1 /* $NetBSD: tmpfs.h,v 1.32 2008/02/06 11:23:53 jmmv Exp $ */ 2 3 /* 4 * Copyright (c) 2005, 2006, 2007 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Julio M. Merino Vidal, developed as part of Google's Summer of Code 9 * 2005 program. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the NetBSD 22 * Foundation, Inc. and its contributors. 23 * 4. Neither the name of The NetBSD Foundation nor the names of its 24 * contributors may be used to endorse or promote products derived 25 * from this software without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 28 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 30 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 31 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 33 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 37 * POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 #ifndef _FS_TMPFS_TMPFS_H_ 41 #define _FS_TMPFS_TMPFS_H_ 42 43 /* --------------------------------------------------------------------- 44 * KERNEL-SPECIFIC DEFINITIONS 45 * --------------------------------------------------------------------- */ 46 #include <sys/dirent.h> 47 #include <sys/mount.h> 48 #include <sys/queue.h> 49 #include <sys/vnode.h> 50 51 #if defined(_KERNEL) 52 #include <fs/tmpfs/tmpfs_pool.h> 53 #endif /* defined(_KERNEL) */ 54 55 /* --------------------------------------------------------------------- */ 56 57 /* 58 * Internal representation of a tmpfs directory entry. 59 */ 60 struct tmpfs_dirent { 61 TAILQ_ENTRY(tmpfs_dirent) td_entries; 62 63 /* Length of the name stored in this directory entry. This avoids 64 * the need to recalculate it every time the name is used. */ 65 uint16_t td_namelen; 66 67 /* The name of the entry, allocated from a string pool. This 68 * string is not required to be zero-terminated; therefore, the 69 * td_namelen field must always be used when accessing its value. */ 70 char * td_name; 71 72 /* Pointer to the node this entry refers to. */ 73 struct tmpfs_node * td_node; 74 }; 75 76 /* A directory in tmpfs holds a sorted list of directory entries, which in 77 * turn point to other files (which can be directories themselves). 78 * 79 * In tmpfs, this list is managed by a tail queue, whose head is defined by 80 * the struct tmpfs_dir type. 81 * 82 * It is imporant to notice that directories do not have entries for . and 83 * .. as other file systems do. These can be generated when requested 84 * based on information available by other means, such as the pointer to 85 * the node itself in the former case or the pointer to the parent directory 86 * in the latter case. This is done to simplify tmpfs's code and, more 87 * importantly, to remove redundancy. */ 88 TAILQ_HEAD(tmpfs_dir, tmpfs_dirent); 89 90 /* Each entry in a directory has a cookie that identifies it. Cookies 91 * supersede offsets within directories because, given how tmpfs stores 92 * directories in memory, there is no such thing as an offset. (Emulating 93 * a real offset could be very difficult.) 94 * 95 * The '.', '..' and the end of directory markers have fixed cookies which 96 * cannot collide with the cookies generated by other entries. The cookies 97 * fot the other entries are generated based on the memory address on which 98 * stores their information is stored. 99 * 100 * Ideally, using the entry's memory pointer as the cookie would be enough 101 * to represent it and it wouldn't cause collisions in any system. 102 * Unfortunately, this results in "offsets" with very large values which 103 * later raise problems in the Linux compatibility layer (and maybe in other 104 * places) as described in PR kern/32034. Hence we need to workaround this 105 * with a rather ugly hack. 106 * 107 * Linux 32-bit binaries, unless built with _FILE_OFFSET_BITS=64, have off_t 108 * set to 'long', which is a 32-bit *signed* long integer. Regardless of 109 * the macro value, GLIBC (2.3 at least) always uses the getdents64 110 * system call (when calling readdir) which internally returns off64_t 111 * offsets. In order to make 32-bit binaries work, *GLIBC* converts the 112 * 64-bit values returned by the kernel to 32-bit ones and aborts with 113 * EOVERFLOW if the conversion results in values that won't fit in 32-bit 114 * integers (which it assumes is because the directory is extremely large). 115 * This wouldn't cause problems if we were dealing with unsigned integers, 116 * but as we have signed integers, this check fails due to sign expansion. 117 * 118 * For example, consider that the kernel returns the 0xc1234567 cookie to 119 * userspace in a off64_t integer. Later on, GLIBC casts this value to 120 * off_t (remember, signed) with code similar to: 121 * system call returns the offset in kernel_value; 122 * off_t casted_value = kernel_value; 123 * if (sizeof(off_t) != sizeof(off64_t) && 124 * kernel_value != casted_value) 125 * error! 126 * In this case, casted_value still has 0xc1234567, but when it is compared 127 * for equality against kernel_value, it is promoted to a 64-bit integer and 128 * becomes 0xffffffffc1234567, which is different than 0x00000000c1234567. 129 * Then, GLIBC assumes this is because the directory is very large. 130 * 131 * Given that all the above happens in user-space, we have no control over 132 * it; therefore we must workaround the issue here. We do this by 133 * truncating the pointer value to a 32-bit integer and hope that there 134 * won't be collisions. In fact, this will not cause any problems in 135 * 32-bit platforms but some might arise in 64-bit machines (I'm not sure 136 * if they can happen at all in practice). 137 * 138 * XXX A nicer solution shall be attempted. */ 139 #if defined(_KERNEL) 140 #define TMPFS_DIRCOOKIE_DOT 0 141 #define TMPFS_DIRCOOKIE_DOTDOT 1 142 #define TMPFS_DIRCOOKIE_EOF 2 143 static __inline 144 off_t 145 tmpfs_dircookie(struct tmpfs_dirent *de) 146 { 147 off_t cookie; 148 149 cookie = ((off_t)(uintptr_t)de >> 1) & 0x7FFFFFFF; 150 KASSERT(cookie != TMPFS_DIRCOOKIE_DOT); 151 KASSERT(cookie != TMPFS_DIRCOOKIE_DOTDOT); 152 KASSERT(cookie != TMPFS_DIRCOOKIE_EOF); 153 154 return cookie; 155 } 156 #endif /* defined(_KERNEL) */ 157 158 /* --------------------------------------------------------------------- */ 159 160 /* 161 * Internal representation of a tmpfs file system node. 162 * 163 * This structure is splitted in two parts: one holds attributes common 164 * to all file types and the other holds data that is only applicable to 165 * a particular type. The code must be careful to only access those 166 * attributes that are actually allowed by the node's type. 167 */ 168 struct tmpfs_node { 169 /* Doubly-linked list entry which links all existing nodes for a 170 * single file system. This is provided to ease the removal of 171 * all nodes during the unmount operation. */ 172 LIST_ENTRY(tmpfs_node) tn_entries; 173 174 /* The node's type. Any of 'VBLK', 'VCHR', 'VDIR', 'VFIFO', 175 * 'VLNK', 'VREG' and 'VSOCK' is allowed. The usage of vnode 176 * types instead of a custom enumeration is to make things simpler 177 * and faster, as we do not need to convert between two types. */ 178 enum vtype tn_type; 179 180 /* Node identifier. */ 181 ino_t tn_id; 182 183 /* Node's internal status. This is used by several file system 184 * operations to do modifications to the node in a delayed 185 * fashion. */ 186 int tn_status; 187 #define TMPFS_NODE_ACCESSED (1 << 1) 188 #define TMPFS_NODE_MODIFIED (1 << 2) 189 #define TMPFS_NODE_CHANGED (1 << 3) 190 191 /* The node size. It does not necessarily match the real amount 192 * of memory consumed by it. */ 193 off_t tn_size; 194 195 /* Generic node attributes. */ 196 uid_t tn_uid; 197 gid_t tn_gid; 198 mode_t tn_mode; 199 int tn_flags; 200 nlink_t tn_links; 201 struct timespec tn_atime; 202 struct timespec tn_mtime; 203 struct timespec tn_ctime; 204 struct timespec tn_birthtime; 205 unsigned long tn_gen; 206 207 /* Head of byte-level lock list (used by tmpfs_advlock). */ 208 struct lockf * tn_lockf; 209 210 /* As there is a single vnode for each active file within the 211 * system, care has to be taken to avoid allocating more than one 212 * vnode per file. In order to do this, a bidirectional association 213 * is kept between vnodes and nodes. 214 * 215 * Whenever a vnode is allocated, its v_data field is updated to 216 * point to the node it references. At the same time, the node's 217 * tn_vnode field is modified to point to the new vnode representing 218 * it. Further attempts to allocate a vnode for this same node will 219 * result in returning a new reference to the value stored in 220 * tn_vnode. 221 * 222 * May be NULL when the node is unused (that is, no vnode has been 223 * allocated for it or it has been reclaimed). */ 224 kmutex_t tn_vlock; 225 struct vnode * tn_vnode; 226 227 union { 228 /* Valid when tn_type == VBLK || tn_type == VCHR. */ 229 struct { 230 dev_t tn_rdev; 231 } tn_dev; 232 233 /* Valid when tn_type == VDIR. */ 234 struct { 235 /* Pointer to the parent directory. The root 236 * directory has a pointer to itself in this field; 237 * this property identifies the root node. */ 238 struct tmpfs_node * tn_parent; 239 240 /* Head of a tail-queue that links the contents of 241 * the directory together. See above for a 242 * description of its contents. */ 243 struct tmpfs_dir tn_dir; 244 245 /* Number and pointer of the first directory entry 246 * returned by the readdir operation if it were 247 * called again to continue reading data from the 248 * same directory as before. This is used to speed 249 * up reads of long directories, assuming that no 250 * more than one read is in progress at a given time. 251 * Otherwise, these values are discarded and a linear 252 * scan is performed from the beginning up to the 253 * point where readdir starts returning values. */ 254 off_t tn_readdir_lastn; 255 struct tmpfs_dirent * tn_readdir_lastp; 256 } tn_dir; 257 258 /* Valid when tn_type == VLNK. */ 259 struct tn_lnk { 260 /* The link's target, allocated from a string pool. */ 261 char * tn_link; 262 } tn_lnk; 263 264 /* Valid when tn_type == VREG. */ 265 struct tn_reg { 266 /* The contents of regular files stored in a tmpfs 267 * file system are represented by a single anonymous 268 * memory object (aobj, for short). The aobj provides 269 * direct access to any position within the file, 270 * because its contents are always mapped in a 271 * contiguous region of virtual memory. It is a task 272 * of the memory management subsystem (see uvm(9)) to 273 * issue the required page ins or page outs whenever 274 * a position within the file is accessed. */ 275 struct uvm_object * tn_aobj; 276 size_t tn_aobj_pages; 277 } tn_reg; 278 } tn_spec; 279 }; 280 281 #if defined(_KERNEL) 282 283 LIST_HEAD(tmpfs_node_list, tmpfs_node); 284 285 /* --------------------------------------------------------------------- */ 286 287 /* 288 * Internal representation of a tmpfs mount point. 289 */ 290 struct tmpfs_mount { 291 /* Maximum number of memory pages available for use by the file 292 * system, set during mount time. This variable must never be 293 * used directly as it may be bigger than the current amount of 294 * free memory; in the extreme case, it will hold the SIZE_MAX 295 * value. Instead, use the TMPFS_PAGES_MAX macro. */ 296 unsigned int tm_pages_max; 297 298 /* Number of pages in use by the file system. Cannot be bigger 299 * than the value returned by TMPFS_PAGES_MAX in any case. */ 300 unsigned int tm_pages_used; 301 302 /* Pointer to the node representing the root directory of this 303 * file system. */ 304 struct tmpfs_node * tm_root; 305 306 /* Maximum number of possible nodes for this file system; set 307 * during mount time. We need a hard limit on the maximum number 308 * of nodes to avoid allocating too much of them; their objects 309 * cannot be released until the file system is unmounted. 310 * Otherwise, we could easily run out of memory by creating lots 311 * of empty files and then simply removing them. */ 312 unsigned int tm_nodes_max; 313 314 /* Number of nodes currently allocated. This number only grows. 315 * When it reaches tm_nodes_max, no more new nodes can be allocated. 316 * Of course, the old, unused ones can be reused. */ 317 unsigned int tm_nodes_cnt; 318 319 /* Node list. */ 320 kmutex_t tm_lock; 321 struct tmpfs_node_list tm_nodes; 322 323 /* Pools used to store file system meta data. These are not shared 324 * across several instances of tmpfs for the reasons described in 325 * tmpfs_pool.c. */ 326 struct tmpfs_pool tm_dirent_pool; 327 struct tmpfs_pool tm_node_pool; 328 struct tmpfs_str_pool tm_str_pool; 329 }; 330 331 /* --------------------------------------------------------------------- */ 332 333 /* 334 * This structure maps a file identifier to a tmpfs node. Used by the 335 * NFS code. 336 */ 337 struct tmpfs_fid { 338 uint16_t tf_len; 339 uint16_t tf_pad; 340 uint32_t tf_gen; 341 ino_t tf_id; 342 }; 343 344 /* --------------------------------------------------------------------- */ 345 346 /* 347 * Prototypes for tmpfs_subr.c. 348 */ 349 350 int tmpfs_alloc_node(struct tmpfs_mount *, enum vtype, 351 uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *, 352 char *, dev_t, struct tmpfs_node **); 353 void tmpfs_free_node(struct tmpfs_mount *, struct tmpfs_node *); 354 int tmpfs_alloc_dirent(struct tmpfs_mount *, struct tmpfs_node *, 355 const char *, uint16_t, struct tmpfs_dirent **); 356 void tmpfs_free_dirent(struct tmpfs_mount *, struct tmpfs_dirent *, 357 bool); 358 int tmpfs_alloc_vp(struct mount *, struct tmpfs_node *, struct vnode **); 359 void tmpfs_free_vp(struct vnode *); 360 int tmpfs_alloc_file(struct vnode *, struct vnode **, struct vattr *, 361 struct componentname *, char *); 362 void tmpfs_dir_attach(struct vnode *, struct tmpfs_dirent *); 363 void tmpfs_dir_detach(struct vnode *, struct tmpfs_dirent *); 364 struct tmpfs_dirent * tmpfs_dir_lookup(struct tmpfs_node *node, 365 struct componentname *cnp); 366 int tmpfs_dir_getdotdent(struct tmpfs_node *, struct uio *); 367 int tmpfs_dir_getdotdotdent(struct tmpfs_node *, struct uio *); 368 struct tmpfs_dirent * tmpfs_dir_lookupbycookie(struct tmpfs_node *, off_t); 369 int tmpfs_dir_getdents(struct tmpfs_node *, struct uio *, off_t *); 370 int tmpfs_reg_resize(struct vnode *, off_t); 371 size_t tmpfs_mem_info(bool); 372 int tmpfs_chflags(struct vnode *, int, kauth_cred_t, struct lwp *); 373 int tmpfs_chmod(struct vnode *, mode_t, kauth_cred_t, struct lwp *); 374 int tmpfs_chown(struct vnode *, uid_t, gid_t, kauth_cred_t, struct lwp *); 375 int tmpfs_chsize(struct vnode *, u_quad_t, kauth_cred_t, struct lwp *); 376 int tmpfs_chtimes(struct vnode *, struct timespec *, struct timespec *, 377 int, kauth_cred_t, struct lwp *); 378 void tmpfs_itimes(struct vnode *, const struct timespec *, 379 const struct timespec *); 380 381 void tmpfs_update(struct vnode *, const struct timespec *, 382 const struct timespec *, int); 383 int tmpfs_truncate(struct vnode *, off_t); 384 385 /* --------------------------------------------------------------------- */ 386 387 /* 388 * Convenience macros to simplify some logical expressions. 389 */ 390 #define IMPLIES(a, b) (!(a) || (b)) 391 #define IFF(a, b) (IMPLIES(a, b) && IMPLIES(b, a)) 392 393 /* --------------------------------------------------------------------- */ 394 395 /* 396 * Checks that the directory entry pointed by 'de' matches the name 'name' 397 * with a length of 'len'. 398 */ 399 #define TMPFS_DIRENT_MATCHES(de, name, len) \ 400 (de->td_namelen == (uint16_t)len && \ 401 memcmp((de)->td_name, (name), (de)->td_namelen) == 0) 402 403 /* --------------------------------------------------------------------- */ 404 405 /* 406 * Ensures that the node pointed by 'node' is a directory and that its 407 * contents are consistent with respect to directories. 408 */ 409 #define TMPFS_VALIDATE_DIR(node) \ 410 KASSERT((node)->tn_type == VDIR); \ 411 KASSERT((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \ 412 KASSERT((node)->tn_spec.tn_dir.tn_readdir_lastp == NULL || \ 413 tmpfs_dircookie((node)->tn_spec.tn_dir.tn_readdir_lastp) == \ 414 (node)->tn_spec.tn_dir.tn_readdir_lastn); 415 416 /* --------------------------------------------------------------------- */ 417 418 /* 419 * Memory management stuff. 420 */ 421 422 /* Amount of memory pages to reserve for the system (e.g., to not use by 423 * tmpfs). 424 * XXX: Should this be tunable through sysctl, for instance? */ 425 #define TMPFS_PAGES_RESERVED (4 * 1024 * 1024 / PAGE_SIZE) 426 427 /* Returns the maximum size allowed for a tmpfs file system. This macro 428 * must be used instead of directly retrieving the value from tm_pages_max. 429 * The reason is that the size of a tmpfs file system is dynamic: it lets 430 * the user store files as long as there is enough free memory (including 431 * physical memory and swap space). Therefore, the amount of memory to be 432 * used is either the limit imposed by the user during mount time or the 433 * amount of available memory, whichever is lower. To avoid consuming all 434 * the memory for a given mount point, the system will always reserve a 435 * minimum of TMPFS_PAGES_RESERVED pages, which is also taken into account 436 * by this macro (see above). */ 437 static __inline size_t 438 TMPFS_PAGES_MAX(struct tmpfs_mount *tmp) 439 { 440 size_t freepages; 441 442 freepages = tmpfs_mem_info(false); 443 if (freepages < TMPFS_PAGES_RESERVED) 444 freepages = 0; 445 else 446 freepages -= TMPFS_PAGES_RESERVED; 447 448 return MIN(tmp->tm_pages_max, freepages + tmp->tm_pages_used); 449 } 450 451 /* Returns the available space for the given file system. */ 452 #define TMPFS_PAGES_AVAIL(tmp) \ 453 ((ssize_t)(TMPFS_PAGES_MAX(tmp) - (tmp)->tm_pages_used)) 454 455 /* --------------------------------------------------------------------- */ 456 457 /* 458 * Macros/functions to convert from generic data structures to tmpfs 459 * specific ones. 460 */ 461 462 static __inline 463 struct tmpfs_mount * 464 VFS_TO_TMPFS(struct mount *mp) 465 { 466 struct tmpfs_mount *tmp; 467 468 #ifdef KASSERT 469 KASSERT((mp) != NULL && (mp)->mnt_data != NULL); 470 #endif 471 tmp = (struct tmpfs_mount *)(mp)->mnt_data; 472 return tmp; 473 } 474 475 #endif /* defined(_KERNEL) */ 476 477 static __inline 478 struct tmpfs_node * 479 VP_TO_TMPFS_NODE(struct vnode *vp) 480 { 481 struct tmpfs_node *node; 482 483 #ifdef KASSERT 484 KASSERT((vp) != NULL && (vp)->v_data != NULL); 485 #endif 486 node = (struct tmpfs_node *)vp->v_data; 487 return node; 488 } 489 490 #if defined(_KERNEL) 491 492 static __inline 493 struct tmpfs_node * 494 VP_TO_TMPFS_DIR(struct vnode *vp) 495 { 496 struct tmpfs_node *node; 497 498 node = VP_TO_TMPFS_NODE(vp); 499 #ifdef KASSERT 500 TMPFS_VALIDATE_DIR(node); 501 #endif 502 return node; 503 } 504 505 #endif /* defined(_KERNEL) */ 506 507 /* --------------------------------------------------------------------- 508 * USER AND KERNEL DEFINITIONS 509 * --------------------------------------------------------------------- */ 510 511 /* 512 * This structure is used to communicate mount parameters between userland 513 * and kernel space. 514 */ 515 #define TMPFS_ARGS_VERSION 1 516 struct tmpfs_args { 517 int ta_version; 518 519 /* Size counters. */ 520 ino_t ta_nodes_max; 521 off_t ta_size_max; 522 523 /* Root node attributes. */ 524 uid_t ta_root_uid; 525 gid_t ta_root_gid; 526 mode_t ta_root_mode; 527 }; 528 #endif /* _FS_TMPFS_TMPFS_H_ */ 529