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NetBSD/sys/fs/tmpfs/tmpfs.h

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/* $NetBSD: tmpfs.h,v 1.24 2006/11/13 11:47:37 jmmv Exp $ */
/*
* Copyright (c) 2005, 2006 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Julio M. Merino Vidal, developed as part of Google's Summer of Code
* 2005 program.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef _FS_TMPFS_TMPFS_H_
#define _FS_TMPFS_TMPFS_H_
/* ---------------------------------------------------------------------
* KERNEL-SPECIFIC DEFINITIONS
* --------------------------------------------------------------------- */
#include <sys/dirent.h>
#include <sys/mount.h>
#include <sys/queue.h>
#include <sys/vnode.h>
#if defined(_KERNEL)
#include <fs/tmpfs/tmpfs_pool.h>
#endif /* defined(_KERNEL) */
/* --------------------------------------------------------------------- */
/*
* Internal representation of a tmpfs directory entry.
*/
struct tmpfs_dirent {
TAILQ_ENTRY(tmpfs_dirent) td_entries;
/* Length of the name stored in this directory entry. This avoids
* the need to recalculate it every time the name is used. */
uint16_t td_namelen;
/* The name of the entry, allocated from a string pool. This
* string is not required to be zero-terminated; therefore, the
* td_namelen field must always be used when accessing its value. */
char * td_name;
/* Pointer to the node this entry refers to. */
struct tmpfs_node * td_node;
};
/* A directory in tmpfs holds a sorted list of directory entries, which in
* turn point to other files (which can be directories themselves).
*
* In tmpfs, this list is managed by a tail queue, whose head is defined by
* the struct tmpfs_dir type.
*
* It is imporant to notice that directories do not have entries for . and
* .. as other file systems do. These can be generated when requested
* based on information available by other means, such as the pointer to
* the node itself in the former case or the pointer to the parent directory
* in the latter case. This is done to simplify tmpfs's code and, more
* importantly, to remove redundancy. */
TAILQ_HEAD(tmpfs_dir, tmpfs_dirent);
/* Each entry in a directory has a cookie that identifies it. Cookies
* supersede offsets within directories because, given how tmpfs stores
* directories in memory, there is no such thing as an offset. (Emulating
* a real offset could be very difficult.)
*
* The '.', '..' and the end of directory markers have fixed cookies which
* cannot collide with the cookies generated by other entries. The cookies
* fot the other entries are generated based on the memory address on which
* stores their information is stored.
*
* Ideally, using the entry's memory pointer as the cookie would be enough
* to represent it and it wouldn't cause collisions in any system.
* Unfortunately, this results in "offsets" with very large values which
* later raise problems in the Linux compatibility layer (and maybe in other
* places) as described in PR kern/32034. Hence we need to workaround this
* with a rather ugly hack.
*
* Linux 32-bit binaries, unless built with _FILE_OFFSET_BITS=64, have off_t
* set to 'long', which is a 32-bit *signed* long integer. Regardless of
* the macro value, GLIBC (2.3 at least) always uses the getdents64
* system call (when calling readdir) which internally returns off64_t
* offsets. In order to make 32-bit binaries work, *GLIBC* converts the
* 64-bit values returned by the kernel to 32-bit ones and aborts with
* EOVERFLOW if the conversion results in values that won't fit in 32-bit
* integers (which it assumes is because the directory is extremely large).
* This wouldn't cause problems if we were dealing with unsigned integers,
* but as we have signed integers, this check fails due to sign expansion.
*
* For example, consider that the kernel returns the 0xc1234567 cookie to
* userspace in a off64_t integer. Later on, GLIBC casts this value to
* off_t (remember, signed) with code similar to:
* system call returns the offset in kernel_value;
* off_t casted_value = kernel_value;
* if (sizeof(off_t) != sizeof(off64_t) &&
* kernel_value != casted_value)
* error!
* In this case, casted_value still has 0xc1234567, but when it is compared
* for equality against kernel_value, it is promoted to a 64-bit integer and
* becomes 0xffffffffc1234567, which is different than 0x00000000c1234567.
* Then, GLIBC assumes this is because the directory is very large.
*
* Given that all the above happens in user-space, we have no control over
* it; therefore we must workaround the issue here. We do this by
* truncating the pointer value to a 32-bit integer and hope that there
* won't be collisions. In fact, this will not cause any problems in
* 32-bit platforms but some might arise in 64-bit machines (I'm not sure
* if they can happen at all in practice).
*
* XXX A nicer solution shall be attempted. */
#if defined(_KERNEL)
#define TMPFS_DIRCOOKIE_DOT 0
#define TMPFS_DIRCOOKIE_DOTDOT 1
#define TMPFS_DIRCOOKIE_EOF 2
static __inline
off_t
tmpfs_dircookie(struct tmpfs_dirent *de)
{
off_t cookie;
cookie = ((off_t)(uintptr_t)de >> 1) & 0x7FFFFFFF;
KASSERT(cookie != TMPFS_DIRCOOKIE_DOT);
KASSERT(cookie != TMPFS_DIRCOOKIE_DOTDOT);
KASSERT(cookie != TMPFS_DIRCOOKIE_EOF);
return cookie;
}
#endif /* defined(_KERNEL) */
/* --------------------------------------------------------------------- */
/*
* Internal representation of a tmpfs file system node.
*
* This structure is splitted in two parts: one holds attributes common
* to all file types and the other holds data that is only applicable to
* a particular type. The code must be careful to only access those
* attributes that are actually allowed by the node's type.
*/
struct tmpfs_node {
/* Doubly-linked list entry which links all existing nodes for a
* single file system. This is provided to ease the removal of
* all nodes during the unmount operation. */
LIST_ENTRY(tmpfs_node) tn_entries;
/* The node's type. Any of 'VBLK', 'VCHR', 'VDIR', 'VFIFO',
* 'VLNK', 'VREG' and 'VSOCK' is allowed. The usage of vnode
* types instead of a custom enumeration is to make things simpler
* and faster, as we do not need to convert between two types. */
enum vtype tn_type;
/* Node identifier. */
ino_t tn_id;
/* Node's internal status. This is used by several file system
* operations to do modifications to the node in a delayed
* fashion. */
int tn_status;
#define TMPFS_NODE_ACCESSED (1 << 1)
#define TMPFS_NODE_MODIFIED (1 << 2)
#define TMPFS_NODE_CHANGED (1 << 3)
/* The node size. It does not necessarily match the real amount
* of memory consumed by it. */
off_t tn_size;
/* Generic node attributes. */
uid_t tn_uid;
gid_t tn_gid;
mode_t tn_mode;
int tn_flags;
nlink_t tn_links;
struct timespec tn_atime;
struct timespec tn_mtime;
struct timespec tn_ctime;
struct timespec tn_birthtime;
unsigned long tn_gen;
/* Head of byte-level lock list (used by tmpfs_advlock). */
struct lockf * tn_lockf;
/* As there is a single vnode for each active file within the
* system, care has to be taken to avoid allocating more than one
* vnode per file. In order to do this, a bidirectional association
* is kept between vnodes and nodes.
*
* Whenever a vnode is allocated, its v_data field is updated to
* point to the node it references. At the same time, the node's
* tn_vnode field is modified to point to the new vnode representing
* it. Further attempts to allocate a vnode for this same node will
* result in returning a new reference to the value stored in
* tn_vnode.
*
* May be NULL when the node is unused (that is, no vnode has been
* allocated for it or it has been reclaimed). */
struct vnode * tn_vnode;
/* Pointer to the node returned by tmpfs_lookup() after doing a
* delete or a rename lookup; its value is only valid in these two
* situations. In case we were looking up . or .., it holds a null
* pointer. */
struct tmpfs_dirent * tn_lookup_dirent;
union {
/* Valid when tn_type == VBLK || tn_type == VCHR. */
struct {
dev_t tn_rdev;
} tn_dev;
/* Valid when tn_type == VDIR. */
struct {
/* Pointer to the parent directory. The root
* directory has a pointer to itself in this field;
* this property identifies the root node. */
struct tmpfs_node * tn_parent;
/* Head of a tail-queue that links the contents of
* the directory together. See above for a
* description of its contents. */
struct tmpfs_dir tn_dir;
/* Number and pointer of the first directory entry
* returned by the readdir operation if it were
* called again to continue reading data from the
* same directory as before. This is used to speed
* up reads of long directories, assuming that no
* more than one read is in progress at a given time.
* Otherwise, these values are discarded and a linear
* scan is performed from the beginning up to the
* point where readdir starts returning values. */
off_t tn_readdir_lastn;
struct tmpfs_dirent * tn_readdir_lastp;
} tn_dir;
/* Valid when tn_type == VLNK. */
struct tn_lnk {
/* The link's target, allocated from a string pool. */
char * tn_link;
} tn_lnk;
/* Valid when tn_type == VREG. */
struct tn_reg {
/* The contents of regular files stored in a tmpfs
* file system are represented by a single anonymous
* memory object (aobj, for short). The aobj provides
* direct access to any position within the file,
* because its contents are always mapped in a
* contiguous region of virtual memory. It is a task
* of the memory management subsystem (see uvm(9)) to
* issue the required page ins or page outs whenever
* a position within the file is accessed. */
struct uvm_object * tn_aobj;
size_t tn_aobj_pages;
} tn_reg;
} tn_spec;
};
#if defined(_KERNEL)
LIST_HEAD(tmpfs_node_list, tmpfs_node);
/* --------------------------------------------------------------------- */
/*
* Internal representation of a tmpfs mount point.
*/
struct tmpfs_mount {
/* Maximum number of memory pages available for use by the file
* system, set during mount time. This variable must never be
* used directly as it may be bigger than the current amount of
* free memory; in the extreme case, it will hold the SIZE_MAX
* value. Instead, use the TMPFS_PAGES_MAX macro. */
size_t tm_pages_max;
/* Number of pages in use by the file system. Cannot be bigger
* than the value returned by TMPFS_PAGES_MAX in any case. */
size_t tm_pages_used;
/* Pointer to the node representing the root directory of this
* file system. */
struct tmpfs_node * tm_root;
/* Maximum number of possible nodes for this file system; set
* during mount time. We need a hard limit on the maximum number
* of nodes to avoid allocating too much of them; their objects
* cannot be released until the file system is unmounted.
* Otherwise, we could easily run out of memory by creating lots
* of empty files and then simply removing them. */
ino_t tm_nodes_max;
/* Number of nodes currently allocated. This number only grows.
* When it reaches tm_nodes_max, no more new nodes can be allocated.
* Of course, the old, unused ones can be reused. */
ino_t tm_nodes_last;
/* Nodes are organized in two different lists. The used list
* contains all nodes that are currently used by the file system;
* i.e., they refer to existing files. The available list contains
* all nodes that are currently available for use by new files.
* Nodes must be kept in this list (instead of deleting them)
* because we need to keep track of their generation number (tn_gen
* field).
*
* Note that nodes are lazily allocated: if the available list is
* empty and we have enough space to create more nodes, they will be
* created and inserted in the used list. Once these are released,
* they will go into the available list, remaining alive until the
* file system is unmounted. */
struct tmpfs_node_list tm_nodes_used;
struct tmpfs_node_list tm_nodes_avail;
/* Pools used to store file system meta data. These are not shared
* across several instances of tmpfs for the reasons described in
* tmpfs_pool.c. */
struct tmpfs_pool tm_dirent_pool;
struct tmpfs_pool tm_node_pool;
struct tmpfs_str_pool tm_str_pool;
};
/* --------------------------------------------------------------------- */
/*
* This structure maps a file identifier to a tmpfs node. Used by the
* NFS code.
*/
struct tmpfs_fid {
uint16_t tf_len;
uint16_t tf_pad;
uint32_t tf_gen;
ino_t tf_id;
};
/* --------------------------------------------------------------------- */
/*
* Prototypes for tmpfs_subr.c.
*/
int tmpfs_alloc_node(struct tmpfs_mount *, enum vtype,
uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *,
char *, dev_t, struct proc *, struct tmpfs_node **);
void tmpfs_free_node(struct tmpfs_mount *, struct tmpfs_node *);
int tmpfs_alloc_dirent(struct tmpfs_mount *, struct tmpfs_node *,
const char *, uint16_t, struct tmpfs_dirent **);
void tmpfs_free_dirent(struct tmpfs_mount *, struct tmpfs_dirent *,
boolean_t);
int tmpfs_alloc_vp(struct mount *, struct tmpfs_node *, struct vnode **);
void tmpfs_free_vp(struct vnode *);
int tmpfs_alloc_file(struct vnode *, struct vnode **, struct vattr *,
struct componentname *, char *);
void tmpfs_dir_attach(struct vnode *, struct tmpfs_dirent *);
void tmpfs_dir_detach(struct vnode *, struct tmpfs_dirent *);
struct tmpfs_dirent * tmpfs_dir_lookup(struct tmpfs_node *node,
struct componentname *cnp);
int tmpfs_dir_getdotdent(struct tmpfs_node *, struct uio *);
int tmpfs_dir_getdotdotdent(struct tmpfs_node *, struct uio *);
struct tmpfs_dirent * tmpfs_dir_lookupbycookie(struct tmpfs_node *, off_t);
int tmpfs_dir_getdents(struct tmpfs_node *, struct uio *, off_t *);
int tmpfs_reg_resize(struct vnode *, off_t);
size_t tmpfs_mem_info(boolean_t);
int tmpfs_chflags(struct vnode *, int, kauth_cred_t, struct lwp *);
int tmpfs_chmod(struct vnode *, mode_t, kauth_cred_t, struct lwp *);
int tmpfs_chown(struct vnode *, uid_t, gid_t, kauth_cred_t, struct lwp *);
int tmpfs_chsize(struct vnode *, u_quad_t, kauth_cred_t, struct lwp *);
int tmpfs_chtimes(struct vnode *, struct timespec *, struct timespec *,
int, kauth_cred_t, struct lwp *);
void tmpfs_itimes(struct vnode *, const struct timespec *,
const struct timespec *);
void tmpfs_update(struct vnode *, const struct timespec *,
const struct timespec *, int);
int tmpfs_truncate(struct vnode *, off_t);
/* --------------------------------------------------------------------- */
/*
* Convenience macros to simplify some logical expressions.
*/
#define IMPLIES(a, b) (!(a) || (b))
#define IFF(a, b) (IMPLIES(a, b) && IMPLIES(b, a))
/* --------------------------------------------------------------------- */
/*
* Checks that the directory entry pointed by 'de' matches the name 'name'
* with a length of 'len'.
*/
#define TMPFS_DIRENT_MATCHES(de, name, len) \
(de->td_namelen == (uint16_t)len && \
memcmp((de)->td_name, (name), (de)->td_namelen) == 0)
/* --------------------------------------------------------------------- */
/*
* Ensures that the node pointed by 'node' is a directory and that its
* contents are consistent with respect to directories.
*/
#define TMPFS_VALIDATE_DIR(node) \
KASSERT((node)->tn_type == VDIR); \
KASSERT((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \
KASSERT((node)->tn_spec.tn_dir.tn_readdir_lastp == NULL || \
tmpfs_dircookie((node)->tn_spec.tn_dir.tn_readdir_lastp) == \
(node)->tn_spec.tn_dir.tn_readdir_lastn);
/* --------------------------------------------------------------------- */
/*
* Memory management stuff.
*/
/* Amount of memory pages to reserve for the system (e.g., to not use by
* tmpfs).
* XXX: Should this be tunable through sysctl, for instance? */
#define TMPFS_PAGES_RESERVED (4 * 1024 * 1024 / PAGE_SIZE)
/* Returns the maximum size allowed for a tmpfs file system. This macro
* must be used instead of directly retrieving the value from tm_pages_max.
* The reason is that the size of a tmpfs file system is dynamic: it lets
* the user store files as long as there is enough free memory (including
* physical memory and swap space). Therefore, the amount of memory to be
* used is either the limit imposed by the user during mount time or the
* amount of available memory, whichever is lower. To avoid consuming all
* the memory for a given mount point, the system will always reserve a
* minimum of TMPFS_PAGES_RESERVED pages, which is also taken into account
* by this macro (see above). */
static __inline size_t
TMPFS_PAGES_MAX(struct tmpfs_mount *tmp)
{
size_t freepages;
freepages = tmpfs_mem_info(FALSE);
if (freepages < TMPFS_PAGES_RESERVED)
freepages = 0;
else
freepages -= TMPFS_PAGES_RESERVED;
return MIN(tmp->tm_pages_max, freepages + tmp->tm_pages_used);
}
/* Returns the available space for the given file system. */
#define TMPFS_PAGES_AVAIL(tmp) (TMPFS_PAGES_MAX(tmp) - (tmp)->tm_pages_used)
/* --------------------------------------------------------------------- */
/*
* Macros/functions to convert from generic data structures to tmpfs
* specific ones.
*/
static __inline
struct tmpfs_mount *
VFS_TO_TMPFS(struct mount *mp)
{
struct tmpfs_mount *tmp;
#ifdef KASSERT
KASSERT((mp) != NULL && (mp)->mnt_data != NULL);
#endif
tmp = (struct tmpfs_mount *)(mp)->mnt_data;
return tmp;
}
#endif /* defined(_KERNEL) */
static __inline
struct tmpfs_node *
VP_TO_TMPFS_NODE(struct vnode *vp)
{
struct tmpfs_node *node;
#ifdef KASSERT
KASSERT((vp) != NULL && (vp)->v_data != NULL);
#endif
node = (struct tmpfs_node *)vp->v_data;
return node;
}
#if defined(_KERNEL)
static __inline
struct tmpfs_node *
VP_TO_TMPFS_DIR(struct vnode *vp)
{
struct tmpfs_node *node;
node = VP_TO_TMPFS_NODE(vp);
#ifdef KASSERT
TMPFS_VALIDATE_DIR(node);
#endif
return node;
}
#endif /* defined(_KERNEL) */
/* ---------------------------------------------------------------------
* USER AND KERNEL DEFINITIONS
* --------------------------------------------------------------------- */
/*
* This structure is used to communicate mount parameters between userland
* and kernel space.
*/
#define TMPFS_ARGS_VERSION 1
struct tmpfs_args {
int ta_version;
/* Size counters. */
ino_t ta_nodes_max;
off_t ta_size_max;
/* Root node attributes. */
uid_t ta_root_uid;
gid_t ta_root_gid;
mode_t ta_root_mode;
};
#endif /* _FS_TMPFS_TMPFS_H_ */
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