tmpfs.h revision 1.33.4.2 1 /* $NetBSD: tmpfs.h,v 1.33.4.2 2008/07/28 14:37:35 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 #include <sys/dirent.h>
37 #include <sys/mount.h>
38 #include <sys/queue.h>
39 #include <sys/vnode.h>
40
41 #include <fs/tmpfs/tmpfs_pool.h>
42
43 /* --------------------------------------------------------------------- */
44
45 /*
46 * Internal representation of a tmpfs directory entry.
47 */
48 struct tmpfs_dirent {
49 TAILQ_ENTRY(tmpfs_dirent) td_entries;
50
51 /* Length of the name stored in this directory entry. This avoids
52 * the need to recalculate it every time the name is used. */
53 uint16_t td_namelen;
54
55 /* The name of the entry, allocated from a string pool. This
56 * string is not required to be zero-terminated; therefore, the
57 * td_namelen field must always be used when accessing its value. */
58 char * td_name;
59
60 /* Pointer to the node this entry refers to. */
61 struct tmpfs_node * td_node;
62 };
63
64 /* A directory in tmpfs holds a sorted list of directory entries, which in
65 * turn point to other files (which can be directories themselves).
66 *
67 * In tmpfs, this list is managed by a tail queue, whose head is defined by
68 * the struct tmpfs_dir type.
69 *
70 * It is imporant to notice that directories do not have entries for . and
71 * .. as other file systems do. These can be generated when requested
72 * based on information available by other means, such as the pointer to
73 * the node itself in the former case or the pointer to the parent directory
74 * in the latter case. This is done to simplify tmpfs's code and, more
75 * importantly, to remove redundancy. */
76 TAILQ_HEAD(tmpfs_dir, tmpfs_dirent);
77
78 /* Each entry in a directory has a cookie that identifies it. Cookies
79 * supersede offsets within directories because, given how tmpfs stores
80 * directories in memory, there is no such thing as an offset. (Emulating
81 * a real offset could be very difficult.)
82 *
83 * The '.', '..' and the end of directory markers have fixed cookies which
84 * cannot collide with the cookies generated by other entries. The cookies
85 * fot the other entries are generated based on the memory address on which
86 * stores their information is stored.
87 *
88 * Ideally, using the entry's memory pointer as the cookie would be enough
89 * to represent it and it wouldn't cause collisions in any system.
90 * Unfortunately, this results in "offsets" with very large values which
91 * later raise problems in the Linux compatibility layer (and maybe in other
92 * places) as described in PR kern/32034. Hence we need to workaround this
93 * with a rather ugly hack.
94 *
95 * Linux 32-bit binaries, unless built with _FILE_OFFSET_BITS=64, have off_t
96 * set to 'long', which is a 32-bit *signed* long integer. Regardless of
97 * the macro value, GLIBC (2.3 at least) always uses the getdents64
98 * system call (when calling readdir) which internally returns off64_t
99 * offsets. In order to make 32-bit binaries work, *GLIBC* converts the
100 * 64-bit values returned by the kernel to 32-bit ones and aborts with
101 * EOVERFLOW if the conversion results in values that won't fit in 32-bit
102 * integers (which it assumes is because the directory is extremely large).
103 * This wouldn't cause problems if we were dealing with unsigned integers,
104 * but as we have signed integers, this check fails due to sign expansion.
105 *
106 * For example, consider that the kernel returns the 0xc1234567 cookie to
107 * userspace in a off64_t integer. Later on, GLIBC casts this value to
108 * off_t (remember, signed) with code similar to:
109 * system call returns the offset in kernel_value;
110 * off_t casted_value = kernel_value;
111 * if (sizeof(off_t) != sizeof(off64_t) &&
112 * kernel_value != casted_value)
113 * error!
114 * In this case, casted_value still has 0xc1234567, but when it is compared
115 * for equality against kernel_value, it is promoted to a 64-bit integer and
116 * becomes 0xffffffffc1234567, which is different than 0x00000000c1234567.
117 * Then, GLIBC assumes this is because the directory is very large.
118 *
119 * Given that all the above happens in user-space, we have no control over
120 * it; therefore we must workaround the issue here. We do this by
121 * truncating the pointer value to a 32-bit integer and hope that there
122 * won't be collisions. In fact, this will not cause any problems in
123 * 32-bit platforms but some might arise in 64-bit machines (I'm not sure
124 * if they can happen at all in practice).
125 *
126 * XXX A nicer solution shall be attempted. */
127 #define TMPFS_DIRCOOKIE_DOT 0
128 #define TMPFS_DIRCOOKIE_DOTDOT 1
129 #define TMPFS_DIRCOOKIE_EOF 2
130 static __inline
131 off_t
132 tmpfs_dircookie(struct tmpfs_dirent *de)
133 {
134 off_t cookie;
135
136 cookie = ((off_t)(uintptr_t)de >> 1) & 0x7FFFFFFF;
137 KASSERT(cookie != TMPFS_DIRCOOKIE_DOT);
138 KASSERT(cookie != TMPFS_DIRCOOKIE_DOTDOT);
139 KASSERT(cookie != TMPFS_DIRCOOKIE_EOF);
140
141 return cookie;
142 }
143
144 /* --------------------------------------------------------------------- */
145
146 /*
147 * Internal representation of a tmpfs file system node.
148 *
149 * This structure is splitted in two parts: one holds attributes common
150 * to all file types and the other holds data that is only applicable to
151 * a particular type. The code must be careful to only access those
152 * attributes that are actually allowed by the node's type.
153 */
154 struct tmpfs_node {
155 /* Doubly-linked list entry which links all existing nodes for a
156 * single file system. This is provided to ease the removal of
157 * all nodes during the unmount operation. */
158 LIST_ENTRY(tmpfs_node) tn_entries;
159
160 /* The node's type. Any of 'VBLK', 'VCHR', 'VDIR', 'VFIFO',
161 * 'VLNK', 'VREG' and 'VSOCK' is allowed. The usage of vnode
162 * types instead of a custom enumeration is to make things simpler
163 * and faster, as we do not need to convert between two types. */
164 enum vtype tn_type;
165
166 /* Node identifier. */
167 ino_t tn_id;
168
169 /* Node's internal status. This is used by several file system
170 * operations to do modifications to the node in a delayed
171 * fashion. */
172 int tn_status;
173 #define TMPFS_NODE_ACCESSED (1 << 1)
174 #define TMPFS_NODE_MODIFIED (1 << 2)
175 #define TMPFS_NODE_CHANGED (1 << 3)
176
177 /* The node size. It does not necessarily match the real amount
178 * of memory consumed by it. */
179 off_t tn_size;
180
181 /* Generic node attributes. */
182 uid_t tn_uid;
183 gid_t tn_gid;
184 mode_t tn_mode;
185 int tn_flags;
186 nlink_t tn_links;
187 struct timespec tn_atime;
188 struct timespec tn_mtime;
189 struct timespec tn_ctime;
190 struct timespec tn_birthtime;
191 unsigned long tn_gen;
192
193 /* Head of byte-level lock list (used by tmpfs_advlock). */
194 struct lockf * tn_lockf;
195
196 /* As there is a single vnode for each active file within the
197 * system, care has to be taken to avoid allocating more than one
198 * vnode per file. In order to do this, a bidirectional association
199 * is kept between vnodes and nodes.
200 *
201 * Whenever a vnode is allocated, its v_data field is updated to
202 * point to the node it references. At the same time, the node's
203 * tn_vnode field is modified to point to the new vnode representing
204 * it. Further attempts to allocate a vnode for this same node will
205 * result in returning a new reference to the value stored in
206 * tn_vnode.
207 *
208 * May be NULL when the node is unused (that is, no vnode has been
209 * allocated for it or it has been reclaimed). */
210 kmutex_t tn_vlock;
211 struct vnode * tn_vnode;
212
213 union {
214 /* Valid when tn_type == VBLK || tn_type == VCHR. */
215 struct {
216 dev_t tn_rdev;
217 } tn_dev;
218
219 /* Valid when tn_type == VDIR. */
220 struct {
221 /* Pointer to the parent directory. The root
222 * directory has a pointer to itself in this field;
223 * this property identifies the root node. */
224 struct tmpfs_node * tn_parent;
225
226 /* Head of a tail-queue that links the contents of
227 * the directory together. See above for a
228 * description of its contents. */
229 struct tmpfs_dir tn_dir;
230
231 /* Number and pointer of the first directory entry
232 * returned by the readdir operation if it were
233 * called again to continue reading data from the
234 * same directory as before. This is used to speed
235 * up reads of long directories, assuming that no
236 * more than one read is in progress at a given time.
237 * Otherwise, these values are discarded and a linear
238 * scan is performed from the beginning up to the
239 * point where readdir starts returning values. */
240 off_t tn_readdir_lastn;
241 struct tmpfs_dirent * tn_readdir_lastp;
242 } tn_dir;
243
244 /* Valid when tn_type == VLNK. */
245 struct tn_lnk {
246 /* The link's target, allocated from a string pool. */
247 char * tn_link;
248 } tn_lnk;
249
250 /* Valid when tn_type == VREG. */
251 struct tn_reg {
252 /* The contents of regular files stored in a tmpfs
253 * file system are represented by a single anonymous
254 * memory object (aobj, for short). The aobj provides
255 * direct access to any position within the file,
256 * because its contents are always mapped in a
257 * contiguous region of virtual memory. It is a task
258 * of the memory management subsystem (see uvm(9)) to
259 * issue the required page ins or page outs whenever
260 * a position within the file is accessed. */
261 struct uvm_object * tn_aobj;
262 size_t tn_aobj_pages;
263 } tn_reg;
264 } tn_spec;
265 };
266
267 LIST_HEAD(tmpfs_node_list, tmpfs_node);
268
269 /* --------------------------------------------------------------------- */
270
271 /*
272 * Internal representation of a tmpfs mount point.
273 */
274 struct tmpfs_mount {
275 /* Maximum number of memory pages available for use by the file
276 * system, set during mount time. This variable must never be
277 * used directly as it may be bigger than the current amount of
278 * free memory; in the extreme case, it will hold the SIZE_MAX
279 * value. Instead, use the TMPFS_PAGES_MAX macro. */
280 unsigned int tm_pages_max;
281
282 /* Number of pages in use by the file system. Cannot be bigger
283 * than the value returned by TMPFS_PAGES_MAX in any case. */
284 unsigned int tm_pages_used;
285
286 /* Pointer to the node representing the root directory of this
287 * file system. */
288 struct tmpfs_node * tm_root;
289
290 /* Maximum number of possible nodes for this file system; set
291 * during mount time. We need a hard limit on the maximum number
292 * of nodes to avoid allocating too much of them; their objects
293 * cannot be released until the file system is unmounted.
294 * Otherwise, we could easily run out of memory by creating lots
295 * of empty files and then simply removing them. */
296 unsigned int tm_nodes_max;
297
298 /* Number of nodes currently allocated. This number only grows.
299 * When it reaches tm_nodes_max, no more new nodes can be allocated.
300 * Of course, the old, unused ones can be reused. */
301 unsigned int tm_nodes_cnt;
302
303 /* Node list. */
304 kmutex_t tm_lock;
305 struct tmpfs_node_list tm_nodes;
306
307 /* Pools used to store file system meta data. These are not shared
308 * across several instances of tmpfs for the reasons described in
309 * tmpfs_pool.c. */
310 struct tmpfs_pool tm_dirent_pool;
311 struct tmpfs_pool tm_node_pool;
312 struct tmpfs_str_pool tm_str_pool;
313 };
314
315 /* --------------------------------------------------------------------- */
316
317 /*
318 * This structure maps a file identifier to a tmpfs node. Used by the
319 * NFS code.
320 */
321 struct tmpfs_fid {
322 uint16_t tf_len;
323 uint16_t tf_pad;
324 uint32_t tf_gen;
325 ino_t tf_id;
326 };
327
328 /* --------------------------------------------------------------------- */
329
330 /*
331 * Prototypes for tmpfs_subr.c.
332 */
333
334 int tmpfs_alloc_node(struct tmpfs_mount *, enum vtype,
335 uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *,
336 char *, dev_t, struct tmpfs_node **);
337 void tmpfs_free_node(struct tmpfs_mount *, struct tmpfs_node *);
338 int tmpfs_alloc_dirent(struct tmpfs_mount *, struct tmpfs_node *,
339 const char *, uint16_t, struct tmpfs_dirent **);
340 void tmpfs_free_dirent(struct tmpfs_mount *, struct tmpfs_dirent *,
341 bool);
342 int tmpfs_alloc_vp(struct mount *, struct tmpfs_node *, struct vnode **);
343 void tmpfs_free_vp(struct vnode *);
344 int tmpfs_alloc_file(struct vnode *, struct vnode **, struct vattr *,
345 struct componentname *, char *);
346 void tmpfs_dir_attach(struct vnode *, struct tmpfs_dirent *);
347 void tmpfs_dir_detach(struct vnode *, struct tmpfs_dirent *);
348 struct tmpfs_dirent * tmpfs_dir_lookup(struct tmpfs_node *node,
349 struct componentname *cnp);
350 int tmpfs_dir_getdotdent(struct tmpfs_node *, struct uio *);
351 int tmpfs_dir_getdotdotdent(struct tmpfs_node *, struct uio *);
352 struct tmpfs_dirent * tmpfs_dir_lookupbycookie(struct tmpfs_node *, off_t);
353 int tmpfs_dir_getdents(struct tmpfs_node *, struct uio *, off_t *);
354 int tmpfs_reg_resize(struct vnode *, off_t);
355 size_t tmpfs_mem_info(bool);
356 int tmpfs_chflags(struct vnode *, int, kauth_cred_t, struct lwp *);
357 int tmpfs_chmod(struct vnode *, mode_t, kauth_cred_t, struct lwp *);
358 int tmpfs_chown(struct vnode *, uid_t, gid_t, kauth_cred_t, struct lwp *);
359 int tmpfs_chsize(struct vnode *, u_quad_t, kauth_cred_t, struct lwp *);
360 int tmpfs_chtimes(struct vnode *, const struct timespec *,
361 const struct timespec *, const struct timespec *, int, kauth_cred_t,
362 struct lwp *);
363 void tmpfs_itimes(struct vnode *, const struct timespec *,
364 const struct timespec *, const struct timespec *);
365
366 void tmpfs_update(struct vnode *, const struct timespec *,
367 const struct timespec *, const struct timespec *, int);
368 int tmpfs_truncate(struct vnode *, off_t);
369
370 /* --------------------------------------------------------------------- */
371
372 /*
373 * Convenience macros to simplify some logical expressions.
374 */
375 #define IMPLIES(a, b) (!(a) || (b))
376 #define IFF(a, b) (IMPLIES(a, b) && IMPLIES(b, a))
377
378 /* --------------------------------------------------------------------- */
379
380 /*
381 * Checks that the directory entry pointed by 'de' matches the name 'name'
382 * with a length of 'len'.
383 */
384 #define TMPFS_DIRENT_MATCHES(de, name, len) \
385 (de->td_namelen == (uint16_t)len && \
386 memcmp((de)->td_name, (name), (de)->td_namelen) == 0)
387
388 /* --------------------------------------------------------------------- */
389
390 /*
391 * Ensures that the node pointed by 'node' is a directory and that its
392 * contents are consistent with respect to directories.
393 */
394 #define TMPFS_VALIDATE_DIR(node) \
395 KASSERT((node)->tn_type == VDIR); \
396 KASSERT((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \
397 KASSERT((node)->tn_spec.tn_dir.tn_readdir_lastp == NULL || \
398 tmpfs_dircookie((node)->tn_spec.tn_dir.tn_readdir_lastp) == \
399 (node)->tn_spec.tn_dir.tn_readdir_lastn);
400
401 /* --------------------------------------------------------------------- */
402
403 /*
404 * Memory management stuff.
405 */
406
407 /* Amount of memory pages to reserve for the system (e.g., to not use by
408 * tmpfs).
409 * XXX: Should this be tunable through sysctl, for instance? */
410 #define TMPFS_PAGES_RESERVED (4 * 1024 * 1024 / PAGE_SIZE)
411
412 /* Returns the maximum size allowed for a tmpfs file system. This macro
413 * must be used instead of directly retrieving the value from tm_pages_max.
414 * The reason is that the size of a tmpfs file system is dynamic: it lets
415 * the user store files as long as there is enough free memory (including
416 * physical memory and swap space). Therefore, the amount of memory to be
417 * used is either the limit imposed by the user during mount time or the
418 * amount of available memory, whichever is lower. To avoid consuming all
419 * the memory for a given mount point, the system will always reserve a
420 * minimum of TMPFS_PAGES_RESERVED pages, which is also taken into account
421 * by this macro (see above). */
422 static __inline size_t
423 TMPFS_PAGES_MAX(struct tmpfs_mount *tmp)
424 {
425 size_t freepages;
426
427 freepages = tmpfs_mem_info(false);
428 if (freepages < TMPFS_PAGES_RESERVED)
429 freepages = 0;
430 else
431 freepages -= TMPFS_PAGES_RESERVED;
432
433 return MIN(tmp->tm_pages_max, freepages + tmp->tm_pages_used);
434 }
435
436 /* Returns the available space for the given file system. */
437 #define TMPFS_PAGES_AVAIL(tmp) \
438 ((ssize_t)(TMPFS_PAGES_MAX(tmp) - (tmp)->tm_pages_used))
439
440 /* --------------------------------------------------------------------- */
441
442 /*
443 * Macros/functions to convert from generic data structures to tmpfs
444 * specific ones.
445 */
446
447 static __inline
448 struct tmpfs_mount *
449 VFS_TO_TMPFS(struct mount *mp)
450 {
451 struct tmpfs_mount *tmp;
452
453 #ifdef KASSERT
454 KASSERT((mp) != NULL && (mp)->mnt_data != NULL);
455 #endif
456 tmp = (struct tmpfs_mount *)(mp)->mnt_data;
457 return tmp;
458 }
459
460 static __inline
461 struct tmpfs_node *
462 VP_TO_TMPFS_NODE(struct vnode *vp)
463 {
464 struct tmpfs_node *node;
465
466 #ifdef KASSERT
467 KASSERT((vp) != NULL && (vp)->v_data != NULL);
468 #endif
469 node = (struct tmpfs_node *)vp->v_data;
470 return node;
471 }
472
473 static __inline
474 struct tmpfs_node *
475 VP_TO_TMPFS_DIR(struct vnode *vp)
476 {
477 struct tmpfs_node *node;
478
479 node = VP_TO_TMPFS_NODE(vp);
480 #ifdef KASSERT
481 TMPFS_VALIDATE_DIR(node);
482 #endif
483 return node;
484 }
485 #endif /* _FS_TMPFS_TMPFS_H_ */
486