuma@netapp.com>
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/nfs4_mount.h>
#include <linux/nfs_fs.h>
#include "delegation.h"
#include "internal.h"
#include "nfs4_fs.h"
#include "nfs4idmap.h"
#include "dns_resolve.h"
#include "pnfs.h"
#include "nfs.h"

#define NFSDBG_FACILITY         NFSDBG_VFS

static int nfs4_write_inode(struct inode *inode, struct writeback_control *wbc);
static void nfs4_evict_inode(struct inode *inode);
static struct dentry *nfs4_remote_mount(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data);
static struct dentry *nfs4_referral_mount(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data);
static struct dentry *nfs4_remote_referral_mount(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data);

static struct file_system_type nfs4_remote_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "nfs4",
        .mount          = nfs4_remote_mount,
        .kill_sb        = nfs_kill_super,
        .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
};

static struct file_system_type nfs4_remote_referral_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "nfs4",
        .mount          = nfs4_remote_referral_mount,
        .kill_sb        = nfs_kill_super,
        .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
};

struct file_system_type nfs4_referral_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "nfs4",
        .mount          = nfs4_referral_mount,
        .kill_sb        = nfs_kill_super,
        .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
};

static const struct super_operations nfs4_sops = {
        .alloc_inode    = nfs_alloc_inode,
        .destroy_inode  = nfs_destroy_inode,
        .write_inode    = nfs4_write_inode,
        .drop_inode     = nfs_drop_inode,
        .statfs         = nfs_statfs,
        .evict_inode    = nfs4_evict_inode,
        .umount_begin   = nfs_umount_begin,
        .show_options   = nfs_show_options,
        .show_devname   = nfs_show_devname,
        .show_path      = nfs_show_path,
        .show_stats     = nfs_show_stats,
        .remount_fs     = nfs_remount,
};

struct nfs_subversion nfs_v4 = {
        .owner = THIS_MODULE,
        .nfs_fs   = &nfs4_fs_type,
        .rpc_vers = &nfs_version4,
        .rpc_ops  = &nfs_v4_clientops,
        .sops     = &nfs4_sops,
        .xattr    = nfs4_xattr_handlers,
};

static int nfs4_write_inode(struct inode *inode, struct writeback_control *wbc)
{
        int ret = nfs_write_inode(inode, wbc);

        if (ret == 0)
                ret = pnfs_layoutcommit_inode(inode,
                                wbc->sync_mode == WB_SYNC_ALL);
        return ret;
}

/*
 * Clean out any remaining NFSv4 state that might be left over due
 * to open() calls that passed nfs_atomic_lookup, but failed to call
 * nfs_open().
 */
static void nfs4_evict_inode(struct inode *inode)
{
        truncate_inode_pages_final(&inode->i_data);
        clear_inode(inode);
        /* If we are holding a delegation, return it! */
        nfs_inode_return_delegation_noreclaim(inode);
        /* Note that above delegreturn would trigger pnfs return-on-close */
        pnfs_return_layout(inode);
        pnfs_destroy_layout(NFS_I(inode));
        /* First call standard NFS clear_inode() code */
        nfs_clear_inode(inode);
}

/*
 * Get the superblock for the NFS4 root partition
 */
static struct dentry *
nfs4_remote_mount(struct file_system_type *fs_type, int flags,
                  const char *dev_name, void *info)
{
        struct nfs_mount_info *mount_info = info;
        struct nfs_server *server;
        struct dentry *mntroot = ERR_PTR(-ENOMEM);

        mount_info->set_security = nfs_set_sb_security;

        /* Get a volume representation */
        server = nfs4_create_server(mount_info, &nfs_v4);
        if (IS_ERR(server)) {
                mntroot = ERR_CAST(server);
                goto out;
        }

        mntroot = nfs_fs_mount_common(server, flags, dev_name, mount_info, &nfs_v4);

out:
        return mntroot;
}

static struct vfsmount *nfs_do_root_mount(struct file_system_type *fs_type,
                int flags, void *data, const char *hostname)
{
        struct vfsmount *root_mnt;
        char *root_devname;
        size_t len;

        len = strlen(hostname) + 5;
        root_devname = kmalloc(len, GFP_KERNEL);
        if (root_devname == NULL)
                return ERR_PTR(-ENOMEM);
        /* Does hostname needs to be enclosed in brackets? */
        if (strchr(hostname, ':'))
                snprintf(root_devname, len, "[%s]:/", hostname);
        else
                snprintf(root_devname, len, "%s:/", hostname);
        root_mnt = vfs_kern_mount(fs_type, flags, root_devname, data);
        kfree(root_devname);
        return root_mnt;
}

struct nfs_referral_count {
        struct list_head list;
        const struct task_struct *task;
        unsigned int referral_count;
};

static LIST_HEAD(nfs_referral_count_list);
static DEFINE_SPINLOCK(nfs_referral_count_list_lock);

static struct nfs_referral_count *nfs_find_referral_count(void)
{
        struct nfs_referral_count *p;

        list_for_each_entry(p, &nfs_referral_count_list, list) {
                if (p->task == current)
                        return p;
        }
        return NULL;
}

#define NFS_MAX_NESTED_REFERRALS 2

static int nfs_referral_loop_protect(void)
{
        struct nfs_referral_count *p, *new;
        int ret = -ENOMEM;

        new = kmalloc(sizeof(*new), GFP_KERNEL);
        if (!new)
                goto out;
        new->task = current;
        new->referral_count = 1;

        ret = 0;
        spin_lock(&nfs_referral_count_list_lock);
        p = nfs_find_referral_count();
        if (p != NULL) {
                if (p->referral_count >= NFS_MAX_NESTED_REFERRALS)
                        ret = -ELOOP;
                else
                        p->referral_count++;
        } else {
                list_add(&new->list, &nfs_referral_count_list);
                new = NULL;
        }
        spin_unlock(&nfs_referral_count_list_lock);
        kfree(new);
out:
        return ret;
}

static void nfs_referral_loop_unprotect(void)
{
        struct nfs_referral_count *p;

        spin_lock(&nfs_referral_count_list_lock);
        p = nfs_find_referral_count();
        p->referral_count--;
        if (p->referral_count == 0)
                list_del(&p->list);
        else
                p = NULL;
        spin_unlock(&nfs_referral_count_list_lock);
        kfree(p);
}

static struct dentry *nfs_follow_remote_path(struct vfsmount *root_mnt,
                const char *export_path)
{
        struct dentry *dentry;
        int err;

        if (IS_ERR(root_mnt))
                return ERR_CAST(root_mnt);

        err = nfs_referral_loop_protect();
        if (err) {
                mntput(root_mnt);
                return ERR_PTR(err);
        }

        dentry = mount_subtree(root_mnt, export_path);
        nfs_referral_loop_unprotect();

        return dentry;
}

struct dentry *nfs4_try_mount(int flags, const char *dev_name,
                              struct nfs_mount_info *mount_info,
                              struct nfs_subversion *nfs_mod)
{
        char *export_path;
        struct vfsmount *root_mnt;
        struct dentry *res;
        struct nfs_parsed_mount_data *data = mount_info->parsed;

        dfprintk(MOUNT, "--> nfs4_try_mount()\n");

        export_path = data->nfs_server.export_path;
        data->nfs_server.export_path = "/";
        root_mnt = nfs_do_root_mount(&nfs4_remote_fs_type, flags, mount_info,
                        data->nfs_server.hostname);
        data->nfs_server.export_path = export_path;

        res = nfs_follow_remote_path(root_mnt, export_path);

        dfprintk(MOUNT, "<-- nfs4_try_mount() = %d%s\n",
                 PTR_ERR_OR_ZERO(res),
                 IS_ERR(res) ? " [error]" : "");
        return res;
}

static struct dentry *
nfs4_remote_referral_mount(struct file_system_type *fs_type, int flags,
                           const char *dev_name, void *raw_data)
{
        struct nfs_mount_info mount_info = {
                .fill_super = nfs_fill_super,
                .set_security = nfs_clone_sb_security,
                .cloned = raw_data,
        };
        struct nfs_server *server;
        struct dentry *mntroot = ERR_PTR(-ENOMEM);

        dprintk("--> nfs4_referral_get_sb()\n");

        mount_info.mntfh = nfs_alloc_fhandle();
        if (mount_info.cloned == NULL || mount_info.mntfh == NULL)
                goto out;

        /* create a new volume representation */
        server = nfs4_create_referral_server(mount_info.cloned, mount_info.mntfh);
        if (IS_ERR(server)) {
                mntroot = ERR_CAST(server);
                goto out;
        }

        mntroot = nfs_fs_mount_common(server, flags, dev_name, &mount_info, &nfs_v4);
out:
        nfs_free_fhandle(mount_info.mntfh);
        return mntroot;
}

/*
 * Create an NFS4 server record on referral traversal
 */
static struct dentry *nfs4_referral_mount(struct file_system_type *fs_type,
                int flags, const char *dev_name, void *raw_data)
{
        struct nfs_clone_mount *data = raw_data;
        char *export_path;
        struct vfsmount *root_mnt;
        struct dentry *res;

        dprintk("--> nfs4_referral_mount()\n");

        export_path = data->mnt_path;
        data->mnt_path = "/";

        root_mnt = nfs_do_root_mount(&nfs4_remote_referral_fs_type,
                        flags, data, data->hostname);
        data->mnt_path = export_path;

        res = nfs_follow_remote_path(root_mnt, export_path);
        dprintk("<-- nfs4_referral_mount() = %d%s\n",
                PTR_ERR_OR_ZERO(res),
                IS_ERR(res) ? " [error]" : "");
        return res;
}


static int __init init_nfs_v4(void)
{
        int err;

        err = nfs_dns_resolver_init();
        if (err)
                goto out;

        err = nfs_idmap_init();
        if (err)
                goto out1;

        err = nfs4_register_sysctl();
        if (err)
                goto out2;

        register_nfs_version(&nfs_v4);
        return 0;
out2:
        nfs_idmap_quit();
out1:
        nfs_dns_resolver_destroy();
out:
        return err;
}

static void __exit exit_nfs_v4(void)
{
        /* Not called in the _init(), conditionally loaded */
        nfs4_pnfs_v3_ds_connect_unload();

        unregister_nfs_version(&nfs_v4);
        nfs4_unregister_sysctl();
        nfs_idmap_quit();
        nfs_dns_resolver_destroy();
}

MODULE_LICENSE("GPL");

module_init(init_nfs_v4);
module_exit(exit_nfs_v4);