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 44 int v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid) 45 { 46 struct v9fs_dentry *dent; 47 48 p9_debug(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 77 static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any) 78 { 79 struct v9fs_dentry *dent; 80 struct p9_fid *fid, *ret; 81 82 p9_debug(P9_DEBUG_VFS, " dentry: %s (%p) uid %d any %d\n", 83 dentry->d_name.name, dentry, from_kuid(&init_user_ns, uid), 84 any); 85 dent = (struct v9fs_dentry *) dentry->d_fsdata; 86 ret = NULL; 87 if (dent) { 88 spin_lock(&dent->lock); 89 list_for_each_entry(fid, &dent->fidlist, dlist) { 90 if (any || uid_eq(fid->uid, uid)) { 91 ret = fid; 92 break; 93 } 94 } 95 spin_unlock(&dent->lock); 96 } 97 98 return ret; 99 } 100 101 /* 102 * We need to hold v9ses->rename_sem as long as we hold references 103 * to returned path array. Array element contain pointers to 104 * dentry names. 105 */ 106 static int build_path_from_dentry(struct v9fs_session_info *v9ses, 107 struct dentry *dentry, char ***names) 108 { 109 int n = 0, i; 110 char **wnames; 111 struct dentry *ds; 112 113 for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent) 114 n++; 115 116 wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL); 117 if (!wnames) 118 goto err_out; 119 120 for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent) 121 wnames[i] = (char *)ds->d_name.name; 122 123 *names = wnames; 124 return n; 125 err_out: 126 return -ENOMEM; 127 } 128 129 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry, 130 kuid_t uid, int any) 131 { 132 struct dentry *ds; 133 char **wnames, *uname; 134 int i, n, l, clone, access; 135 struct v9fs_session_info *v9ses; 136 struct p9_fid *fid, *old_fid = NULL; 137 138 v9ses = v9fs_dentry2v9ses(dentry); 139 access = v9ses->flags & V9FS_ACCESS_MASK; 140 fid = v9fs_fid_find(dentry, uid, any); 141 if (fid) 142 return fid; 143 /* 144 * we don't have a matching fid. To do a TWALK we need 145 * parent fid. We need to prevent rename when we want to 146 * look at the parent. 147 */ 148 down_read(&v9ses->rename_sem); 149 ds = dentry->d_parent; 150 fid = v9fs_fid_find(ds, uid, any); 151 if (fid) { 152 /* Found the parent fid do a lookup with that */ 153 fid = p9_client_walk(fid, 1, (char **)&dentry->d_name.name, 1); 154 goto fid_out; 155 } 156 up_read(&v9ses->rename_sem); 157 158 /* start from the root and try to do a lookup */ 159 fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any); 160 if (!fid) { 161 /* the user is not attached to the fs yet */ 162 if (access == V9FS_ACCESS_SINGLE) 163 return ERR_PTR(-EPERM); 164 165 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses)) 166 uname = NULL; 167 else 168 uname = v9ses->uname; 169 170 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid, 171 v9ses->aname); 172 if (IS_ERR(fid)) 173 return fid; 174 175 v9fs_fid_add(dentry->d_sb->s_root, fid); 176 } 177 /* If we are root ourself just return that */ 178 if (dentry->d_sb->s_root == dentry) 179 return fid; 180 /* 181 * Do a multipath walk with attached root. 182 * When walking parent we need to make sure we 183 * don't have a parallel rename happening 184 */ 185 down_read(&v9ses->rename_sem); 186 n = build_path_from_dentry(v9ses, dentry, &wnames); 187 if (n < 0) { 188 fid = ERR_PTR(n); 189 goto err_out; 190 } 191 clone = 1; 192 i = 0; 193 while (i < n) { 194 l = min(n - i, P9_MAXWELEM); 195 /* 196 * We need to hold rename lock when doing a multipath 197 * walk to ensure none of the patch component change 198 */ 199 fid = p9_client_walk(fid, l, &wnames[i], clone); 200 if (IS_ERR(fid)) { 201 if (old_fid) { 202 /* 203 * If we fail, clunk fid which are mapping 204 * to path component and not the last component 205 * of the path. 206 */ 207 p9_client_clunk(old_fid); 208 } 209 kfree(wnames); 210 goto err_out; 211 } 212 old_fid = fid; 213 i += l; 214 clone = 0; 215 } 216 kfree(wnames); 217 fid_out: 218 if (!IS_ERR(fid)) 219 v9fs_fid_add(dentry, fid); 220 err_out: 221 up_read(&v9ses->rename_sem); 222 return fid; 223 } 224 225 /** 226 * v9fs_fid_lookup - lookup for a fid, try to walk if not found 227 * @dentry: dentry to look for fid in 228 * 229 * Look for a fid in the specified dentry for the current user. 230 * If no fid is found, try to create one walking from a fid from the parent 231 * dentry (if it has one), or the root dentry. If the user haven't accessed 232 * the fs yet, attach now and walk from the root. 233 */ 234 235 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) 236 { 237 kuid_t uid; 238 int any, access; 239 struct v9fs_session_info *v9ses; 240 241 v9ses = v9fs_dentry2v9ses(dentry); 242 access = v9ses->flags & V9FS_ACCESS_MASK; 243 switch (access) { 244 case V9FS_ACCESS_SINGLE: 245 case V9FS_ACCESS_USER: 246 case V9FS_ACCESS_CLIENT: 247 uid = current_fsuid(); 248 any = 0; 249 break; 250 251 case V9FS_ACCESS_ANY: 252 uid = v9ses->uid; 253 any = 1; 254 break; 255 256 default: 257 uid = INVALID_UID; 258 any = 0; 259 break; 260 } 261 return v9fs_fid_lookup_with_uid(dentry, uid, any); 262 } 263 264 struct p9_fid *v9fs_fid_clone(struct dentry *dentry) 265 { 266 struct p9_fid *fid, *ret; 267 268 fid = v9fs_fid_lookup(dentry); 269 if (IS_ERR(fid)) 270 return fid; 271 272 ret = p9_client_walk(fid, 0, NULL, 1); 273 return ret; 274 } 275 276 static struct p9_fid *v9fs_fid_clone_with_uid(struct dentry *dentry, kuid_t uid) 277 { 278 struct p9_fid *fid, *ret; 279 280 fid = v9fs_fid_lookup_with_uid(dentry, uid, 0); 281 if (IS_ERR(fid)) 282 return fid; 283 284 ret = p9_client_walk(fid, 0, NULL, 1); 285 return ret; 286 } 287 288 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry) 289 { 290 int err; 291 struct p9_fid *fid; 292 293 fid = v9fs_fid_clone_with_uid(dentry, GLOBAL_ROOT_UID); 294 if (IS_ERR(fid)) 295 goto error_out; 296 /* 297 * writeback fid will only be used to write back the 298 * dirty pages. We always request for the open fid in read-write 299 * mode so that a partial page write which result in page 300 * read can work. 301 */ 302 err = p9_client_open(fid, O_RDWR); 303 if (err < 0) { 304 p9_client_clunk(fid); 305 fid = ERR_PTR(err); 306 goto error_out; 307 } 308 error_out: 309 return fid; 310 } 311