FreeBSD/Linux Kernel Cross Reference
sys/fs/tmpfs/tmpfs.h
1 /* $NetBSD: tmpfs.h,v 1.26 2007/02/22 06:37:00 thorpej Exp $ */
2
3 /*-
4 * Copyright (c) 2005, 2006 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 * $FreeBSD$
33 */
34
35 #ifndef _FS_TMPFS_TMPFS_H_
36 #define _FS_TMPFS_TMPFS_H_
37
38 /* ---------------------------------------------------------------------
39 * KERNEL-SPECIFIC DEFINITIONS
40 * --------------------------------------------------------------------- */
41 #include <sys/dirent.h>
42 #include <sys/mount.h>
43 #include <sys/queue.h>
44 #include <sys/vnode.h>
45 #include <sys/file.h>
46 #include <sys/lock.h>
47 #include <sys/mutex.h>
48
49 /* --------------------------------------------------------------------- */
50 #include <sys/malloc.h>
51 #include <sys/systm.h>
52 #include <sys/vmmeter.h>
53 #include <vm/swap_pager.h>
54
55 MALLOC_DECLARE(M_TMPFSMNT);
56 MALLOC_DECLARE(M_TMPFSNAME);
57
58 /* --------------------------------------------------------------------- */
59
60 /*
61 * Internal representation of a tmpfs directory entry.
62 */
63 struct tmpfs_dirent {
64 TAILQ_ENTRY(tmpfs_dirent) td_entries;
65
66 /* Length of the name stored in this directory entry. This avoids
67 * the need to recalculate it every time the name is used. */
68 uint16_t td_namelen;
69
70 /* The name of the entry, allocated from a string pool. This
71 * string is not required to be zero-terminated; therefore, the
72 * td_namelen field must always be used when accessing its value. */
73 char * td_name;
74
75 /* Pointer to the node this entry refers to. In case this field
76 * is NULL, the node is a whiteout. */
77 struct tmpfs_node * td_node;
78 };
79
80 /* A directory in tmpfs holds a sorted list of directory entries, which in
81 * turn point to other files (which can be directories themselves).
82 *
83 * In tmpfs, this list is managed by a tail queue, whose head is defined by
84 * the struct tmpfs_dir type.
85 *
86 * It is imporant to notice that directories do not have entries for . and
87 * .. as other file systems do. These can be generated when requested
88 * based on information available by other means, such as the pointer to
89 * the node itself in the former case or the pointer to the parent directory
90 * in the latter case. This is done to simplify tmpfs's code and, more
91 * importantly, to remove redundancy. */
92 TAILQ_HEAD(tmpfs_dir, tmpfs_dirent);
93
94 /* Each entry in a directory has a cookie that identifies it. Cookies
95 * supersede offsets within directories because, given how tmpfs stores
96 * directories in memory, there is no such thing as an offset. (Emulating
97 * a real offset could be very difficult.)
98 *
99 * The '.', '..' and the end of directory markers have fixed cookies which
100 * cannot collide with the cookies generated by other entries. The cookies
101 * fot the other entries are generated based on the memory address on which
102 * stores their information is stored.
103 *
104 * Ideally, using the entry's memory pointer as the cookie would be enough
105 * to represent it and it wouldn't cause collisions in any system.
106 * Unfortunately, this results in "offsets" with very large values which
107 * later raise problems in the Linux compatibility layer (and maybe in other
108 * places) as described in PR kern/32034. Hence we need to workaround this
109 * with a rather ugly hack.
110 *
111 * Linux 32-bit binaries, unless built with _FILE_OFFSET_BITS=64, have off_t
112 * set to 'long', which is a 32-bit *signed* long integer. Regardless of
113 * the macro value, GLIBC (2.3 at least) always uses the getdents64
114 * system call (when calling readdir) which internally returns off64_t
115 * offsets. In order to make 32-bit binaries work, *GLIBC* converts the
116 * 64-bit values returned by the kernel to 32-bit ones and aborts with
117 * EOVERFLOW if the conversion results in values that won't fit in 32-bit
118 * integers (which it assumes is because the directory is extremely large).
119 * This wouldn't cause problems if we were dealing with unsigned integers,
120 * but as we have signed integers, this check fails due to sign expansion.
121 *
122 * For example, consider that the kernel returns the 0xc1234567 cookie to
123 * userspace in a off64_t integer. Later on, GLIBC casts this value to
124 * off_t (remember, signed) with code similar to:
125 * system call returns the offset in kernel_value;
126 * off_t casted_value = kernel_value;
127 * if (sizeof(off_t) != sizeof(off64_t) &&
128 * kernel_value != casted_value)
129 * error!
130 * In this case, casted_value still has 0xc1234567, but when it is compared
131 * for equality against kernel_value, it is promoted to a 64-bit integer and
132 * becomes 0xffffffffc1234567, which is different than 0x00000000c1234567.
133 * Then, GLIBC assumes this is because the directory is very large.
134 *
135 * Given that all the above happens in user-space, we have no control over
136 * it; therefore we must workaround the issue here. We do this by
137 * truncating the pointer value to a 32-bit integer and hope that there
138 * won't be collisions. In fact, this will not cause any problems in
139 * 32-bit platforms but some might arise in 64-bit machines (I'm not sure
140 * if they can happen at all in practice).
141 *
142 * XXX A nicer solution shall be attempted. */
143 #ifdef _KERNEL
144 #define TMPFS_DIRCOOKIE_DOT 0
145 #define TMPFS_DIRCOOKIE_DOTDOT 1
146 #define TMPFS_DIRCOOKIE_EOF 2
147 static __inline
148 off_t
149 tmpfs_dircookie(struct tmpfs_dirent *de)
150 {
151 off_t cookie;
152
153 cookie = ((off_t)(uintptr_t)de >> 1) & 0x7FFFFFFF;
154 MPASS(cookie != TMPFS_DIRCOOKIE_DOT);
155 MPASS(cookie != TMPFS_DIRCOOKIE_DOTDOT);
156 MPASS(cookie != TMPFS_DIRCOOKIE_EOF);
157
158 return cookie;
159 }
160 #endif
161
162 /* --------------------------------------------------------------------- */
163
164 /*
165 * Internal representation of a tmpfs file system node.
166 *
167 * This structure is splitted in two parts: one holds attributes common
168 * to all file types and the other holds data that is only applicable to
169 * a particular type. The code must be careful to only access those
170 * attributes that are actually allowed by the node's type.
171 *
172 *
173 * Below is the key of locks used to protected the fields in the following
174 * structures.
175 *
176 */
177 struct tmpfs_node {
178 /* Doubly-linked list entry which links all existing nodes for a
179 * single file system. This is provided to ease the removal of
180 * all nodes during the unmount operation. */
181 LIST_ENTRY(tmpfs_node) tn_entries;
182
183 /* The node's type. Any of 'VBLK', 'VCHR', 'VDIR', 'VFIFO',
184 * 'VLNK', 'VREG' and 'VSOCK' is allowed. The usage of vnode
185 * types instead of a custom enumeration is to make things simpler
186 * and faster, as we do not need to convert between two types. */
187 enum vtype tn_type;
188
189 /* Node identifier. */
190 ino_t tn_id;
191
192 /* Node's internal status. This is used by several file system
193 * operations to do modifications to the node in a delayed
194 * fashion. */
195 int tn_status;
196 #define TMPFS_NODE_ACCESSED (1 << 1)
197 #define TMPFS_NODE_MODIFIED (1 << 2)
198 #define TMPFS_NODE_CHANGED (1 << 3)
199
200 /* The node size. It does not necessarily match the real amount
201 * of memory consumed by it. */
202 off_t tn_size;
203
204 /* Generic node attributes. */
205 uid_t tn_uid;
206 gid_t tn_gid;
207 mode_t tn_mode;
208 int tn_flags;
209 nlink_t tn_links;
210 struct timespec tn_atime;
211 struct timespec tn_mtime;
212 struct timespec tn_ctime;
213 struct timespec tn_birthtime;
214 unsigned long tn_gen;
215
216 /* As there is a single vnode for each active file within the
217 * system, care has to be taken to avoid allocating more than one
218 * vnode per file. In order to do this, a bidirectional association
219 * is kept between vnodes and nodes.
220 *
221 * Whenever a vnode is allocated, its v_data field is updated to
222 * point to the node it references. At the same time, the node's
223 * tn_vnode field is modified to point to the new vnode representing
224 * it. Further attempts to allocate a vnode for this same node will
225 * result in returning a new reference to the value stored in
226 * tn_vnode.
227 *
228 * May be NULL when the node is unused (that is, no vnode has been
229 * allocated for it or it has been reclaimed). */
230 struct vnode * tn_vnode;
231
232 /* interlock to protect tn_vpstate */
233 struct mtx tn_interlock;
234
235 /* Identify if current node has vnode assiocate with
236 * or allocating vnode.
237 */
238 int tn_vpstate;
239
240 /* misc data field for different tn_type node */
241 union {
242 /* Valid when tn_type == VBLK || tn_type == VCHR. */
243 dev_t tn_rdev;
244
245 /* Valid when tn_type == VDIR. */
246 struct tn_dir{
247 /* Pointer to the parent directory. The root
248 * directory has a pointer to itself in this field;
249 * this property identifies the root node. */
250 struct tmpfs_node * tn_parent;
251
252 /* Head of a tail-queue that links the contents of
253 * the directory together. See above for a
254 * description of its contents. */
255 struct tmpfs_dir tn_dirhead;
256
257 /* Number and pointer of the first directory entry
258 * returned by the readdir operation if it were
259 * called again to continue reading data from the
260 * same directory as before. This is used to speed
261 * up reads of long directories, assuming that no
262 * more than one read is in progress at a given time.
263 * Otherwise, these values are discarded and a linear
264 * scan is performed from the beginning up to the
265 * point where readdir starts returning values. */
266 off_t tn_readdir_lastn;
267 struct tmpfs_dirent * tn_readdir_lastp;
268 }tn_dir;
269
270 /* Valid when tn_type == VLNK. */
271 /* The link's target, allocated from a string pool. */
272 char * tn_link;
273
274 /* Valid when tn_type == VREG. */
275 struct tn_reg {
276 /* The contents of regular files stored in a tmpfs
277 * file system are represented by a single anonymous
278 * memory object (aobj, for short). The aobj provides
279 * direct access to any position within the file,
280 * because its contents are always mapped in a
281 * contiguous region of virtual memory. It is a task
282 * of the memory management subsystem (see uvm(9)) to
283 * issue the required page ins or page outs whenever
284 * a position within the file is accessed. */
285 vm_object_t tn_aobj;
286
287 }tn_reg;
288
289 /* Valid when tn_type = VFIFO */
290 struct tn_fifo {
291 fo_rdwr_t *tn_fo_read;
292 fo_rdwr_t *tn_fo_write;
293 }tn_fifo;
294 }tn_spec;
295 };
296 LIST_HEAD(tmpfs_node_list, tmpfs_node);
297
298 #define tn_rdev tn_spec.tn_rdev
299 #define tn_dir tn_spec.tn_dir
300 #define tn_link tn_spec.tn_link
301 #define tn_reg tn_spec.tn_reg
302 #define tn_fifo tn_spec.tn_fifo
303
304 #define TMPFS_NODE_LOCK(node) mtx_lock(&(node)->tn_interlock)
305 #define TMPFS_NODE_UNLOCK(node) mtx_unlock(&(node)->tn_interlock)
306 #define TMPFS_NODE_MTX(node) (&(node)->tn_interlock)
307
308 #ifdef INVARIANTS
309 #define TMPFS_ASSERT_LOCKED(node) do { \
310 MPASS(node != NULL); \
311 MPASS(node->tn_vnode != NULL); \
312 if (!VOP_ISLOCKED(node->tn_vnode) && \
313 !mtx_owned(TMPFS_NODE_MTX(node))) \
314 panic("tmpfs: node is not locked: %p", node); \
315 } while (0)
316 #define TMPFS_ASSERT_ELOCKED(node) do { \
317 MPASS((node) != NULL); \
318 MPASS((node)->tn_vnode != NULL); \
319 mtx_assert(TMPFS_NODE_MTX(node), MA_OWNED); \
320 ASSERT_VOP_LOCKED((node)->tn_vnode, "tmpfs"); \
321 } while (0)
322 #else
323 #define TMPFS_ASSERT_LOCKED(node) (void)0
324 #define TMPFS_ASSERT_ELOCKED(node) (void)0
325 #endif
326
327 #define TMPFS_VNODE_ALLOCATING 1
328 #define TMPFS_VNODE_WANT 2
329 #define TMPFS_VNODE_DOOMED 4
330 #define TMPFS_VNODE_WRECLAIM 8
331 /* --------------------------------------------------------------------- */
332
333 /*
334 * Internal representation of a tmpfs mount point.
335 */
336 struct tmpfs_mount {
337 /* Maximum number of memory pages available for use by the file
338 * system, set during mount time. This variable must never be
339 * used directly as it may be bigger than the current amount of
340 * free memory; in the extreme case, it will hold the SIZE_MAX
341 * value. */
342 size_t tm_pages_max;
343
344 /* Number of pages in use by the file system. */
345 size_t tm_pages_used;
346
347 /* Pointer to the node representing the root directory of this
348 * file system. */
349 struct tmpfs_node * tm_root;
350
351 /* Maximum number of possible nodes for this file system; set
352 * during mount time. We need a hard limit on the maximum number
353 * of nodes to avoid allocating too much of them; their objects
354 * cannot be released until the file system is unmounted.
355 * Otherwise, we could easily run out of memory by creating lots
356 * of empty files and then simply removing them. */
357 ino_t tm_nodes_max;
358
359 /* unrhdr used to allocate inode numbers */
360 struct unrhdr * tm_ino_unr;
361
362 /* Number of nodes currently that are in use. */
363 ino_t tm_nodes_inuse;
364
365 /* maximum representable file size */
366 u_int64_t tm_maxfilesize;
367
368 /* Nodes are organized in two different lists. The used list
369 * contains all nodes that are currently used by the file system;
370 * i.e., they refer to existing files. The available list contains
371 * all nodes that are currently available for use by new files.
372 * Nodes must be kept in this list (instead of deleting them)
373 * because we need to keep track of their generation number (tn_gen
374 * field).
375 *
376 * Note that nodes are lazily allocated: if the available list is
377 * empty and we have enough space to create more nodes, they will be
378 * created and inserted in the used list. Once these are released,
379 * they will go into the available list, remaining alive until the
380 * file system is unmounted. */
381 struct tmpfs_node_list tm_nodes_used;
382
383 /* All node lock to protect the node list and tmp_pages_used */
384 struct mtx allnode_lock;
385
386 /* Pools used to store file system meta data. These are not shared
387 * across several instances of tmpfs for the reasons described in
388 * tmpfs_pool.c. */
389 uma_zone_t tm_dirent_pool;
390 uma_zone_t tm_node_pool;
391
392 /* Read-only status. */
393 int tm_ronly;
394 };
395 #define TMPFS_LOCK(tm) mtx_lock(&(tm)->allnode_lock)
396 #define TMPFS_UNLOCK(tm) mtx_unlock(&(tm)->allnode_lock)
397
398 /* --------------------------------------------------------------------- */
399
400 /*
401 * This structure maps a file identifier to a tmpfs node. Used by the
402 * NFS code.
403 */
404 struct tmpfs_fid {
405 uint16_t tf_len;
406 uint16_t tf_pad;
407 ino_t tf_id;
408 unsigned long tf_gen;
409 };
410
411 /* --------------------------------------------------------------------- */
412
413 #ifdef _KERNEL
414 /*
415 * Prototypes for tmpfs_subr.c.
416 */
417
418 int tmpfs_alloc_node(struct tmpfs_mount *, enum vtype,
419 uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *,
420 char *, dev_t, struct tmpfs_node **);
421 void tmpfs_free_node(struct tmpfs_mount *, struct tmpfs_node *);
422 int tmpfs_alloc_dirent(struct tmpfs_mount *, struct tmpfs_node *,
423 const char *, uint16_t, struct tmpfs_dirent **);
424 void tmpfs_free_dirent(struct tmpfs_mount *, struct tmpfs_dirent *,
425 boolean_t);
426 int tmpfs_alloc_vp(struct mount *, struct tmpfs_node *, int,
427 struct vnode **);
428 void tmpfs_free_vp(struct vnode *);
429 int tmpfs_alloc_file(struct vnode *, struct vnode **, struct vattr *,
430 struct componentname *, char *);
431 void tmpfs_dir_attach(struct vnode *, struct tmpfs_dirent *);
432 void tmpfs_dir_detach(struct vnode *, struct tmpfs_dirent *);
433 struct tmpfs_dirent * tmpfs_dir_lookup(struct tmpfs_node *node,
434 struct tmpfs_node *f,
435 struct componentname *cnp);
436 int tmpfs_dir_getdotdent(struct tmpfs_node *, struct uio *);
437 int tmpfs_dir_getdotdotdent(struct tmpfs_node *, struct uio *);
438 struct tmpfs_dirent * tmpfs_dir_lookupbycookie(struct tmpfs_node *, off_t);
439 int tmpfs_dir_getdents(struct tmpfs_node *, struct uio *, off_t *);
440 int tmpfs_dir_whiteout_add(struct vnode *, struct componentname *);
441 void tmpfs_dir_whiteout_remove(struct vnode *, struct componentname *);
442 int tmpfs_reg_resize(struct vnode *, off_t, boolean_t);
443 int tmpfs_chflags(struct vnode *, int, struct ucred *, struct thread *);
444 int tmpfs_chmod(struct vnode *, mode_t, struct ucred *, struct thread *);
445 int tmpfs_chown(struct vnode *, uid_t, gid_t, struct ucred *,
446 struct thread *);
447 int tmpfs_chsize(struct vnode *, u_quad_t, struct ucred *, struct thread *);
448 int tmpfs_chtimes(struct vnode *, struct timespec *, struct timespec *,
449 struct timespec *, int, struct ucred *, struct thread *);
450 void tmpfs_itimes(struct vnode *, const struct timespec *,
451 const struct timespec *);
452
453 void tmpfs_update(struct vnode *);
454 int tmpfs_truncate(struct vnode *, off_t);
455
456 /* --------------------------------------------------------------------- */
457
458 /*
459 * Convenience macros to simplify some logical expressions.
460 */
461 #define IMPLIES(a, b) (!(a) || (b))
462 #define IFF(a, b) (IMPLIES(a, b) && IMPLIES(b, a))
463
464 /* --------------------------------------------------------------------- */
465
466 /*
467 * Checks that the directory entry pointed by 'de' matches the name 'name'
468 * with a length of 'len'.
469 */
470 #define TMPFS_DIRENT_MATCHES(de, name, len) \
471 (de->td_namelen == (uint16_t)len && \
472 bcmp((de)->td_name, (name), (de)->td_namelen) == 0)
473
474 /* --------------------------------------------------------------------- */
475
476 /*
477 * Ensures that the node pointed by 'node' is a directory and that its
478 * contents are consistent with respect to directories.
479 */
480 #define TMPFS_VALIDATE_DIR(node) \
481 MPASS((node)->tn_type == VDIR); \
482 MPASS((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \
483 MPASS((node)->tn_dir.tn_readdir_lastp == NULL || \
484 tmpfs_dircookie((node)->tn_dir.tn_readdir_lastp) == (node)->tn_dir.tn_readdir_lastn);
485
486 /* --------------------------------------------------------------------- */
487
488 /*
489 * Memory management stuff.
490 */
491
492 /*
493 * Amount of memory pages to reserve for the system (e.g., to not use by
494 * tmpfs).
495 */
496 #define TMPFS_PAGES_MINRESERVED (4 * 1024 * 1024 / PAGE_SIZE)
497
498 size_t tmpfs_mem_avail(void);
499
500 size_t tmpfs_pages_used(struct tmpfs_mount *tmp);
501
502 #endif
503
504 /* --------------------------------------------------------------------- */
505
506 /*
507 * Macros/functions to convert from generic data structures to tmpfs
508 * specific ones.
509 */
510
511 static inline
512 struct tmpfs_mount *
513 VFS_TO_TMPFS(struct mount *mp)
514 {
515 struct tmpfs_mount *tmp;
516
517 MPASS((mp) != NULL && (mp)->mnt_data != NULL);
518 tmp = (struct tmpfs_mount *)(mp)->mnt_data;
519 return tmp;
520 }
521
522 static inline
523 struct tmpfs_node *
524 VP_TO_TMPFS_NODE(struct vnode *vp)
525 {
526 struct tmpfs_node *node;
527
528 MPASS((vp) != NULL && (vp)->v_data != NULL);
529 node = (struct tmpfs_node *)vp->v_data;
530 return node;
531 }
532
533 static inline
534 struct tmpfs_node *
535 VP_TO_TMPFS_DIR(struct vnode *vp)
536 {
537 struct tmpfs_node *node;
538
539 node = VP_TO_TMPFS_NODE(vp);
540 TMPFS_VALIDATE_DIR(node);
541 return node;
542 }
543
544 #endif /* _FS_TMPFS_TMPFS_H_ */
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