mntpt.c

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/* mountpoint management
 *
 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * 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:
    page_cache_release(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{%p{%s},%s}",
           dir,
           dentry,
           dentry->d_parent,
           dentry->d_parent ?
           dentry->d_parent->d_name.name : (const unsigned char *) "",
           dentry->d_name.name);

    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{%p{%s},%s}",
           inode, file,
           file->f_path.dentry->d_parent,
           file->f_path.dentry->d_parent ?
           file->f_path.dentry->d_parent->d_name.name :
           (const unsigned char *) "",
           file->f_path.dentry->d_name.name);

    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("{%s}", mntpt->d_name.name);

    BUG_ON(!mntpt->d_inode);

    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(mntpt->d_inode);
    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(mntpt->d_inode);
        char *buf;

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

        page = read_mapping_page(mntpt->d_inode->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);
        page_cache_release(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:
    page_cache_release(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("{%s}", path->dentry->d_name.name);

    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);
}