FreeBSD/Linux Kernel Cross Reference
sys/fs/tmpfs/tmpfs.h

     /*      $NetBSD: tmpfs.h,v 1.26 2007/02/22 06:37:00 thorpej Exp $       */
     
     /*-
      * SPDX-License-Identifier: BSD-2-Clause-NetBSD
      *
      * 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.
     *
     * 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.
     *
     * $FreeBSD$
     */
    
    #ifndef _FS_TMPFS_TMPFS_H_
    #define _FS_TMPFS_TMPFS_H_
    
    #include <sys/cdefs.h>
    #include <sys/queue.h>
    #include <sys/tree.h>
    
    #ifdef  _SYS_MALLOC_H_
    MALLOC_DECLARE(M_TMPFSNAME);
    #endif
    
    /*
     * Internal representation of a tmpfs directory entry.
     */
    
    LIST_HEAD(tmpfs_dir_duphead, tmpfs_dirent);
    
    struct tmpfs_dirent {
            /*
             * Depending on td_cookie flag entry can be of 3 types:
             * - regular -- no hash collisions, stored in RB-Tree
             * - duphead -- synthetic linked list head for dup entries
             * - dup -- stored in linked list instead of RB-Tree
             */
            union {
                    /* regular and duphead entry types */
                    RB_ENTRY(tmpfs_dirent)          td_entries;
    
                    /* dup entry type */
                    struct {
                            LIST_ENTRY(tmpfs_dirent) entries;
                            LIST_ENTRY(tmpfs_dirent) index_entries;
                    } td_dup;
            } uh;
    
            uint32_t                        td_cookie;
            uint32_t                        td_hash;
            u_int                           td_namelen;
    
            /*
             * Pointer to the node this entry refers to.  In case this field
             * is NULL, the node is a whiteout.
             */
            struct tmpfs_node *             td_node;
    
            union {
                    /*
                     * The name of the entry, allocated from a string pool.  This
                     * string is not required to be zero-terminated.
                     */
                    char *                  td_name;        /* regular, dup */
                    struct tmpfs_dir_duphead td_duphead;    /* duphead */
            } ud;
    };
    
    /*
     * A directory in tmpfs holds a collection of directory entries, which
     * in turn point to other files (which can be directories themselves).
     *
     * In tmpfs, this collection is managed by a RB-Tree, whose head is
     * defined by the struct tmpfs_dir type.
     *
     * It is important 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.
    */
   RB_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.
    *
    * The '.', '..' and the end of directory markers have fixed cookies which
    * cannot collide with the cookies generated by other entries.  The cookies
    * for the other entries are generated based on the file name hash value or
    * unique number in case of name hash collision.
    *
    * To preserve compatibility cookies are limited to 31 bits.
    */
   
   #define TMPFS_DIRCOOKIE_DOT             0
   #define TMPFS_DIRCOOKIE_DOTDOT          1
   #define TMPFS_DIRCOOKIE_EOF             2
   #define TMPFS_DIRCOOKIE_MASK            ((off_t)0x3fffffffU)
   #define TMPFS_DIRCOOKIE_MIN             ((off_t)0x00000004U)
   #define TMPFS_DIRCOOKIE_DUP             ((off_t)0x40000000U)
   #define TMPFS_DIRCOOKIE_DUPHEAD         ((off_t)0x80000000U)
   #define TMPFS_DIRCOOKIE_DUP_MIN         TMPFS_DIRCOOKIE_DUP
   #define TMPFS_DIRCOOKIE_DUP_MAX         \
           (TMPFS_DIRCOOKIE_DUP | TMPFS_DIRCOOKIE_MASK)
   
   /*
    * 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.
    *
    * Below is the key of locks used to protected the fields in the following
    * structures.
    * (v)  vnode lock in exclusive mode
    * (vi) vnode lock in exclusive mode, or vnode lock in shared vnode and
    *      tn_interlock
    * (i)  tn_interlock
    * (m)  tmpfs_mount tm_allnode_lock
    * (c)  stable after creation
    */
   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, and to support
            * the implementation of VOP_VNTOCNP().  tn_attached is false
            * when the node is removed from list and unlocked.
            */
           LIST_ENTRY(tmpfs_node)  tn_entries;     /* (m) */
   
           /* Node identifier. */
           ino_t                   tn_id;          /* (c) */
   
           /*
            * 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;        /* (c) */
   
           /*
            * See the top comment. Reordered here to fill LP64 hole.
            */
           bool                    tn_attached;    /* (m) */
   
           /*
            * Node's internal status.  This is used by several file system
            * operations to do modifications to the node in a delayed
            * fashion.
            *
            * tn_accessed has a dedicated byte to allow update by store without
            * using atomics.  This provides a micro-optimization to e.g.
            * tmpfs_read_pgcache().
            */
           uint8_t                 tn_status;      /* (vi) */
           uint8_t                 tn_accessed;    /* unlocked */
   
           /*
            * The node size.  It does not necessarily match the real amount
            * of memory consumed by it.
            */
           off_t                   tn_size;        /* (v) */
   
           /* Generic node attributes. */
           uid_t                   tn_uid;         /* (v) */
           gid_t                   tn_gid;         /* (v) */
           mode_t                  tn_mode;        /* (v) */
           int                     tn_links;       /* (v) */
           u_long                  tn_flags;       /* (v) */
           struct timespec         tn_atime;       /* (vi) */
           struct timespec         tn_mtime;       /* (vi) */
           struct timespec         tn_ctime;       /* (vi) */
           struct timespec         tn_birthtime;   /* (v) */
           unsigned long           tn_gen;         /* (c) */
   
           /*
            * 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;       /* (i) */
   
           /*
            * Interlock to protect tn_vpstate, and tn_status under shared
            * vnode lock.
            */
           struct mtx      tn_interlock;
   
           /*
            * Identify if current node has vnode assiocate with
            * or allocating vnode.
            */
           int             tn_vpstate;             /* (i) */
   
           /* Transient refcounter on this node. */
           u_int           tn_refcount;            /* 0<->1 (m) + (i) */
   
           /* misc data field for different tn_type node */
           union {
                   /* Valid when tn_type == VBLK || tn_type == VCHR. */
                   dev_t                   tn_rdev;        /* (c) */
   
                   /* Valid when tn_type == VDIR. */
                   struct tn_dir {
                           /*
                            * 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 tree that links the contents of
                            * the directory together.
                            */
                           struct tmpfs_dir        tn_dirhead;
   
                           /*
                            * Head of a list the contains fake directory entries
                            * heads, i.e. entries with TMPFS_DIRCOOKIE_DUPHEAD
                            * flag.
                            */
                           struct tmpfs_dir_duphead tn_dupindex;
   
                           /*
                            * 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.
                            */
                           off_t                   tn_readdir_lastn;
                           struct tmpfs_dirent *   tn_readdir_lastp;
                   } tn_dir;
   
                   /* Valid when tn_type == VLNK. */
                   /* The link's target, allocated from a string pool. */
                   struct tn_link {
                           char *                  tn_link_target; /* (c) */
                           char                    tn_link_smr;    /* (c) */
                   } tn_link;
   
                   /* 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.  It is a task
                            * of the memory management subsystem to issue
                            * the required page ins or page outs whenever
                            * a position within the file is accessed.
                            */
                           vm_object_t             tn_aobj;        /* (c) */
                           struct tmpfs_mount      *tn_tmp;        /* (c) */
                   } tn_reg;
           } tn_spec;      /* (v) */
   };
   LIST_HEAD(tmpfs_node_list, tmpfs_node);
   
   #define tn_rdev tn_spec.tn_rdev
   #define tn_dir tn_spec.tn_dir
   #define tn_link_target tn_spec.tn_link.tn_link_target
   #define tn_link_smr tn_spec.tn_link.tn_link_smr
   #define tn_reg tn_spec.tn_reg
   #define tn_fifo tn_spec.tn_fifo
   
   #define TMPFS_LINK_MAX INT_MAX
   
   #define TMPFS_NODE_LOCK(node) mtx_lock(&(node)->tn_interlock)
   #define TMPFS_NODE_UNLOCK(node) mtx_unlock(&(node)->tn_interlock)
   #define TMPFS_NODE_MTX(node) (&(node)->tn_interlock)
   #define TMPFS_NODE_ASSERT_LOCKED(node) mtx_assert(TMPFS_NODE_MTX(node), \
       MA_OWNED)
   
   #ifdef INVARIANTS
   #define TMPFS_ASSERT_LOCKED(node) do {                                  \
                   MPASS((node) != NULL);                                  \
                   MPASS((node)->tn_vnode != NULL);                        \
                   ASSERT_VOP_LOCKED((node)->tn_vnode, "tmpfs assert");    \
           } while (0)
   #else
   #define TMPFS_ASSERT_LOCKED(node) (void)0
   #endif
   
   /* tn_vpstate */
   #define TMPFS_VNODE_ALLOCATING  1
   #define TMPFS_VNODE_WANT        2
   #define TMPFS_VNODE_DOOMED      4
   #define TMPFS_VNODE_WRECLAIM    8
   
   /* tn_status */
   #define TMPFS_NODE_MODIFIED     0x01
   #define TMPFS_NODE_CHANGED      0x02
   
   /*
    * Internal representation of a tmpfs mount point.
    */
   struct tmpfs_mount {
           /*
            * Original value of the "size" parameter, for reference purposes,
            * mostly.
            */
           off_t                   tm_size_max;
           /*
            * 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 ULONG_MAX
            * value.
            */
           u_long                  tm_pages_max;
   
           /* Number of pages in use by the file system. */
           u_long                  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;
   
           /* unrhdr used to allocate inode numbers */
           struct unrhdr64         tm_ino_unr;
   
           /* Number of nodes currently that are in use. */
           ino_t                   tm_nodes_inuse;
   
           /* Refcounter on this struct tmpfs_mount. */
           uint64_t                tm_refcount;
   
           /* maximum representable file size */
           u_int64_t               tm_maxfilesize;
   
           /*
            * The used list contains all nodes that are currently used by
            * the file system; i.e., they refer to existing files.
            */
           struct tmpfs_node_list  tm_nodes_used;
   
           /* All node lock to protect the node list and tmp_pages_used. */
           struct mtx              tm_allnode_lock;
   
           /* Read-only status. */
           bool                    tm_ronly;
           /* Do not use namecache. */
           bool                    tm_nonc;
           /* Do not update mtime on writes through mmaped areas. */
           bool                    tm_nomtime;
   };
   #define TMPFS_LOCK(tm) mtx_lock(&(tm)->tm_allnode_lock)
   #define TMPFS_UNLOCK(tm) mtx_unlock(&(tm)->tm_allnode_lock)
   #define TMPFS_MP_ASSERT_LOCKED(tm) mtx_assert(&(tm)->tm_allnode_lock, MA_OWNED)
   
   /*
    * This structure maps a file identifier to a tmpfs node.  Used by the
    * NFS code.
    */
   struct tmpfs_fid_data {
           ino_t                   tfd_id;
           unsigned long           tfd_gen;
   };
   _Static_assert(sizeof(struct tmpfs_fid_data) <= MAXFIDSZ,
       "(struct tmpfs_fid_data) is larger than (struct fid).fid_data");
   
   struct tmpfs_dir_cursor {
           struct tmpfs_dirent     *tdc_current;
           struct tmpfs_dirent     *tdc_tree;
   };
   
   #ifdef _KERNEL
   /*
    * Prototypes for tmpfs_subr.c.
    */
   
   void    tmpfs_ref_node(struct tmpfs_node *node);
   int     tmpfs_alloc_node(struct mount *mp, struct tmpfs_mount *, enum vtype,
               uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *,
               const char *, dev_t, struct tmpfs_node **);
   int     tmpfs_fo_close(struct file *fp, struct thread *td);
   void    tmpfs_free_node(struct tmpfs_mount *, struct tmpfs_node *);
   bool    tmpfs_free_node_locked(struct tmpfs_mount *, struct tmpfs_node *, bool);
   void    tmpfs_free_tmp(struct tmpfs_mount *);
   int     tmpfs_alloc_dirent(struct tmpfs_mount *, struct tmpfs_node *,
               const char *, u_int, struct tmpfs_dirent **);
   void    tmpfs_free_dirent(struct tmpfs_mount *, struct tmpfs_dirent *);
   void    tmpfs_dirent_init(struct tmpfs_dirent *, const char *, u_int);
   void    tmpfs_destroy_vobject(struct vnode *vp, vm_object_t obj);
   int     tmpfs_alloc_vp(struct mount *, struct tmpfs_node *, int,
               struct vnode **);
   void    tmpfs_free_vp(struct vnode *);
   int     tmpfs_alloc_file(struct vnode *, struct vnode **, struct vattr *,
               struct componentname *, const char *);
   void    tmpfs_check_mtime(struct vnode *);
   void    tmpfs_dir_attach(struct vnode *, struct tmpfs_dirent *);
   void    tmpfs_dir_detach(struct vnode *, struct tmpfs_dirent *);
   void    tmpfs_dir_destroy(struct tmpfs_mount *, struct tmpfs_node *);
   struct tmpfs_dirent *   tmpfs_dir_lookup(struct tmpfs_node *node,
                               struct tmpfs_node *f,
                               struct componentname *cnp);
   int     tmpfs_dir_getdents(struct tmpfs_mount *, struct tmpfs_node *,
               struct uio *, int, u_long *, int *);
   int     tmpfs_dir_whiteout_add(struct vnode *, struct componentname *);
   void    tmpfs_dir_whiteout_remove(struct vnode *, struct componentname *);
   int     tmpfs_reg_resize(struct vnode *, off_t, boolean_t);
   int     tmpfs_chflags(struct vnode *, u_long, struct ucred *, struct thread *);
   int     tmpfs_chmod(struct vnode *, mode_t, struct ucred *, struct thread *);
   int     tmpfs_chown(struct vnode *, uid_t, gid_t, struct ucred *,
               struct thread *);
   int     tmpfs_chsize(struct vnode *, u_quad_t, struct ucred *, struct thread *);
   int     tmpfs_chtimes(struct vnode *, struct vattr *, struct ucred *cred,
               struct thread *);
   void    tmpfs_itimes(struct vnode *, const struct timespec *,
               const struct timespec *);
   
   void    tmpfs_set_accessed(struct tmpfs_mount *tm, struct tmpfs_node *node);
   void    tmpfs_set_status(struct tmpfs_mount *tm, struct tmpfs_node *node,
               int status);
   int     tmpfs_truncate(struct vnode *, off_t);
   struct tmpfs_dirent *tmpfs_dir_first(struct tmpfs_node *dnode,
               struct tmpfs_dir_cursor *dc);
   struct tmpfs_dirent *tmpfs_dir_next(struct tmpfs_node *dnode,
               struct tmpfs_dir_cursor *dc);
   static __inline void
   tmpfs_update(struct vnode *vp)
   {
   
           tmpfs_itimes(vp, NULL, NULL);
   }
   
   /*
    * 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 == len && \
       bcmp((de)->ud.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) do { \
           MPASS((node)->tn_type == VDIR); \
           MPASS((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \
   } while (0)
   
   /*
    * Amount of memory pages to reserve for the system (e.g., to not use by
    * tmpfs).
    */
   #if !defined(TMPFS_PAGES_MINRESERVED)
   #define TMPFS_PAGES_MINRESERVED         (4 * 1024 * 1024 / PAGE_SIZE)
   #endif
   
   size_t tmpfs_mem_avail(void);
   size_t tmpfs_pages_used(struct tmpfs_mount *tmp);
   void tmpfs_subr_init(void);
   void tmpfs_subr_uninit(void);
   
   /*
    * 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;
   
           MPASS(mp != NULL && mp->mnt_data != NULL);
           tmp = (struct tmpfs_mount *)mp->mnt_data;
           return (tmp);
   }
   
   static inline struct tmpfs_node *
   VP_TO_TMPFS_NODE(struct vnode *vp)
   {
           struct tmpfs_node *node;
   
           MPASS(vp != NULL && vp->v_data != NULL);
           node = (struct tmpfs_node *)vp->v_data;
           return (node);
   }
   
   #define VP_TO_TMPFS_NODE_SMR(vp)        \
           ((struct tmpfs_node *)vn_load_v_data_smr(vp))
   
   static inline struct tmpfs_node *
   VP_TO_TMPFS_DIR(struct vnode *vp)
   {
           struct tmpfs_node *node;
   
           node = VP_TO_TMPFS_NODE(vp);
           TMPFS_VALIDATE_DIR(node);
           return (node);
   }
   
   static inline bool
   tmpfs_use_nc(struct vnode *vp)
   {
   
           return (!(VFS_TO_TMPFS(vp->v_mount)->tm_nonc));
   }
   
   static inline void
   tmpfs_update_getattr(struct vnode *vp)
   {
           struct tmpfs_node *node;
   
           node = VP_TO_TMPFS_NODE(vp);
           if (__predict_false((node->tn_status & (TMPFS_NODE_MODIFIED |
               TMPFS_NODE_CHANGED)) != 0 || node->tn_accessed))
                   tmpfs_update(vp);
   }
   
   extern struct fileops tmpfs_fnops;
   
   #endif /* _KERNEL */
   
   #endif /* _FS_TMPFS_TMPFS_H_ */

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