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 * @fid: fid to add 32 * 33 */ 34 void v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid) 35 { 36 spin_lock(&dentry->d_lock); 37 __add_fid(dentry, fid); 38 spin_unlock(&dentry->d_lock); 39 } 40 41 /** 42 * v9fs_fid_find_inode - search for an open fid off of the inode list 43 * @inode: return a fid pointing to a specific inode 44 * @uid: return a fid belonging to the specified user 45 * 46 */ 47 48 static struct p9_fid *v9fs_fid_find_inode(struct inode *inode, kuid_t uid) 49 { 50 struct hlist_head *h; 51 struct p9_fid *fid, *ret = NULL; 52 53 p9_debug(P9_DEBUG_VFS, " inode: %p\n", inode); 54 55 spin_lock(&inode->i_lock); 56 h = (struct hlist_head *)&inode->i_private; 57 hlist_for_each_entry(fid, h, ilist) { 58 if (uid_eq(fid->uid, uid)) { 59 refcount_inc(&fid->count); 60 ret = fid; 61 break; 62 } 63 } 64 spin_unlock(&inode->i_lock); 65 return ret; 66 } 67 68 /** 69 * v9fs_open_fid_add - add an open fid to an inode 70 * @inode: inode that the fid is being added to 71 * @fid: fid to add 72 * 73 */ 74 75 void v9fs_open_fid_add(struct inode *inode, struct p9_fid *fid) 76 { 77 spin_lock(&inode->i_lock); 78 hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private); 79 spin_unlock(&inode->i_lock); 80 } 81 82 83 /** 84 * v9fs_fid_find - retrieve a fid that belongs to the specified uid 85 * @dentry: dentry to look for fid in 86 * @uid: return fid that belongs to the specified user 87 * @any: if non-zero, return any fid associated with the dentry 88 * 89 */ 90 91 static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any) 92 { 93 struct p9_fid *fid, *ret; 94 95 p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n", 96 dentry, dentry, from_kuid(&init_user_ns, uid), 97 any); 98 ret = NULL; 99 /* we'll recheck under lock if there's anything to look in */ 100 if (dentry->d_fsdata) { 101 struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata; 102 103 spin_lock(&dentry->d_lock); 104 hlist_for_each_entry(fid, h, dlist) { 105 if (any || uid_eq(fid->uid, uid)) { 106 ret = fid; 107 refcount_inc(&ret->count); 108 break; 109 } 110 } 111 spin_unlock(&dentry->d_lock); 112 } else { 113 if (dentry->d_inode) 114 ret = v9fs_fid_find_inode(dentry->d_inode, uid); 115 } 116 117 return ret; 118 } 119 120 /* 121 * We need to hold v9ses->rename_sem as long as we hold references 122 * to returned path array. Array element contain pointers to 123 * dentry names. 124 */ 125 static int build_path_from_dentry(struct v9fs_session_info *v9ses, 126 struct dentry *dentry, const unsigned char ***names) 127 { 128 int n = 0, i; 129 const unsigned char **wnames; 130 struct dentry *ds; 131 132 for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent) 133 n++; 134 135 wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL); 136 if (!wnames) 137 goto err_out; 138 139 for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent) 140 wnames[i] = ds->d_name.name; 141 142 *names = wnames; 143 return n; 144 err_out: 145 return -ENOMEM; 146 } 147 148 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry, 149 kuid_t uid, int any) 150 { 151 struct dentry *ds; 152 const unsigned char **wnames, *uname; 153 int i, n, l, clone, access; 154 struct v9fs_session_info *v9ses; 155 struct p9_fid *fid, *old_fid = NULL; 156 157 v9ses = v9fs_dentry2v9ses(dentry); 158 access = v9ses->flags & V9FS_ACCESS_MASK; 159 fid = v9fs_fid_find(dentry, uid, any); 160 if (fid) 161 return fid; 162 /* 163 * we don't have a matching fid. To do a TWALK we need 164 * parent fid. We need to prevent rename when we want to 165 * look at the parent. 166 */ 167 down_read(&v9ses->rename_sem); 168 ds = dentry->d_parent; 169 fid = v9fs_fid_find(ds, uid, any); 170 if (fid) { 171 /* Found the parent fid do a lookup with that */ 172 struct p9_fid *ofid = fid; 173 174 fid = p9_client_walk(ofid, 1, &dentry->d_name.name, 1); 175 p9_client_clunk(ofid); 176 goto fid_out; 177 } 178 up_read(&v9ses->rename_sem); 179 180 /* start from the root and try to do a lookup */ 181 fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any); 182 if (!fid) { 183 /* the user is not attached to the fs yet */ 184 if (access == V9FS_ACCESS_SINGLE) 185 return ERR_PTR(-EPERM); 186 187 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses)) 188 uname = NULL; 189 else 190 uname = v9ses->uname; 191 192 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid, 193 v9ses->aname); 194 if (IS_ERR(fid)) 195 return fid; 196 197 v9fs_fid_add(dentry->d_sb->s_root, fid); 198 } 199 /* If we are root ourself just return that */ 200 if (dentry->d_sb->s_root == dentry) { 201 refcount_inc(&fid->count); 202 return fid; 203 } 204 /* 205 * Do a multipath walk with attached root. 206 * When walking parent we need to make sure we 207 * don't have a parallel rename happening 208 */ 209 down_read(&v9ses->rename_sem); 210 n = build_path_from_dentry(v9ses, dentry, &wnames); 211 if (n < 0) { 212 fid = ERR_PTR(n); 213 goto err_out; 214 } 215 clone = 1; 216 i = 0; 217 while (i < n) { 218 l = min(n - i, P9_MAXWELEM); 219 /* 220 * We need to hold rename lock when doing a multipath 221 * walk to ensure none of the patch component change 222 */ 223 fid = p9_client_walk(fid, l, &wnames[i], clone); 224 if (IS_ERR(fid)) { 225 if (old_fid) { 226 /* 227 * If we fail, clunk fid which are mapping 228 * to path component and not the last component 229 * of the path. 230 */ 231 p9_client_clunk(old_fid); 232 } 233 kfree(wnames); 234 goto err_out; 235 } 236 old_fid = fid; 237 i += l; 238 clone = 0; 239 } 240 kfree(wnames); 241 fid_out: 242 if (!IS_ERR(fid)) { 243 spin_lock(&dentry->d_lock); 244 if (d_unhashed(dentry)) { 245 spin_unlock(&dentry->d_lock); 246 p9_client_clunk(fid); 247 fid = ERR_PTR(-ENOENT); 248 } else { 249 __add_fid(dentry, fid); 250 refcount_inc(&fid->count); 251 spin_unlock(&dentry->d_lock); 252 } 253 } 254 err_out: 255 up_read(&v9ses->rename_sem); 256 return fid; 257 } 258 259 /** 260 * v9fs_fid_lookup - lookup for a fid, try to walk if not found 261 * @dentry: dentry to look for fid in 262 * 263 * Look for a fid in the specified dentry for the current user. 264 * If no fid is found, try to create one walking from a fid from the parent 265 * dentry (if it has one), or the root dentry. If the user haven't accessed 266 * the fs yet, attach now and walk from the root. 267 */ 268 269 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) 270 { 271 kuid_t uid; 272 int any, access; 273 struct v9fs_session_info *v9ses; 274 275 v9ses = v9fs_dentry2v9ses(dentry); 276 access = v9ses->flags & V9FS_ACCESS_MASK; 277 switch (access) { 278 case V9FS_ACCESS_SINGLE: 279 case V9FS_ACCESS_USER: 280 case V9FS_ACCESS_CLIENT: 281 uid = current_fsuid(); 282 any = 0; 283 break; 284 285 case V9FS_ACCESS_ANY: 286 uid = v9ses->uid; 287 any = 1; 288 break; 289 290 default: 291 uid = INVALID_UID; 292 any = 0; 293 break; 294 } 295 return v9fs_fid_lookup_with_uid(dentry, uid, any); 296 } 297 298 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry) 299 { 300 int err; 301 struct p9_fid *fid, *ofid; 302 303 ofid = v9fs_fid_lookup_with_uid(dentry, GLOBAL_ROOT_UID, 0); 304 fid = clone_fid(ofid); 305 if (IS_ERR(fid)) 306 goto error_out; 307 p9_client_clunk(ofid); 308 /* 309 * writeback fid will only be used to write back the 310 * dirty pages. We always request for the open fid in read-write 311 * mode so that a partial page write which result in page 312 * read can work. 313 */ 314 err = p9_client_open(fid, O_RDWR); 315 if (err < 0) { 316 p9_client_clunk(fid); 317 fid = ERR_PTR(err); 318 goto error_out; 319 } 320 error_out: 321 return fid; 322 } 323