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tmpfs.h revision 1.16.2.3
      1 /*	$NetBSD: tmpfs.h,v 1.16.2.3 2006/06/26 12:52:55 yamt 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  * 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 #include <sys/dirent.h>
     47 #include <sys/mount.h>
     48 #include <sys/queue.h>
     49 #include <sys/vnode.h>
     50 
     51 #if defined(_KERNEL)
     52 #include <fs/tmpfs/tmpfs_pool.h>
     53 #endif /* defined(_KERNEL) */
     54 
     55 /* --------------------------------------------------------------------- */
     56 
     57 /*
     58  * Internal representation of a tmpfs directory entry.
     59  */
     60 struct tmpfs_dirent {
     61 	TAILQ_ENTRY(tmpfs_dirent)	td_entries;
     62 
     63 	/* Length of the name stored in this directory entry.  This avoids
     64 	 * the need to recalculate it every time the name is used. */
     65 	uint16_t			td_namelen;
     66 
     67 	/* The name of the entry, allocated from a string pool.  This
     68 	* string is not required to be zero-terminated; therefore, the
     69 	* td_namelen field must always be used when accessing its value. */
     70 	char *				td_name;
     71 
     72 	/* Pointer to the node this entry refers to. */
     73 	struct tmpfs_node *		td_node;
     74 };
     75 
     76 /* A directory in tmpfs holds a sorted list of directory entries, which in
     77  * turn point to other files (which can be directories themselves).
     78  *
     79  * In tmpfs, this list is managed by a tail queue, whose head is defined by
     80  * the struct tmpfs_dir type.
     81  *
     82  * It is imporant to notice that directories do not have entries for . and
     83  * .. as other file systems do.  These can be generated when requested
     84  * based on information available by other means, such as the pointer to
     85  * the node itself in the former case or the pointer to the parent directory
     86  * in the latter case.  This is done to simplify tmpfs's code and, more
     87  * importantly, to remove redundancy. */
     88 TAILQ_HEAD(tmpfs_dir, tmpfs_dirent);
     89 
     90 #define	TMPFS_DIRCOOKIE(dirent)	((off_t)(uintptr_t)(dirent))
     91 #define	TMPFS_DIRCOOKIE_DOT	0
     92 #define	TMPFS_DIRCOOKIE_DOTDOT	1
     93 #define	TMPFS_DIRCOOKIE_EOF	2
     94 
     95 /* --------------------------------------------------------------------- */
     96 
     97 /*
     98  * Internal representation of a tmpfs file system node.
     99  *
    100  * This structure is splitted in two parts: one holds attributes common
    101  * to all file types and the other holds data that is only applicable to
    102  * a particular type.  The code must be careful to only access those
    103  * attributes that are actually allowed by the node's type.
    104  */
    105 struct tmpfs_node {
    106 	/* Doubly-linked list entry which links all existing nodes for a
    107 	 * single file system.  This is provided to ease the removal of
    108 	 * all nodes during the unmount operation. */
    109 	LIST_ENTRY(tmpfs_node)	tn_entries;
    110 
    111 	/* The node's type.  Any of 'VBLK', 'VCHR', 'VDIR', 'VFIFO',
    112 	 * 'VLNK', 'VREG' and 'VSOCK' is allowed.  The usage of vnode
    113 	 * types instead of a custom enumeration is to make things simpler
    114 	 * and faster, as we do not need to convert between two types. */
    115 	enum vtype		tn_type;
    116 
    117 	/* Node identifier. */
    118 	ino_t			tn_id;
    119 
    120 	/* Node's internal status.  This is used by several file system
    121 	 * operations to do modifications to the node in a delayed
    122 	 * fashion. */
    123 	int			tn_status;
    124 #define	TMPFS_NODE_ACCESSED	(1 << 1)
    125 #define	TMPFS_NODE_MODIFIED	(1 << 2)
    126 #define	TMPFS_NODE_CHANGED	(1 << 3)
    127 
    128 	/* The node size.  It does not necessarily match the real amount
    129 	 * of memory consumed by it. */
    130 	off_t			tn_size;
    131 
    132 	/* Generic node attributes. */
    133 	uid_t			tn_uid;
    134 	gid_t			tn_gid;
    135 	mode_t			tn_mode;
    136 	int			tn_flags;
    137 	nlink_t			tn_links;
    138 	struct timespec		tn_atime;
    139 	struct timespec		tn_mtime;
    140 	struct timespec		tn_ctime;
    141 	struct timespec		tn_birthtime;
    142 	unsigned long		tn_gen;
    143 
    144 	/* Head of byte-level lock list (used by tmpfs_advlock). */
    145 	struct lockf *		tn_lockf;
    146 
    147 	/* As there is a single vnode for each active file within the
    148 	 * system, care has to be taken to avoid allocating more than one
    149 	 * vnode per file.  In order to do this, a bidirectional association
    150 	 * is kept between vnodes and nodes.
    151 	 *
    152 	 * Whenever a vnode is allocated, its v_data field is updated to
    153 	 * point to the node it references.  At the same time, the node's
    154 	 * tn_vnode field is modified to point to the new vnode representing
    155 	 * it.  Further attempts to allocate a vnode for this same node will
    156 	 * result in returning a new reference to the value stored in
    157 	 * tn_vnode.
    158 	 *
    159 	 * May be NULL when the node is unused (that is, no vnode has been
    160 	 * allocated for it or it has been reclaimed). */
    161 	struct vnode *		tn_vnode;
    162 
    163 	/* Pointer to the node returned by tmpfs_lookup() after doing a
    164 	 * delete or a rename lookup; its value is only valid in these two
    165 	 * situations.  In case we were looking up . or .., it holds a null
    166 	 * pointer. */
    167 	struct tmpfs_dirent *	tn_lookup_dirent;
    168 
    169 	union {
    170 		/* Valid when tn_type == VBLK || tn_type == VCHR. */
    171 		struct {
    172 			dev_t			tn_rdev;
    173 		} tn_dev;
    174 
    175 		/* Valid when tn_type == VDIR. */
    176 		struct {
    177 			/* Pointer to the parent directory.  The root
    178 			 * directory has a pointer to itself in this field;
    179 			 * this property identifies the root node. */
    180 			struct tmpfs_node *	tn_parent;
    181 
    182 			/* Head of a tail-queue that links the contents of
    183 			 * the directory together.  See above for a
    184 			 * description of its contents. */
    185 			struct tmpfs_dir	tn_dir;
    186 
    187 			/* Number and pointer of the first directory entry
    188 			 * returned by the readdir operation if it were
    189 			 * called again to continue reading data from the
    190 			 * same directory as before.  This is used to speed
    191 			 * up reads of long directories, assuming that no
    192 			 * more than one read is in progress at a given time.
    193 			 * Otherwise, these values are discarded and a linear
    194 			 * scan is performed from the beginning up to the
    195 			 * point where readdir starts returning values. */
    196 			off_t			tn_readdir_lastn;
    197 			struct tmpfs_dirent *	tn_readdir_lastp;
    198 		} tn_dir;
    199 
    200 		/* Valid when tn_type == VLNK. */
    201 		struct tn_lnk {
    202 			/* The link's target, allocated from a string pool. */
    203 			char *			tn_link;
    204 		} tn_lnk;
    205 
    206 		/* Valid when tn_type == VREG. */
    207 		struct tn_reg {
    208 			/* The contents of regular files stored in a tmpfs
    209 			 * file system are represented by a single anonymous
    210 			 * memory object (aobj, for short).  The aobj provides
    211 			 * direct access to any position within the file,
    212 			 * because its contents are always mapped in a
    213 			 * contiguous region of virtual memory.  It is a task
    214 			 * of the memory management subsystem (see uvm(9)) to
    215 			 * issue the required page ins or page outs whenever
    216 			 * a position within the file is accessed. */
    217 			struct uvm_object *	tn_aobj;
    218 			size_t			tn_aobj_pages;
    219 		} tn_reg;
    220 	} tn_spec;
    221 };
    222 
    223 #if defined(_KERNEL)
    224 
    225 LIST_HEAD(tmpfs_node_list, tmpfs_node);
    226 
    227 /* --------------------------------------------------------------------- */
    228 
    229 /*
    230  * Internal representation of a tmpfs mount point.
    231  */
    232 struct tmpfs_mount {
    233 	/* Maximum number of memory pages available for use by the file
    234 	 * system, set during mount time.  This variable must never be
    235 	 * used directly as it may be bigger that the current amount of
    236 	 * free memory; in the extreme case, it will hold the SIZE_MAX
    237 	 * value.  Instead, use the TMPFS_PAGES_MAX macro. */
    238 	size_t			tm_pages_max;
    239 
    240 	/* Number of pages in use by the file system.  Cannot be bigger
    241 	 * than the value returned by TMPFS_PAGES_MAX in any case. */
    242 	size_t			tm_pages_used;
    243 
    244 	/* Pointer to the node representing the root directory of this
    245 	 * file system. */
    246 	struct tmpfs_node *	tm_root;
    247 
    248 	/* Maximum number of possible nodes for this file system; set
    249 	 * during mount time.  We need a hard limit on the maximum number
    250 	 * of nodes to avoid allocating too much of them; their objects
    251 	 * cannot be released until the file system is unmounted.
    252 	 * Otherwise, we could easily run out of memory by creating lots
    253 	 * of empty files and then simply removing them. */
    254 	ino_t			tm_nodes_max;
    255 
    256 	/* Number of nodes currently allocated.  This number only grows.
    257 	 * When it reaches tm_nodes_max, no more new nodes can be allocated.
    258 	 * Of course, the old, unused ones can be reused. */
    259 	ino_t			tm_nodes_last;
    260 
    261 	/* Nodes are organized in two different lists.  The used list
    262 	 * contains all nodes that are currently used by the file system;
    263 	 * i.e., they refer to existing files.  The available list contains
    264 	 * all nodes that are currently available for use by new files.
    265 	 * Nodes must be kept in this list (instead of deleting them)
    266 	 * because we need to keep track of their generation number (tn_gen
    267 	 * field).
    268 	 *
    269 	 * Note that nodes are lazily allocated: if the available list is
    270 	 * empty and we have enough space to create more nodes, they will be
    271 	 * created and inserted in the used list.  Once these are released,
    272 	 * they will go into the available list, remaining alive until the
    273 	 * file system is unmounted. */
    274 	struct tmpfs_node_list	tm_nodes_used;
    275 	struct tmpfs_node_list	tm_nodes_avail;
    276 
    277 	/* Pools used to store file system meta data.  These are not shared
    278 	 * across several instances of tmpfs for the reasons described in
    279 	 * tmpfs_pool.c. */
    280 	struct tmpfs_pool	tm_dirent_pool;
    281 	struct tmpfs_pool	tm_node_pool;
    282 	struct tmpfs_str_pool	tm_str_pool;
    283 };
    284 
    285 /* --------------------------------------------------------------------- */
    286 
    287 /*
    288  * This structure maps a file identifier to a tmpfs node.  Used by the
    289  * NFS code.
    290  */
    291 struct tmpfs_fid {
    292 	uint16_t		tf_len;
    293 	uint16_t		tf_pad;
    294 	uint32_t		tf_gen;
    295 	ino_t			tf_id;
    296 };
    297 
    298 /* --------------------------------------------------------------------- */
    299 
    300 /*
    301  * Prototypes for tmpfs_subr.c.
    302  */
    303 
    304 int	tmpfs_alloc_node(struct tmpfs_mount *, enum vtype,
    305 	    uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *,
    306 	    char *, dev_t, struct proc *, struct tmpfs_node **);
    307 void	tmpfs_free_node(struct tmpfs_mount *, struct tmpfs_node *);
    308 int	tmpfs_alloc_dirent(struct tmpfs_mount *, struct tmpfs_node *,
    309 	    const char *, uint16_t, struct tmpfs_dirent **);
    310 void	tmpfs_free_dirent(struct tmpfs_mount *, struct tmpfs_dirent *,
    311 	    boolean_t);
    312 int	tmpfs_alloc_vp(struct mount *, struct tmpfs_node *, struct vnode **);
    313 void	tmpfs_free_vp(struct vnode *);
    314 int	tmpfs_alloc_file(struct vnode *, struct vnode **, struct vattr *,
    315 	    struct componentname *, char *);
    316 void	tmpfs_dir_attach(struct vnode *, struct tmpfs_dirent *);
    317 void	tmpfs_dir_detach(struct vnode *, struct tmpfs_dirent *);
    318 struct tmpfs_dirent *	tmpfs_dir_lookup(struct tmpfs_node *node,
    319 			    struct componentname *cnp);
    320 int	tmpfs_dir_getdotdent(struct tmpfs_node *, struct uio *);
    321 int	tmpfs_dir_getdotdotdent(struct tmpfs_node *, struct uio *);
    322 struct tmpfs_dirent *	tmpfs_dir_lookupbycookie(struct tmpfs_node *, off_t);
    323 int	tmpfs_dir_getdents(struct tmpfs_node *, struct uio *, off_t *);
    324 int	tmpfs_reg_resize(struct vnode *, off_t);
    325 size_t	tmpfs_mem_info(boolean_t);
    326 int	tmpfs_chflags(struct vnode *, int, kauth_cred_t, struct proc *);
    327 int	tmpfs_chmod(struct vnode *, mode_t, kauth_cred_t, struct proc *);
    328 int	tmpfs_chown(struct vnode *, uid_t, gid_t, kauth_cred_t, struct proc *);
    329 int	tmpfs_chsize(struct vnode *, u_quad_t, kauth_cred_t, struct proc *);
    330 int	tmpfs_chtimes(struct vnode *, struct timespec *, struct timespec *,
    331 	    int, kauth_cred_t, struct lwp *);
    332 void	tmpfs_itimes(struct vnode *, const struct timespec *,
    333 	    const struct timespec *);
    334 
    335 void	tmpfs_update(struct vnode *, const struct timespec *,
    336 	    const struct timespec *, int);
    337 int	tmpfs_truncate(struct vnode *, off_t);
    338 
    339 /* --------------------------------------------------------------------- */
    340 
    341 /*
    342  * Convenience macros to simplify some logical expressions.
    343  */
    344 #define IMPLIES(a, b) (!(a) || (b))
    345 #define IFF(a, b) (IMPLIES(a, b) && IMPLIES(b, a))
    346 
    347 /* --------------------------------------------------------------------- */
    348 
    349 /*
    350  * Checks that the directory entry pointed by 'de' matches the name 'name'
    351  * with a length of 'len'.
    352  */
    353 #define TMPFS_DIRENT_MATCHES(de, name, len) \
    354     (de->td_namelen == (uint16_t)len && \
    355     memcmp((de)->td_name, (name), (de)->td_namelen) == 0)
    356 
    357 /* --------------------------------------------------------------------- */
    358 
    359 /*
    360  * Ensures that the node pointed by 'node' is a directory and that its
    361  * contents are consistent with respect to directories.
    362  */
    363 #define TMPFS_VALIDATE_DIR(node) \
    364     KASSERT((node)->tn_type == VDIR); \
    365     KASSERT((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \
    366     KASSERT((node)->tn_spec.tn_dir.tn_readdir_lastp == NULL || \
    367         TMPFS_DIRCOOKIE((node)->tn_spec.tn_dir.tn_readdir_lastp) == \
    368         (node)->tn_spec.tn_dir.tn_readdir_lastn);
    369 
    370 /* --------------------------------------------------------------------- */
    371 
    372 /*
    373  * Memory management stuff.
    374  */
    375 
    376 /* Amount of memory pages to reserve for the system (e.g., to not use by
    377  * tmpfs).
    378  * XXX: Should this be tunable through sysctl, for instance? */
    379 #define TMPFS_PAGES_RESERVED (4 * 1024 * 1024 / PAGE_SIZE)
    380 
    381 /* Returns the maximum size allowed for a tmpfs file system.  This macro
    382  * must be used instead of directly retrieving the value from tm_pages_max.
    383  * The reason is that the size of a tmpfs file system is dynamic: it lets
    384  * the user store files as long as there is enough free memory (including
    385  * physical memory and swap space).  Therefore, the amount of memory to be
    386  * used is either the limit imposed by the user during mount time or the
    387  * amount of available memory, whichever is lower.  To avoid consuming all
    388  * the memory for a given mount point, the system will always reserve a
    389  * minimum of TMPFS_PAGES_RESERVED pages, which is also taken into account
    390  * by this macro (see above). */
    391 static __inline size_t
    392 TMPFS_PAGES_MAX(struct tmpfs_mount *tmp)
    393 {
    394 	size_t freepages;
    395 
    396 	freepages = tmpfs_mem_info(FALSE);
    397 	if (freepages < TMPFS_PAGES_RESERVED)
    398 		freepages = 0;
    399 	else
    400 		freepages -= TMPFS_PAGES_RESERVED;
    401 
    402 	return MIN(tmp->tm_pages_max, freepages + tmp->tm_pages_used);
    403 }
    404 
    405 /* Returns the available space for the given file system. */
    406 #define TMPFS_PAGES_AVAIL(tmp) (TMPFS_PAGES_MAX(tmp) - (tmp)->tm_pages_used)
    407 
    408 /* --------------------------------------------------------------------- */
    409 
    410 /*
    411  * Macros/functions to convert from generic data structures to tmpfs
    412  * specific ones.
    413  */
    414 
    415 static __inline
    416 struct tmpfs_mount *
    417 VFS_TO_TMPFS(struct mount *mp)
    418 {
    419 	struct tmpfs_mount *tmp;
    420 
    421 #ifdef KASSERT
    422 	KASSERT((mp) != NULL && (mp)->mnt_data != NULL);
    423 #endif
    424 	tmp = (struct tmpfs_mount *)(mp)->mnt_data;
    425 	return tmp;
    426 }
    427 
    428 #endif /* defined(_KERNEL) */
    429 
    430 static __inline
    431 struct tmpfs_node *
    432 VP_TO_TMPFS_NODE(struct vnode *vp)
    433 {
    434 	struct tmpfs_node *node;
    435 
    436 #ifdef KASSERT
    437 	KASSERT((vp) != NULL && (vp)->v_data != NULL);
    438 #endif
    439 	node = (struct tmpfs_node *)vp->v_data;
    440 	return node;
    441 }
    442 
    443 #if defined(_KERNEL)
    444 
    445 static __inline
    446 struct tmpfs_node *
    447 VP_TO_TMPFS_DIR(struct vnode *vp)
    448 {
    449 	struct tmpfs_node *node;
    450 
    451 	node = VP_TO_TMPFS_NODE(vp);
    452 #ifdef KASSERT
    453 	TMPFS_VALIDATE_DIR(node);
    454 #endif
    455 	return node;
    456 }
    457 
    458 #endif /* defined(_KERNEL) */
    459 
    460 /* ---------------------------------------------------------------------
    461  * USER AND KERNEL DEFINITIONS
    462  * --------------------------------------------------------------------- */
    463 
    464 /*
    465  * This structure is used to communicate mount parameters between userland
    466  * and kernel space.
    467  */
    468 #define TMPFS_ARGS_VERSION	1
    469 struct tmpfs_args {
    470 	int			ta_version;
    471 
    472 	/* Size counters. */
    473 	ino_t			ta_nodes_max;
    474 	off_t			ta_size_max;
    475 
    476 	/* Root node attributes. */
    477 	uid_t			ta_root_uid;
    478 	gid_t			ta_root_gid;
    479 	mode_t			ta_root_mode;
    480 };
    481 #endif /* _FS_TMPFS_TMPFS_H_ */
    482