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; 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 refcount_inc(&fid->count); 198 v9fs_fid_add(dentry->d_sb->s_root, fid); 199 } 200 /* If we are root ourself just return that */ 201 if (dentry->d_sb->s_root == dentry) 202 return fid; 203 /* 204 * Do a multipath walk with attached root. 205 * When walking parent we need to make sure we 206 * don't have a parallel rename happening 207 */ 208 down_read(&v9ses->rename_sem); 209 n = build_path_from_dentry(v9ses, dentry, &wnames); 210 if (n < 0) { 211 fid = ERR_PTR(n); 212 goto err_out; 213 } 214 old_fid = fid; 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 /* non-cloning walk will return the same fid */ 225 if (fid != old_fid) { 226 p9_client_clunk(old_fid); 227 old_fid = fid; 228 } 229 if (IS_ERR(fid)) { 230 kfree(wnames); 231 goto err_out; 232 } 233 i += l; 234 clone = 0; 235 } 236 kfree(wnames); 237 fid_out: 238 if (!IS_ERR(fid)) { 239 spin_lock(&dentry->d_lock); 240 if (d_unhashed(dentry)) { 241 spin_unlock(&dentry->d_lock); 242 p9_client_clunk(fid); 243 fid = ERR_PTR(-ENOENT); 244 } else { 245 __add_fid(dentry, fid); 246 refcount_inc(&fid->count); 247 spin_unlock(&dentry->d_lock); 248 } 249 } 250 err_out: 251 up_read(&v9ses->rename_sem); 252 return fid; 253 } 254 255 /** 256 * v9fs_fid_lookup - lookup for a fid, try to walk if not found 257 * @dentry: dentry to look for fid in 258 * 259 * Look for a fid in the specified dentry for the current user. 260 * If no fid is found, try to create one walking from a fid from the parent 261 * dentry (if it has one), or the root dentry. If the user haven't accessed 262 * the fs yet, attach now and walk from the root. 263 */ 264 265 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) 266 { 267 kuid_t uid; 268 int any, access; 269 struct v9fs_session_info *v9ses; 270 271 v9ses = v9fs_dentry2v9ses(dentry); 272 access = v9ses->flags & V9FS_ACCESS_MASK; 273 switch (access) { 274 case V9FS_ACCESS_SINGLE: 275 case V9FS_ACCESS_USER: 276 case V9FS_ACCESS_CLIENT: 277 uid = current_fsuid(); 278 any = 0; 279 break; 280 281 case V9FS_ACCESS_ANY: 282 uid = v9ses->uid; 283 any = 1; 284 break; 285 286 default: 287 uid = INVALID_UID; 288 any = 0; 289 break; 290 } 291 return v9fs_fid_lookup_with_uid(dentry, uid, any); 292 } 293 294 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry) 295 { 296 int err; 297 struct p9_fid *fid, *ofid; 298 299 ofid = v9fs_fid_lookup_with_uid(dentry, GLOBAL_ROOT_UID, 0); 300 fid = clone_fid(ofid); 301 if (IS_ERR(fid)) 302 goto error_out; 303 p9_client_clunk(ofid); 304 /* 305 * writeback fid will only be used to write back the 306 * dirty pages. We always request for the open fid in read-write 307 * mode so that a partial page write which result in page 308 * read can work. 309 */ 310 err = p9_client_open(fid, O_RDWR); 311 if (err < 0) { 312 p9_client_clunk(fid); 313 fid = ERR_PTR(err); 314 goto error_out; 315 } 316 error_out: 317 return fid; 318 } 319