sys/fs/tmpfs/tmpfs_pool.h

   1 /*      $NetBSD: tmpfs_pool.h,v 1.6 2006/11/09 16:20:56 jmmv Exp $      */
   2
   3 /*
   4  * Copyright (c) 2005, 2006 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_POOL_H_
  34 #define _FS_TMPFS_TMPFS_POOL_H_
  35
  36
  37 /* --------------------------------------------------------------------- */
  38
  39 /*
  40  * tmpfs_pool is an extension of regular system pools to also hold data
  41  * specific to tmpfs.  More specifically, we want a pointer to the
  42  * tmpfs_mount structure using the pool so that we can update its memory
  43  * usage statistics.
  44  */
  45 struct tmpfs_pool {
  46         struct pool             tp_pool;
  47
  48         /* Reference to the mount point that holds the pool.  This is used
  49          * by the tmpfs_pool_allocator to access and modify the memory
  50          * accounting variables for the mount point. */
  51         struct tmpfs_mount *    tp_mount;
  52
  53         /* The pool's name.  Used as the wait channel. */
  54         char                    tp_name[64];
  55 };
  56
  57 /* --------------------------------------------------------------------- */
  58
  59 /*
  60  * tmpfs uses variable-length strings to store file names and to store
  61  * link targets.  Reserving a fixed-size buffer for each of them is
  62  * inefficient because it will consume a lot more memory than is really
  63  * necessary.  However, managing variable-sized buffers is difficult as
  64  * regards memory allocation and very inefficient in computation time.
  65  * This is why tmpfs provides an hybrid scheme to store strings: string
  66  * pools.
  67  *
  68  * A string pool is a collection of memory pools, each one with elements
  69  * of a fixed size.  In tmpfs's case, a string pool contains independent
  70  * memory pools for 16-byte, 32-byte, 64-byte, 128-byte, 256-byte,
  71  * 512-byte and 1024-byte long objects.  Whenever an object is requested
  72  * from the pool, the new object's size is rounded to the closest upper
  73  * match and an item from the corresponding pool is returned.
  74  */
  75 struct tmpfs_str_pool {
  76         struct tmpfs_pool       tsp_pool_16;
  77         struct tmpfs_pool       tsp_pool_32;
  78         struct tmpfs_pool       tsp_pool_64;
  79         struct tmpfs_pool       tsp_pool_128;
  80         struct tmpfs_pool       tsp_pool_256;
  81         struct tmpfs_pool       tsp_pool_512;
  82         struct tmpfs_pool       tsp_pool_1024;
  83 };
  84
  85 /* --------------------------------------------------------------------- */
  86 #ifdef _KERNEL
  87
  88 /*
  89  * Convenience functions and macros to manipulate a tmpfs_pool.
  90  */
  91
  92 void    tmpfs_pool_init(struct tmpfs_pool *tpp, size_t size,
  93             const char *what, struct tmpfs_mount *tmp);
  94 void    tmpfs_pool_destroy(struct tmpfs_pool *tpp);
  95
  96 #define TMPFS_POOL_GET(tpp, flags) pool_get((struct pool *)(tpp), flags)
  97 #define TMPFS_POOL_PUT(tpp, v) pool_put((struct pool *)(tpp), v)
  98
  99 /* --------------------------------------------------------------------- */
 100
 101 /*
 102  * Functions to manipulate a tmpfs_str_pool.
 103  */
 104
 105 void    tmpfs_str_pool_init(struct tmpfs_str_pool *, struct tmpfs_mount *);
 106 void    tmpfs_str_pool_destroy(struct tmpfs_str_pool *);
 107 char *  tmpfs_str_pool_get(struct tmpfs_str_pool *, size_t, int);
 108 void    tmpfs_str_pool_put(struct tmpfs_str_pool *, char *, size_t);
 109
 110 #endif
 111
 112 #endif /* _FS_TMPFS_TMPFS_POOL_H_ */