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 static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid) 45 { 46 hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata); 47 } 48 49 void v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid) 50 { 51 spin_lock(&dentry->d_lock); 52 __add_fid(dentry, fid); 53 spin_unlock(&dentry->d_lock); 54 } 55 56 /** 57 * v9fs_fid_find - retrieve a fid that belongs to the specified uid 58 * @dentry: dentry to look for fid in 59 * @uid: return fid that belongs to the specified user 60 * @any: if non-zero, return any fid associated with the dentry 61 * 62 */ 63 64 static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any) 65 { 66 struct p9_fid *fid, *ret; 67 68 p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n", 69 dentry, dentry, from_kuid(&init_user_ns, uid), 70 any); 71 ret = NULL; 72 /* we'll recheck under lock if there's anything to look in */ 73 if (dentry->d_fsdata) { 74 struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata; 75 spin_lock(&dentry->d_lock); 76 hlist_for_each_entry(fid, h, dlist) { 77 if (any || uid_eq(fid->uid, uid)) { 78 ret = fid; 79 break; 80 } 81 } 82 spin_unlock(&dentry->d_lock); 83 } 84 85 return ret; 86 } 87 88 /* 89 * We need to hold v9ses->rename_sem as long as we hold references 90 * to returned path array. Array element contain pointers to 91 * dentry names. 92 */ 93 static int build_path_from_dentry(struct v9fs_session_info *v9ses, 94 struct dentry *dentry, char ***names) 95 { 96 int n = 0, i; 97 char **wnames; 98 struct dentry *ds; 99 100 for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent) 101 n++; 102 103 wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL); 104 if (!wnames) 105 goto err_out; 106 107 for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent) 108 wnames[i] = (char *)ds->d_name.name; 109 110 *names = wnames; 111 return n; 112 err_out: 113 return -ENOMEM; 114 } 115 116 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry, 117 kuid_t uid, int any) 118 { 119 struct dentry *ds; 120 char **wnames, *uname; 121 int i, n, l, clone, access; 122 struct v9fs_session_info *v9ses; 123 struct p9_fid *fid, *old_fid = NULL; 124 125 v9ses = v9fs_dentry2v9ses(dentry); 126 access = v9ses->flags & V9FS_ACCESS_MASK; 127 fid = v9fs_fid_find(dentry, uid, any); 128 if (fid) 129 return fid; 130 /* 131 * we don't have a matching fid. To do a TWALK we need 132 * parent fid. We need to prevent rename when we want to 133 * look at the parent. 134 */ 135 down_read(&v9ses->rename_sem); 136 ds = dentry->d_parent; 137 fid = v9fs_fid_find(ds, uid, any); 138 if (fid) { 139 /* Found the parent fid do a lookup with that */ 140 fid = p9_client_walk(fid, 1, (char **)&dentry->d_name.name, 1); 141 goto fid_out; 142 } 143 up_read(&v9ses->rename_sem); 144 145 /* start from the root and try to do a lookup */ 146 fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any); 147 if (!fid) { 148 /* the user is not attached to the fs yet */ 149 if (access == V9FS_ACCESS_SINGLE) 150 return ERR_PTR(-EPERM); 151 152 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses)) 153 uname = NULL; 154 else 155 uname = v9ses->uname; 156 157 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid, 158 v9ses->aname); 159 if (IS_ERR(fid)) 160 return fid; 161 162 v9fs_fid_add(dentry->d_sb->s_root, fid); 163 } 164 /* If we are root ourself just return that */ 165 if (dentry->d_sb->s_root == dentry) 166 return fid; 167 /* 168 * Do a multipath walk with attached root. 169 * When walking parent we need to make sure we 170 * don't have a parallel rename happening 171 */ 172 down_read(&v9ses->rename_sem); 173 n = build_path_from_dentry(v9ses, dentry, &wnames); 174 if (n < 0) { 175 fid = ERR_PTR(n); 176 goto err_out; 177 } 178 clone = 1; 179 i = 0; 180 while (i < n) { 181 l = min(n - i, P9_MAXWELEM); 182 /* 183 * We need to hold rename lock when doing a multipath 184 * walk to ensure none of the patch component change 185 */ 186 fid = p9_client_walk(fid, l, &wnames[i], clone); 187 if (IS_ERR(fid)) { 188 if (old_fid) { 189 /* 190 * If we fail, clunk fid which are mapping 191 * to path component and not the last component 192 * of the path. 193 */ 194 p9_client_clunk(old_fid); 195 } 196 kfree(wnames); 197 goto err_out; 198 } 199 old_fid = fid; 200 i += l; 201 clone = 0; 202 } 203 kfree(wnames); 204 fid_out: 205 if (!IS_ERR(fid)) { 206 spin_lock(&dentry->d_lock); 207 if (d_unhashed(dentry)) { 208 spin_unlock(&dentry->d_lock); 209 p9_client_clunk(fid); 210 fid = ERR_PTR(-ENOENT); 211 } else { 212 __add_fid(dentry, fid); 213 spin_unlock(&dentry->d_lock); 214 } 215 } 216 err_out: 217 up_read(&v9ses->rename_sem); 218 return fid; 219 } 220 221 /** 222 * v9fs_fid_lookup - lookup for a fid, try to walk if not found 223 * @dentry: dentry to look for fid in 224 * 225 * Look for a fid in the specified dentry for the current user. 226 * If no fid is found, try to create one walking from a fid from the parent 227 * dentry (if it has one), or the root dentry. If the user haven't accessed 228 * the fs yet, attach now and walk from the root. 229 */ 230 231 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) 232 { 233 kuid_t uid; 234 int any, access; 235 struct v9fs_session_info *v9ses; 236 237 v9ses = v9fs_dentry2v9ses(dentry); 238 access = v9ses->flags & V9FS_ACCESS_MASK; 239 switch (access) { 240 case V9FS_ACCESS_SINGLE: 241 case V9FS_ACCESS_USER: 242 case V9FS_ACCESS_CLIENT: 243 uid = current_fsuid(); 244 any = 0; 245 break; 246 247 case V9FS_ACCESS_ANY: 248 uid = v9ses->uid; 249 any = 1; 250 break; 251 252 default: 253 uid = INVALID_UID; 254 any = 0; 255 break; 256 } 257 return v9fs_fid_lookup_with_uid(dentry, uid, any); 258 } 259 260 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry) 261 { 262 int err; 263 struct p9_fid *fid; 264 265 fid = clone_fid(v9fs_fid_lookup_with_uid(dentry, GLOBAL_ROOT_UID, 0)); 266 if (IS_ERR(fid)) 267 goto error_out; 268 /* 269 * writeback fid will only be used to write back the 270 * dirty pages. We always request for the open fid in read-write 271 * mode so that a partial page write which result in page 272 * read can work. 273 */ 274 err = p9_client_open(fid, O_RDWR); 275 if (err < 0) { 276 p9_client_clunk(fid); 277 fid = ERR_PTR(err); 278 goto error_out; 279 } 280 error_out: 281 return fid; 282 } 283