tmpfs.h revision 1.28.2.3 1 /* $NetBSD: tmpfs.h,v 1.28.2.3 2007/12/12 17:33:14 ad 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 /* Pointer to the node returned by tmpfs_lookup() after doing a
228 * delete or a rename lookup; its value is only valid in these two
229 * situations. In case we were looking up . or .., it holds a null
230 * pointer. */
231 struct tmpfs_dirent * tn_lookup_dirent;
232
233 union {
234 /* Valid when tn_type == VBLK || tn_type == VCHR. */
235 struct {
236 dev_t tn_rdev;
237 } tn_dev;
238
239 /* Valid when tn_type == VDIR. */
240 struct {
241 /* Pointer to the parent directory. The root
242 * directory has a pointer to itself in this field;
243 * this property identifies the root node. */
244 struct tmpfs_node * tn_parent;
245
246 /* Head of a tail-queue that links the contents of
247 * the directory together. See above for a
248 * description of its contents. */
249 struct tmpfs_dir tn_dir;
250
251 /* Number and pointer of the first directory entry
252 * returned by the readdir operation if it were
253 * called again to continue reading data from the
254 * same directory as before. This is used to speed
255 * up reads of long directories, assuming that no
256 * more than one read is in progress at a given time.
257 * Otherwise, these values are discarded and a linear
258 * scan is performed from the beginning up to the
259 * point where readdir starts returning values. */
260 off_t tn_readdir_lastn;
261 struct tmpfs_dirent * tn_readdir_lastp;
262 } tn_dir;
263
264 /* Valid when tn_type == VLNK. */
265 struct tn_lnk {
266 /* The link's target, allocated from a string pool. */
267 char * tn_link;
268 } tn_lnk;
269
270 /* Valid when tn_type == VREG. */
271 struct tn_reg {
272 /* The contents of regular files stored in a tmpfs
273 * file system are represented by a single anonymous
274 * memory object (aobj, for short). The aobj provides
275 * direct access to any position within the file,
276 * because its contents are always mapped in a
277 * contiguous region of virtual memory. It is a task
278 * of the memory management subsystem (see uvm(9)) to
279 * issue the required page ins or page outs whenever
280 * a position within the file is accessed. */
281 struct uvm_object * tn_aobj;
282 size_t tn_aobj_pages;
283 } tn_reg;
284 } tn_spec;
285 };
286
287 #if defined(_KERNEL)
288
289 LIST_HEAD(tmpfs_node_list, tmpfs_node);
290
291 /* --------------------------------------------------------------------- */
292
293 /*
294 * Internal representation of a tmpfs mount point.
295 */
296 struct tmpfs_mount {
297 /* Maximum number of memory pages available for use by the file
298 * system, set during mount time. This variable must never be
299 * used directly as it may be bigger than the current amount of
300 * free memory; in the extreme case, it will hold the SIZE_MAX
301 * value. Instead, use the TMPFS_PAGES_MAX macro. */
302 u_int tm_pages_max;
303
304 /* Number of pages in use by the file system. Cannot be bigger
305 * than the value returned by TMPFS_PAGES_MAX in any case. */
306 u_int tm_pages_used;
307
308 /* Pointer to the node representing the root directory of this
309 * file system. */
310 struct tmpfs_node * tm_root;
311
312 /* Maximum number of possible nodes for this file system; set
313 * during mount time. We need a hard limit on the maximum number
314 * of nodes to avoid allocating too much of them; their objects
315 * cannot be released until the file system is unmounted.
316 * Otherwise, we could easily run out of memory by creating lots
317 * of empty files and then simply removing them. */
318 u_int tm_nodes_max;
319
320 /* Number of nodes currently allocated. This number only grows.
321 * When it reaches tm_nodes_max, no more new nodes can be allocated.
322 * Of course, the old, unused ones can be reused. */
323 u_int tm_nodes_cnt;
324
325 /* Node list. */
326 kmutex_t tm_lock;
327 struct tmpfs_node_list tm_nodes;
328
329 /* Pools used to store file system meta data. These are not shared
330 * across several instances of tmpfs for the reasons described in
331 * tmpfs_pool.c. */
332 struct tmpfs_pool tm_dirent_pool;
333 struct tmpfs_pool tm_node_pool;
334 struct tmpfs_str_pool tm_str_pool;
335 };
336
337 /* --------------------------------------------------------------------- */
338
339 /*
340 * This structure maps a file identifier to a tmpfs node. Used by the
341 * NFS code.
342 */
343 struct tmpfs_fid {
344 uint16_t tf_len;
345 uint16_t tf_pad;
346 uint32_t tf_gen;
347 ino_t tf_id;
348 };
349
350 /* --------------------------------------------------------------------- */
351
352 /*
353 * Prototypes for tmpfs_subr.c.
354 */
355
356 int tmpfs_alloc_node(struct tmpfs_mount *, enum vtype,
357 uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *,
358 char *, dev_t, struct proc *, struct tmpfs_node **);
359 void tmpfs_free_node(struct tmpfs_mount *, struct tmpfs_node *);
360 int tmpfs_alloc_dirent(struct tmpfs_mount *, struct tmpfs_node *,
361 const char *, uint16_t, struct tmpfs_dirent **);
362 void tmpfs_free_dirent(struct tmpfs_mount *, struct tmpfs_dirent *,
363 bool);
364 int tmpfs_alloc_vp(struct mount *, struct tmpfs_node *, struct vnode **);
365 void tmpfs_free_vp(struct vnode *);
366 int tmpfs_alloc_file(struct vnode *, struct vnode **, struct vattr *,
367 struct componentname *, char *);
368 void tmpfs_dir_attach(struct vnode *, struct tmpfs_dirent *);
369 void tmpfs_dir_detach(struct vnode *, struct tmpfs_dirent *);
370 struct tmpfs_dirent * tmpfs_dir_lookup(struct tmpfs_node *node,
371 struct componentname *cnp);
372 int tmpfs_dir_getdotdent(struct tmpfs_node *, struct uio *);
373 int tmpfs_dir_getdotdotdent(struct tmpfs_node *, struct uio *);
374 struct tmpfs_dirent * tmpfs_dir_lookupbycookie(struct tmpfs_node *, off_t);
375 int tmpfs_dir_getdents(struct tmpfs_node *, struct uio *, off_t *);
376 int tmpfs_reg_resize(struct vnode *, off_t);
377 size_t tmpfs_mem_info(bool);
378 int tmpfs_chflags(struct vnode *, int, kauth_cred_t, struct lwp *);
379 int tmpfs_chmod(struct vnode *, mode_t, kauth_cred_t, struct lwp *);
380 int tmpfs_chown(struct vnode *, uid_t, gid_t, kauth_cred_t, struct lwp *);
381 int tmpfs_chsize(struct vnode *, u_quad_t, kauth_cred_t, struct lwp *);
382 int tmpfs_chtimes(struct vnode *, struct timespec *, struct timespec *,
383 int, kauth_cred_t, struct lwp *);
384 void tmpfs_itimes(struct vnode *, const struct timespec *,
385 const struct timespec *);
386
387 void tmpfs_update(struct vnode *, const struct timespec *,
388 const struct timespec *, int);
389 int tmpfs_truncate(struct vnode *, off_t);
390
391 /* --------------------------------------------------------------------- */
392
393 /*
394 * Convenience macros to simplify some logical expressions.
395 */
396 #define IMPLIES(a, b) (!(a) || (b))
397 #define IFF(a, b) (IMPLIES(a, b) && IMPLIES(b, a))
398
399 /* --------------------------------------------------------------------- */
400
401 /*
402 * Checks that the directory entry pointed by 'de' matches the name 'name'
403 * with a length of 'len'.
404 */
405 #define TMPFS_DIRENT_MATCHES(de, name, len) \
406 (de->td_namelen == (uint16_t)len && \
407 memcmp((de)->td_name, (name), (de)->td_namelen) == 0)
408
409 /* --------------------------------------------------------------------- */
410
411 /*
412 * Ensures that the node pointed by 'node' is a directory and that its
413 * contents are consistent with respect to directories.
414 */
415 #define TMPFS_VALIDATE_DIR(node) \
416 KASSERT((node)->tn_type == VDIR); \
417 KASSERT((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \
418 KASSERT((node)->tn_spec.tn_dir.tn_readdir_lastp == NULL || \
419 tmpfs_dircookie((node)->tn_spec.tn_dir.tn_readdir_lastp) == \
420 (node)->tn_spec.tn_dir.tn_readdir_lastn);
421
422 /* --------------------------------------------------------------------- */
423
424 /*
425 * Memory management stuff.
426 */
427
428 /* Amount of memory pages to reserve for the system (e.g., to not use by
429 * tmpfs).
430 * XXX: Should this be tunable through sysctl, for instance? */
431 #define TMPFS_PAGES_RESERVED (4 * 1024 * 1024 / PAGE_SIZE)
432
433 /* Returns the maximum size allowed for a tmpfs file system. This macro
434 * must be used instead of directly retrieving the value from tm_pages_max.
435 * The reason is that the size of a tmpfs file system is dynamic: it lets
436 * the user store files as long as there is enough free memory (including
437 * physical memory and swap space). Therefore, the amount of memory to be
438 * used is either the limit imposed by the user during mount time or the
439 * amount of available memory, whichever is lower. To avoid consuming all
440 * the memory for a given mount point, the system will always reserve a
441 * minimum of TMPFS_PAGES_RESERVED pages, which is also taken into account
442 * by this macro (see above). */
443 static __inline size_t
444 TMPFS_PAGES_MAX(struct tmpfs_mount *tmp)
445 {
446 size_t freepages;
447
448 freepages = tmpfs_mem_info(false);
449 if (freepages < TMPFS_PAGES_RESERVED)
450 freepages = 0;
451 else
452 freepages -= TMPFS_PAGES_RESERVED;
453
454 return MIN(tmp->tm_pages_max, freepages + tmp->tm_pages_used);
455 }
456
457 /* Returns the available space for the given file system. */
458 #define TMPFS_PAGES_AVAIL(tmp) (TMPFS_PAGES_MAX(tmp) - (tmp)->tm_pages_used)
459
460 /* --------------------------------------------------------------------- */
461
462 /*
463 * Macros/functions to convert from generic data structures to tmpfs
464 * specific ones.
465 */
466
467 static __inline
468 struct tmpfs_mount *
469 VFS_TO_TMPFS(struct mount *mp)
470 {
471 struct tmpfs_mount *tmp;
472
473 #ifdef KASSERT
474 KASSERT((mp) != NULL && (mp)->mnt_data != NULL);
475 #endif
476 tmp = (struct tmpfs_mount *)(mp)->mnt_data;
477 return tmp;
478 }
479
480 #endif /* defined(_KERNEL) */
481
482 static __inline
483 struct tmpfs_node *
484 VP_TO_TMPFS_NODE(struct vnode *vp)
485 {
486 struct tmpfs_node *node;
487
488 #ifdef KASSERT
489 KASSERT((vp) != NULL && (vp)->v_data != NULL);
490 #endif
491 node = (struct tmpfs_node *)vp->v_data;
492 return node;
493 }
494
495 #if defined(_KERNEL)
496
497 static __inline
498 struct tmpfs_node *
499 VP_TO_TMPFS_DIR(struct vnode *vp)
500 {
501 struct tmpfs_node *node;
502
503 node = VP_TO_TMPFS_NODE(vp);
504 #ifdef KASSERT
505 TMPFS_VALIDATE_DIR(node);
506 #endif
507 return node;
508 }
509
510 #endif /* defined(_KERNEL) */
511
512 /* ---------------------------------------------------------------------
513 * USER AND KERNEL DEFINITIONS
514 * --------------------------------------------------------------------- */
515
516 /*
517 * This structure is used to communicate mount parameters between userland
518 * and kernel space.
519 */
520 #define TMPFS_ARGS_VERSION 1
521 struct tmpfs_args {
522 int ta_version;
523
524 /* Size counters. */
525 ino_t ta_nodes_max;
526 off_t ta_size_max;
527
528 /* Root node attributes. */
529 uid_t ta_root_uid;
530 gid_t ta_root_gid;
531 mode_t ta_root_mode;
532 };
533 #endif /* _FS_TMPFS_TMPFS_H_ */
534