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6f7b6c68 KM |
1 | /* |
2 | * Copyright (c) 1989 The Regents of the University of California. | |
3 | * All rights reserved. | |
4 | * | |
5 | * Redistribution and use in source and binary forms are permitted | |
6 | * provided that the above copyright notice and this paragraph are | |
7 | * duplicated in all such forms and that any documentation, | |
8 | * advertising materials, and other materials related to such | |
9 | * distribution and use acknowledge that the software was developed | |
10 | * by the University of California, Berkeley. The name of the | |
11 | * University may not be used to endorse or promote products derived | |
12 | * from this software without specific prior written permission. | |
13 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR | |
14 | * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED | |
15 | * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. | |
16 | * | |
1dfa72b1 | 17 | * @(#)vfs_cache.c 7.5 (Berkeley) %G% |
6f7b6c68 KM |
18 | */ |
19 | ||
20 | #include "param.h" | |
21 | #include "systm.h" | |
22 | #include "time.h" | |
23 | #include "vnode.h" | |
6f7b6c68 | 24 | #include "namei.h" |
ea5eb849 | 25 | #include "errno.h" |
1dfa72b1 | 26 | #include "malloc.h" |
6f7b6c68 KM |
27 | |
28 | /* | |
29 | * Name caching works as follows: | |
30 | * | |
31 | * Names found by directory scans are retained in a cache | |
32 | * for future reference. It is managed LRU, so frequently | |
33 | * used names will hang around. Cache is indexed by hash value | |
ea5eb849 KM |
34 | * obtained from (vp, name) where vp refers to the directory |
35 | * containing name. | |
6f7b6c68 KM |
36 | * |
37 | * For simplicity (and economy of storage), names longer than | |
38 | * a maximum length of NCHNAMLEN are not cached; they occur | |
39 | * infrequently in any case, and are almost never of interest. | |
40 | * | |
41 | * Upon reaching the last segment of a path, if the reference | |
42 | * is for DELETE, or NOCACHE is set (rewrite), and the | |
43 | * name is located in the cache, it will be dropped. | |
44 | */ | |
45 | ||
46 | /* | |
47 | * Structures associated with name cacheing. | |
48 | */ | |
6f7b6c68 KM |
49 | union nchash { |
50 | union nchash *nch_head[2]; | |
51 | struct namecache *nch_chain[2]; | |
1dfa72b1 | 52 | } *nchashtbl; |
6f7b6c68 KM |
53 | #define nch_forw nch_chain[0] |
54 | #define nch_back nch_chain[1] | |
55 | ||
1dfa72b1 KM |
56 | u_long nchash; /* size of hash table - 1 */ |
57 | long numcache; /* number of cache entries allocated */ | |
6f7b6c68 KM |
58 | struct namecache *nchhead, **nchtail; /* LRU chain pointers */ |
59 | struct nchstats nchstats; /* cache effectiveness statistics */ | |
60 | ||
ea5eb849 KM |
61 | int doingcache = 1; /* 1 => enable the cache */ |
62 | ||
6f7b6c68 KM |
63 | /* |
64 | * Look for a the name in the cache. We don't do this | |
65 | * if the segment name is long, simply so the cache can avoid | |
66 | * holding long names (which would either waste space, or | |
67 | * add greatly to the complexity). | |
ea5eb849 KM |
68 | * |
69 | * Lookup is called with ni_dvp pointing to the directory to search, | |
70 | * ni_ptr pointing to the name of the entry being sought, ni_namelen | |
71 | * tells the length of the name, and ni_hash contains a hash of | |
72 | * the name. If the lookup succeeds, the vnode is returned in ni_vp | |
73 | * and a status of -1 is returned. If the lookup determines that | |
74 | * the name does not exist (negative cacheing), a status of ENOENT | |
75 | * is returned. If the lookup fails, a status of zero is returned. | |
6f7b6c68 | 76 | */ |
6f7b6c68 KM |
77 | cache_lookup(ndp) |
78 | register struct nameidata *ndp; | |
79 | { | |
ea5eb849 | 80 | register struct vnode *dvp; |
6f7b6c68 KM |
81 | register struct namecache *ncp; |
82 | union nchash *nhp; | |
83 | ||
ea5eb849 KM |
84 | if (!doingcache) |
85 | return (0); | |
86 | if (ndp->ni_namelen > NCHNAMLEN) { | |
6f7b6c68 KM |
87 | nchstats.ncs_long++; |
88 | ndp->ni_makeentry = 0; | |
89 | return (0); | |
90 | } | |
ea5eb849 | 91 | dvp = ndp->ni_dvp; |
1dfa72b1 | 92 | nhp = &nchashtbl[ndp->ni_hash & nchash]; |
6f7b6c68 KM |
93 | for (ncp = nhp->nch_forw; ncp != (struct namecache *)nhp; |
94 | ncp = ncp->nc_forw) { | |
ea5eb849 KM |
95 | if (ncp->nc_dvp == dvp && |
96 | ncp->nc_dvpid == dvp->v_id && | |
97 | ncp->nc_nlen == ndp->ni_namelen && | |
98 | !bcmp(ncp->nc_name, ndp->ni_ptr, (unsigned)ncp->nc_nlen)) | |
6f7b6c68 KM |
99 | break; |
100 | } | |
101 | if (ncp == (struct namecache *)nhp) { | |
102 | nchstats.ncs_miss++; | |
6f7b6c68 KM |
103 | return (0); |
104 | } | |
ea5eb849 KM |
105 | if (!ndp->ni_makeentry) { |
106 | nchstats.ncs_badhits++; | |
107 | } else if (ncp->nc_vp == NULL) { | |
108 | nchstats.ncs_neghits++; | |
6f7b6c68 | 109 | /* |
ea5eb849 | 110 | * move this slot to end of LRU chain, if not already there |
6f7b6c68 KM |
111 | */ |
112 | if (ncp->nc_nxt) { | |
113 | /* remove from LRU chain */ | |
114 | *ncp->nc_prev = ncp->nc_nxt; | |
115 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
6f7b6c68 KM |
116 | /* and replace at end of it */ |
117 | ncp->nc_nxt = NULL; | |
118 | ncp->nc_prev = nchtail; | |
119 | *nchtail = ncp; | |
120 | nchtail = &ncp->nc_nxt; | |
121 | } | |
ea5eb849 KM |
122 | return (ENOENT); |
123 | } else if (ncp->nc_vpid != ncp->nc_vp->v_id) { | |
124 | nchstats.ncs_falsehits++; | |
125 | } else { | |
6f7b6c68 | 126 | nchstats.ncs_goodhits++; |
ea5eb849 KM |
127 | /* |
128 | * move this slot to end of LRU chain, if not already there | |
129 | */ | |
130 | if (ncp->nc_nxt) { | |
131 | /* remove from LRU chain */ | |
132 | *ncp->nc_prev = ncp->nc_nxt; | |
133 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
134 | /* and replace at end of it */ | |
135 | ncp->nc_nxt = NULL; | |
136 | ncp->nc_prev = nchtail; | |
137 | *nchtail = ncp; | |
138 | nchtail = &ncp->nc_nxt; | |
139 | } | |
140 | ndp->ni_vp = ncp->nc_vp; | |
141 | return (-1); | |
6f7b6c68 KM |
142 | } |
143 | ||
144 | /* | |
145 | * Last component and we are renaming or deleting, | |
146 | * the cache entry is invalid, or otherwise don't | |
147 | * want cache entry to exist. | |
148 | */ | |
6f7b6c68 KM |
149 | /* remove from LRU chain */ |
150 | *ncp->nc_prev = ncp->nc_nxt; | |
151 | if (ncp->nc_nxt) | |
152 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
153 | else | |
154 | nchtail = ncp->nc_prev; | |
ea5eb849 KM |
155 | /* remove from hash chain */ |
156 | remque(ncp); | |
6f7b6c68 KM |
157 | /* insert at head of LRU list (first to grab) */ |
158 | ncp->nc_nxt = nchhead; | |
159 | ncp->nc_prev = &nchhead; | |
160 | nchhead->nc_prev = &ncp->nc_nxt; | |
161 | nchhead = ncp; | |
162 | /* and make a dummy hash chain */ | |
163 | ncp->nc_forw = ncp; | |
164 | ncp->nc_back = ncp; | |
6f7b6c68 KM |
165 | return (0); |
166 | } | |
167 | ||
168 | /* | |
169 | * Add an entry to the cache | |
170 | */ | |
171 | cache_enter(ndp) | |
172 | register struct nameidata *ndp; | |
173 | { | |
174 | register struct namecache *ncp; | |
175 | union nchash *nhp; | |
176 | ||
ea5eb849 KM |
177 | if (!doingcache) |
178 | return; | |
6f7b6c68 KM |
179 | /* |
180 | * Free the cache slot at head of lru chain. | |
181 | */ | |
1dfa72b1 KM |
182 | if (numcache < desiredvnodes) { |
183 | ncp = (struct namecache *) | |
184 | malloc(sizeof *ncp, M_CACHE, M_WAITOK); | |
185 | bzero((char *)ncp, sizeof *ncp); | |
186 | numcache++; | |
187 | } else if (ncp = nchhead) { | |
6f7b6c68 KM |
188 | /* remove from lru chain */ |
189 | *ncp->nc_prev = ncp->nc_nxt; | |
190 | if (ncp->nc_nxt) | |
191 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
192 | else | |
193 | nchtail = ncp->nc_prev; | |
ea5eb849 KM |
194 | /* remove from old hash chain */ |
195 | remque(ncp); | |
1dfa72b1 KM |
196 | } else |
197 | return; | |
198 | /* grab the vnode we just found */ | |
199 | ncp->nc_vp = ndp->ni_vp; | |
200 | if (ndp->ni_vp) | |
201 | ncp->nc_vpid = ndp->ni_vp->v_id; | |
202 | else | |
203 | ncp->nc_vpid = 0; | |
204 | /* fill in cache info */ | |
205 | ncp->nc_dvp = ndp->ni_dvp; | |
206 | ncp->nc_dvpid = ndp->ni_dvp->v_id; | |
207 | ncp->nc_nlen = ndp->ni_namelen; | |
208 | bcopy(ndp->ni_ptr, ncp->nc_name, (unsigned)ncp->nc_nlen); | |
209 | /* link at end of lru chain */ | |
210 | ncp->nc_nxt = NULL; | |
211 | ncp->nc_prev = nchtail; | |
212 | *nchtail = ncp; | |
213 | nchtail = &ncp->nc_nxt; | |
214 | /* and insert on hash chain */ | |
215 | nhp = &nchashtbl[ndp->ni_hash & nchash]; | |
216 | insque(ncp, nhp); | |
6f7b6c68 KM |
217 | } |
218 | ||
219 | /* | |
1dfa72b1 | 220 | * Name cache initialization, from vfs_init() when we are booting |
6f7b6c68 KM |
221 | */ |
222 | nchinit() | |
223 | { | |
224 | register union nchash *nchp; | |
1dfa72b1 | 225 | long nchashsize; |
6f7b6c68 KM |
226 | |
227 | nchhead = 0; | |
228 | nchtail = &nchhead; | |
1dfa72b1 KM |
229 | nchashsize = roundup((desiredvnodes + 1) * sizeof *nchp / 2, |
230 | NBPG * CLSIZE); | |
231 | nchashtbl = (union nchash *)malloc(nchashsize, M_CACHE, M_WAITOK); | |
232 | for (nchash = 1; nchash <= nchashsize / sizeof *nchp; nchash <<= 1) | |
233 | /* void */; | |
234 | nchash = (nchash >> 1) - 1; | |
235 | for (nchp = &nchashtbl[nchash]; nchp >= nchashtbl; nchp--) { | |
6f7b6c68 KM |
236 | nchp->nch_head[0] = nchp; |
237 | nchp->nch_head[1] = nchp; | |
238 | } | |
239 | } | |
240 | ||
241 | /* | |
242 | * Cache flush, a particular vnode; called when a vnode is renamed to | |
ea5eb849 | 243 | * hide entries that would now be invalid |
6f7b6c68 KM |
244 | */ |
245 | cache_purge(vp) | |
ea5eb849 | 246 | struct vnode *vp; |
6f7b6c68 | 247 | { |
1dfa72b1 | 248 | union nchash *nhp; |
ea5eb849 | 249 | struct namecache *ncp; |
6f7b6c68 | 250 | |
ea5eb849 KM |
251 | vp->v_id = ++nextvnodeid; |
252 | if (nextvnodeid != 0) | |
253 | return; | |
1dfa72b1 KM |
254 | for (nhp = &nchashtbl[nchash]; nhp >= nchashtbl; nhp--) { |
255 | for (ncp = nhp->nch_forw; ncp != (struct namecache *)nhp; | |
256 | ncp = ncp->nc_forw) { | |
257 | ncp->nc_vpid = 0; | |
258 | ncp->nc_dvpid = 0; | |
259 | } | |
6f7b6c68 | 260 | } |
ea5eb849 | 261 | vp->v_id = ++nextvnodeid; |
6f7b6c68 KM |
262 | } |
263 | ||
264 | /* | |
265 | * Cache flush, a whole filesystem; called when filesys is umounted to | |
266 | * remove entries that would now be invalid | |
267 | * | |
268 | * The line "nxtcp = nchhead" near the end is to avoid potential problems | |
269 | * if the cache lru chain is modified while we are dumping the | |
270 | * inode. This makes the algorithm O(n^2), but do you think I care? | |
271 | */ | |
272 | cache_purgevfs(mp) | |
273 | register struct mount *mp; | |
274 | { | |
275 | register struct namecache *ncp, *nxtcp; | |
276 | ||
277 | for (ncp = nchhead; ncp; ncp = nxtcp) { | |
278 | nxtcp = ncp->nc_nxt; | |
ea5eb849 | 279 | if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) |
6f7b6c68 KM |
280 | continue; |
281 | /* free the resources we had */ | |
282 | ncp->nc_vp = NULL; | |
ea5eb849 | 283 | ncp->nc_dvp = NULL; |
6f7b6c68 KM |
284 | remque(ncp); /* remove entry from its hash chain */ |
285 | ncp->nc_forw = ncp; /* and make a dummy one */ | |
286 | ncp->nc_back = ncp; | |
287 | /* delete this entry from LRU chain */ | |
288 | *ncp->nc_prev = nxtcp; | |
289 | if (nxtcp) | |
290 | nxtcp->nc_prev = ncp->nc_prev; | |
291 | else | |
292 | nchtail = ncp->nc_prev; | |
293 | /* cause rescan of list, it may have altered */ | |
294 | nxtcp = nchhead; | |
295 | /* put the now-free entry at head of LRU */ | |
296 | ncp->nc_nxt = nxtcp; | |
297 | ncp->nc_prev = &nchhead; | |
298 | nxtcp->nc_prev = &ncp->nc_nxt; | |
299 | nchhead = ncp; | |
300 | } | |
301 | } |