tmpfs.h revision 1.36 1 /* $NetBSD: tmpfs.h,v 1.36 2008/07/28 18:00:20 pooka 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 #include <fs/tmpfs/tmpfs_args.h>
43
44 /* --------------------------------------------------------------------- */
45
46 /* Each entry in a directory has a cookie that identifies it. Cookies
47 * supersede offsets within directories because, given how tmpfs stores
48 * directories in memory, there is no such thing as an offset. (Emulating
49 * a real offset could be very difficult.)
50 *
51 * The '.', '..' and the end of directory markers have fixed cookies which
52 * cannot collide with the cookies generated by other entries. The cookies
53 * fot the other entries are generated based on the memory address on which
54 * stores their information is stored.
55 *
56 * Ideally, using the entry's memory pointer as the cookie would be enough
57 * to represent it and it wouldn't cause collisions in any system.
58 * Unfortunately, this results in "offsets" with very large values which
59 * later raise problems in the Linux compatibility layer (and maybe in other
60 * places) as described in PR kern/32034. Hence we need to workaround this
61 * with a rather ugly hack.
62 *
63 * Linux 32-bit binaries, unless built with _FILE_OFFSET_BITS=64, have off_t
64 * set to 'long', which is a 32-bit *signed* long integer. Regardless of
65 * the macro value, GLIBC (2.3 at least) always uses the getdents64
66 * system call (when calling readdir) which internally returns off64_t
67 * offsets. In order to make 32-bit binaries work, *GLIBC* converts the
68 * 64-bit values returned by the kernel to 32-bit ones and aborts with
69 * EOVERFLOW if the conversion results in values that won't fit in 32-bit
70 * integers (which it assumes is because the directory is extremely large).
71 * This wouldn't cause problems if we were dealing with unsigned integers,
72 * but as we have signed integers, this check fails due to sign expansion.
73 *
74 * For example, consider that the kernel returns the 0xc1234567 cookie to
75 * userspace in a off64_t integer. Later on, GLIBC casts this value to
76 * off_t (remember, signed) with code similar to:
77 * system call returns the offset in kernel_value;
78 * off_t casted_value = kernel_value;
79 * if (sizeof(off_t) != sizeof(off64_t) &&
80 * kernel_value != casted_value)
81 * error!
82 * In this case, casted_value still has 0xc1234567, but when it is compared
83 * for equality against kernel_value, it is promoted to a 64-bit integer and
84 * becomes 0xffffffffc1234567, which is different than 0x00000000c1234567.
85 * Then, GLIBC assumes this is because the directory is very large.
86 *
87 * Given that all the above happens in user-space, we have no control over
88 * it; therefore we must workaround the issue here. We do this by
89 * truncating the pointer value to a 32-bit integer and hope that there
90 * won't be collisions. In fact, this will not cause any problems in
91 * 32-bit platforms but some might arise in 64-bit machines (I'm not sure
92 * if they can happen at all in practice).
93 *
94 * XXX A nicer solution shall be attempted. */
95 #define TMPFS_DIRCOOKIE_DOT 0
96 #define TMPFS_DIRCOOKIE_DOTDOT 1
97 #define TMPFS_DIRCOOKIE_EOF 2
98 static __inline
99 off_t
100 tmpfs_dircookie(struct tmpfs_dirent *de)
101 {
102 off_t cookie;
103
104 cookie = ((off_t)(uintptr_t)de >> 1) & 0x7FFFFFFF;
105 KASSERT(cookie != TMPFS_DIRCOOKIE_DOT);
106 KASSERT(cookie != TMPFS_DIRCOOKIE_DOTDOT);
107 KASSERT(cookie != TMPFS_DIRCOOKIE_EOF);
108
109 return cookie;
110 }
111
112 /* --------------------------------------------------------------------- */
113
114 LIST_HEAD(tmpfs_node_list, tmpfs_node);
115
116 /* --------------------------------------------------------------------- */
117
118 /*
119 * Internal representation of a tmpfs mount point.
120 */
121 struct tmpfs_mount {
122 /* Maximum number of memory pages available for use by the file
123 * system, set during mount time. This variable must never be
124 * used directly as it may be bigger than the current amount of
125 * free memory; in the extreme case, it will hold the SIZE_MAX
126 * value. Instead, use the TMPFS_PAGES_MAX macro. */
127 unsigned int tm_pages_max;
128
129 /* Number of pages in use by the file system. Cannot be bigger
130 * than the value returned by TMPFS_PAGES_MAX in any case. */
131 unsigned int tm_pages_used;
132
133 /* Pointer to the node representing the root directory of this
134 * file system. */
135 struct tmpfs_node * tm_root;
136
137 /* Maximum number of possible nodes for this file system; set
138 * during mount time. We need a hard limit on the maximum number
139 * of nodes to avoid allocating too much of them; their objects
140 * cannot be released until the file system is unmounted.
141 * Otherwise, we could easily run out of memory by creating lots
142 * of empty files and then simply removing them. */
143 unsigned int tm_nodes_max;
144
145 /* Number of nodes currently allocated. This number only grows.
146 * When it reaches tm_nodes_max, no more new nodes can be allocated.
147 * Of course, the old, unused ones can be reused. */
148 unsigned int tm_nodes_cnt;
149
150 /* Node list. */
151 kmutex_t tm_lock;
152 struct tmpfs_node_list tm_nodes;
153
154 /* Pools used to store file system meta data. These are not shared
155 * across several instances of tmpfs for the reasons described in
156 * tmpfs_pool.c. */
157 struct tmpfs_pool tm_dirent_pool;
158 struct tmpfs_pool tm_node_pool;
159 struct tmpfs_str_pool tm_str_pool;
160 };
161
162 /* --------------------------------------------------------------------- */
163
164 /*
165 * This structure maps a file identifier to a tmpfs node. Used by the
166 * NFS code.
167 */
168 struct tmpfs_fid {
169 uint16_t tf_len;
170 uint16_t tf_pad;
171 uint32_t tf_gen;
172 ino_t tf_id;
173 };
174
175 /* --------------------------------------------------------------------- */
176
177 /*
178 * Prototypes for tmpfs_subr.c.
179 */
180
181 int tmpfs_alloc_node(struct tmpfs_mount *, enum vtype,
182 uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *,
183 char *, dev_t, struct tmpfs_node **);
184 void tmpfs_free_node(struct tmpfs_mount *, struct tmpfs_node *);
185 int tmpfs_alloc_dirent(struct tmpfs_mount *, struct tmpfs_node *,
186 const char *, uint16_t, struct tmpfs_dirent **);
187 void tmpfs_free_dirent(struct tmpfs_mount *, struct tmpfs_dirent *,
188 bool);
189 int tmpfs_alloc_vp(struct mount *, struct tmpfs_node *, struct vnode **);
190 void tmpfs_free_vp(struct vnode *);
191 int tmpfs_alloc_file(struct vnode *, struct vnode **, struct vattr *,
192 struct componentname *, char *);
193 void tmpfs_dir_attach(struct vnode *, struct tmpfs_dirent *);
194 void tmpfs_dir_detach(struct vnode *, struct tmpfs_dirent *);
195 struct tmpfs_dirent * tmpfs_dir_lookup(struct tmpfs_node *node,
196 struct componentname *cnp);
197 int tmpfs_dir_getdotdent(struct tmpfs_node *, struct uio *);
198 int tmpfs_dir_getdotdotdent(struct tmpfs_node *, struct uio *);
199 struct tmpfs_dirent * tmpfs_dir_lookupbycookie(struct tmpfs_node *, off_t);
200 int tmpfs_dir_getdents(struct tmpfs_node *, struct uio *, off_t *);
201 int tmpfs_reg_resize(struct vnode *, off_t);
202 size_t tmpfs_mem_info(bool);
203 int tmpfs_chflags(struct vnode *, int, kauth_cred_t, struct lwp *);
204 int tmpfs_chmod(struct vnode *, mode_t, kauth_cred_t, struct lwp *);
205 int tmpfs_chown(struct vnode *, uid_t, gid_t, kauth_cred_t, struct lwp *);
206 int tmpfs_chsize(struct vnode *, u_quad_t, kauth_cred_t, struct lwp *);
207 int tmpfs_chtimes(struct vnode *, const struct timespec *,
208 const struct timespec *, const struct timespec *, int, kauth_cred_t,
209 struct lwp *);
210 void tmpfs_itimes(struct vnode *, const struct timespec *,
211 const struct timespec *, const struct timespec *);
212
213 void tmpfs_update(struct vnode *, const struct timespec *,
214 const struct timespec *, const struct timespec *, int);
215 int tmpfs_truncate(struct vnode *, off_t);
216
217 /* --------------------------------------------------------------------- */
218
219 /*
220 * Convenience macros to simplify some logical expressions.
221 */
222 #define IMPLIES(a, b) (!(a) || (b))
223 #define IFF(a, b) (IMPLIES(a, b) && IMPLIES(b, a))
224
225 /* --------------------------------------------------------------------- */
226
227 /*
228 * Checks that the directory entry pointed by 'de' matches the name 'name'
229 * with a length of 'len'.
230 */
231 #define TMPFS_DIRENT_MATCHES(de, name, len) \
232 (de->td_namelen == (uint16_t)len && \
233 memcmp((de)->td_name, (name), (de)->td_namelen) == 0)
234
235 /* --------------------------------------------------------------------- */
236
237 /*
238 * Ensures that the node pointed by 'node' is a directory and that its
239 * contents are consistent with respect to directories.
240 */
241 #define TMPFS_VALIDATE_DIR(node) \
242 KASSERT((node)->tn_type == VDIR); \
243 KASSERT((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \
244 KASSERT((node)->tn_spec.tn_dir.tn_readdir_lastp == NULL || \
245 tmpfs_dircookie((node)->tn_spec.tn_dir.tn_readdir_lastp) == \
246 (node)->tn_spec.tn_dir.tn_readdir_lastn);
247
248 /* --------------------------------------------------------------------- */
249
250 /*
251 * Memory management stuff.
252 */
253
254 /* Amount of memory pages to reserve for the system (e.g., to not use by
255 * tmpfs).
256 * XXX: Should this be tunable through sysctl, for instance? */
257 #define TMPFS_PAGES_RESERVED (4 * 1024 * 1024 / PAGE_SIZE)
258
259 /* Returns the maximum size allowed for a tmpfs file system. This macro
260 * must be used instead of directly retrieving the value from tm_pages_max.
261 * The reason is that the size of a tmpfs file system is dynamic: it lets
262 * the user store files as long as there is enough free memory (including
263 * physical memory and swap space). Therefore, the amount of memory to be
264 * used is either the limit imposed by the user during mount time or the
265 * amount of available memory, whichever is lower. To avoid consuming all
266 * the memory for a given mount point, the system will always reserve a
267 * minimum of TMPFS_PAGES_RESERVED pages, which is also taken into account
268 * by this macro (see above). */
269 static __inline size_t
270 TMPFS_PAGES_MAX(struct tmpfs_mount *tmp)
271 {
272 size_t freepages;
273
274 freepages = tmpfs_mem_info(false);
275 if (freepages < TMPFS_PAGES_RESERVED)
276 freepages = 0;
277 else
278 freepages -= TMPFS_PAGES_RESERVED;
279
280 return MIN(tmp->tm_pages_max, freepages + tmp->tm_pages_used);
281 }
282
283 /* Returns the available space for the given file system. */
284 #define TMPFS_PAGES_AVAIL(tmp) \
285 ((ssize_t)(TMPFS_PAGES_MAX(tmp) - (tmp)->tm_pages_used))
286
287 /* --------------------------------------------------------------------- */
288
289 /*
290 * Macros/functions to convert from generic data structures to tmpfs
291 * specific ones.
292 */
293
294 static __inline
295 struct tmpfs_mount *
296 VFS_TO_TMPFS(struct mount *mp)
297 {
298 struct tmpfs_mount *tmp;
299
300 #ifdef KASSERT
301 KASSERT((mp) != NULL && (mp)->mnt_data != NULL);
302 #endif
303 tmp = (struct tmpfs_mount *)(mp)->mnt_data;
304 return tmp;
305 }
306
307 static __inline
308 struct tmpfs_node *
309 VP_TO_TMPFS_DIR(struct vnode *vp)
310 {
311 struct tmpfs_node *node;
312
313 node = VP_TO_TMPFS_NODE(vp);
314 #ifdef KASSERT
315 TMPFS_VALIDATE_DIR(node);
316 #endif
317 return node;
318 }
319 #endif /* _FS_TMPFS_TMPFS_H_ */
320