/* mountpoint management
 *
 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/gfp.h>
#include "internal.h"


static struct dentry *afs_mntpt_lookup(struct inode *dir,
                                       struct dentry *dentry,
                                       unsigned int flags);
static int afs_mntpt_open(struct inode *inode, struct file *file);
static void afs_mntpt_expiry_timed_out(struct work_struct *work);

const struct file_operations afs_mntpt_file_operations = {
        .open           = afs_mntpt_open,
        .llseek         = noop_llseek,
};

const struct inode_operations afs_mntpt_inode_operations = {
        .lookup         = afs_mntpt_lookup,
        .readlink       = page_readlink,
        .getattr        = afs_getattr,
};

const struct inode_operations afs_autocell_inode_operations = {
        .getattr        = afs_getattr,
};

static LIST_HEAD(afs_vfsmounts);
static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);

static unsigned long afs_mntpt_expiry_timeout = 10 * 60;

/*
 * check a symbolic link to see whether it actually encodes a mountpoint
 * - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
 */
int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)
{
        struct page *page;
        size_t size;
        char *buf;
        int ret;

        _enter("{%x:%u,%u}",
               vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);

        /* read the contents of the symlink into the pagecache */
        page = read_cache_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0,
                               afs_page_filler, key);
        if (IS_ERR(page)) {
                ret = PTR_ERR(page);
                goto out;
        }

        ret = -EIO;
        if (PageError(page))
                goto out_free;

        buf = kmap(page);

        /* examine the symlink's contents */
        size = vnode->status.size;
        _debug("symlink to %*.*s", (int) size, (int) size, buf);

        if (size > 2 &&
            (buf[0] == '%' || buf[0] == '#') &&
            buf[size - 1] == '.'
            ) {
                _debug("symlink is a mountpoint");
                spin_lock(&vnode->lock);
                set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
                vnode->vfs_inode.i_flags |= S_AUTOMOUNT;
                spin_unlock(&vnode->lock);
        }

        ret = 0;

        kunmap(page);
out_free:
        put_page(page);
out:
        _leave(" = %d", ret);
        return ret;
}

/*
 * no valid lookup procedure on this sort of dir
 */
static struct dentry *afs_mntpt_lookup(struct inode *dir,
                                       struct dentry *dentry,
                                       unsigned int flags)
{
        _enter("%p,%p{%pd2}", dir, dentry, dentry);
        return ERR_PTR(-EREMOTE);
}

/*
 * no valid open procedure on this sort of dir
 */
static int afs_mntpt_open(struct inode *inode, struct file *file)
{
        _enter("%p,%p{%pD2}", inode, file, file);
        return -EREMOTE;
}

/*
 * create a vfsmount to be automounted
 */
static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
{
        struct afs_super_info *super;
        struct vfsmount *mnt;
        struct afs_vnode *vnode;
        struct page *page;
        char *devname, *options;
        bool rwpath = false;
        int ret;

        _enter("{%pd}", mntpt);

        BUG_ON(!d_inode(mntpt));

        ret = -ENOMEM;
        devname = (char *) get_zeroed_page(GFP_KERNEL);
        if (!devname)
                goto error_no_devname;

        options = (char *) get_zeroed_page(GFP_KERNEL);
        if (!options)
                goto error_no_options;

        vnode = AFS_FS_I(d_inode(mntpt));
        if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
                /* if the directory is a pseudo directory, use the d_name */
                static const char afs_root_cell[] = ":root.cell.";
                unsigned size = mntpt->d_name.len;

                ret = -ENOENT;
                if (size < 2 || size > AFS_MAXCELLNAME)
                        goto error_no_page;

                if (mntpt->d_name.name[0] == '.') {
                        devname[0] = '#';
                        memcpy(devname + 1, mntpt->d_name.name, size - 1);
                        memcpy(devname + size, afs_root_cell,
                               sizeof(afs_root_cell));
                        rwpath = true;
                } else {
                        devname[0] = '%';
                        memcpy(devname + 1, mntpt->d_name.name, size);
                        memcpy(devname + size + 1, afs_root_cell,
                               sizeof(afs_root_cell));
                }
        } else {
                /* read the contents of the AFS special symlink */
                loff_t size = i_size_read(d_inode(mntpt));
                char *buf;

                ret = -EINVAL;
                if (size > PAGE_SIZE - 1)
                        goto error_no_page;

                page = read_mapping_page(d_inode(mntpt)->i_mapping, 0, NULL);
                if (IS_ERR(page)) {
                        ret = PTR_ERR(page);
                        goto error_no_page;
                }

                ret = -EIO;
                if (PageError(page))
                        goto error;

                buf = kmap_atomic(page);
                memcpy(devname, buf, size);
                kunmap_atomic(buf);
                put_page(page);
                page = NULL;
        }

        /* work out what options we want */
        super = AFS_FS_S(mntpt->d_sb);
        memcpy(options, "cell=", 5);
        strcpy(options + 5, super->volume->cell->name);
        if (super->volume->type == AFSVL_RWVOL || rwpath)
                strcat(options, ",rwpath");

        /* try and do the mount */
        _debug("--- attempting mount %s -o %s ---", devname, options);
        mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);
        _debug("--- mount result %p ---", mnt);

        free_page((unsigned long) devname);
        free_page((unsigned long) options);
        _leave(" = %p", mnt);
        return mnt;

error:
        put_page(page);
error_no_page:
        free_page((unsigned long) options);
error_no_options:
        free_page((unsigned long) devname);
error_no_devname:
        _leave(" = %d", ret);
        return ERR_PTR(ret);
}

/*
 * handle an automount point
 */
struct vfsmount *afs_d_automount(struct path *path)
{
        struct vfsmount *newmnt;

        _enter("{%pd}", path->dentry);

        newmnt = afs_mntpt_do_automount(path->dentry);
        if (IS_ERR(newmnt))
                return newmnt;

        mntget(newmnt); /* prevent immediate expiration */
        mnt_set_expiry(newmnt, &afs_vfsmounts);
        queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
                           afs_mntpt_expiry_timeout * HZ);
        _leave(" = %p", newmnt);
        return newmnt;
}

/*
 * handle mountpoint expiry timer going off
 */
static void afs_mntpt_expiry_timed_out(struct work_struct *work)
{
        _enter("");

        if (!list_empty(&afs_vfsmounts)) {
                mark_mounts_for_expiry(&afs_vfsmounts);
                queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
                                   afs_mntpt_expiry_timeout * HZ);
        }

        _leave("");
}

/*
 * kill the AFS mountpoint timer if it's still running
 */
void afs_mntpt_kill_timer(void)
{
        _enter("");

        ASSERT(list_empty(&afs_vfsmounts));
        cancel_delayed_work_sync(&afs_mntpt_expiry_timer);
}