xref: /freebsd/sys/fs/tmpfs/tmpfs.h (revision bb15ca603fa442c72dde3f3cb8b46db6970e3950)
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 /* --------------------------------------------------------------------- */
331 
332 /*
333  * Internal representation of a tmpfs mount point.
334  */
335 struct tmpfs_mount {
336 	/* Maximum number of memory pages available for use by the file
337 	 * system, set during mount time.  This variable must never be
338 	 * used directly as it may be bigger than the current amount of
339 	 * free memory; in the extreme case, it will hold the SIZE_MAX
340 	 * value.  Instead, use the TMPFS_PAGES_MAX macro. */
341 	size_t			tm_pages_max;
342 
343 	/* Number of pages in use by the file system.  Cannot be bigger
344 	 * than the value returned by TMPFS_PAGES_MAX in any case. */
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 #define TMPFS_LOCK(tm) mtx_lock(&(tm)->allnode_lock)
393 #define TMPFS_UNLOCK(tm) mtx_unlock(&(tm)->allnode_lock)
394 
395 /* --------------------------------------------------------------------- */
396 
397 /*
398  * This structure maps a file identifier to a tmpfs node.  Used by the
399  * NFS code.
400  */
401 struct tmpfs_fid {
402 	uint16_t		tf_len;
403 	uint16_t		tf_pad;
404 	ino_t			tf_id;
405 	unsigned long		tf_gen;
406 };
407 
408 /* --------------------------------------------------------------------- */
409 
410 #ifdef _KERNEL
411 /*
412  * Prototypes for tmpfs_subr.c.
413  */
414 
415 int	tmpfs_alloc_node(struct tmpfs_mount *, enum vtype,
416 	    uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *,
417 	    char *, dev_t, struct tmpfs_node **);
418 void	tmpfs_free_node(struct tmpfs_mount *, struct tmpfs_node *);
419 int	tmpfs_alloc_dirent(struct tmpfs_mount *, struct tmpfs_node *,
420 	    const char *, uint16_t, struct tmpfs_dirent **);
421 void	tmpfs_free_dirent(struct tmpfs_mount *, struct tmpfs_dirent *,
422 	    boolean_t);
423 int	tmpfs_alloc_vp(struct mount *, struct tmpfs_node *, int,
424 	    struct vnode **);
425 void	tmpfs_free_vp(struct vnode *);
426 int	tmpfs_alloc_file(struct vnode *, struct vnode **, struct vattr *,
427 	    struct componentname *, char *);
428 void	tmpfs_dir_attach(struct vnode *, struct tmpfs_dirent *);
429 void	tmpfs_dir_detach(struct vnode *, struct tmpfs_dirent *);
430 struct tmpfs_dirent *	tmpfs_dir_lookup(struct tmpfs_node *node,
431 			    struct tmpfs_node *f,
432 			    struct componentname *cnp);
433 int	tmpfs_dir_getdotdent(struct tmpfs_node *, struct uio *);
434 int	tmpfs_dir_getdotdotdent(struct tmpfs_node *, struct uio *);
435 struct tmpfs_dirent *	tmpfs_dir_lookupbycookie(struct tmpfs_node *, off_t);
436 int	tmpfs_dir_getdents(struct tmpfs_node *, struct uio *, off_t *);
437 int	tmpfs_dir_whiteout_add(struct vnode *, struct componentname *);
438 void	tmpfs_dir_whiteout_remove(struct vnode *, struct componentname *);
439 int	tmpfs_reg_resize(struct vnode *, off_t);
440 int	tmpfs_chflags(struct vnode *, int, struct ucred *, struct thread *);
441 int	tmpfs_chmod(struct vnode *, mode_t, struct ucred *, struct thread *);
442 int	tmpfs_chown(struct vnode *, uid_t, gid_t, struct ucred *,
443 	    struct thread *);
444 int	tmpfs_chsize(struct vnode *, u_quad_t, struct ucred *, struct thread *);
445 int	tmpfs_chtimes(struct vnode *, struct timespec *, struct timespec *,
446 	    struct timespec *, int, struct ucred *, struct thread *);
447 void	tmpfs_itimes(struct vnode *, const struct timespec *,
448 	    const struct timespec *);
449 
450 void	tmpfs_update(struct vnode *);
451 int	tmpfs_truncate(struct vnode *, off_t);
452 
453 /* --------------------------------------------------------------------- */
454 
455 /*
456  * Convenience macros to simplify some logical expressions.
457  */
458 #define IMPLIES(a, b) (!(a) || (b))
459 #define IFF(a, b) (IMPLIES(a, b) && IMPLIES(b, a))
460 
461 /* --------------------------------------------------------------------- */
462 
463 /*
464  * Checks that the directory entry pointed by 'de' matches the name 'name'
465  * with a length of 'len'.
466  */
467 #define TMPFS_DIRENT_MATCHES(de, name, len) \
468     (de->td_namelen == (uint16_t)len && \
469     bcmp((de)->td_name, (name), (de)->td_namelen) == 0)
470 
471 /* --------------------------------------------------------------------- */
472 
473 /*
474  * Ensures that the node pointed by 'node' is a directory and that its
475  * contents are consistent with respect to directories.
476  */
477 #define TMPFS_VALIDATE_DIR(node) \
478     MPASS((node)->tn_type == VDIR); \
479     MPASS((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \
480     MPASS((node)->tn_dir.tn_readdir_lastp == NULL || \
481 	tmpfs_dircookie((node)->tn_dir.tn_readdir_lastp) == (node)->tn_dir.tn_readdir_lastn);
482 
483 /* --------------------------------------------------------------------- */
484 
485 /*
486  * Memory management stuff.
487  */
488 
489 /* Amount of memory pages to reserve for the system (e.g., to not use by
490  * tmpfs).
491  * XXX: Should this be tunable through sysctl, for instance? */
492 #define TMPFS_PAGES_RESERVED (4 * 1024 * 1024 / PAGE_SIZE)
493 
494 /*
495  * Returns information about the number of available memory pages,
496  * including physical and virtual ones.
497  *
498  * Remember to remove TMPFS_PAGES_RESERVED from the returned value to avoid
499  * excessive memory usage.
500  *
501  */
502 static __inline size_t
503 tmpfs_mem_info(void)
504 {
505 
506 	return (swap_pager_avail + cnt.v_free_count + cnt.v_cache_count);
507 }
508 
509 /* Returns the maximum size allowed for a tmpfs file system.  This macro
510  * must be used instead of directly retrieving the value from tm_pages_max.
511  * The reason is that the size of a tmpfs file system is dynamic: it lets
512  * the user store files as long as there is enough free memory (including
513  * physical memory and swap space).  Therefore, the amount of memory to be
514  * used is either the limit imposed by the user during mount time or the
515  * amount of available memory, whichever is lower.  To avoid consuming all
516  * the memory for a given mount point, the system will always reserve a
517  * minimum of TMPFS_PAGES_RESERVED pages, which is also taken into account
518  * by this macro (see above). */
519 static __inline size_t
520 TMPFS_PAGES_MAX(struct tmpfs_mount *tmp)
521 {
522 	size_t freepages;
523 
524 	freepages = tmpfs_mem_info();
525 	freepages -= freepages < TMPFS_PAGES_RESERVED ?
526 	    freepages : TMPFS_PAGES_RESERVED;
527 
528 	return MIN(tmp->tm_pages_max, freepages + tmp->tm_pages_used);
529 }
530 
531 /* Returns the available space for the given file system. */
532 #define TMPFS_META_PAGES(tmp) (howmany((tmp)->tm_nodes_inuse * (sizeof(struct tmpfs_node) \
533 				+ sizeof(struct tmpfs_dirent)), PAGE_SIZE))
534 #define TMPFS_FILE_PAGES(tmp) ((tmp)->tm_pages_used)
535 
536 #define TMPFS_PAGES_AVAIL(tmp) (TMPFS_PAGES_MAX(tmp) > \
537 			TMPFS_META_PAGES(tmp)+TMPFS_FILE_PAGES(tmp)? \
538 			TMPFS_PAGES_MAX(tmp) - TMPFS_META_PAGES(tmp) \
539 			- TMPFS_FILE_PAGES(tmp):0)
540 
541 #endif
542 
543 /* --------------------------------------------------------------------- */
544 
545 /*
546  * Macros/functions to convert from generic data structures to tmpfs
547  * specific ones.
548  */
549 
550 static inline
551 struct tmpfs_mount *
552 VFS_TO_TMPFS(struct mount *mp)
553 {
554 	struct tmpfs_mount *tmp;
555 
556 	MPASS((mp) != NULL && (mp)->mnt_data != NULL);
557 	tmp = (struct tmpfs_mount *)(mp)->mnt_data;
558 	return tmp;
559 }
560 
561 static inline
562 struct tmpfs_node *
563 VP_TO_TMPFS_NODE(struct vnode *vp)
564 {
565 	struct tmpfs_node *node;
566 
567 	MPASS((vp) != NULL && (vp)->v_data != NULL);
568 	node = (struct tmpfs_node *)vp->v_data;
569 	return node;
570 }
571 
572 static inline
573 struct tmpfs_node *
574 VP_TO_TMPFS_DIR(struct vnode *vp)
575 {
576 	struct tmpfs_node *node;
577 
578 	node = VP_TO_TMPFS_NODE(vp);
579 	TMPFS_VALIDATE_DIR(node);
580 	return node;
581 }
582 
583 #endif /* _FS_TMPFS_TMPFS_H_ */
584