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tmpfs.h revision 1.13
      1 /*	$NetBSD: tmpfs.h,v 1.13 2005/12/24 12:31:57 jmmv Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2005 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  * 3. All advertising materials mentioning features or use of this software
     20  *    must display the following acknowledgement:
     21  *        This product includes software developed by the NetBSD
     22  *        Foundation, Inc. and its contributors.
     23  * 4. Neither the name of The NetBSD Foundation nor the names of its
     24  *    contributors may be used to endorse or promote products derived
     25  *    from this software without specific prior written permission.
     26  *
     27  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     28  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     29  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     30  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     31  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     32  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     33  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     34  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     35  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     36  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     37  * POSSIBILITY OF SUCH DAMAGE.
     38  */
     39 
     40 #ifndef _FS_TMPFS_TMPFS_H_
     41 #define _FS_TMPFS_TMPFS_H_
     42 
     43 /* ---------------------------------------------------------------------
     44  * KERNEL-SPECIFIC DEFINITIONS
     45  * --------------------------------------------------------------------- */
     46 
     47 #if defined(_KERNEL)
     48 
     49 #include <sys/dirent.h>
     50 #include <sys/mount.h>
     51 #include <sys/queue.h>
     52 #include <sys/vnode.h>
     53 
     54 #include <fs/tmpfs/tmpfs_pool.h>
     55 
     56 /* --------------------------------------------------------------------- */
     57 
     58 /*
     59  * Internal representation of a tmpfs directory entry.
     60  */
     61 struct tmpfs_dirent {
     62 	TAILQ_ENTRY(tmpfs_dirent)	td_entries;
     63 
     64 	/* Length of the name stored in this directory entry.  This avoids
     65 	 * the need to recalculate it every time the name is used. */
     66 	uint16_t			td_namelen;
     67 
     68 	/* The name of the entry, allocated from a string pool.  This
     69 	* string is not required to be zero-terminated; therefore, the
     70 	* td_namelen field must always be used when accessing its value. */
     71 	char *				td_name;
     72 
     73 	/* Pointer to the node this entry refers to. */
     74 	struct tmpfs_node *		td_node;
     75 };
     76 
     77 /* A directory in tmpfs holds a sorted list of directory entries, which in
     78  * turn point to other files (which can be directories themselves).
     79  *
     80  * In tmpfs, this list is managed by a tail queue, whose head is defined by
     81  * the struct tmpfs_dir type.
     82  *
     83  * It is imporant to notice that directories do not have entries for . and
     84  * .. as other file systems do.  These can be generated when requested
     85  * based on information available by other means, such as the pointer to
     86  * the node itself in the former case or the pointer to the parent directory
     87  * in the latter case.  This is done to simplify tmpfs's code and, more
     88  * importantly, to remove redundancy. */
     89 TAILQ_HEAD(tmpfs_dir, tmpfs_dirent);
     90 
     91 #define	TMPFS_DIRCOOKIE(dirent)	((off_t)(uintptr_t)(dirent))
     92 #define	TMPFS_DIRCOOKIE_DOT	0
     93 #define	TMPFS_DIRCOOKIE_DOTDOT	1
     94 #define	TMPFS_DIRCOOKIE_EOF	2
     95 
     96 /* --------------------------------------------------------------------- */
     97 
     98 /*
     99  * Internal representation of a tmpfs file system node.
    100  *
    101  * This structure is splitted in two parts: one holds attributes common
    102  * to all file types and the other holds data that is only applicable to
    103  * a particular type.  The code must be careful to only access those
    104  * attributes that are actually allowed by the node's type.
    105  */
    106 struct tmpfs_node {
    107 	/* Doubly-linked list entry which links all existing nodes for a
    108 	 * single file system.  This is provided to ease the removal of
    109 	 * all nodes during the unmount operation. */
    110 	LIST_ENTRY(tmpfs_node)	tn_entries;
    111 
    112 	/* The node's type.  Any of 'VBLK', 'VCHR', 'VDIR', 'VFIFO',
    113 	 * 'VLNK', 'VREG' and 'VSOCK' is allowed.  The usage of vnode
    114 	 * types instead of a custom enumeration is to make things simpler
    115 	 * and faster, as we do not need to convert between two types. */
    116 	enum vtype		tn_type;
    117 
    118 	/* Node identifier. */
    119 	ino_t			tn_id;
    120 
    121 	/* Node's internal status.  This is used by several file system
    122 	 * operations to do modifications to the node in a delayed
    123 	 * fashion. */
    124 	int			tn_status;
    125 #define	TMPFS_NODE_ACCESSED	(1 << 1)
    126 #define	TMPFS_NODE_MODIFIED	(1 << 2)
    127 #define	TMPFS_NODE_CHANGED	(1 << 3)
    128 
    129 	/* The node size.  It does not necessarily match the real amount
    130 	 * of memory consumed by it. */
    131 	off_t			tn_size;
    132 
    133 	/* Generic node attributes. */
    134 	uid_t			tn_uid;
    135 	gid_t			tn_gid;
    136 	mode_t			tn_mode;
    137 	int			tn_flags;
    138 	nlink_t			tn_links;
    139 	struct timespec		tn_atime;
    140 	struct timespec		tn_mtime;
    141 	struct timespec		tn_ctime;
    142 	struct timespec		tn_birthtime;
    143 	unsigned long		tn_gen;
    144 
    145 	/* Head of byte-level lock list (used by tmpfs_advlock). */
    146 	struct lockf *		tn_lockf;
    147 
    148 	/* As there is a single vnode for each active file within the
    149 	 * system, care has to be taken to avoid allocating more than one
    150 	 * vnode per file.  In order to do this, a bidirectional association
    151 	 * is kept between vnodes and nodes.
    152 	 *
    153 	 * Whenever a vnode is allocated, its v_data field is updated to
    154 	 * point to the node it references.  At the same time, the node's
    155 	 * tn_vnode field is modified to point to the new vnode representing
    156 	 * it.  Further attempts to allocate a vnode for this same node will
    157 	 * result in returning a new reference to the value stored in
    158 	 * tn_vnode.
    159 	 *
    160 	 * May be NULL when the node is unused (that is, no vnode has been
    161 	 * allocated for it or it has been reclaimed). */
    162 	struct vnode *		tn_vnode;
    163 
    164 	/* Pointer to the node returned by tmpfs_lookup() after doing a
    165 	 * delete or a rename lookup; its value is only valid in these two
    166 	 * situations.  In case we were looking up . or .., it holds a null
    167 	 * pointer. */
    168 	struct tmpfs_dirent *	tn_lookup_dirent;
    169 
    170 	union {
    171 		/* Valid when tn_type == VBLK || tn_type == VCHR. */
    172 		struct {
    173 			dev_t			tn_rdev;
    174 		};
    175 
    176 		/* Valid when tn_type == VDIR. */
    177 		struct {
    178 			/* Pointer to the parent directory.  The root
    179 			 * directory has a pointer to itself in this field;
    180 			 * this property identifies the root node. */
    181 			struct tmpfs_node *	tn_parent;
    182 
    183 			/* Head of a tail-queue that links the contents of
    184 			 * the directory together.  See above for a
    185 			 * description of its contents. */
    186 			struct tmpfs_dir	tn_dir;
    187 
    188 			/* Number and pointer of the first directory entry
    189 			 * returned by the readdir operation if it were
    190 			 * called again to continue reading data from the
    191 			 * same directory as before.  This is used to speed
    192 			 * up reads of long directories, assuming that no
    193 			 * more than one read is in progress at a given time.
    194 			 * Otherwise, these values are discarded and a linear
    195 			 * scan is performed from the beginning up to the
    196 			 * point where readdir starts returning values. */
    197 			off_t			tn_readdir_lastn;
    198 			struct tmpfs_dirent *	tn_readdir_lastp;
    199 		};
    200 
    201 		/* Valid when tn_type == VLNK. */
    202 		struct {
    203 			/* The link's target, allocated from a string pool. */
    204 			char *			tn_link;
    205 		};
    206 
    207 		/* Valid when tn_type == VREG. */
    208 		struct {
    209 			/* The contents of regular files stored in a tmpfs
    210 			 * file system are represented by a single anonymous
    211 			 * memory object (aobj, for short).  The aobj provides
    212 			 * direct access to any position within the file,
    213 			 * because its contents are always mapped in a
    214 			 * contiguous region of virtual memory.  It is a task
    215 			 * of the memory management subsystem (see uvm(9)) to
    216 			 * issue the required page ins or page outs whenever
    217 			 * a position within the file is accessed. */
    218 			struct uvm_object *	tn_aobj;
    219 			size_t			tn_aobj_pages;
    220 		};
    221 	};
    222 };
    223 LIST_HEAD(tmpfs_node_list, tmpfs_node);
    224 
    225 /* --------------------------------------------------------------------- */
    226 
    227 /*
    228  * Internal representation of a tmpfs mount point.
    229  */
    230 struct tmpfs_mount {
    231 	/* Maximum number of memory pages available for use by the file
    232 	 * system, set during mount time.  This variable must never be
    233 	 * used directly as it may be bigger that the current amount of
    234 	 * free memory; in the extreme case, it will hold the SIZE_MAX
    235 	 * value.  Instead, use the TMPFS_PAGES_MAX macro. */
    236 	size_t			tm_pages_max;
    237 
    238 	/* Number of pages in use by the file system.  Cannot be bigger
    239 	 * than the value returned by TMPFS_PAGES_MAX in any case. */
    240 	size_t			tm_pages_used;
    241 
    242 	/* Pointer to the node representing the root directory of this
    243 	 * file system. */
    244 	struct tmpfs_node *	tm_root;
    245 
    246 	/* Maximum number of possible nodes for this file system; set
    247 	 * during mount time.  We need a hard limit on the maximum number
    248 	 * of nodes to avoid allocating too much of them; their objects
    249 	 * cannot be released until the file system is unmounted.
    250 	 * Otherwise, we could easily run out of memory by creating lots
    251 	 * of empty files and then simply removing them. */
    252 	ino_t			tm_nodes_max;
    253 
    254 	/* Number of nodes currently allocated.  This number only grows.
    255 	 * When it reaches tm_nodes_max, no more new nodes can be allocated.
    256 	 * Of course, the old, unused ones can be reused. */
    257 	ino_t			tm_nodes_last;
    258 
    259 	/* Nodes are organized in two different lists.  The used list
    260 	 * contains all nodes that are currently used by the file system;
    261 	 * i.e., they refer to existing files.  The available list contains
    262 	 * all nodes that are currently available for use by new files.
    263 	 * Nodes must be kept in this list (instead of deleting them)
    264 	 * because we need to keep track of their generation number (tn_gen
    265 	 * field).
    266 	 *
    267 	 * Note that nodes are lazily allocated: if the available list is
    268 	 * empty and we have enough space to create more nodes, they will be
    269 	 * created and inserted in the used list.  Once these are released,
    270 	 * they will go into the available list, remaining alive until the
    271 	 * file system is unmounted. */
    272 	struct tmpfs_node_list	tm_nodes_used;
    273 	struct tmpfs_node_list	tm_nodes_avail;
    274 
    275 	/* Pools used to store file system meta data.  These are not shared
    276 	 * across several instances of tmpfs for the reasons described in
    277 	 * tmpfs_pool.c. */
    278 	struct tmpfs_pool	tm_dirent_pool;
    279 	struct tmpfs_pool	tm_node_pool;
    280 	struct tmpfs_str_pool	tm_str_pool;
    281 };
    282 
    283 /* --------------------------------------------------------------------- */
    284 
    285 /*
    286  * This structure maps a file identifier to a tmpfs node.  Used by the
    287  * NFS code.
    288  */
    289 struct tmpfs_fid {
    290 	uint16_t		tf_len;
    291 	uint16_t		tf_pad;
    292 	ino_t			tf_id;
    293 	unsigned long		tf_gen;
    294 };
    295 
    296 /* --------------------------------------------------------------------- */
    297 
    298 /*
    299  * Prototypes for tmpfs_subr.c.
    300  */
    301 
    302 int	tmpfs_alloc_node(struct tmpfs_mount *, enum vtype,
    303 	    uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *,
    304 	    char *, dev_t, struct proc *, struct tmpfs_node **);
    305 void	tmpfs_free_node(struct tmpfs_mount *, struct tmpfs_node *);
    306 int	tmpfs_alloc_dirent(struct tmpfs_mount *, struct tmpfs_node *,
    307 	    const char *, uint16_t, struct tmpfs_dirent **);
    308 void	tmpfs_free_dirent(struct tmpfs_mount *, struct tmpfs_dirent *,
    309 	    boolean_t);
    310 int	tmpfs_alloc_vp(struct mount *, struct tmpfs_node *, struct vnode **);
    311 void	tmpfs_free_vp(struct vnode *);
    312 int	tmpfs_alloc_file(struct vnode *, struct vnode **, struct vattr *,
    313 	    struct componentname *, char *);
    314 void	tmpfs_dir_attach(struct vnode *, struct tmpfs_dirent *);
    315 void	tmpfs_dir_detach(struct vnode *, struct tmpfs_dirent *);
    316 struct tmpfs_dirent *	tmpfs_dir_lookup(struct tmpfs_node *node,
    317 			    struct componentname *cnp);
    318 int	tmpfs_dir_getdotdent(struct tmpfs_node *, struct uio *);
    319 int	tmpfs_dir_getdotdotdent(struct tmpfs_node *, struct uio *);
    320 struct tmpfs_dirent *	tmpfs_dir_lookupbycookie(struct tmpfs_node *, off_t);
    321 int	tmpfs_dir_getdents(struct tmpfs_node *, struct uio *, off_t *);
    322 int	tmpfs_reg_resize(struct vnode *, off_t);
    323 size_t	tmpfs_mem_info(boolean_t);
    324 int	tmpfs_chflags(struct vnode *, int, struct ucred *, struct proc *);
    325 int	tmpfs_chmod(struct vnode *, mode_t, struct ucred *, struct proc *);
    326 int	tmpfs_chown(struct vnode *, uid_t, gid_t, struct ucred *,
    327 	    struct proc *);
    328 int	tmpfs_chsize(struct vnode *, u_quad_t, struct ucred *, struct proc *);
    329 int	tmpfs_chtimes(struct vnode *, struct timespec *, struct timespec *,
    330 	    int, struct ucred *, struct lwp *);
    331 void	tmpfs_itimes(struct vnode *, const struct timespec *,
    332 	    const struct timespec *);
    333 
    334 void	tmpfs_update(struct vnode *, const struct timespec *,
    335 	    const struct timespec *, int);
    336 int	tmpfs_truncate(struct vnode *, off_t);
    337 
    338 /* --------------------------------------------------------------------- */
    339 
    340 /*
    341  * Convenience macros to simplify some logical expressions.
    342  */
    343 #define IMPLIES(a, b) (!(a) || (b))
    344 #define IFF(a, b) (IMPLIES(a, b) && IMPLIES(b, a))
    345 
    346 /* --------------------------------------------------------------------- */
    347 
    348 /*
    349  * Checks that the directory entry pointed by 'de' matches the name 'name'
    350  * with a length of 'len'.
    351  */
    352 #define TMPFS_DIRENT_MATCHES(de, name, len) \
    353     (de->td_namelen == (uint16_t)len && \
    354     memcmp((de)->td_name, (name), (de)->td_namelen) == 0)
    355 
    356 /* --------------------------------------------------------------------- */
    357 
    358 /*
    359  * Ensures that the node pointed by 'node' is a directory and that its
    360  * contents are consistent with respect to directories.
    361  */
    362 #define TMPFS_VALIDATE_DIR(node) \
    363     KASSERT((node)->tn_type == VDIR); \
    364     KASSERT((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \
    365     KASSERT((node)->tn_readdir_lastp == NULL || \
    366 	TMPFS_DIRCOOKIE((node)->tn_readdir_lastp) == (node)->tn_readdir_lastn);
    367 
    368 /* --------------------------------------------------------------------- */
    369 
    370 /*
    371  * Memory management stuff.
    372  */
    373 
    374 /* Amount of memory pages to reserve for the system (e.g., to not use by
    375  * tmpfs).
    376  * XXX: Should this be tunable through sysctl, for instance? */
    377 #define TMPFS_PAGES_RESERVED (4 * 1024 * 1024 / PAGE_SIZE)
    378 
    379 /* Returns the maximum size allowed for a tmpfs file system.  This macro
    380  * must be used instead of directly retrieving the value from tm_pages_max.
    381  * The reason is that the size of a tmpfs file system is dynamic: it lets
    382  * the user store files as long as there is enough free memory (including
    383  * physical memory and swap space).  Therefore, the amount of memory to be
    384  * used is either the limit imposed by the user during mount time or the
    385  * amount of available memory, whichever is lower.  To avoid consuming all
    386  * the memory for a given mount point, the system will always reserve a
    387  * minimum of TMPFS_PAGES_RESERVED pages, which is also taken into account
    388  * by this macro (see above). */
    389 static inline size_t
    390 TMPFS_PAGES_MAX(struct tmpfs_mount *tmp)
    391 {
    392 	size_t freepages;
    393 
    394 	freepages = tmpfs_mem_info(FALSE);
    395 	if (freepages < TMPFS_PAGES_RESERVED)
    396 		freepages = 0;
    397 	else
    398 		freepages -= TMPFS_PAGES_RESERVED;
    399 
    400 	return MIN(tmp->tm_pages_max, freepages + tmp->tm_pages_used);
    401 }
    402 
    403 /* Returns the available space for the given file system. */
    404 #define TMPFS_PAGES_AVAIL(tmp) (TMPFS_PAGES_MAX(tmp) - (tmp)->tm_pages_used)
    405 
    406 /* --------------------------------------------------------------------- */
    407 
    408 /*
    409  * Macros/functions to convert from generic data structures to tmpfs
    410  * specific ones.
    411  */
    412 
    413 static inline
    414 struct tmpfs_mount *
    415 VFS_TO_TMPFS(struct mount *mp)
    416 {
    417 	struct tmpfs_mount *tmp;
    418 
    419 	KASSERT((mp) != NULL && (mp)->mnt_data != NULL);
    420 	tmp = (struct tmpfs_mount *)(mp)->mnt_data;
    421 	return tmp;
    422 }
    423 
    424 static inline
    425 struct tmpfs_node *
    426 VP_TO_TMPFS_NODE(struct vnode *vp)
    427 {
    428 	struct tmpfs_node *node;
    429 
    430 	KASSERT((vp) != NULL && (vp)->v_data != NULL);
    431 	node = (struct tmpfs_node *)vp->v_data;
    432 	return node;
    433 }
    434 
    435 static inline
    436 struct tmpfs_node *
    437 VP_TO_TMPFS_DIR(struct vnode *vp)
    438 {
    439 	struct tmpfs_node *node;
    440 
    441 	node = VP_TO_TMPFS_NODE(vp);
    442 	TMPFS_VALIDATE_DIR(node);
    443 	return node;
    444 }
    445 
    446 #endif /* _KERNEL */
    447 
    448 /* ---------------------------------------------------------------------
    449  * USER AND KERNEL DEFINITIONS
    450  * --------------------------------------------------------------------- */
    451 
    452 /*
    453  * This structure is used to communicate mount parameters between userland
    454  * and kernel space.
    455  */
    456 #define TMPFS_ARGS_VERSION	1
    457 struct tmpfs_args {
    458 	int			ta_version;
    459 
    460 	/* Size counters. */
    461 	ino_t			ta_nodes_max;
    462 	off_t			ta_size_max;
    463 
    464 	/* Root node attributes. */
    465 	uid_t			ta_root_uid;
    466 	gid_t			ta_root_gid;
    467 	mode_t			ta_root_mode;
    468 };
    469 #endif /* _FS_TMPFS_TMPFS_H_ */
    470