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 <linux/idr.h> 15 #include <net/9p/9p.h> 16 #include <net/9p/client.h> 17 18 #include "v9fs.h" 19 #include "v9fs_vfs.h" 20 #include "fid.h" 21 22 static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid) 23 { 24 hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata); 25 } 26 27 28 /** 29 * v9fs_fid_add - add a fid to a dentry 30 * @dentry: dentry that the fid is being added to 31 * @pfid: fid to add, NULLed out 32 * 33 */ 34 void v9fs_fid_add(struct dentry *dentry, struct p9_fid **pfid) 35 { 36 struct p9_fid *fid = *pfid; 37 38 spin_lock(&dentry->d_lock); 39 __add_fid(dentry, fid); 40 spin_unlock(&dentry->d_lock); 41 42 *pfid = NULL; 43 } 44 45 /** 46 * v9fs_fid_find_inode - search for an open fid off of the inode list 47 * @inode: return a fid pointing to a specific inode 48 * @uid: return a fid belonging to the specified user 49 * 50 */ 51 52 static struct p9_fid *v9fs_fid_find_inode(struct inode *inode, kuid_t uid) 53 { 54 struct hlist_head *h; 55 struct p9_fid *fid, *ret = NULL; 56 57 p9_debug(P9_DEBUG_VFS, " inode: %p\n", inode); 58 59 spin_lock(&inode->i_lock); 60 h = (struct hlist_head *)&inode->i_private; 61 hlist_for_each_entry(fid, h, ilist) { 62 if (uid_eq(fid->uid, uid)) { 63 p9_fid_get(fid); 64 ret = fid; 65 break; 66 } 67 } 68 spin_unlock(&inode->i_lock); 69 return ret; 70 } 71 72 /** 73 * v9fs_open_fid_add - add an open fid to an inode 74 * @inode: inode that the fid is being added to 75 * @pfid: fid to add, NULLed out 76 * 77 */ 78 79 void v9fs_open_fid_add(struct inode *inode, struct p9_fid **pfid) 80 { 81 struct p9_fid *fid = *pfid; 82 83 spin_lock(&inode->i_lock); 84 hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private); 85 spin_unlock(&inode->i_lock); 86 87 *pfid = NULL; 88 } 89 90 91 /** 92 * v9fs_fid_find - retrieve a fid that belongs to the specified uid 93 * @dentry: dentry to look for fid in 94 * @uid: return fid that belongs to the specified user 95 * @any: if non-zero, return any fid associated with the dentry 96 * 97 */ 98 99 static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any) 100 { 101 struct p9_fid *fid, *ret; 102 103 p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n", 104 dentry, dentry, from_kuid(&init_user_ns, uid), 105 any); 106 ret = NULL; 107 /* we'll recheck under lock if there's anything to look in */ 108 if (dentry->d_fsdata) { 109 struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata; 110 111 spin_lock(&dentry->d_lock); 112 hlist_for_each_entry(fid, h, dlist) { 113 if (any || uid_eq(fid->uid, uid)) { 114 ret = fid; 115 p9_fid_get(ret); 116 break; 117 } 118 } 119 spin_unlock(&dentry->d_lock); 120 } else { 121 if (dentry->d_inode) 122 ret = v9fs_fid_find_inode(dentry->d_inode, uid); 123 } 124 125 return ret; 126 } 127 128 /* 129 * We need to hold v9ses->rename_sem as long as we hold references 130 * to returned path array. Array element contain pointers to 131 * dentry names. 132 */ 133 static int build_path_from_dentry(struct v9fs_session_info *v9ses, 134 struct dentry *dentry, const unsigned char ***names) 135 { 136 int n = 0, i; 137 const unsigned char **wnames; 138 struct dentry *ds; 139 140 for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent) 141 n++; 142 143 wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL); 144 if (!wnames) 145 goto err_out; 146 147 for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent) 148 wnames[i] = ds->d_name.name; 149 150 *names = wnames; 151 return n; 152 err_out: 153 return -ENOMEM; 154 } 155 156 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry, 157 kuid_t uid, int any) 158 { 159 struct dentry *ds; 160 const unsigned char **wnames, *uname; 161 int i, n, l, access; 162 struct v9fs_session_info *v9ses; 163 struct p9_fid *fid, *root_fid, *old_fid; 164 165 v9ses = v9fs_dentry2v9ses(dentry); 166 access = v9ses->flags & V9FS_ACCESS_MASK; 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 old_fid = fid; 181 182 fid = p9_client_walk(old_fid, 1, &dentry->d_name.name, 1); 183 p9_fid_put(old_fid); 184 goto fid_out; 185 } 186 up_read(&v9ses->rename_sem); 187 188 /* start from the root and try to do a lookup */ 189 root_fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any); 190 if (!root_fid) { 191 /* the user is not attached to the fs yet */ 192 if (access == V9FS_ACCESS_SINGLE) 193 return ERR_PTR(-EPERM); 194 195 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses)) 196 uname = NULL; 197 else 198 uname = v9ses->uname; 199 200 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid, 201 v9ses->aname); 202 if (IS_ERR(fid)) 203 return fid; 204 205 root_fid = p9_fid_get(fid); 206 v9fs_fid_add(dentry->d_sb->s_root, &fid); 207 } 208 /* If we are root ourself just return that */ 209 if (dentry->d_sb->s_root == dentry) 210 return root_fid; 211 212 /* 213 * Do a multipath walk with attached root. 214 * When walking parent we need to make sure we 215 * don't have a parallel rename happening 216 */ 217 down_read(&v9ses->rename_sem); 218 n = build_path_from_dentry(v9ses, dentry, &wnames); 219 if (n < 0) { 220 fid = ERR_PTR(n); 221 goto err_out; 222 } 223 fid = root_fid; 224 old_fid = root_fid; 225 i = 0; 226 while (i < n) { 227 l = min(n - i, P9_MAXWELEM); 228 /* 229 * We need to hold rename lock when doing a multipath 230 * walk to ensure none of the path components change 231 */ 232 fid = p9_client_walk(old_fid, l, &wnames[i], 233 old_fid == root_fid /* clone */); 234 /* non-cloning walk will return the same fid */ 235 if (fid != old_fid) { 236 p9_fid_put(old_fid); 237 old_fid = fid; 238 } 239 if (IS_ERR(fid)) { 240 kfree(wnames); 241 goto err_out; 242 } 243 i += l; 244 } 245 kfree(wnames); 246 fid_out: 247 if (!IS_ERR(fid)) { 248 spin_lock(&dentry->d_lock); 249 if (d_unhashed(dentry)) { 250 spin_unlock(&dentry->d_lock); 251 p9_fid_put(fid); 252 fid = ERR_PTR(-ENOENT); 253 } else { 254 __add_fid(dentry, fid); 255 p9_fid_get(fid); 256 spin_unlock(&dentry->d_lock); 257 } 258 } 259 err_out: 260 up_read(&v9ses->rename_sem); 261 return fid; 262 } 263 264 /** 265 * v9fs_fid_lookup - lookup for a fid, try to walk if not found 266 * @dentry: dentry to look for fid in 267 * 268 * Look for a fid in the specified dentry for the current user. 269 * If no fid is found, try to create one walking from a fid from the parent 270 * dentry (if it has one), or the root dentry. If the user haven't accessed 271 * the fs yet, attach now and walk from the root. 272 */ 273 274 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) 275 { 276 kuid_t uid; 277 int any, access; 278 struct v9fs_session_info *v9ses; 279 280 v9ses = v9fs_dentry2v9ses(dentry); 281 access = v9ses->flags & V9FS_ACCESS_MASK; 282 switch (access) { 283 case V9FS_ACCESS_SINGLE: 284 case V9FS_ACCESS_USER: 285 case V9FS_ACCESS_CLIENT: 286 uid = current_fsuid(); 287 any = 0; 288 break; 289 290 case V9FS_ACCESS_ANY: 291 uid = v9ses->uid; 292 any = 1; 293 break; 294 295 default: 296 uid = INVALID_UID; 297 any = 0; 298 break; 299 } 300 return v9fs_fid_lookup_with_uid(dentry, uid, any); 301 } 302 303 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry) 304 { 305 int err; 306 struct p9_fid *fid, *ofid; 307 308 ofid = v9fs_fid_lookup_with_uid(dentry, GLOBAL_ROOT_UID, 0); 309 fid = clone_fid(ofid); 310 if (IS_ERR(fid)) 311 goto error_out; 312 p9_fid_put(ofid); 313 /* 314 * writeback fid will only be used to write back the 315 * dirty pages. We always request for the open fid in read-write 316 * mode so that a partial page write which result in page 317 * read can work. 318 */ 319 err = p9_client_open(fid, O_RDWR); 320 if (err < 0) { 321 p9_fid_put(fid); 322 fid = ERR_PTR(err); 323 goto error_out; 324 } 325 error_out: 326 return fid; 327 } 328