1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * V9FS FID Management 4 * 5 * Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net> 6 * Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com> 7 */ 8 9 #include <linux/module.h> 10 #include <linux/errno.h> 11 #include <linux/fs.h> 12 #include <linux/slab.h> 13 #include <linux/sched.h> 14 #include <net/9p/9p.h> 15 #include <net/9p/client.h> 16 17 #include "v9fs.h" 18 #include "v9fs_vfs.h" 19 #include "fid.h" 20 21 static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid) 22 { 23 hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata); 24 } 25 26 27 /** 28 * v9fs_fid_add - add a fid to a dentry 29 * @dentry: dentry that the fid is being added to 30 * @pfid: fid to add, NULLed out 31 * 32 */ 33 void v9fs_fid_add(struct dentry *dentry, struct p9_fid **pfid) 34 { 35 struct p9_fid *fid = *pfid; 36 37 spin_lock(&dentry->d_lock); 38 __add_fid(dentry, fid); 39 spin_unlock(&dentry->d_lock); 40 41 *pfid = NULL; 42 } 43 44 /** 45 * v9fs_fid_find_inode - search for an open fid off of the inode list 46 * @inode: return a fid pointing to a specific inode 47 * @uid: return a fid belonging to the specified user 48 * 49 */ 50 51 static struct p9_fid *v9fs_fid_find_inode(struct inode *inode, kuid_t uid) 52 { 53 struct hlist_head *h; 54 struct p9_fid *fid, *ret = NULL; 55 56 p9_debug(P9_DEBUG_VFS, " inode: %p\n", inode); 57 58 spin_lock(&inode->i_lock); 59 h = (struct hlist_head *)&inode->i_private; 60 hlist_for_each_entry(fid, h, ilist) { 61 if (uid_eq(fid->uid, uid)) { 62 p9_fid_get(fid); 63 ret = fid; 64 break; 65 } 66 } 67 spin_unlock(&inode->i_lock); 68 return ret; 69 } 70 71 /** 72 * v9fs_open_fid_add - add an open fid to an inode 73 * @inode: inode that the fid is being added to 74 * @pfid: fid to add, NULLed out 75 * 76 */ 77 78 void v9fs_open_fid_add(struct inode *inode, struct p9_fid **pfid) 79 { 80 struct p9_fid *fid = *pfid; 81 82 spin_lock(&inode->i_lock); 83 hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private); 84 spin_unlock(&inode->i_lock); 85 86 *pfid = NULL; 87 } 88 89 90 /** 91 * v9fs_fid_find - retrieve a fid that belongs to the specified uid 92 * @dentry: dentry to look for fid in 93 * @uid: return fid that belongs to the specified user 94 * @any: if non-zero, return any fid associated with the dentry 95 * 96 */ 97 98 static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any) 99 { 100 struct p9_fid *fid, *ret; 101 102 p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n", 103 dentry, dentry, from_kuid(&init_user_ns, uid), 104 any); 105 ret = NULL; 106 /* we'll recheck under lock if there's anything to look in */ 107 if (dentry->d_fsdata) { 108 struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata; 109 110 spin_lock(&dentry->d_lock); 111 hlist_for_each_entry(fid, h, dlist) { 112 if (any || uid_eq(fid->uid, uid)) { 113 ret = fid; 114 p9_fid_get(ret); 115 break; 116 } 117 } 118 spin_unlock(&dentry->d_lock); 119 } else { 120 if (dentry->d_inode) 121 ret = v9fs_fid_find_inode(dentry->d_inode, uid); 122 } 123 124 return ret; 125 } 126 127 /* 128 * We need to hold v9ses->rename_sem as long as we hold references 129 * to returned path array. Array element contain pointers to 130 * dentry names. 131 */ 132 static int build_path_from_dentry(struct v9fs_session_info *v9ses, 133 struct dentry *dentry, const unsigned char ***names) 134 { 135 int n = 0, i; 136 const unsigned char **wnames; 137 struct dentry *ds; 138 139 for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent) 140 n++; 141 142 wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL); 143 if (!wnames) 144 goto err_out; 145 146 for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent) 147 wnames[i] = ds->d_name.name; 148 149 *names = wnames; 150 return n; 151 err_out: 152 return -ENOMEM; 153 } 154 155 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry, 156 kuid_t uid, int any) 157 { 158 struct dentry *ds; 159 const unsigned char **wnames, *uname; 160 int i, n, l, access; 161 struct v9fs_session_info *v9ses; 162 struct p9_fid *fid, *root_fid, *old_fid; 163 164 v9ses = v9fs_dentry2v9ses(dentry); 165 access = v9ses->flags & V9FS_ACCESS_MASK; 166 fid = v9fs_fid_find(dentry, uid, any); 167 if (fid) 168 return fid; 169 /* 170 * we don't have a matching fid. To do a TWALK we need 171 * parent fid. We need to prevent rename when we want to 172 * look at the parent. 173 */ 174 down_read(&v9ses->rename_sem); 175 ds = dentry->d_parent; 176 fid = v9fs_fid_find(ds, uid, any); 177 if (fid) { 178 /* Found the parent fid do a lookup with that */ 179 old_fid = fid; 180 181 fid = p9_client_walk(old_fid, 1, &dentry->d_name.name, 1); 182 p9_fid_put(old_fid); 183 goto fid_out; 184 } 185 up_read(&v9ses->rename_sem); 186 187 /* start from the root and try to do a lookup */ 188 root_fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any); 189 if (!root_fid) { 190 /* the user is not attached to the fs yet */ 191 if (access == V9FS_ACCESS_SINGLE) 192 return ERR_PTR(-EPERM); 193 194 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses)) 195 uname = NULL; 196 else 197 uname = v9ses->uname; 198 199 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid, 200 v9ses->aname); 201 if (IS_ERR(fid)) 202 return fid; 203 204 root_fid = p9_fid_get(fid); 205 v9fs_fid_add(dentry->d_sb->s_root, &fid); 206 } 207 /* If we are root ourself just return that */ 208 if (dentry->d_sb->s_root == dentry) 209 return root_fid; 210 211 /* 212 * Do a multipath walk with attached root. 213 * When walking parent we need to make sure we 214 * don't have a parallel rename happening 215 */ 216 down_read(&v9ses->rename_sem); 217 n = build_path_from_dentry(v9ses, dentry, &wnames); 218 if (n < 0) { 219 fid = ERR_PTR(n); 220 goto err_out; 221 } 222 fid = root_fid; 223 old_fid = root_fid; 224 i = 0; 225 while (i < n) { 226 l = min(n - i, P9_MAXWELEM); 227 /* 228 * We need to hold rename lock when doing a multipath 229 * walk to ensure none of the path components change 230 */ 231 fid = p9_client_walk(old_fid, l, &wnames[i], 232 old_fid == root_fid /* clone */); 233 /* non-cloning walk will return the same fid */ 234 if (fid != old_fid) { 235 p9_fid_put(old_fid); 236 old_fid = fid; 237 } 238 if (IS_ERR(fid)) { 239 kfree(wnames); 240 goto err_out; 241 } 242 i += l; 243 } 244 kfree(wnames); 245 fid_out: 246 if (!IS_ERR(fid)) { 247 spin_lock(&dentry->d_lock); 248 if (d_unhashed(dentry)) { 249 spin_unlock(&dentry->d_lock); 250 p9_fid_put(fid); 251 fid = ERR_PTR(-ENOENT); 252 } else { 253 __add_fid(dentry, fid); 254 p9_fid_get(fid); 255 spin_unlock(&dentry->d_lock); 256 } 257 } 258 err_out: 259 up_read(&v9ses->rename_sem); 260 return fid; 261 } 262 263 /** 264 * v9fs_fid_lookup - lookup for a fid, try to walk if not found 265 * @dentry: dentry to look for fid in 266 * 267 * Look for a fid in the specified dentry for the current user. 268 * If no fid is found, try to create one walking from a fid from the parent 269 * dentry (if it has one), or the root dentry. If the user haven't accessed 270 * the fs yet, attach now and walk from the root. 271 */ 272 273 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) 274 { 275 kuid_t uid; 276 int any, access; 277 struct v9fs_session_info *v9ses; 278 279 v9ses = v9fs_dentry2v9ses(dentry); 280 access = v9ses->flags & V9FS_ACCESS_MASK; 281 switch (access) { 282 case V9FS_ACCESS_SINGLE: 283 case V9FS_ACCESS_USER: 284 case V9FS_ACCESS_CLIENT: 285 uid = current_fsuid(); 286 any = 0; 287 break; 288 289 case V9FS_ACCESS_ANY: 290 uid = v9ses->uid; 291 any = 1; 292 break; 293 294 default: 295 uid = INVALID_UID; 296 any = 0; 297 break; 298 } 299 return v9fs_fid_lookup_with_uid(dentry, uid, any); 300 } 301 302 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry) 303 { 304 int err; 305 struct p9_fid *fid, *ofid; 306 307 ofid = v9fs_fid_lookup_with_uid(dentry, GLOBAL_ROOT_UID, 0); 308 fid = clone_fid(ofid); 309 if (IS_ERR(fid)) 310 goto error_out; 311 p9_fid_put(ofid); 312 /* 313 * writeback fid will only be used to write back the 314 * dirty pages. We always request for the open fid in read-write 315 * mode so that a partial page write which result in page 316 * read can work. 317 */ 318 err = p9_client_open(fid, O_RDWR); 319 if (err < 0) { 320 p9_fid_put(fid); 321 fid = ERR_PTR(err); 322 goto error_out; 323 } 324 error_out: 325 return fid; 326 } 327