fs/reiser4/plugin/item/static_stat.h

   1 /* Copyright 2001, 2002, 2003 by Hans Reiser, licensing governed by reiser4/README */
   2
   3 /* This describes the static_stat item, used to hold all information needed by the stat() syscall.
   4
   5 In the case where each file has not less than the fields needed by the
   6 stat() syscall, it is more compact to store those fields in this
   7 struct.
   8
   9 If this item does not exist, then all stats are dynamically resolved.
  10 At the moment, we either resolve all stats dynamically or all of them
  11 statically.  If you think this is not fully optimal, and the rest of
  12 reiser4 is working, then fix it...:-)
  13
  14 */
  15
  16 #if !defined( __FS_REISER4_PLUGIN_ITEM_STATIC_STAT_H__ )
  17 #define __FS_REISER4_PLUGIN_ITEM_STATIC_STAT_H__
  18
  19 #include "../../forward.h"
  20 #include "../../dformat.h"
  21
  22 #include <linux/fs.h>           /* for struct inode */
  23
  24 /* Stat data layout: goals and implementation.
  25
  26    We want to be able to have lightweight files which have complete flexibility in what semantic metadata is attached to
  27    them, including not having semantic metadata attached to them.
  28
  29    There is one problem with doing that, which is that if in fact you have exactly the same metadata for most files you
  30    want to store, then it takes more space to store that metadata in a dynamically sized structure than in a statically
  31    sized structure because the statically sized structure knows without recording it what the names and lengths of the
  32    attributes are.
  33
  34    This leads to a natural compromise, which is to special case those files which have simply the standard unix file
  35    attributes, and only employ the full dynamic stat data mechanism for those files that differ from the standard unix
  36    file in their use of file attributes.
  37
  38    Yet this compromise deserves to be compromised a little.
  39
  40    We accommodate the case where you have no more than the standard unix file attributes by using an "extension
  41    bitmask": each bit in it indicates presence or absence of or particular stat data extension (see sd_ext_bits enum).
  42
  43    If the first bit of the extension bitmask bit is 0, we have light-weight file whose attributes are either inherited
  44    from parent directory (as uid, gid) or initialised to some sane values.
  45
  46    To capitalize on existing code infrastructure, extensions are
  47    implemented as plugins of type REISER4_SD_EXT_PLUGIN_TYPE.
  48    Each stat-data extension plugin implements four methods:
  49
  50     ->present() called by sd_load() when this extension is found in stat-data
  51     ->absent() called by sd_load() when this extension is not found in stat-data
  52     ->save_len() called by sd_len() to calculate total length of stat-data
  53     ->save() called by sd_save() to store extension data into stat-data
  54
  55     Implementation is in fs/reiser4/plugin/item/static_stat.c
  56 */
  57
  58 /* stat-data extension. Please order this by presumed frequency of use */
  59 typedef enum {
  60         /* support for light-weight files */
  61         LIGHT_WEIGHT_STAT,
  62         /* data required to implement unix stat(2) call. Layout is in
  63            reiser4_unix_stat. If this is not present, file is light-weight */
  64         UNIX_STAT,
  65         /* this contains additional set of 32bit [anc]time fields to implement
  66            nanosecond resolution. Layout is in reiser4_large_times_stat. Usage
  67            if this extension is governed by 32bittimes mount option. */
  68         LARGE_TIMES_STAT,
  69         /* stat data has link name included */
  70         SYMLINK_STAT,
  71         /* on-disk slots of non-standard plugins for main plugin table
  72            (@reiser4_inode->pset), that is, plugins that cannot be deduced
  73            from file mode bits), for example, aggregation, interpolation etc. */
  74         PLUGIN_STAT,
  75         /* this extension contains persistent inode flags. These flags are
  76            single bits: immutable, append, only, etc. Layout is in
  77            reiser4_flags_stat. */
  78         FLAGS_STAT,
  79         /* this extension contains capabilities sets, associated with this
  80            file. Layout is in reiser4_capabilities_stat */
  81         CAPABILITIES_STAT,
  82         /* this extension contains size and public id of the secret key.
  83            Layout is in reiser4_crypto_stat */
  84         CRYPTO_STAT,
  85         /* on-disk slots of non-default plugins for inheritance, which
  86            are extracted to special plugin table (@reiser4_inode->hset).
  87            By default, children of the object will inherit plugins from
  88            its main plugin table (pset). */
  89         HEIR_STAT,
  90         LAST_SD_EXTENSION,
  91         /*
  92          * init_inode_static_sd() iterates over extension mask until all
  93          * non-zero bits are processed. This means, that neither ->present(),
  94          * nor ->absent() methods will be called for stat-data extensions that
  95          * go after last present extension. But some basic extensions, we want
  96          * either ->absent() or ->present() method to be called, because these
  97          * extensions set up something in inode even when they are not
  98          * present. This is what LAST_IMPORTANT_SD_EXTENSION is for: for all
  99          * extensions before and including LAST_IMPORTANT_SD_EXTENSION either
 100          * ->present(), or ->absent() method will be called, independently of
 101          * what other extensions are present.
 102          */
 103         LAST_IMPORTANT_SD_EXTENSION = PLUGIN_STAT
 104 } sd_ext_bits;
 105
 106 /* minimal stat-data. This allows to support light-weight files. */
 107 typedef struct reiser4_stat_data_base {
 108         /*  0 */ __le16 extmask;
 109         /*  2 */
 110 } PACKED reiser4_stat_data_base;
 111
 112 typedef struct reiser4_light_weight_stat {
 113         /*  0 */ __le16 mode;
 114         /*  2 */ __le32 nlink;
 115         /*  6 */ __le64 size;
 116         /* size in bytes */
 117         /* 14 */
 118 } PACKED reiser4_light_weight_stat;
 119
 120 typedef struct reiser4_unix_stat {
 121         /* owner id */
 122         /*  0 */ __le32 uid;
 123         /* group id */
 124         /*  4 */ __le32 gid;
 125         /* access time */
 126         /*  8 */ __le32 atime;
 127         /* modification time */
 128         /* 12 */ __le32 mtime;
 129         /* change time */
 130         /* 16 */ __le32 ctime;
 131         union {
 132                 /* minor:major for device files */
 133                 /* 20 */ __le64 rdev;
 134                 /* bytes used by file */
 135                 /* 20 */ __le64 bytes;
 136         } u;
 137         /* 28 */
 138 } PACKED reiser4_unix_stat;
 139
 140 /* symlink stored as part of inode */
 141 typedef struct reiser4_symlink_stat {
 142         char body[0];
 143 } PACKED reiser4_symlink_stat;
 144
 145 typedef struct reiser4_plugin_slot {
 146         /*  0 */ __le16 pset_memb;
 147         /*  2 */ __le16 id;
 148         /*  4 *//* here plugin stores its persistent state */
 149 } PACKED reiser4_plugin_slot;
 150
 151 /* stat-data extension for files with non-standard plugin. */
 152 typedef struct reiser4_plugin_stat {
 153         /* number of additional plugins, associated with this object */
 154         /*  0 */ __le16 plugins_no;
 155         /*  2 */ reiser4_plugin_slot slot[0];
 156         /*  2 */
 157 } PACKED reiser4_plugin_stat;
 158
 159 /* stat-data extension for inode flags. Currently it is just fixed-width 32
 160  * bit mask. If need arise, this can be replaced with variable width
 161  * bitmask. */
 162 typedef struct reiser4_flags_stat {
 163         /*  0 */ __le32 flags;
 164         /*  4 */
 165 } PACKED reiser4_flags_stat;
 166
 167 typedef struct reiser4_capabilities_stat {
 168         /*  0 */ __le32 effective;
 169         /*  8 */ __le32 permitted;
 170         /* 16 */
 171 } PACKED reiser4_capabilities_stat;
 172
 173 typedef struct reiser4_cluster_stat {
 174 /* this defines cluster size (an attribute of cryptcompress objects) as PAGE_SIZE << cluster shift */
 175         /* 0 */ d8 cluster_shift;
 176         /* 1 */
 177 } PACKED reiser4_cluster_stat;
 178
 179 typedef struct reiser4_crypto_stat {
 180         /* secret key size, bits */
 181         /*  0 */ d16 keysize;
 182         /* secret key id */
 183         /*  2 */ d8 keyid[0];
 184         /* 2 */
 185 } PACKED reiser4_crypto_stat;
 186
 187 typedef struct reiser4_large_times_stat {
 188         /* access time */
 189         /* 0 */ d32 atime;
 190         /* modification time */
 191         /* 4 */ d32 mtime;
 192         /* change time */
 193         /* 8 */ d32 ctime;
 194         /* 12 */
 195 } PACKED reiser4_large_times_stat;
 196
 197 /* this structure is filled by sd_item_stat */
 198 typedef struct sd_stat {
 199         int dirs;
 200         int files;
 201         int others;
 202 } sd_stat;
 203
 204 /* plugin->item.common.* */
 205 extern void print_sd(const char *prefix, coord_t * coord);
 206 extern void item_stat_static_sd(const coord_t * coord, void *vp);
 207
 208 /* plugin->item.s.sd.* */
 209 extern int init_inode_static_sd(struct inode *inode, char *sd, int len);
 210 extern int save_len_static_sd(struct inode *inode);
 211 extern int save_static_sd(struct inode *inode, char **area);
 212
 213 /* __FS_REISER4_PLUGIN_ITEM_STATIC_STAT_H__ */
 214 #endif
 215
 216 /* Make Linus happy.
 217    Local variables:
 218    c-indentation-style: "K&R"
 219    mode-name: "LC"
 220    c-basic-offset: 8
 221    tab-width: 8
 222    fill-column: 120
 223    End:
 224 */