namespace.c

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/*
 * linux/fs/nfs/namespace.c
 *
 * Copyright (C) 2005 Trond Myklebust <[email protected]>
 * - Modified by David Howells <[email protected]>
 *
 * NFS namespace
 */

#include <linux/module.h>
#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;

/*
 * 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
 * @flags - options (see below)
 *
 * 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.
 *
 * Supported flags:
 * NFS_PATH_CANONICAL: ensure there is exactly one slash after
 *             the original device (export) name
 *             (if unset, the original name is returned verbatim)
 */
char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen,
           unsigned flags)
{
    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 ((flags & NFS_PATH_CANONICAL) && *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);
    if (flags & NFS_PATH_CANONICAL) {
        /* 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);
}
EXPORT_SYMBOL_GPL(nfs_path);

/*
 * 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 nfs_server *server = NFS_SERVER(path->dentry->d_inode);
    struct nfs_fh *fh = NULL;
    struct nfs_fattr *fattr = NULL;

    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__);

    mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
    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)
{
    return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
}

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;
}
EXPORT_SYMBOL_GPL(nfs_do_submount);

struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
                  struct nfs_fh *fh, struct nfs_fattr *fattr)
{
    int err;
    struct dentry *parent = dget_parent(dentry);

    /* Look it up again to get its attributes */
    err = server->nfs_client->rpc_ops->lookup(parent->d_inode, &dentry->d_name, fh, fattr);
    dput(parent);
    if (err != 0)
        return ERR_PTR(err);

    return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
}
EXPORT_SYMBOL_GPL(nfs_submount);