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tmpfs.h revision 1.33.4.3
      1 /*	$NetBSD: tmpfs.h,v 1.33.4.3 2008/07/29 07:00:30 simonb 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