linux/fs/9p/fid.c
Al Viro 5e608671df 9p: if v9fs_fid_lookup() gets to asking server, it'd better have hashed dentry
... otherwise the path we'd built isn't worth much.  Don't accept such fids
obtained from paths unless dentry is still alived by the end of the work.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-02-28 01:50:20 -05:00

308 lines
7.3 KiB
C

/*
* V9FS FID Management
*
* Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net>
* Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to:
* Free Software Foundation
* 51 Franklin Street, Fifth Floor
* Boston, MA 02111-1301 USA
*
*/
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/idr.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>
#include "v9fs.h"
#include "v9fs_vfs.h"
#include "fid.h"
/**
* v9fs_fid_add - add a fid to a dentry
* @dentry: dentry that the fid is being added to
* @fid: fid to add
*
*/
static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid)
{
hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata);
}
void v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid)
{
spin_lock(&dentry->d_lock);
__add_fid(dentry, fid);
spin_unlock(&dentry->d_lock);
}
/**
* v9fs_fid_find - retrieve a fid that belongs to the specified uid
* @dentry: dentry to look for fid in
* @uid: return fid that belongs to the specified user
* @any: if non-zero, return any fid associated with the dentry
*
*/
static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any)
{
struct p9_fid *fid, *ret;
p9_debug(P9_DEBUG_VFS, " dentry: %s (%p) uid %d any %d\n",
dentry->d_name.name, dentry, from_kuid(&init_user_ns, uid),
any);
ret = NULL;
/* we'll recheck under lock if there's anything to look in */
if (dentry->d_fsdata) {
struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata;
struct hlist_node *n;
spin_lock(&dentry->d_lock);
hlist_for_each_entry(fid, n, h, dlist) {
if (any || uid_eq(fid->uid, uid)) {
ret = fid;
break;
}
}
spin_unlock(&dentry->d_lock);
}
return ret;
}
/*
* We need to hold v9ses->rename_sem as long as we hold references
* to returned path array. Array element contain pointers to
* dentry names.
*/
static int build_path_from_dentry(struct v9fs_session_info *v9ses,
struct dentry *dentry, char ***names)
{
int n = 0, i;
char **wnames;
struct dentry *ds;
for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
n++;
wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);
if (!wnames)
goto err_out;
for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
wnames[i] = (char *)ds->d_name.name;
*names = wnames;
return n;
err_out:
return -ENOMEM;
}
static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
kuid_t uid, int any)
{
struct dentry *ds;
char **wnames, *uname;
int i, n, l, clone, access;
struct v9fs_session_info *v9ses;
struct p9_fid *fid, *old_fid = NULL;
v9ses = v9fs_dentry2v9ses(dentry);
access = v9ses->flags & V9FS_ACCESS_MASK;
fid = v9fs_fid_find(dentry, uid, any);
if (fid)
return fid;
/*
* we don't have a matching fid. To do a TWALK we need
* parent fid. We need to prevent rename when we want to
* look at the parent.
*/
down_read(&v9ses->rename_sem);
ds = dentry->d_parent;
fid = v9fs_fid_find(ds, uid, any);
if (fid) {
/* Found the parent fid do a lookup with that */
fid = p9_client_walk(fid, 1, (char **)&dentry->d_name.name, 1);
goto fid_out;
}
up_read(&v9ses->rename_sem);
/* start from the root and try to do a lookup */
fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
if (!fid) {
/* the user is not attached to the fs yet */
if (access == V9FS_ACCESS_SINGLE)
return ERR_PTR(-EPERM);
if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
uname = NULL;
else
uname = v9ses->uname;
fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
v9ses->aname);
if (IS_ERR(fid))
return fid;
v9fs_fid_add(dentry->d_sb->s_root, fid);
}
/* If we are root ourself just return that */
if (dentry->d_sb->s_root == dentry)
return fid;
/*
* Do a multipath walk with attached root.
* When walking parent we need to make sure we
* don't have a parallel rename happening
*/
down_read(&v9ses->rename_sem);
n = build_path_from_dentry(v9ses, dentry, &wnames);
if (n < 0) {
fid = ERR_PTR(n);
goto err_out;
}
clone = 1;
i = 0;
while (i < n) {
l = min(n - i, P9_MAXWELEM);
/*
* We need to hold rename lock when doing a multipath
* walk to ensure none of the patch component change
*/
fid = p9_client_walk(fid, l, &wnames[i], clone);
if (IS_ERR(fid)) {
if (old_fid) {
/*
* If we fail, clunk fid which are mapping
* to path component and not the last component
* of the path.
*/
p9_client_clunk(old_fid);
}
kfree(wnames);
goto err_out;
}
old_fid = fid;
i += l;
clone = 0;
}
kfree(wnames);
fid_out:
if (!IS_ERR(fid)) {
spin_lock(&dentry->d_lock);
if (d_unhashed(dentry)) {
spin_unlock(&dentry->d_lock);
p9_client_clunk(fid);
fid = ERR_PTR(-ENOENT);
} else {
__add_fid(dentry, fid);
spin_unlock(&dentry->d_lock);
}
}
err_out:
up_read(&v9ses->rename_sem);
return fid;
}
/**
* v9fs_fid_lookup - lookup for a fid, try to walk if not found
* @dentry: dentry to look for fid in
*
* Look for a fid in the specified dentry for the current user.
* If no fid is found, try to create one walking from a fid from the parent
* dentry (if it has one), or the root dentry. If the user haven't accessed
* the fs yet, attach now and walk from the root.
*/
struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
{
kuid_t uid;
int any, access;
struct v9fs_session_info *v9ses;
v9ses = v9fs_dentry2v9ses(dentry);
access = v9ses->flags & V9FS_ACCESS_MASK;
switch (access) {
case V9FS_ACCESS_SINGLE:
case V9FS_ACCESS_USER:
case V9FS_ACCESS_CLIENT:
uid = current_fsuid();
any = 0;
break;
case V9FS_ACCESS_ANY:
uid = v9ses->uid;
any = 1;
break;
default:
uid = INVALID_UID;
any = 0;
break;
}
return v9fs_fid_lookup_with_uid(dentry, uid, any);
}
struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
{
struct p9_fid *fid, *ret;
fid = v9fs_fid_lookup(dentry);
if (IS_ERR(fid))
return fid;
ret = p9_client_walk(fid, 0, NULL, 1);
return ret;
}
static struct p9_fid *v9fs_fid_clone_with_uid(struct dentry *dentry, kuid_t uid)
{
struct p9_fid *fid, *ret;
fid = v9fs_fid_lookup_with_uid(dentry, uid, 0);
if (IS_ERR(fid))
return fid;
ret = p9_client_walk(fid, 0, NULL, 1);
return ret;
}
struct p9_fid *v9fs_writeback_fid(struct dentry *dentry)
{
int err;
struct p9_fid *fid;
fid = v9fs_fid_clone_with_uid(dentry, GLOBAL_ROOT_UID);
if (IS_ERR(fid))
goto error_out;
/*
* writeback fid will only be used to write back the
* dirty pages. We always request for the open fid in read-write
* mode so that a partial page write which result in page
* read can work.
*/
err = p9_client_open(fid, O_RDWR);
if (err < 0) {
p9_client_clunk(fid);
fid = ERR_PTR(err);
goto error_out;
}
error_out:
return fid;
}