/* $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 #include #include #include #if defined(_KERNEL) #include #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_ */