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

     /*      $NetBSD: tmpfs.h,v 1.26 2007/02/22 06:37:00 thorpej 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.
     *
     * 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_
    
    /* ---------------------------------------------------------------------
     * KERNEL-SPECIFIC DEFINITIONS
     * --------------------------------------------------------------------- */
    #include <sys/dirent.h>
    #include <sys/mount.h>
    #include <sys/queue.h>
    #include <sys/vnode.h>
    #include <sys/file.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    
    /* --------------------------------------------------------------------- */
    #include <sys/malloc.h>
    #include <sys/systm.h>
    #include <sys/vmmeter.h>
    #include <vm/swap_pager.h>
    
    MALLOC_DECLARE(M_TMPFSMNT);
    MALLOC_DECLARE(M_TMPFSNAME);
    
    /* --------------------------------------------------------------------- */
    
    /*
     * 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. */
   #ifdef _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;
           MPASS(cookie != TMPFS_DIRCOOKIE_DOT);
           MPASS(cookie != TMPFS_DIRCOOKIE_DOTDOT);
           MPASS(cookie != TMPFS_DIRCOOKIE_EOF);
   
           return cookie;
   }
   #endif
   
   /* --------------------------------------------------------------------- */
   
   /*
    * 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.
    *
    */
   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;
   
           /* 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;
   
           /* interlock to protect tn_vpstate */
           struct mtx      tn_interlock;
   
           /* Identify if current node has vnode assiocate with
            * or allocating vnode.
            */
           int             tn_vpstate;
   
           /* misc data field for different tn_type node */
           union {
                   /* Valid when tn_type == VBLK || tn_type == VCHR. */
                   dev_t                   tn_rdev;
   
                   /* 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 tail-queue that links the contents of
                            * the directory together.  See above for a
                            * description of its contents. */
                           struct tmpfs_dir        tn_dirhead;
   
                           /* 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. */
                   /* The link's target, allocated from a string pool. */
                   char *                  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,
                            * 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. */
                           vm_object_t             tn_aobj;
                           size_t                  tn_aobj_pages;
   
                   }tn_reg;
   
                   /* Valid when tn_type = VFIFO */
                   struct tn_fifo {
                           fo_rdwr_t               *tn_fo_read;
                           fo_rdwr_t               *tn_fo_write;
                   }tn_fifo;
           }tn_spec;
   };
   LIST_HEAD(tmpfs_node_list, tmpfs_node);
   
   #define tn_rdev tn_spec.tn_rdev
   #define tn_dir tn_spec.tn_dir
   #define tn_link tn_spec.tn_link
   #define tn_reg tn_spec.tn_reg
   #define tn_fifo tn_spec.tn_fifo
   
   #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_VNODE_ALLOCATING  1
   #define TMPFS_VNODE_WANT        2
   /* --------------------------------------------------------------------- */
   
   /*
    * 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;
   
           /* unrhdr used to allocate inode numbers */
           struct unrhdr *         tm_ino_unr;
   
           /* Number of nodes currently that are in use. */
           ino_t                   tm_nodes_inuse;
   
           /* maximum representable file size */
           u_int64_t               tm_maxfilesize;
   
           /* 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;
   
           /* All node lock to protect the node list and tmp_pages_used */
           struct mtx allnode_lock;
   
           /* 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. */
           uma_zone_t              tm_dirent_pool;
           uma_zone_t              tm_node_pool;
   };
   #define TMPFS_LOCK(tm) mtx_lock(&(tm)->allnode_lock)
   #define TMPFS_UNLOCK(tm) mtx_unlock(&(tm)->allnode_lock)
   
   /* --------------------------------------------------------------------- */
   
   /*
    * 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;
           ino_t                   tf_id;
           unsigned long           tf_gen;
   };
   
   /* --------------------------------------------------------------------- */
   
   #ifdef _KERNEL
   /*
    * 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 thread *, 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 *, int,
               struct vnode **, struct thread *);
   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 tmpfs_node *f,
                               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);
   int     tmpfs_chflags(struct vnode *, int, 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 timespec *, struct timespec *,
               struct timespec *, int, struct ucred *, struct thread *);
   void    tmpfs_itimes(struct vnode *, const struct timespec *,
               const struct timespec *);
   
   void    tmpfs_update(struct vnode *);
   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) \
       MPASS((node)->tn_type == VDIR); \
       MPASS((node)->tn_size % sizeof(struct tmpfs_dirent) == 0); \
       MPASS((node)->tn_dir.tn_readdir_lastp == NULL || \
           tmpfs_dircookie((node)->tn_dir.tn_readdir_lastp) == (node)->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 information about the number of available memory pages,
    * including physical and virtual ones.
    *
    * If 'total' is TRUE, the value returned is the total amount of memory
    * pages configured for the system (either in use or free).
    * If it is FALSE, the value returned is the amount of free memory pages.
    *
    * Remember to remove TMPFS_PAGES_RESERVED from the returned value to avoid
    * excessive memory usage.
    *
    */
   static __inline size_t
   tmpfs_mem_info(void)
   {
           size_t size;
   
           size = swap_pager_avail + cnt.v_free_count + cnt.v_inactive_count;
           size -= size > cnt.v_wire_count ? cnt.v_wire_count : size;
           return 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();
           freepages -= freepages < TMPFS_PAGES_RESERVED ?
               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_META_PAGES(tmp) (howmany((tmp)->tm_nodes_inuse * (sizeof(struct tmpfs_node) \
                                   + sizeof(struct tmpfs_dirent)), PAGE_SIZE))
   #define TMPFS_FILE_PAGES(tmp) ((tmp)->tm_pages_used)
   
   #define TMPFS_PAGES_AVAIL(tmp) (TMPFS_PAGES_MAX(tmp) > \
                           TMPFS_META_PAGES(tmp)+TMPFS_FILE_PAGES(tmp)? \
                           TMPFS_PAGES_MAX(tmp) - TMPFS_META_PAGES(tmp) \
                           - TMPFS_FILE_PAGES(tmp):0)
   
   #endif
   
   /* --------------------------------------------------------------------- */
   
   /*
    * 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;
   }
   
   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;
   }
   
   #endif /* _FS_TMPFS_TMPFS_H_ */

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