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