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tmpfs.h revision 1.17
      1 /*	$NetBSD: tmpfs.h,v 1.17 2006/03/26 20:18:58 martin 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 #include <fs/tmpfs/tmpfs_pool.h>
     52 
     53 /* --------------------------------------------------------------------- */
     54 
     55 /*
     56  * Internal representation of a tmpfs directory entry.
     57  */
     58 struct tmpfs_dirent {
     59 	TAILQ_ENTRY(tmpfs_dirent)	td_entries;
     60 
     61 	/* Length of the name stored in this directory entry.  This avoids
     62 	 * the need to recalculate it every time the name is used. */
     63 	uint16_t			td_namelen;
     64 
     65 	/* The name of the entry, allocated from a string pool.  This
     66 	* string is not required to be zero-terminated; therefore, the
     67 	* td_namelen field must always be used when accessing its value. */
     68 	char *				td_name;
     69 
     70 	/* Pointer to the node this entry refers to. */
     71 	struct tmpfs_node *		td_node;
     72 };
     73 
     74 /* A directory in tmpfs holds a sorted list of directory entries, which in
     75  * turn point to other files (which can be directories themselves).
     76  *
     77  * In tmpfs, this list is managed by a tail queue, whose head is defined by
     78  * the struct tmpfs_dir type.
     79  *
     80  * It is imporant to notice that directories do not have entries for . and
     81  * .. as other file systems do.  These can be generated when requested
     82  * based on information available by other means, such as the pointer to
     83  * the node itself in the former case or the pointer to the parent directory
     84  * in the latter case.  This is done to simplify tmpfs's code and, more
     85  * importantly, to remove redundancy. */
     86 TAILQ_HEAD(tmpfs_dir, tmpfs_dirent);
     87 
     88 #define	TMPFS_DIRCOOKIE(dirent)	((off_t)(uintptr_t)(dirent))
     89 #define	TMPFS_DIRCOOKIE_DOT	0
     90 #define	TMPFS_DIRCOOKIE_DOTDOT	1
     91 #define	TMPFS_DIRCOOKIE_EOF	2
     92 
     93 /* --------------------------------------------------------------------- */
     94 
     95 /*
     96  * Internal representation of a tmpfs file system node.
     97  *
     98  * This structure is splitted in two parts: one holds attributes common
     99  * to all file types and the other holds data that is only applicable to
    100  * a particular type.  The code must be careful to only access those
    101  * attributes that are actually allowed by the node's type.
    102  */
    103 struct tmpfs_node {
    104 	/* Doubly-linked list entry which links all existing nodes for a
    105 	 * single file system.  This is provided to ease the removal of
    106 	 * all nodes during the unmount operation. */
    107 	LIST_ENTRY(tmpfs_node)	tn_entries;
    108 
    109 	/* The node's type.  Any of 'VBLK', 'VCHR', 'VDIR', 'VFIFO',
    110 	 * 'VLNK', 'VREG' and 'VSOCK' is allowed.  The usage of vnode
    111 	 * types instead of a custom enumeration is to make things simpler
    112 	 * and faster, as we do not need to convert between two types. */
    113 	enum vtype		tn_type;
    114 
    115 	/* Node identifier. */
    116 	ino_t			tn_id;
    117 
    118 	/* Node's internal status.  This is used by several file system
    119 	 * operations to do modifications to the node in a delayed
    120 	 * fashion. */
    121 	int			tn_status;
    122 #define	TMPFS_NODE_ACCESSED	(1 << 1)
    123 #define	TMPFS_NODE_MODIFIED	(1 << 2)
    124 #define	TMPFS_NODE_CHANGED	(1 << 3)
    125 
    126 	/* The node size.  It does not necessarily match the real amount
    127 	 * of memory consumed by it. */
    128 	off_t			tn_size;
    129 
    130 	/* Generic node attributes. */
    131 	uid_t			tn_uid;
    132 	gid_t			tn_gid;
    133 	mode_t			tn_mode;
    134 	int			tn_flags;
    135 	nlink_t			tn_links;
    136 	struct timespec		tn_atime;
    137 	struct timespec		tn_mtime;
    138 	struct timespec		tn_ctime;
    139 	struct timespec		tn_birthtime;
    140 	unsigned long		tn_gen;
    141 
    142 	/* Head of byte-level lock list (used by tmpfs_advlock). */
    143 	struct lockf *		tn_lockf;
    144 
    145 	/* As there is a single vnode for each active file within the
    146 	 * system, care has to be taken to avoid allocating more than one
    147 	 * vnode per file.  In order to do this, a bidirectional association
    148 	 * is kept between vnodes and nodes.
    149 	 *
    150 	 * Whenever a vnode is allocated, its v_data field is updated to
    151 	 * point to the node it references.  At the same time, the node's
    152 	 * tn_vnode field is modified to point to the new vnode representing
    153 	 * it.  Further attempts to allocate a vnode for this same node will
    154 	 * result in returning a new reference to the value stored in
    155 	 * tn_vnode.
    156 	 *
    157 	 * May be NULL when the node is unused (that is, no vnode has been
    158 	 * allocated for it or it has been reclaimed). */
    159 	struct vnode *		tn_vnode;
    160 
    161 	/* Pointer to the node returned by tmpfs_lookup() after doing a
    162 	 * delete or a rename lookup; its value is only valid in these two
    163 	 * situations.  In case we were looking up . or .., it holds a null
    164 	 * pointer. */
    165 	struct tmpfs_dirent *	tn_lookup_dirent;
    166 
    167 	union {
    168 		/* Valid when tn_type == VBLK || tn_type == VCHR. */
    169 		struct {
    170 			dev_t			tn_rdev;
    171 		} tn_dev;
    172 
    173 		/* Valid when tn_type == VDIR. */
    174 		struct {
    175 			/* Pointer to the parent directory.  The root
    176 			 * directory has a pointer to itself in this field;
    177 			 * this property identifies the root node. */
    178 			struct tmpfs_node *	tn_parent;
    179 
    180 			/* Head of a tail-queue that links the contents of
    181 			 * the directory together.  See above for a
    182 			 * description of its contents. */
    183 			struct tmpfs_dir	tn_dir;
    184 
    185 			/* Number and pointer of the first directory entry
    186 			 * returned by the readdir operation if it were
    187 			 * called again to continue reading data from the
    188 			 * same directory as before.  This is used to speed
    189 			 * up reads of long directories, assuming that no
    190 			 * more than one read is in progress at a given time.
    191 			 * Otherwise, these values are discarded and a linear
    192 			 * scan is performed from the beginning up to the
    193 			 * point where readdir starts returning values. */
    194 			off_t			tn_readdir_lastn;
    195 			struct tmpfs_dirent *	tn_readdir_lastp;
    196 		} tn_dir;
    197 
    198 		/* Valid when tn_type == VLNK. */
    199 		struct tn_lnk {
    200 			/* The link's target, allocated from a string pool. */
    201 			char *			tn_link;
    202 		} tn_lnk;
    203 
    204 		/* Valid when tn_type == VREG. */
    205 		struct tn_reg {
    206 			/* The contents of regular files stored in a tmpfs
    207 			 * file system are represented by a single anonymous
    208 			 * memory object (aobj, for short).  The aobj provides
    209 			 * direct access to any position within the file,
    210 			 * because its contents are always mapped in a
    211 			 * contiguous region of virtual memory.  It is a task
    212 			 * of the memory management subsystem (see uvm(9)) to
    213 			 * issue the required page ins or page outs whenever
    214 			 * a position within the file is accessed. */
    215 			struct uvm_object *	tn_aobj;
    216 			size_t			tn_aobj_pages;
    217 		} tn_reg;
    218 	} tn_spec;
    219 };
    220 LIST_HEAD(tmpfs_node_list, tmpfs_node);
    221 
    222 /* --------------------------------------------------------------------- */
    223 
    224 /*
    225  * Internal representation of a tmpfs mount point.
    226  */
    227 struct tmpfs_mount {
    228 	/* Maximum number of memory pages available for use by the file
    229 	 * system, set during mount time.  This variable must never be
    230 	 * used directly as it may be bigger that the current amount of
    231 	 * free memory; in the extreme case, it will hold the SIZE_MAX
    232 	 * value.  Instead, use the TMPFS_PAGES_MAX macro. */
    233 	size_t			tm_pages_max;
    234 
    235 	/* Number of pages in use by the file system.  Cannot be bigger
    236 	 * than the value returned by TMPFS_PAGES_MAX in any case. */
    237 	size_t			tm_pages_used;
    238 
    239 	/* Pointer to the node representing the root directory of this
    240 	 * file system. */
    241 	struct tmpfs_node *	tm_root;
    242 
    243 	/* Maximum number of possible nodes for this file system; set
    244 	 * during mount time.  We need a hard limit on the maximum number
    245 	 * of nodes to avoid allocating too much of them; their objects
    246 	 * cannot be released until the file system is unmounted.
    247 	 * Otherwise, we could easily run out of memory by creating lots
    248 	 * of empty files and then simply removing them. */
    249 	ino_t			tm_nodes_max;
    250 
    251 	/* Number of nodes currently allocated.  This number only grows.
    252 	 * When it reaches tm_nodes_max, no more new nodes can be allocated.
    253 	 * Of course, the old, unused ones can be reused. */
    254 	ino_t			tm_nodes_last;
    255 
    256 	/* Nodes are organized in two different lists.  The used list
    257 	 * contains all nodes that are currently used by the file system;
    258 	 * i.e., they refer to existing files.  The available list contains
    259 	 * all nodes that are currently available for use by new files.
    260 	 * Nodes must be kept in this list (instead of deleting them)
    261 	 * because we need to keep track of their generation number (tn_gen
    262 	 * field).
    263 	 *
    264 	 * Note that nodes are lazily allocated: if the available list is
    265 	 * empty and we have enough space to create more nodes, they will be
    266 	 * created and inserted in the used list.  Once these are released,
    267 	 * they will go into the available list, remaining alive until the
    268 	 * file system is unmounted. */
    269 	struct tmpfs_node_list	tm_nodes_used;
    270 	struct tmpfs_node_list	tm_nodes_avail;
    271 
    272 	/* Pools used to store file system meta data.  These are not shared
    273 	 * across several instances of tmpfs for the reasons described in
    274 	 * tmpfs_pool.c. */
    275 	struct tmpfs_pool	tm_dirent_pool;
    276 	struct tmpfs_pool	tm_node_pool;
    277 	struct tmpfs_str_pool	tm_str_pool;
    278 };
    279 
    280 /* --------------------------------------------------------------------- */
    281 
    282 /*
    283  * This structure maps a file identifier to a tmpfs node.  Used by the
    284  * NFS code.
    285  */
    286 struct tmpfs_fid {
    287 	uint16_t		tf_len;
    288 	uint16_t		tf_pad;
    289 	ino_t			tf_id;
    290 	uint32_t		tf_gen;
    291 };
    292 
    293 /* --------------------------------------------------------------------- */
    294 
    295 #ifdef _KERNEL
    296 /*
    297  * Prototypes for tmpfs_subr.c.
    298  */
    299 
    300 int	tmpfs_alloc_node(struct tmpfs_mount *, enum vtype,
    301 	    uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *,
    302 	    char *, dev_t, struct proc *, struct tmpfs_node **);
    303 void	tmpfs_free_node(struct tmpfs_mount *, struct tmpfs_node *);
    304 int	tmpfs_alloc_dirent(struct tmpfs_mount *, struct tmpfs_node *,
    305 	    const char *, uint16_t, struct tmpfs_dirent **);
    306 void	tmpfs_free_dirent(struct tmpfs_mount *, struct tmpfs_dirent *,
    307 	    boolean_t);
    308 int	tmpfs_alloc_vp(struct mount *, struct tmpfs_node *, struct vnode **);
    309 void	tmpfs_free_vp(struct vnode *);
    310 int	tmpfs_alloc_file(struct vnode *, struct vnode **, struct vattr *,
    311 	    struct componentname *, char *);
    312 void	tmpfs_dir_attach(struct vnode *, struct tmpfs_dirent *);
    313 void	tmpfs_dir_detach(struct vnode *, struct tmpfs_dirent *);
    314 struct tmpfs_dirent *	tmpfs_dir_lookup(struct tmpfs_node *node,
    315 			    struct componentname *cnp);
    316 int	tmpfs_dir_getdotdent(struct tmpfs_node *, struct uio *);
    317 int	tmpfs_dir_getdotdotdent(struct tmpfs_node *, struct uio *);
    318 struct tmpfs_dirent *	tmpfs_dir_lookupbycookie(struct tmpfs_node *, off_t);
    319 int	tmpfs_dir_getdents(struct tmpfs_node *, struct uio *, off_t *);
    320 int	tmpfs_reg_resize(struct vnode *, off_t);
    321 size_t	tmpfs_mem_info(boolean_t);
    322 int	tmpfs_chflags(struct vnode *, int, struct ucred *, struct proc *);
    323 int	tmpfs_chmod(struct vnode *, mode_t, struct ucred *, struct proc *);
    324 int	tmpfs_chown(struct vnode *, uid_t, gid_t, struct ucred *,
    325 	    struct proc *);
    326 int	tmpfs_chsize(struct vnode *, u_quad_t, struct ucred *, struct proc *);
    327 int	tmpfs_chtimes(struct vnode *, struct timespec *, struct timespec *,
    328 	    int, struct ucred *, struct lwp *);
    329 void	tmpfs_itimes(struct vnode *, const struct timespec *,
    330 	    const struct timespec *);
    331 
    332 void	tmpfs_update(struct vnode *, const struct timespec *,
    333 	    const struct timespec *, int);
    334 int	tmpfs_truncate(struct vnode *, off_t);
    335 
    336 /* --------------------------------------------------------------------- */
    337 
    338 /*
    339  * Convenience macros to simplify some logical expressions.
    340  */
    341 #define IMPLIES(a, b) (!(a) || (b))
    342 #define IFF(a, b) (IMPLIES(a, b) && IMPLIES(b, a))
    343 
    344 /* --------------------------------------------------------------------- */
    345 
    346 /*
    347  * Checks that the directory entry pointed by 'de' matches the name 'name'
    348  * with a length of 'len'.
    349  */
    350 #define TMPFS_DIRENT_MATCHES(de, name, len) \
    351     (de->td_namelen == (uint16_t)len && \
    352     memcmp((de)->td_name, (name), (de)->td_namelen) == 0)
    353 
    354 /* --------------------------------------------------------------------- */
    355 
    356 /*
    357  * Ensures that the node pointed by 'node' is a directory and that its
    358  * contents are consistent with respect to directories.
    359  */
    360 #define TMPFS_VALIDATE_DIR(node) \
    361     KASSERT((node)->tn_type == VDIR); \
    362     KASSERT((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \
    363     KASSERT((node)->tn_spec.tn_dir.tn_readdir_lastp == NULL || \
    364         TMPFS_DIRCOOKIE((node)->tn_spec.tn_dir.tn_readdir_lastp) == \
    365         (node)->tn_spec.tn_dir.tn_readdir_lastn);
    366 
    367 /* --------------------------------------------------------------------- */
    368 
    369 /*
    370  * Memory management stuff.
    371  */
    372 
    373 /* Amount of memory pages to reserve for the system (e.g., to not use by
    374  * tmpfs).
    375  * XXX: Should this be tunable through sysctl, for instance? */
    376 #define TMPFS_PAGES_RESERVED (4 * 1024 * 1024 / PAGE_SIZE)
    377 
    378 /* Returns the maximum size allowed for a tmpfs file system.  This macro
    379  * must be used instead of directly retrieving the value from tm_pages_max.
    380  * The reason is that the size of a tmpfs file system is dynamic: it lets
    381  * the user store files as long as there is enough free memory (including
    382  * physical memory and swap space).  Therefore, the amount of memory to be
    383  * used is either the limit imposed by the user during mount time or the
    384  * amount of available memory, whichever is lower.  To avoid consuming all
    385  * the memory for a given mount point, the system will always reserve a
    386  * minimum of TMPFS_PAGES_RESERVED pages, which is also taken into account
    387  * by this macro (see above). */
    388 static __inline size_t
    389 TMPFS_PAGES_MAX(struct tmpfs_mount *tmp)
    390 {
    391 	size_t freepages;
    392 
    393 	freepages = tmpfs_mem_info(FALSE);
    394 	if (freepages < TMPFS_PAGES_RESERVED)
    395 		freepages = 0;
    396 	else
    397 		freepages -= TMPFS_PAGES_RESERVED;
    398 
    399 	return MIN(tmp->tm_pages_max, freepages + tmp->tm_pages_used);
    400 }
    401 
    402 /* Returns the available space for the given file system. */
    403 #define TMPFS_PAGES_AVAIL(tmp) (TMPFS_PAGES_MAX(tmp) - (tmp)->tm_pages_used)
    404 
    405 #endif
    406 
    407 /* --------------------------------------------------------------------- */
    408 
    409 /*
    410  * Macros/functions to convert from generic data structures to tmpfs
    411  * specific ones.
    412  */
    413 
    414 static __inline
    415 struct tmpfs_mount *
    416 VFS_TO_TMPFS(struct mount *mp)
    417 {
    418 	struct tmpfs_mount *tmp;
    419 
    420 #ifdef KASSERT
    421 	KASSERT((mp) != NULL && (mp)->mnt_data != NULL);
    422 #endif
    423 	tmp = (struct tmpfs_mount *)(mp)->mnt_data;
    424 	return tmp;
    425 }
    426 
    427 static __inline
    428 struct tmpfs_node *
    429 VP_TO_TMPFS_NODE(struct vnode *vp)
    430 {
    431 	struct tmpfs_node *node;
    432 
    433 #ifdef KASSERT
    434 	KASSERT((vp) != NULL && (vp)->v_data != NULL);
    435 #endif
    436 	node = (struct tmpfs_node *)vp->v_data;
    437 	return node;
    438 }
    439 
    440 static __inline
    441 struct tmpfs_node *
    442 VP_TO_TMPFS_DIR(struct vnode *vp)
    443 {
    444 	struct tmpfs_node *node;
    445 
    446 	node = VP_TO_TMPFS_NODE(vp);
    447 #ifdef KASSERT
    448 	TMPFS_VALIDATE_DIR(node);
    449 #endif
    450 	return node;
    451 }
    452 
    453 /* ---------------------------------------------------------------------
    454  * USER AND KERNEL DEFINITIONS
    455  * --------------------------------------------------------------------- */
    456 
    457 /*
    458  * This structure is used to communicate mount parameters between userland
    459  * and kernel space.
    460  */
    461 #define TMPFS_ARGS_VERSION	1
    462 struct tmpfs_args {
    463 	int			ta_version;
    464 
    465 	/* Size counters. */
    466 	ino_t			ta_nodes_max;
    467 	off_t			ta_size_max;
    468 
    469 	/* Root node attributes. */
    470 	uid_t			ta_root_uid;
    471 	gid_t			ta_root_gid;
    472 	mode_t			ta_root_mode;
    473 };
    474 #endif /* _FS_TMPFS_TMPFS_H_ */
    475