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- /*
- * 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: %pd (%p) uid %d any %d\n",
- dentry, 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;
- spin_lock(&dentry->d_lock);
- hlist_for_each_entry(fid, 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;
- }
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