fs/reiser4/plugin/fibration.c

   1 /* Copyright 2004 by Hans Reiser, licensing governed by
   2  * reiser4/README */
   3
   4 /* Directory fibrations */
   5
   6 /*
   7  * Suppose we have a directory tree with sources of some project. During
   8  * compilation .o files are created within this tree. This makes access
   9  * to the original source files less efficient, because source files are
  10  * now "diluted" by object files: default directory plugin uses prefix
  11  * of a file name as a part of the key for directory entry (and this
  12  * part is also inherited by the key of file body). This means that
  13  * foo.o will be located close to foo.c and foo.h in the tree.
  14  *
  15  * To avoid this effect directory plugin fill highest 7 (unused
  16  * originally) bits of the second component of the directory entry key
  17  * by bit-pattern depending on the file name (see
  18  * fs/reiser4/kassign.c:build_entry_key_common()). These bits are called
  19  * "fibre". Fibre of the file name key is inherited by key of stat data
  20  * and keys of file body (in the case of REISER4_LARGE_KEY).
  21  *
  22  * Fibre for a given file is chosen by per-directory fibration
  23  * plugin. Names within given fibre are ordered lexicographically.
  24  */
  25
  26 #include "../debug.h"
  27 #include "plugin_header.h"
  28 #include "plugin.h"
  29 #include "../super.h"
  30 #include "../inode.h"
  31
  32 #include <linux/types.h>
  33
  34 static const int fibre_shift = 57;
  35
  36 #define FIBRE_NO(n) (((__u64)(n)) << fibre_shift)
  37
  38 /*
  39  * Trivial fibration: all files of directory are just ordered
  40  * lexicographically.
  41  */
  42 static __u64 fibre_trivial(const struct inode *dir, const char *name, int len)
  43 {
  44         return FIBRE_NO(0);
  45 }
  46
  47 /*
  48  * dot-o fibration: place .o files after all others.
  49  */
  50 static __u64 fibre_dot_o(const struct inode *dir, const char *name, int len)
  51 {
  52         /* special treatment for .*\.o */
  53         if (len > 2 && name[len - 1] == 'o' && name[len - 2] == '.')
  54                 return FIBRE_NO(1);
  55         else
  56                 return FIBRE_NO(0);
  57 }
  58
  59 /*
  60  * ext.1 fibration: subdivide directory into 128 fibrations one for each
  61  * 7bit extension character (file "foo.h" goes into fibre "h"), plus
  62  * default fibre for the rest.
  63  */
  64 static __u64 fibre_ext_1(const struct inode *dir, const char *name, int len)
  65 {
  66         if (len > 2 && name[len - 2] == '.')
  67                 return FIBRE_NO(name[len - 1]);
  68         else
  69                 return FIBRE_NO(0);
  70 }
  71
  72 /*
  73  * ext.3 fibration: try to separate files with different 3-character
  74  * extensions from each other.
  75  */
  76 static __u64 fibre_ext_3(const struct inode *dir, const char *name, int len)
  77 {
  78         if (len > 4 && name[len - 4] == '.')
  79                 return FIBRE_NO(name[len - 3] + name[len - 2] + name[len - 1]);
  80         else
  81                 return FIBRE_NO(0);
  82 }
  83
  84 static int change_fibration(struct inode *inode,
  85                             reiser4_plugin * plugin,
  86                             pset_member memb)
  87 {
  88         int result;
  89
  90         assert("nikita-3503", inode != NULL);
  91         assert("nikita-3504", plugin != NULL);
  92
  93         assert("nikita-3505", is_reiser4_inode(inode));
  94         assert("nikita-3506", inode_dir_plugin(inode) != NULL);
  95         assert("nikita-3507",
  96                plugin->h.type_id == REISER4_FIBRATION_PLUGIN_TYPE);
  97
  98         result = 0;
  99         if (inode_fibration_plugin(inode) == NULL ||
 100             inode_fibration_plugin(inode)->h.id != plugin->h.id) {
 101                 if (is_dir_empty(inode) == 0)
 102                         result = aset_set_unsafe(&reiser4_inode_data(inode)->pset,
 103                                                  PSET_FIBRATION, plugin);
 104                 else
 105                         result = RETERR(-ENOTEMPTY);
 106
 107         }
 108         return result;
 109 }
 110
 111 static reiser4_plugin_ops fibration_plugin_ops = {
 112         .init = NULL,
 113         .load = NULL,
 114         .save_len = NULL,
 115         .save = NULL,
 116         .change = change_fibration
 117 };
 118
 119 /* fibration plugins */
 120 fibration_plugin fibration_plugins[LAST_FIBRATION_ID] = {
 121         [FIBRATION_LEXICOGRAPHIC] = {
 122                 .h = {
 123                         .type_id = REISER4_FIBRATION_PLUGIN_TYPE,
 124                         .id = FIBRATION_LEXICOGRAPHIC,
 125                         .pops = &fibration_plugin_ops,
 126                         .label = "lexicographic",
 127                         .desc = "no fibration",
 128                         .linkage = {NULL, NULL}
 129                 },
 130                 .fibre = fibre_trivial
 131         },
 132         [FIBRATION_DOT_O] = {
 133                 .h = {
 134                         .type_id = REISER4_FIBRATION_PLUGIN_TYPE,
 135                         .id = FIBRATION_DOT_O,
 136                         .pops = &fibration_plugin_ops,
 137                         .label = "dot-o",
 138                         .desc = "fibrate .o files separately",
 139                         .linkage = {NULL, NULL}
 140                 },
 141                 .fibre = fibre_dot_o
 142         },
 143         [FIBRATION_EXT_1] = {
 144                 .h = {
 145                         .type_id = REISER4_FIBRATION_PLUGIN_TYPE,
 146                         .id = FIBRATION_EXT_1,
 147                         .pops = &fibration_plugin_ops,
 148                         .label = "ext-1",
 149                         .desc = "fibrate file by single character extension",
 150                         .linkage = {NULL, NULL}
 151                 },
 152                 .fibre = fibre_ext_1
 153         },
 154         [FIBRATION_EXT_3] = {
 155                 .h = {
 156                         .type_id = REISER4_FIBRATION_PLUGIN_TYPE,
 157                         .id = FIBRATION_EXT_3,
 158                         .pops = &fibration_plugin_ops,
 159                         .label = "ext-3",
 160                         .desc = "fibrate file by three character extension",
 161                         .linkage = {NULL, NULL}
 162                 },
 163                 .fibre = fibre_ext_3
 164         }
 165 };
 166
 167 /*
 168  * Local variables:
 169  * c-indentation-style: "K&R"
 170  * mode-name: "LC"
 171  * c-basic-offset: 8
 172  * tab-width: 8
 173  * fill-column: 79
 174  * End:
 175  */