1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 */ 24 25 /* Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T */ 26 /* All Rights Reserved */ 27 28 /* 29 * University Copyright- Copyright (c) 1982, 1986, 1988 30 * The Regents of the University of California 31 * All Rights Reserved 32 * 33 * University Acknowledgment- Portions of this document are derived from 34 * software developed by the University of California, Berkeley, and its 35 * contributors. 36 */ 37 38 #ifndef _SYS_DNLC_H 39 #define _SYS_DNLC_H 40 41 #ifdef __cplusplus 42 extern "C" { 43 #endif 44 45 #include <sys/kstat.h> 46 47 /* 48 * DNLC - Directory name lookup cache. 49 * There are now two sorts of name caching: 50 * 51 * Standard dnlc: This original cache holds recent mappings 52 * of <directory vnode, name> to vnode mappings. 53 * 54 * Directory caches: Entire large directories can be cached, subject to 55 * memory availability and tunables. A directory cache 56 * anchor point must be provided in the xxnode for 57 * a directory. 58 */ 59 60 61 /* 62 * Standard dnlc 63 * ============= 64 */ 65 66 /* 67 * This structure describes the elements in the cache of recent 68 * names looked up. 69 * 70 * Note namlen is a uchar_t to conserve space 71 * and alignment padding. The max length of any 72 * pathname component is defined as MAXNAMELEN 73 * which is 256 (including the terminating null). 74 * So provided this doesn't change, we don't include the null, 75 * we always use bcmp to compare strings, and we don't start 76 * storing full names, then we are ok. The space savings are worth it. 77 */ 78 typedef struct ncache { 79 struct ncache *hash_next; /* hash chain, MUST BE FIRST */ 80 struct ncache *hash_prev; 81 struct vnode *vp; /* vnode the name refers to */ 82 struct vnode *dp; /* vnode of parent of name */ 83 int hash; /* hash signature */ 84 uchar_t namlen; /* length of name */ 85 char name[1]; /* segment name - null terminated */ 86 } ncache_t; 87 88 /* 89 * Hash table bucket structure of name cache entries for fast lookup. 90 */ 91 typedef struct nc_hash { 92 ncache_t *hash_next; 93 ncache_t *hash_prev; 94 kmutex_t hash_lock; 95 } nc_hash_t; 96 97 /* 98 * Statistics on name cache 99 * Not protected by locks 100 */ 101 /* 102 * ncstats has been deprecated, due to the integer size of the counters 103 * which can easily overflow in the dnlc. 104 * It is maintained (at some expense) for compatability. 105 * The preferred interface is the kstat accessible nc_stats below, ehich 106 * is actually shared with directory caching. 107 */ 108 struct ncstats { 109 int hits; /* hits that we can really use */ 110 int misses; /* cache misses */ 111 int enters; /* number of enters done */ 112 int dbl_enters; /* number of enters tried when already cached */ 113 int long_enter; /* deprecated, no longer accounted */ 114 int long_look; /* deprecated, no longer accounted */ 115 int move_to_front; /* entry moved to front of hash chain */ 116 int purges; /* number of purges of cache */ 117 }; 118 119 struct nc_stats { 120 kstat_named_t ncs_hits; /* cache hits */ 121 kstat_named_t ncs_misses; /* cache misses */ 122 kstat_named_t ncs_neg_hits; /* negative cache hits */ 123 kstat_named_t ncs_enters; /* enters */ 124 kstat_named_t ncs_dbl_enters; /* enters when entry already cached */ 125 kstat_named_t ncs_purge_total; /* total entries prurged */ 126 kstat_named_t ncs_purge_all; /* dnlc_purge() calls */ 127 kstat_named_t ncs_purge_vp; /* dnlc_purge_vp() calls */ 128 kstat_named_t ncs_purge_vfs; /* dnlc_purge_vfs() calls */ 129 kstat_named_t ncs_purge_fs1; /* dnlc_purge_fs1() calls */ 130 kstat_named_t ncs_pick_free; /* found a free ncache */ 131 kstat_named_t ncs_pick_heur; /* found ncache w/ NULL vpages */ 132 kstat_named_t ncs_pick_last; /* found last ncache on chain */ 133 134 /* directory caching stats */ 135 136 kstat_named_t ncs_dir_hits; /* dir cache hits */ 137 kstat_named_t ncs_dir_misses; /* dir cache misses */ 138 kstat_named_t ncs_cur_dirs; /* current # directories cached */ 139 kstat_named_t ncs_dir_num_ents; /* current # entries cached */ 140 kstat_named_t ncs_dirs_cached; /* total # directories cached */ 141 kstat_named_t ncs_dir_start_nm; /* dir start no memory */ 142 kstat_named_t ncs_dir_add_nm; /* add entry/space - no memory */ 143 kstat_named_t ncs_dir_addabort; /* add entry/space - abort */ 144 kstat_named_t ncs_dir_add_max; /* add entry/space - max exceeded */ 145 kstat_named_t ncs_dir_reme_fai; /* remove entry fail */ 146 kstat_named_t ncs_dir_rems_fai; /* remove space fail */ 147 kstat_named_t ncs_dir_upd_fail; /* update space fail */ 148 kstat_named_t ncs_dir_finipurg; /* fini purges */ 149 kstat_named_t ncs_dir_rec_last; /* reclaim last */ 150 kstat_named_t ncs_dir_recl_any; /* reclaim any */ 151 }; 152 153 /* 154 * The dnlc hashing function. 155 * Although really a kernel macro we export it to allow validation 156 * of ncache_t entries by mdb. Note, mdb can handle the ASSERT. 157 * 158 * 'hash' and 'namlen' must be l-values. A check is made to ensure 159 * the name length fits into an unsigned char (see ncache_t). 160 */ 161 #define DNLCHASH(name, dvp, hash, namlen) \ 162 { \ 163 char Xc; \ 164 const char *Xcp; \ 165 hash = (int)((uintptr_t)(dvp)) >> 8; \ 166 for (Xcp = (name); (Xc = *Xcp) != 0; Xcp++) \ 167 (hash) = ((hash) << 4) + (hash) + Xc; \ 168 ASSERT((Xcp - (name)) <= ((1 << NBBY) - 1)); \ 169 (namlen) = Xcp - (name); \ 170 } 171 172 #if defined(_KERNEL) || defined(_FAKE_KERNEL) 173 174 #include <sys/vfs.h> 175 #include <sys/vnode.h> 176 177 extern int ncsize; /* set in param_init() # of dnlc entries */ 178 extern vnode_t negative_cache_vnode; 179 #define DNLC_NO_VNODE &negative_cache_vnode 180 181 void dnlc_init(void); 182 void dnlc_enter(vnode_t *, const char *, vnode_t *); 183 void dnlc_update(vnode_t *, const char *, vnode_t *); 184 vnode_t *dnlc_lookup(vnode_t *, const char *); 185 void dnlc_purge(void); 186 void dnlc_purge_vp(vnode_t *); 187 int dnlc_purge_vfsp(vfs_t *, int); 188 void dnlc_remove(vnode_t *, const char *); 189 int dnlc_fs_purge1(struct vnodeops *); 190 void dnlc_reduce_cache(void *); 191 192 #endif /* defined(_KERNEL) */ 193 194 195 /* 196 * Directory caching interfaces 197 * ============================ 198 */ 199 200 /* 201 * Typically for large directories, the file names will be the same or 202 * at least similar lengths. So there's no point in anything more elaborate 203 * than a simple unordered linked list of free space entries. 204 * For small directories the name length distribution doesn't really matter. 205 */ 206 typedef struct dcfree { 207 uint64_t df_handle; /* fs supplied handle */ 208 struct dcfree *df_next; /* link to next free entry in bucket */ 209 uint_t df_len; /* length of free entry */ 210 } dcfree_t; 211 212 typedef struct dcentry { 213 uint64_t de_handle; /* fs supplied and returned data */ 214 struct dcentry *de_next; /* link to next name entry in bucket */ 215 int de_hash; /* hash signature */ 216 uchar_t de_namelen; /* length of name excluding null */ 217 char de_name[1]; /* null terminated name */ 218 } dcentry_t; 219 220 typedef struct dircache { 221 struct dircache *dc_next; /* chain - for purge purposes */ 222 struct dircache *dc_prev; /* chain - for purge purposes */ 223 int64_t dc_actime; /* dir access time, from lbolt64 */ 224 dcentry_t **dc_namehash; /* entry hash table pointer */ 225 dcfree_t **dc_freehash; /* free entry hash table pointer */ 226 uint_t dc_num_entries; /* no of named entries */ 227 uint_t dc_num_free; /* no of free space entries */ 228 uint_t dc_nhash_mask; /* name hash table size - 1 */ 229 uint_t dc_fhash_mask; /* free space hash table size - 1 */ 230 struct dcanchor *dc_anchor; /* back ptr to anchor */ 231 boolean_t dc_complete; /* cache complete boolean */ 232 } dircache_t; 233 234 typedef struct dcanchor { 235 void *dca_dircache; /* pointer to directory cache */ 236 kmutex_t dca_lock; /* protects the directory cache */ 237 } dcanchor_t; 238 239 /* 240 * Head struct for doubly linked chain of dircache_t 241 * The next and prev fields must match those of a dircache_t 242 */ 243 typedef struct { 244 dircache_t *dch_next; /* next in chain */ 245 dircache_t *dch_prev; /* prev in chain */ 246 kmutex_t dch_lock; /* lock for the chain */ 247 } dchead_t; 248 249 250 #if defined(_KERNEL) 251 252 /* 253 * Status returns from the directory cache interfaces 254 */ 255 typedef enum { 256 DOK, /* operation sucessful */ 257 DNOCACHE, /* there is no cache */ 258 DFOUND, /* entry found */ 259 DNOENT, /* no entry found */ 260 DTOOBIG, /* exceeds tunable dnlc_max_dir_cache */ 261 DNOMEM /* no memory */ 262 } dcret_t; 263 264 /* 265 * dnlc_dir_start() requests that a directory be cached. 266 * This must be called initially to enable caching on a directory. 267 * After a successful call, directory entries and free space can be 268 * added (see below) until the directory is marked complete. 269 * "num_entries" is an estimate of the current number of 270 * directory entries. The request is rejected with DNOCACHE 271 * if num_entries falls below the tunable dnlc_dir_min_size (see 272 * below), and rejected with DTOOBIG if it's above dnlc_dir_max_size. 273 * Returns DOK, DNOCACHE, DTOOBIG, DNOMEM. 274 * 275 * Due to memory shortages, directory caches can be purged at 276 * any time. If the last directory cache is purged due to memory 277 * shortage, then the directory cache is marked internally 278 * as "no memory". Future returns will all be DNOCACHE until 279 * the next dnlc_start_dir() which will return DNOMEM once. 280 * This memory shortage may only be transient. It's up to the 281 * file system as to what to do about this condition, but an 282 * attempt to immediately re-build the cache will very likely 283 * lead to the same shortage of memory and a thrashing situation. 284 * 285 * It's file system policy as to when and what size directories to cache. 286 */ 287 dcret_t dnlc_dir_start(dcanchor_t *dcap, uint_t num_entries); 288 289 /* 290 * dnlc_dir_add_entry() adds an entry (name and handle) into a 291 * partial or complete cache. "handle" is a file system specific 292 * quantity that is returned on calls to dnlc_dir_lookup() - see below. 293 * For example, "handle" for ufs holds the inumber and a directory 294 * entry offset. Returns DOK, DNOCACHE, DTOOBIG. 295 */ 296 dcret_t dnlc_dir_add_entry(dcanchor_t *dcap, const char *name, uint64_t handle); 297 298 /* 299 * dnlc_dir_add_space adds free space (length and file system specific 300 * handle) into a partial or complete cache. "handle" is a file 301 * system specific quantity that is returned on calls to 302 * dnlc_dir_rem_space_by_len(). For example, "handle" for ufs holds 303 * the directory entry offset. Returns DOK, DNOCACHE, DTOOBIG. 304 */ 305 dcret_t dnlc_dir_add_space(dcanchor_t *dcap, uint_t len, uint64_t handle); 306 307 /* 308 * dnlc_dir_complete() indicates the previously partial cache is now complete. 309 */ 310 void dnlc_dir_complete(dcanchor_t *dcap); 311 312 /* 313 * dnlc_dir_purge() deletes a partial or complete directory cache 314 */ 315 void dnlc_dir_purge(dcanchor_t *dcap); 316 317 /* 318 * dnlc_dir_lookup() lookups a file name in a directory cache 319 * and returns the file system handle specified on dnlc_dir_add_entry() 320 * in "handlep". Returns DFOUND, DNOENT, DNOCACHE. 321 */ 322 dcret_t dnlc_dir_lookup(dcanchor_t *dcap, const char *name, uint64_t *handlep); 323 324 /* 325 * dnlc_dir_update() amends the handle for an entry in a directory cache 326 * "handle" is the new file system specific handle for the file "name". 327 * Returns DFOUND, DNOENT, DNOCACHE. 328 */ 329 dcret_t dnlc_dir_update(dcanchor_t *dcap, const char *name, uint64_t handle); 330 331 /* 332 * dnlc_dir_rem_entry() removes an entry form a directory cache. 333 * Returns the handle if "handlep" non null. 334 * Returns DFOUND, DNOENT, DNOCACHE. 335 */ 336 dcret_t dnlc_dir_rem_entry(dcanchor_t *dcap, const char *name, 337 uint64_t *handlep); 338 339 /* 340 * dnlc_dir_rem_space_by_len() looks up and returns free space in a 341 * directory cache of at least the given "len". Returns in "handlep" 342 * the handle supplied when adding the free space in dnlc_dir_add_space(). 343 * Returns DFOUND, DNOENT, DNOCACHE. 344 */ 345 dcret_t dnlc_dir_rem_space_by_len(dcanchor_t *dcap, uint_t len, 346 uint64_t *handlep); 347 348 /* 349 * dnlc_dir_rem_space_by_handle() looks up and removes the free space in 350 * a directory cache with the given handle. Returns DFOUND, DNOENT, DNOCACHE. 351 */ 352 dcret_t dnlc_dir_rem_space_by_handle(dcanchor_t *dcap, uint64_t handle); 353 354 /* 355 * dnlc_dir_init() initialises a directory anchor 356 */ 357 #define dnlc_dir_init(dcap) { \ 358 (dcap)->dca_dircache = NULL; \ 359 mutex_init(&(dcap)->dca_lock, NULL, MUTEX_DEFAULT, NULL); } 360 361 /* 362 * dnlc_dir_fini() is called to indicate the anchor is no longer used. 363 * It ensures there's no directory cache and mutex_destroys the lock 364 */ 365 void dnlc_dir_fini(dcanchor_t *dcap); 366 367 #endif /* defined(_KERNEL) */ 368 369 #ifdef __cplusplus 370 } 371 #endif 372 373 #endif /* _SYS_DNLC_H */ 374