1/* 2 * V9FS FID Management 3 * 4 * Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net> 5 * Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 9 * as published by the Free Software Foundation. 10 * 11 * This program is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 * GNU General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License 17 * along with this program; if not, write to: 18 * Free Software Foundation 19 * 51 Franklin Street, Fifth Floor 20 * Boston, MA 02111-1301 USA 21 * 22 */ 23 24#include <linux/module.h> 25#include <linux/errno.h> 26#include <linux/fs.h> 27#include <linux/slab.h> 28#include <linux/sched.h> 29#include <linux/idr.h> 30#include <net/9p/9p.h> 31#include <net/9p/client.h> 32 33#include "v9fs.h" 34#include "v9fs_vfs.h" 35#include "fid.h" 36 37/** 38 * v9fs_fid_add - add a fid to a dentry 39 * @dentry: dentry that the fid is being added to 40 * @fid: fid to add 41 * 42 */ 43 44int v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid) 45{ 46 struct v9fs_dentry *dent; 47 48 P9_DPRINTK(P9_DEBUG_VFS, "fid %d dentry %s\n", 49 fid->fid, dentry->d_name.name); 50 51 dent = dentry->d_fsdata; 52 if (!dent) { 53 dent = kmalloc(sizeof(struct v9fs_dentry), GFP_KERNEL); 54 if (!dent) 55 return -ENOMEM; 56 57 spin_lock_init(&dent->lock); 58 INIT_LIST_HEAD(&dent->fidlist); 59 dentry->d_fsdata = dent; 60 } 61 62 spin_lock(&dent->lock); 63 list_add(&fid->dlist, &dent->fidlist); 64 spin_unlock(&dent->lock); 65 66 return 0; 67} 68 69/** 70 * v9fs_fid_find - retrieve a fid that belongs to the specified uid 71 * @dentry: dentry to look for fid in 72 * @uid: return fid that belongs to the specified user 73 * @any: if non-zero, return any fid associated with the dentry 74 * 75 */ 76 77static struct p9_fid *v9fs_fid_find(struct dentry *dentry, u32 uid, int any) 78{ 79 struct v9fs_dentry *dent; 80 struct p9_fid *fid, *ret; 81 82 P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p) uid %d any %d\n", 83 dentry->d_name.name, dentry, uid, any); 84 dent = (struct v9fs_dentry *) dentry->d_fsdata; 85 ret = NULL; 86 if (dent) { 87 spin_lock(&dent->lock); 88 list_for_each_entry(fid, &dent->fidlist, dlist) { 89 if (any || fid->uid == uid) { 90 ret = fid; 91 break; 92 } 93 } 94 spin_unlock(&dent->lock); 95 } 96 97 return ret; 98} 99 100/* 101 * We need to hold v9ses->rename_sem as long as we hold references 102 * to returned path array. Array element contain pointers to 103 * dentry names. 104 */ 105static int build_path_from_dentry(struct v9fs_session_info *v9ses, 106 struct dentry *dentry, char ***names) 107{ 108 int n = 0, i; 109 char **wnames; 110 struct dentry *ds; 111 112 for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent) 113 n++; 114 115 wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL); 116 if (!wnames) 117 goto err_out; 118 119 for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent) 120 wnames[i] = (char *)ds->d_name.name; 121 122 *names = wnames; 123 return n; 124err_out: 125 return -ENOMEM; 126} 127 128/** 129 * v9fs_fid_lookup - lookup for a fid, try to walk if not found 130 * @dentry: dentry to look for fid in 131 * 132 * Look for a fid in the specified dentry for the current user. 133 * If no fid is found, try to create one walking from a fid from the parent 134 * dentry (if it has one), or the root dentry. If the user haven't accessed 135 * the fs yet, attach now and walk from the root. 136 */ 137 138struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) 139{ 140 int i, n, l, clone, any, access; 141 u32 uid; 142 struct p9_fid *fid, *old_fid = NULL; 143 struct dentry *ds; 144 struct v9fs_session_info *v9ses; 145 char **wnames, *uname; 146 147 v9ses = v9fs_inode2v9ses(dentry->d_inode); 148 access = v9ses->flags & V9FS_ACCESS_MASK; 149 switch (access) { 150 case V9FS_ACCESS_SINGLE: 151 case V9FS_ACCESS_USER: 152 uid = current_fsuid(); 153 any = 0; 154 break; 155 156 case V9FS_ACCESS_ANY: 157 uid = v9ses->uid; 158 any = 1; 159 break; 160 161 default: 162 uid = ~0; 163 any = 0; 164 break; 165 } 166 167 fid = v9fs_fid_find(dentry, uid, any); 168 if (fid) 169 return fid; 170 /* 171 * we don't have a matching fid. To do a TWALK we need 172 * parent fid. We need to prevent rename when we want to 173 * look at the parent. 174 */ 175 down_read(&v9ses->rename_sem); 176 ds = dentry->d_parent; 177 fid = v9fs_fid_find(ds, uid, any); 178 if (fid) { 179 /* Found the parent fid do a lookup with that */ 180 fid = p9_client_walk(fid, 1, (char **)&dentry->d_name.name, 1); 181 goto fid_out; 182 } 183 up_read(&v9ses->rename_sem); 184 185 /* start from the root and try to do a lookup */ 186 fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any); 187 if (!fid) { 188 /* the user is not attached to the fs yet */ 189 if (access == V9FS_ACCESS_SINGLE) 190 return ERR_PTR(-EPERM); 191 192 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses)) 193 uname = NULL; 194 else 195 uname = v9ses->uname; 196 197 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid, 198 v9ses->aname); 199 if (IS_ERR(fid)) 200 return fid; 201 202 v9fs_fid_add(dentry->d_sb->s_root, fid); 203 } 204 /* If we are root ourself just return that */ 205 if (dentry->d_sb->s_root == dentry) 206 return fid; 207 /* 208 * Do a multipath walk with attached root. 209 * When walking parent we need to make sure we 210 * don't have a parallel rename happening 211 */ 212 down_read(&v9ses->rename_sem); 213 n = build_path_from_dentry(v9ses, dentry, &wnames); 214 if (n < 0) { 215 fid = ERR_PTR(n); 216 goto err_out; 217 } 218 clone = 1; 219 i = 0; 220 while (i < n) { 221 l = min(n - i, P9_MAXWELEM); 222 /* 223 * We need to hold rename lock when doing a multipath 224 * walk to ensure none of the patch component change 225 */ 226 fid = p9_client_walk(fid, l, &wnames[i], clone); 227 if (IS_ERR(fid)) { 228 if (old_fid) { 229 /* 230 * If we fail, clunk fid which are mapping 231 * to path component and not the last component 232 * of the path. 233 */ 234 p9_client_clunk(old_fid); 235 } 236 kfree(wnames); 237 goto err_out; 238 } 239 old_fid = fid; 240 i += l; 241 clone = 0; 242 } 243 kfree(wnames); 244fid_out: 245 if (!IS_ERR(fid)) 246 v9fs_fid_add(dentry, fid); 247err_out: 248 up_read(&v9ses->rename_sem); 249 return fid; 250} 251 252struct p9_fid *v9fs_fid_clone(struct dentry *dentry) 253{ 254 struct p9_fid *fid, *ret; 255 256 fid = v9fs_fid_lookup(dentry); 257 if (IS_ERR(fid)) 258 return fid; 259 260 ret = p9_client_walk(fid, 0, NULL, 1); 261 return ret; 262} 263