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; 99 100 if (d_inode(dentry)) 101 ret = v9fs_fid_find_inode(d_inode(dentry), uid); 102 103 /* we'll recheck under lock if there's anything to look in */ 104 if (!ret && dentry->d_fsdata) { 105 struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata; 106 107 spin_lock(&dentry->d_lock); 108 hlist_for_each_entry(fid, h, dlist) { 109 if (any || uid_eq(fid->uid, uid)) { 110 ret = fid; 111 refcount_inc(&ret->count); 112 break; 113 } 114 } 115 spin_unlock(&dentry->d_lock); 116 } 117 118 return ret; 119 } 120 121 /* 122 * We need to hold v9ses->rename_sem as long as we hold references 123 * to returned path array. Array element contain pointers to 124 * dentry names. 125 */ 126 static int build_path_from_dentry(struct v9fs_session_info *v9ses, 127 struct dentry *dentry, const unsigned char ***names) 128 { 129 int n = 0, i; 130 const unsigned char **wnames; 131 struct dentry *ds; 132 133 for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent) 134 n++; 135 136 wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL); 137 if (!wnames) 138 goto err_out; 139 140 for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent) 141 wnames[i] = ds->d_name.name; 142 143 *names = wnames; 144 return n; 145 err_out: 146 return -ENOMEM; 147 } 148 149 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry, 150 kuid_t uid, int any) 151 { 152 struct dentry *ds; 153 const unsigned char **wnames, *uname; 154 int i, n, l, clone, access; 155 struct v9fs_session_info *v9ses; 156 struct p9_fid *fid, *old_fid = NULL; 157 158 v9ses = v9fs_dentry2v9ses(dentry); 159 access = v9ses->flags & V9FS_ACCESS_MASK; 160 fid = v9fs_fid_find(dentry, uid, any); 161 if (fid) 162 return fid; 163 /* 164 * we don't have a matching fid. To do a TWALK we need 165 * parent fid. We need to prevent rename when we want to 166 * look at the parent. 167 */ 168 down_read(&v9ses->rename_sem); 169 ds = dentry->d_parent; 170 fid = v9fs_fid_find(ds, uid, any); 171 if (fid) { 172 /* Found the parent fid do a lookup with that */ 173 struct p9_fid *ofid = fid; 174 175 fid = p9_client_walk(ofid, 1, &dentry->d_name.name, 1); 176 p9_client_clunk(ofid); 177 goto fid_out; 178 } 179 up_read(&v9ses->rename_sem); 180 181 /* start from the root and try to do a lookup */ 182 fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any); 183 if (!fid) { 184 /* the user is not attached to the fs yet */ 185 if (access == V9FS_ACCESS_SINGLE) 186 return ERR_PTR(-EPERM); 187 188 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses)) 189 uname = NULL; 190 else 191 uname = v9ses->uname; 192 193 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid, 194 v9ses->aname); 195 if (IS_ERR(fid)) 196 return fid; 197 198 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 refcount_inc(&fid->count); 203 return fid; 204 } 205 /* 206 * Do a multipath walk with attached root. 207 * When walking parent we need to make sure we 208 * don't have a parallel rename happening 209 */ 210 down_read(&v9ses->rename_sem); 211 n = build_path_from_dentry(v9ses, dentry, &wnames); 212 if (n < 0) { 213 fid = ERR_PTR(n); 214 goto err_out; 215 } 216 clone = 1; 217 i = 0; 218 while (i < n) { 219 l = min(n - i, P9_MAXWELEM); 220 /* 221 * We need to hold rename lock when doing a multipath 222 * walk to ensure none of the patch component change 223 */ 224 fid = p9_client_walk(fid, l, &wnames[i], clone); 225 if (IS_ERR(fid)) { 226 if (old_fid) { 227 /* 228 * If we fail, clunk fid which are mapping 229 * to path component and not the last component 230 * of the path. 231 */ 232 p9_client_clunk(old_fid); 233 } 234 kfree(wnames); 235 goto err_out; 236 } 237 old_fid = fid; 238 i += l; 239 clone = 0; 240 } 241 kfree(wnames); 242 fid_out: 243 if (!IS_ERR(fid)) { 244 spin_lock(&dentry->d_lock); 245 if (d_unhashed(dentry)) { 246 spin_unlock(&dentry->d_lock); 247 p9_client_clunk(fid); 248 fid = ERR_PTR(-ENOENT); 249 } else { 250 __add_fid(dentry, fid); 251 refcount_inc(&fid->count); 252 spin_unlock(&dentry->d_lock); 253 } 254 } 255 err_out: 256 up_read(&v9ses->rename_sem); 257 return fid; 258 } 259 260 /** 261 * v9fs_fid_lookup - lookup for a fid, try to walk if not found 262 * @dentry: dentry to look for fid in 263 * 264 * Look for a fid in the specified dentry for the current user. 265 * If no fid is found, try to create one walking from a fid from the parent 266 * dentry (if it has one), or the root dentry. If the user haven't accessed 267 * the fs yet, attach now and walk from the root. 268 */ 269 270 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) 271 { 272 kuid_t uid; 273 int any, access; 274 struct v9fs_session_info *v9ses; 275 276 v9ses = v9fs_dentry2v9ses(dentry); 277 access = v9ses->flags & V9FS_ACCESS_MASK; 278 switch (access) { 279 case V9FS_ACCESS_SINGLE: 280 case V9FS_ACCESS_USER: 281 case V9FS_ACCESS_CLIENT: 282 uid = current_fsuid(); 283 any = 0; 284 break; 285 286 case V9FS_ACCESS_ANY: 287 uid = v9ses->uid; 288 any = 1; 289 break; 290 291 default: 292 uid = INVALID_UID; 293 any = 0; 294 break; 295 } 296 return v9fs_fid_lookup_with_uid(dentry, uid, any); 297 } 298 299 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry) 300 { 301 int err; 302 struct p9_fid *fid, *ofid; 303 304 ofid = v9fs_fid_lookup_with_uid(dentry, GLOBAL_ROOT_UID, 0); 305 fid = clone_fid(ofid); 306 if (IS_ERR(fid)) 307 goto error_out; 308 p9_client_clunk(ofid); 309 /* 310 * writeback fid will only be used to write back the 311 * dirty pages. We always request for the open fid in read-write 312 * mode so that a partial page write which result in page 313 * read can work. 314 */ 315 err = p9_client_open(fid, O_RDWR); 316 if (err < 0) { 317 p9_client_clunk(fid); 318 fid = ERR_PTR(err); 319 goto error_out; 320 } 321 error_out: 322 return fid; 323 } 324