tmpfs.h revision 1.33.4.1 1 /* $NetBSD: tmpfs.h,v 1.33.4.1 2008/06/27 15:11:29 simonb 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 *
20 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
22 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
23 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
24 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
25 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
26 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
27 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
28 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
29 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
30 * POSSIBILITY OF SUCH DAMAGE.
31 */
32
33 #ifndef _FS_TMPFS_TMPFS_H_
34 #define _FS_TMPFS_TMPFS_H_
35
36 /* ---------------------------------------------------------------------
37 * KERNEL-SPECIFIC DEFINITIONS
38 * --------------------------------------------------------------------- */
39 #include <sys/dirent.h>
40 #include <sys/mount.h>
41 #include <sys/queue.h>
42 #include <sys/vnode.h>
43
44 #if defined(_KERNEL)
45 #include <fs/tmpfs/tmpfs_pool.h>
46 #endif /* defined(_KERNEL) */
47
48 /* --------------------------------------------------------------------- */
49
50 /*
51 * Internal representation of a tmpfs directory entry.
52 */
53 struct tmpfs_dirent {
54 TAILQ_ENTRY(tmpfs_dirent) td_entries;
55
56 /* Length of the name stored in this directory entry. This avoids
57 * the need to recalculate it every time the name is used. */
58 uint16_t td_namelen;
59
60 /* The name of the entry, allocated from a string pool. This
61 * string is not required to be zero-terminated; therefore, the
62 * td_namelen field must always be used when accessing its value. */
63 char * td_name;
64
65 /* Pointer to the node this entry refers to. */
66 struct tmpfs_node * td_node;
67 };
68
69 /* A directory in tmpfs holds a sorted list of directory entries, which in
70 * turn point to other files (which can be directories themselves).
71 *
72 * In tmpfs, this list is managed by a tail queue, whose head is defined by
73 * the struct tmpfs_dir type.
74 *
75 * It is imporant to notice that directories do not have entries for . and
76 * .. as other file systems do. These can be generated when requested
77 * based on information available by other means, such as the pointer to
78 * the node itself in the former case or the pointer to the parent directory
79 * in the latter case. This is done to simplify tmpfs's code and, more
80 * importantly, to remove redundancy. */
81 TAILQ_HEAD(tmpfs_dir, tmpfs_dirent);
82
83 /* Each entry in a directory has a cookie that identifies it. Cookies
84 * supersede offsets within directories because, given how tmpfs stores
85 * directories in memory, there is no such thing as an offset. (Emulating
86 * a real offset could be very difficult.)
87 *
88 * The '.', '..' and the end of directory markers have fixed cookies which
89 * cannot collide with the cookies generated by other entries. The cookies
90 * fot the other entries are generated based on the memory address on which
91 * stores their information is stored.
92 *
93 * Ideally, using the entry's memory pointer as the cookie would be enough
94 * to represent it and it wouldn't cause collisions in any system.
95 * Unfortunately, this results in "offsets" with very large values which
96 * later raise problems in the Linux compatibility layer (and maybe in other
97 * places) as described in PR kern/32034. Hence we need to workaround this
98 * with a rather ugly hack.
99 *
100 * Linux 32-bit binaries, unless built with _FILE_OFFSET_BITS=64, have off_t
101 * set to 'long', which is a 32-bit *signed* long integer. Regardless of
102 * the macro value, GLIBC (2.3 at least) always uses the getdents64
103 * system call (when calling readdir) which internally returns off64_t
104 * offsets. In order to make 32-bit binaries work, *GLIBC* converts the
105 * 64-bit values returned by the kernel to 32-bit ones and aborts with
106 * EOVERFLOW if the conversion results in values that won't fit in 32-bit
107 * integers (which it assumes is because the directory is extremely large).
108 * This wouldn't cause problems if we were dealing with unsigned integers,
109 * but as we have signed integers, this check fails due to sign expansion.
110 *
111 * For example, consider that the kernel returns the 0xc1234567 cookie to
112 * userspace in a off64_t integer. Later on, GLIBC casts this value to
113 * off_t (remember, signed) with code similar to:
114 * system call returns the offset in kernel_value;
115 * off_t casted_value = kernel_value;
116 * if (sizeof(off_t) != sizeof(off64_t) &&
117 * kernel_value != casted_value)
118 * error!
119 * In this case, casted_value still has 0xc1234567, but when it is compared
120 * for equality against kernel_value, it is promoted to a 64-bit integer and
121 * becomes 0xffffffffc1234567, which is different than 0x00000000c1234567.
122 * Then, GLIBC assumes this is because the directory is very large.
123 *
124 * Given that all the above happens in user-space, we have no control over
125 * it; therefore we must workaround the issue here. We do this by
126 * truncating the pointer value to a 32-bit integer and hope that there
127 * won't be collisions. In fact, this will not cause any problems in
128 * 32-bit platforms but some might arise in 64-bit machines (I'm not sure
129 * if they can happen at all in practice).
130 *
131 * XXX A nicer solution shall be attempted. */
132 #if defined(_KERNEL)
133 #define TMPFS_DIRCOOKIE_DOT 0
134 #define TMPFS_DIRCOOKIE_DOTDOT 1
135 #define TMPFS_DIRCOOKIE_EOF 2
136 static __inline
137 off_t
138 tmpfs_dircookie(struct tmpfs_dirent *de)
139 {
140 off_t cookie;
141
142 cookie = ((off_t)(uintptr_t)de >> 1) & 0x7FFFFFFF;
143 KASSERT(cookie != TMPFS_DIRCOOKIE_DOT);
144 KASSERT(cookie != TMPFS_DIRCOOKIE_DOTDOT);
145 KASSERT(cookie != TMPFS_DIRCOOKIE_EOF);
146
147 return cookie;
148 }
149 #endif /* defined(_KERNEL) */
150
151 /* --------------------------------------------------------------------- */
152
153 /*
154 * Internal representation of a tmpfs file system node.
155 *
156 * This structure is splitted in two parts: one holds attributes common
157 * to all file types and the other holds data that is only applicable to
158 * a particular type. The code must be careful to only access those
159 * attributes that are actually allowed by the node's type.
160 */
161 struct tmpfs_node {
162 /* Doubly-linked list entry which links all existing nodes for a
163 * single file system. This is provided to ease the removal of
164 * all nodes during the unmount operation. */
165 LIST_ENTRY(tmpfs_node) tn_entries;
166
167 /* The node's type. Any of 'VBLK', 'VCHR', 'VDIR', 'VFIFO',
168 * 'VLNK', 'VREG' and 'VSOCK' is allowed. The usage of vnode
169 * types instead of a custom enumeration is to make things simpler
170 * and faster, as we do not need to convert between two types. */
171 enum vtype tn_type;
172
173 /* Node identifier. */
174 ino_t tn_id;
175
176 /* Node's internal status. This is used by several file system
177 * operations to do modifications to the node in a delayed
178 * fashion. */
179 int tn_status;
180 #define TMPFS_NODE_ACCESSED (1 << 1)
181 #define TMPFS_NODE_MODIFIED (1 << 2)
182 #define TMPFS_NODE_CHANGED (1 << 3)
183
184 /* The node size. It does not necessarily match the real amount
185 * of memory consumed by it. */
186 off_t tn_size;
187
188 /* Generic node attributes. */
189 uid_t tn_uid;
190 gid_t tn_gid;
191 mode_t tn_mode;
192 int tn_flags;
193 nlink_t tn_links;
194 struct timespec tn_atime;
195 struct timespec tn_mtime;
196 struct timespec tn_ctime;
197 struct timespec tn_birthtime;
198 unsigned long tn_gen;
199
200 /* Head of byte-level lock list (used by tmpfs_advlock). */
201 struct lockf * tn_lockf;
202
203 /* As there is a single vnode for each active file within the
204 * system, care has to be taken to avoid allocating more than one
205 * vnode per file. In order to do this, a bidirectional association
206 * is kept between vnodes and nodes.
207 *
208 * Whenever a vnode is allocated, its v_data field is updated to
209 * point to the node it references. At the same time, the node's
210 * tn_vnode field is modified to point to the new vnode representing
211 * it. Further attempts to allocate a vnode for this same node will
212 * result in returning a new reference to the value stored in
213 * tn_vnode.
214 *
215 * May be NULL when the node is unused (that is, no vnode has been
216 * allocated for it or it has been reclaimed). */
217 kmutex_t tn_vlock;
218 struct vnode * tn_vnode;
219
220 union {
221 /* Valid when tn_type == VBLK || tn_type == VCHR. */
222 struct {
223 dev_t tn_rdev;
224 } tn_dev;
225
226 /* Valid when tn_type == VDIR. */
227 struct {
228 /* Pointer to the parent directory. The root
229 * directory has a pointer to itself in this field;
230 * this property identifies the root node. */
231 struct tmpfs_node * tn_parent;
232
233 /* Head of a tail-queue that links the contents of
234 * the directory together. See above for a
235 * description of its contents. */
236 struct tmpfs_dir tn_dir;
237
238 /* Number and pointer of the first directory entry
239 * returned by the readdir operation if it were
240 * called again to continue reading data from the
241 * same directory as before. This is used to speed
242 * up reads of long directories, assuming that no
243 * more than one read is in progress at a given time.
244 * Otherwise, these values are discarded and a linear
245 * scan is performed from the beginning up to the
246 * point where readdir starts returning values. */
247 off_t tn_readdir_lastn;
248 struct tmpfs_dirent * tn_readdir_lastp;
249 } tn_dir;
250
251 /* Valid when tn_type == VLNK. */
252 struct tn_lnk {
253 /* The link's target, allocated from a string pool. */
254 char * tn_link;
255 } tn_lnk;
256
257 /* Valid when tn_type == VREG. */
258 struct tn_reg {
259 /* The contents of regular files stored in a tmpfs
260 * file system are represented by a single anonymous
261 * memory object (aobj, for short). The aobj provides
262 * direct access to any position within the file,
263 * because its contents are always mapped in a
264 * contiguous region of virtual memory. It is a task
265 * of the memory management subsystem (see uvm(9)) to
266 * issue the required page ins or page outs whenever
267 * a position within the file is accessed. */
268 struct uvm_object * tn_aobj;
269 size_t tn_aobj_pages;
270 } tn_reg;
271 } tn_spec;
272 };
273
274 #if defined(_KERNEL)
275
276 LIST_HEAD(tmpfs_node_list, tmpfs_node);
277
278 /* --------------------------------------------------------------------- */
279
280 /*
281 * Internal representation of a tmpfs mount point.
282 */
283 struct tmpfs_mount {
284 /* Maximum number of memory pages available for use by the file
285 * system, set during mount time. This variable must never be
286 * used directly as it may be bigger than the current amount of
287 * free memory; in the extreme case, it will hold the SIZE_MAX
288 * value. Instead, use the TMPFS_PAGES_MAX macro. */
289 unsigned int tm_pages_max;
290
291 /* Number of pages in use by the file system. Cannot be bigger
292 * than the value returned by TMPFS_PAGES_MAX in any case. */
293 unsigned int tm_pages_used;
294
295 /* Pointer to the node representing the root directory of this
296 * file system. */
297 struct tmpfs_node * tm_root;
298
299 /* Maximum number of possible nodes for this file system; set
300 * during mount time. We need a hard limit on the maximum number
301 * of nodes to avoid allocating too much of them; their objects
302 * cannot be released until the file system is unmounted.
303 * Otherwise, we could easily run out of memory by creating lots
304 * of empty files and then simply removing them. */
305 unsigned int tm_nodes_max;
306
307 /* Number of nodes currently allocated. This number only grows.
308 * When it reaches tm_nodes_max, no more new nodes can be allocated.
309 * Of course, the old, unused ones can be reused. */
310 unsigned int tm_nodes_cnt;
311
312 /* Node list. */
313 kmutex_t tm_lock;
314 struct tmpfs_node_list tm_nodes;
315
316 /* Pools used to store file system meta data. These are not shared
317 * across several instances of tmpfs for the reasons described in
318 * tmpfs_pool.c. */
319 struct tmpfs_pool tm_dirent_pool;
320 struct tmpfs_pool tm_node_pool;
321 struct tmpfs_str_pool tm_str_pool;
322 };
323
324 /* --------------------------------------------------------------------- */
325
326 /*
327 * This structure maps a file identifier to a tmpfs node. Used by the
328 * NFS code.
329 */
330 struct tmpfs_fid {
331 uint16_t tf_len;
332 uint16_t tf_pad;
333 uint32_t tf_gen;
334 ino_t tf_id;
335 };
336
337 /* --------------------------------------------------------------------- */
338
339 /*
340 * Prototypes for tmpfs_subr.c.
341 */
342
343 int tmpfs_alloc_node(struct tmpfs_mount *, enum vtype,
344 uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *,
345 char *, dev_t, struct tmpfs_node **);
346 void tmpfs_free_node(struct tmpfs_mount *, struct tmpfs_node *);
347 int tmpfs_alloc_dirent(struct tmpfs_mount *, struct tmpfs_node *,
348 const char *, uint16_t, struct tmpfs_dirent **);
349 void tmpfs_free_dirent(struct tmpfs_mount *, struct tmpfs_dirent *,
350 bool);
351 int tmpfs_alloc_vp(struct mount *, struct tmpfs_node *, struct vnode **);
352 void tmpfs_free_vp(struct vnode *);
353 int tmpfs_alloc_file(struct vnode *, struct vnode **, struct vattr *,
354 struct componentname *, char *);
355 void tmpfs_dir_attach(struct vnode *, struct tmpfs_dirent *);
356 void tmpfs_dir_detach(struct vnode *, struct tmpfs_dirent *);
357 struct tmpfs_dirent * tmpfs_dir_lookup(struct tmpfs_node *node,
358 struct componentname *cnp);
359 int tmpfs_dir_getdotdent(struct tmpfs_node *, struct uio *);
360 int tmpfs_dir_getdotdotdent(struct tmpfs_node *, struct uio *);
361 struct tmpfs_dirent * tmpfs_dir_lookupbycookie(struct tmpfs_node *, off_t);
362 int tmpfs_dir_getdents(struct tmpfs_node *, struct uio *, off_t *);
363 int tmpfs_reg_resize(struct vnode *, off_t);
364 size_t tmpfs_mem_info(bool);
365 int tmpfs_chflags(struct vnode *, int, kauth_cred_t, struct lwp *);
366 int tmpfs_chmod(struct vnode *, mode_t, kauth_cred_t, struct lwp *);
367 int tmpfs_chown(struct vnode *, uid_t, gid_t, kauth_cred_t, struct lwp *);
368 int tmpfs_chsize(struct vnode *, u_quad_t, kauth_cred_t, struct lwp *);
369 int tmpfs_chtimes(struct vnode *, const struct timespec *,
370 const struct timespec *, const struct timespec *, int, kauth_cred_t,
371 struct lwp *);
372 void tmpfs_itimes(struct vnode *, const struct timespec *,
373 const struct timespec *, const struct timespec *);
374
375 void tmpfs_update(struct vnode *, const struct timespec *,
376 const struct timespec *, const struct timespec *, int);
377 int tmpfs_truncate(struct vnode *, off_t);
378
379 /* --------------------------------------------------------------------- */
380
381 /*
382 * Convenience macros to simplify some logical expressions.
383 */
384 #define IMPLIES(a, b) (!(a) || (b))
385 #define IFF(a, b) (IMPLIES(a, b) && IMPLIES(b, a))
386
387 /* --------------------------------------------------------------------- */
388
389 /*
390 * Checks that the directory entry pointed by 'de' matches the name 'name'
391 * with a length of 'len'.
392 */
393 #define TMPFS_DIRENT_MATCHES(de, name, len) \
394 (de->td_namelen == (uint16_t)len && \
395 memcmp((de)->td_name, (name), (de)->td_namelen) == 0)
396
397 /* --------------------------------------------------------------------- */
398
399 /*
400 * Ensures that the node pointed by 'node' is a directory and that its
401 * contents are consistent with respect to directories.
402 */
403 #define TMPFS_VALIDATE_DIR(node) \
404 KASSERT((node)->tn_type == VDIR); \
405 KASSERT((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \
406 KASSERT((node)->tn_spec.tn_dir.tn_readdir_lastp == NULL || \
407 tmpfs_dircookie((node)->tn_spec.tn_dir.tn_readdir_lastp) == \
408 (node)->tn_spec.tn_dir.tn_readdir_lastn);
409
410 /* --------------------------------------------------------------------- */
411
412 /*
413 * Memory management stuff.
414 */
415
416 /* Amount of memory pages to reserve for the system (e.g., to not use by
417 * tmpfs).
418 * XXX: Should this be tunable through sysctl, for instance? */
419 #define TMPFS_PAGES_RESERVED (4 * 1024 * 1024 / PAGE_SIZE)
420
421 /* Returns the maximum size allowed for a tmpfs file system. This macro
422 * must be used instead of directly retrieving the value from tm_pages_max.
423 * The reason is that the size of a tmpfs file system is dynamic: it lets
424 * the user store files as long as there is enough free memory (including
425 * physical memory and swap space). Therefore, the amount of memory to be
426 * used is either the limit imposed by the user during mount time or the
427 * amount of available memory, whichever is lower. To avoid consuming all
428 * the memory for a given mount point, the system will always reserve a
429 * minimum of TMPFS_PAGES_RESERVED pages, which is also taken into account
430 * by this macro (see above). */
431 static __inline size_t
432 TMPFS_PAGES_MAX(struct tmpfs_mount *tmp)
433 {
434 size_t freepages;
435
436 freepages = tmpfs_mem_info(false);
437 if (freepages < TMPFS_PAGES_RESERVED)
438 freepages = 0;
439 else
440 freepages -= TMPFS_PAGES_RESERVED;
441
442 return MIN(tmp->tm_pages_max, freepages + tmp->tm_pages_used);
443 }
444
445 /* Returns the available space for the given file system. */
446 #define TMPFS_PAGES_AVAIL(tmp) \
447 ((ssize_t)(TMPFS_PAGES_MAX(tmp) - (tmp)->tm_pages_used))
448
449 /* --------------------------------------------------------------------- */
450
451 /*
452 * Macros/functions to convert from generic data structures to tmpfs
453 * specific ones.
454 */
455
456 static __inline
457 struct tmpfs_mount *
458 VFS_TO_TMPFS(struct mount *mp)
459 {
460 struct tmpfs_mount *tmp;
461
462 #ifdef KASSERT
463 KASSERT((mp) != NULL && (mp)->mnt_data != NULL);
464 #endif
465 tmp = (struct tmpfs_mount *)(mp)->mnt_data;
466 return tmp;
467 }
468
469 #endif /* defined(_KERNEL) */
470
471 static __inline
472 struct tmpfs_node *
473 VP_TO_TMPFS_NODE(struct vnode *vp)
474 {
475 struct tmpfs_node *node;
476
477 #ifdef KASSERT
478 KASSERT((vp) != NULL && (vp)->v_data != NULL);
479 #endif
480 node = (struct tmpfs_node *)vp->v_data;
481 return node;
482 }
483
484 #if defined(_KERNEL)
485
486 static __inline
487 struct tmpfs_node *
488 VP_TO_TMPFS_DIR(struct vnode *vp)
489 {
490 struct tmpfs_node *node;
491
492 node = VP_TO_TMPFS_NODE(vp);
493 #ifdef KASSERT
494 TMPFS_VALIDATE_DIR(node);
495 #endif
496 return node;
497 }
498
499 #endif /* defined(_KERNEL) */
500
501 /* ---------------------------------------------------------------------
502 * USER AND KERNEL DEFINITIONS
503 * --------------------------------------------------------------------- */
504
505 /*
506 * This structure is used to communicate mount parameters between userland
507 * and kernel space.
508 */
509 #define TMPFS_ARGS_VERSION 1
510 struct tmpfs_args {
511 int ta_version;
512
513 /* Size counters. */
514 ino_t ta_nodes_max;
515 off_t ta_size_max;
516
517 /* Root node attributes. */
518 uid_t ta_root_uid;
519 gid_t ta_root_gid;
520 mode_t ta_root_mode;
521 };
522 #endif /* _FS_TMPFS_TMPFS_H_ */
523