linux/fs/nfs/namespace.c
Ben Hutchings 97a5486826 nfs: Show original device name verbatim in /proc/*/mount{s,info}
Since commit c7f404b ('vfs: new superblock methods to override
/proc/*/mount{s,info}'), nfs_path() is used to generate the mounted
device name reported back to userland.

nfs_path() always generates a trailing slash when the given dentry is
the root of an NFS mount, but userland may expect the original device
name to be returned verbatim (as it used to be).  Make this
canonicalisation optional and change the callers accordingly.

[jrnieder@gmail.com: use flag instead of bool argument]
Reported-and-tested-by: Chris Hiestand <chiestand@salk.edu>
Reference: http://bugs.debian.org/669314
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: <stable@vger.kernel.org> # v2.6.39+
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2012-10-31 16:26:26 -04:00

271 lines
6.9 KiB
C

/*
* 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/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);
}
/**
* 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
*
*/
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);