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, u32 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, 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 */ 105 static 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; 124 err_out: 125 return -ENOMEM; 126 } 127 128 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry, 129 uid_t uid, int any) 130 { 131 struct dentry *ds; 132 char **wnames, *uname; 133 int i, n, l, clone, access; 134 struct v9fs_session_info *v9ses; 135 struct p9_fid *fid, *old_fid = NULL; 136 137 v9ses = v9fs_dentry2v9ses(dentry); 138 access = v9ses->flags & V9FS_ACCESS_MASK; 139 fid = v9fs_fid_find(dentry, uid, any); 140 if (fid) 141 return fid; 142 /* 143 * we don't have a matching fid. To do a TWALK we need 144 * parent fid. We need to prevent rename when we want to 145 * look at the parent. 146 */ 147 down_read(&v9ses->rename_sem); 148 ds = dentry->d_parent; 149 fid = v9fs_fid_find(ds, uid, any); 150 if (fid) { 151 /* Found the parent fid do a lookup with that */ 152 fid = p9_client_walk(fid, 1, (char **)&dentry->d_name.name, 1); 153 goto fid_out; 154 } 155 up_read(&v9ses->rename_sem); 156 157 /* start from the root and try to do a lookup */ 158 fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any); 159 if (!fid) { 160 /* the user is not attached to the fs yet */ 161 if (access == V9FS_ACCESS_SINGLE) 162 return ERR_PTR(-EPERM); 163 164 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses)) 165 uname = NULL; 166 else 167 uname = v9ses->uname; 168 169 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid, 170 v9ses->aname); 171 if (IS_ERR(fid)) 172 return fid; 173 174 v9fs_fid_add(dentry->d_sb->s_root, fid); 175 } 176 /* If we are root ourself just return that */ 177 if (dentry->d_sb->s_root == dentry) 178 return fid; 179 /* 180 * Do a multipath walk with attached root. 181 * When walking parent we need to make sure we 182 * don't have a parallel rename happening 183 */ 184 down_read(&v9ses->rename_sem); 185 n = build_path_from_dentry(v9ses, dentry, &wnames); 186 if (n < 0) { 187 fid = ERR_PTR(n); 188 goto err_out; 189 } 190 clone = 1; 191 i = 0; 192 while (i < n) { 193 l = min(n - i, P9_MAXWELEM); 194 /* 195 * We need to hold rename lock when doing a multipath 196 * walk to ensure none of the patch component change 197 */ 198 fid = p9_client_walk(fid, l, &wnames[i], clone); 199 if (IS_ERR(fid)) { 200 if (old_fid) { 201 /* 202 * If we fail, clunk fid which are mapping 203 * to path component and not the last component 204 * of the path. 205 */ 206 p9_client_clunk(old_fid); 207 } 208 kfree(wnames); 209 goto err_out; 210 } 211 old_fid = fid; 212 i += l; 213 clone = 0; 214 } 215 kfree(wnames); 216 fid_out: 217 if (!IS_ERR(fid)) 218 v9fs_fid_add(dentry, fid); 219 err_out: 220 up_read(&v9ses->rename_sem); 221 return fid; 222 } 223 224 /** 225 * v9fs_fid_lookup - lookup for a fid, try to walk if not found 226 * @dentry: dentry to look for fid in 227 * 228 * Look for a fid in the specified dentry for the current user. 229 * If no fid is found, try to create one walking from a fid from the parent 230 * dentry (if it has one), or the root dentry. If the user haven't accessed 231 * the fs yet, attach now and walk from the root. 232 */ 233 234 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) 235 { 236 uid_t uid; 237 int any, access; 238 struct v9fs_session_info *v9ses; 239 240 v9ses = v9fs_dentry2v9ses(dentry); 241 access = v9ses->flags & V9FS_ACCESS_MASK; 242 switch (access) { 243 case V9FS_ACCESS_SINGLE: 244 case V9FS_ACCESS_USER: 245 case V9FS_ACCESS_CLIENT: 246 uid = current_fsuid(); 247 any = 0; 248 break; 249 250 case V9FS_ACCESS_ANY: 251 uid = v9ses->uid; 252 any = 1; 253 break; 254 255 default: 256 uid = ~0; 257 any = 0; 258 break; 259 } 260 return v9fs_fid_lookup_with_uid(dentry, uid, any); 261 } 262 263 struct p9_fid *v9fs_fid_clone(struct dentry *dentry) 264 { 265 struct p9_fid *fid, *ret; 266 267 fid = v9fs_fid_lookup(dentry); 268 if (IS_ERR(fid)) 269 return fid; 270 271 ret = p9_client_walk(fid, 0, NULL, 1); 272 return ret; 273 } 274 275 static struct p9_fid *v9fs_fid_clone_with_uid(struct dentry *dentry, uid_t uid) 276 { 277 struct p9_fid *fid, *ret; 278 279 fid = v9fs_fid_lookup_with_uid(dentry, uid, 0); 280 if (IS_ERR(fid)) 281 return fid; 282 283 ret = p9_client_walk(fid, 0, NULL, 1); 284 return ret; 285 } 286 287 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry) 288 { 289 int err; 290 struct p9_fid *fid; 291 292 fid = v9fs_fid_clone_with_uid(dentry, 0); 293 if (IS_ERR(fid)) 294 goto error_out; 295 /* 296 * writeback fid will only be used to write back the 297 * dirty pages. We always request for the open fid in read-write 298 * mode so that a partial page write which result in page 299 * read can work. 300 */ 301 err = p9_client_open(fid, O_RDWR); 302 if (err < 0) { 303 p9_client_clunk(fid); 304 fid = ERR_PTR(err); 305 goto error_out; 306 } 307 error_out: 308 return fid; 309 } 310