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6f7b6c68 KM |
1 | /* |
2 | * Copyright (c) 1989 The Regents of the University of California. | |
3 | * All rights reserved. | |
4 | * | |
dbf0c423 | 5 | * %sccs.include.redist.c% |
6f7b6c68 | 6 | * |
dbf0c423 | 7 | * @(#)vfs_cache.c 7.6 (Berkeley) %G% |
6f7b6c68 KM |
8 | */ |
9 | ||
10 | #include "param.h" | |
11 | #include "systm.h" | |
12 | #include "time.h" | |
13 | #include "vnode.h" | |
6f7b6c68 | 14 | #include "namei.h" |
ea5eb849 | 15 | #include "errno.h" |
1dfa72b1 | 16 | #include "malloc.h" |
6f7b6c68 KM |
17 | |
18 | /* | |
19 | * Name caching works as follows: | |
20 | * | |
21 | * Names found by directory scans are retained in a cache | |
22 | * for future reference. It is managed LRU, so frequently | |
23 | * used names will hang around. Cache is indexed by hash value | |
ea5eb849 KM |
24 | * obtained from (vp, name) where vp refers to the directory |
25 | * containing name. | |
6f7b6c68 KM |
26 | * |
27 | * For simplicity (and economy of storage), names longer than | |
28 | * a maximum length of NCHNAMLEN are not cached; they occur | |
29 | * infrequently in any case, and are almost never of interest. | |
30 | * | |
31 | * Upon reaching the last segment of a path, if the reference | |
32 | * is for DELETE, or NOCACHE is set (rewrite), and the | |
33 | * name is located in the cache, it will be dropped. | |
34 | */ | |
35 | ||
36 | /* | |
37 | * Structures associated with name cacheing. | |
38 | */ | |
6f7b6c68 KM |
39 | union nchash { |
40 | union nchash *nch_head[2]; | |
41 | struct namecache *nch_chain[2]; | |
1dfa72b1 | 42 | } *nchashtbl; |
6f7b6c68 KM |
43 | #define nch_forw nch_chain[0] |
44 | #define nch_back nch_chain[1] | |
45 | ||
1dfa72b1 KM |
46 | u_long nchash; /* size of hash table - 1 */ |
47 | long numcache; /* number of cache entries allocated */ | |
6f7b6c68 KM |
48 | struct namecache *nchhead, **nchtail; /* LRU chain pointers */ |
49 | struct nchstats nchstats; /* cache effectiveness statistics */ | |
50 | ||
ea5eb849 KM |
51 | int doingcache = 1; /* 1 => enable the cache */ |
52 | ||
6f7b6c68 KM |
53 | /* |
54 | * Look for a the name in the cache. We don't do this | |
55 | * if the segment name is long, simply so the cache can avoid | |
56 | * holding long names (which would either waste space, or | |
57 | * add greatly to the complexity). | |
ea5eb849 KM |
58 | * |
59 | * Lookup is called with ni_dvp pointing to the directory to search, | |
60 | * ni_ptr pointing to the name of the entry being sought, ni_namelen | |
61 | * tells the length of the name, and ni_hash contains a hash of | |
62 | * the name. If the lookup succeeds, the vnode is returned in ni_vp | |
63 | * and a status of -1 is returned. If the lookup determines that | |
64 | * the name does not exist (negative cacheing), a status of ENOENT | |
65 | * is returned. If the lookup fails, a status of zero is returned. | |
6f7b6c68 | 66 | */ |
6f7b6c68 KM |
67 | cache_lookup(ndp) |
68 | register struct nameidata *ndp; | |
69 | { | |
ea5eb849 | 70 | register struct vnode *dvp; |
6f7b6c68 KM |
71 | register struct namecache *ncp; |
72 | union nchash *nhp; | |
73 | ||
ea5eb849 KM |
74 | if (!doingcache) |
75 | return (0); | |
76 | if (ndp->ni_namelen > NCHNAMLEN) { | |
6f7b6c68 KM |
77 | nchstats.ncs_long++; |
78 | ndp->ni_makeentry = 0; | |
79 | return (0); | |
80 | } | |
ea5eb849 | 81 | dvp = ndp->ni_dvp; |
1dfa72b1 | 82 | nhp = &nchashtbl[ndp->ni_hash & nchash]; |
6f7b6c68 KM |
83 | for (ncp = nhp->nch_forw; ncp != (struct namecache *)nhp; |
84 | ncp = ncp->nc_forw) { | |
ea5eb849 KM |
85 | if (ncp->nc_dvp == dvp && |
86 | ncp->nc_dvpid == dvp->v_id && | |
87 | ncp->nc_nlen == ndp->ni_namelen && | |
88 | !bcmp(ncp->nc_name, ndp->ni_ptr, (unsigned)ncp->nc_nlen)) | |
6f7b6c68 KM |
89 | break; |
90 | } | |
91 | if (ncp == (struct namecache *)nhp) { | |
92 | nchstats.ncs_miss++; | |
6f7b6c68 KM |
93 | return (0); |
94 | } | |
ea5eb849 KM |
95 | if (!ndp->ni_makeentry) { |
96 | nchstats.ncs_badhits++; | |
97 | } else if (ncp->nc_vp == NULL) { | |
98 | nchstats.ncs_neghits++; | |
6f7b6c68 | 99 | /* |
ea5eb849 | 100 | * move this slot to end of LRU chain, if not already there |
6f7b6c68 KM |
101 | */ |
102 | if (ncp->nc_nxt) { | |
103 | /* remove from LRU chain */ | |
104 | *ncp->nc_prev = ncp->nc_nxt; | |
105 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
6f7b6c68 KM |
106 | /* and replace at end of it */ |
107 | ncp->nc_nxt = NULL; | |
108 | ncp->nc_prev = nchtail; | |
109 | *nchtail = ncp; | |
110 | nchtail = &ncp->nc_nxt; | |
111 | } | |
ea5eb849 KM |
112 | return (ENOENT); |
113 | } else if (ncp->nc_vpid != ncp->nc_vp->v_id) { | |
114 | nchstats.ncs_falsehits++; | |
115 | } else { | |
6f7b6c68 | 116 | nchstats.ncs_goodhits++; |
ea5eb849 KM |
117 | /* |
118 | * move this slot to end of LRU chain, if not already there | |
119 | */ | |
120 | if (ncp->nc_nxt) { | |
121 | /* remove from LRU chain */ | |
122 | *ncp->nc_prev = ncp->nc_nxt; | |
123 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
124 | /* and replace at end of it */ | |
125 | ncp->nc_nxt = NULL; | |
126 | ncp->nc_prev = nchtail; | |
127 | *nchtail = ncp; | |
128 | nchtail = &ncp->nc_nxt; | |
129 | } | |
130 | ndp->ni_vp = ncp->nc_vp; | |
131 | return (-1); | |
6f7b6c68 KM |
132 | } |
133 | ||
134 | /* | |
135 | * Last component and we are renaming or deleting, | |
136 | * the cache entry is invalid, or otherwise don't | |
137 | * want cache entry to exist. | |
138 | */ | |
6f7b6c68 KM |
139 | /* remove from LRU chain */ |
140 | *ncp->nc_prev = ncp->nc_nxt; | |
141 | if (ncp->nc_nxt) | |
142 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
143 | else | |
144 | nchtail = ncp->nc_prev; | |
ea5eb849 KM |
145 | /* remove from hash chain */ |
146 | remque(ncp); | |
6f7b6c68 KM |
147 | /* insert at head of LRU list (first to grab) */ |
148 | ncp->nc_nxt = nchhead; | |
149 | ncp->nc_prev = &nchhead; | |
150 | nchhead->nc_prev = &ncp->nc_nxt; | |
151 | nchhead = ncp; | |
152 | /* and make a dummy hash chain */ | |
153 | ncp->nc_forw = ncp; | |
154 | ncp->nc_back = ncp; | |
6f7b6c68 KM |
155 | return (0); |
156 | } | |
157 | ||
158 | /* | |
159 | * Add an entry to the cache | |
160 | */ | |
161 | cache_enter(ndp) | |
162 | register struct nameidata *ndp; | |
163 | { | |
164 | register struct namecache *ncp; | |
165 | union nchash *nhp; | |
166 | ||
ea5eb849 KM |
167 | if (!doingcache) |
168 | return; | |
6f7b6c68 KM |
169 | /* |
170 | * Free the cache slot at head of lru chain. | |
171 | */ | |
1dfa72b1 KM |
172 | if (numcache < desiredvnodes) { |
173 | ncp = (struct namecache *) | |
174 | malloc(sizeof *ncp, M_CACHE, M_WAITOK); | |
175 | bzero((char *)ncp, sizeof *ncp); | |
176 | numcache++; | |
177 | } else if (ncp = nchhead) { | |
6f7b6c68 KM |
178 | /* remove from lru chain */ |
179 | *ncp->nc_prev = ncp->nc_nxt; | |
180 | if (ncp->nc_nxt) | |
181 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
182 | else | |
183 | nchtail = ncp->nc_prev; | |
ea5eb849 KM |
184 | /* remove from old hash chain */ |
185 | remque(ncp); | |
1dfa72b1 KM |
186 | } else |
187 | return; | |
188 | /* grab the vnode we just found */ | |
189 | ncp->nc_vp = ndp->ni_vp; | |
190 | if (ndp->ni_vp) | |
191 | ncp->nc_vpid = ndp->ni_vp->v_id; | |
192 | else | |
193 | ncp->nc_vpid = 0; | |
194 | /* fill in cache info */ | |
195 | ncp->nc_dvp = ndp->ni_dvp; | |
196 | ncp->nc_dvpid = ndp->ni_dvp->v_id; | |
197 | ncp->nc_nlen = ndp->ni_namelen; | |
198 | bcopy(ndp->ni_ptr, ncp->nc_name, (unsigned)ncp->nc_nlen); | |
199 | /* link at end of lru chain */ | |
200 | ncp->nc_nxt = NULL; | |
201 | ncp->nc_prev = nchtail; | |
202 | *nchtail = ncp; | |
203 | nchtail = &ncp->nc_nxt; | |
204 | /* and insert on hash chain */ | |
205 | nhp = &nchashtbl[ndp->ni_hash & nchash]; | |
206 | insque(ncp, nhp); | |
6f7b6c68 KM |
207 | } |
208 | ||
209 | /* | |
1dfa72b1 | 210 | * Name cache initialization, from vfs_init() when we are booting |
6f7b6c68 KM |
211 | */ |
212 | nchinit() | |
213 | { | |
214 | register union nchash *nchp; | |
1dfa72b1 | 215 | long nchashsize; |
6f7b6c68 KM |
216 | |
217 | nchhead = 0; | |
218 | nchtail = &nchhead; | |
1dfa72b1 KM |
219 | nchashsize = roundup((desiredvnodes + 1) * sizeof *nchp / 2, |
220 | NBPG * CLSIZE); | |
221 | nchashtbl = (union nchash *)malloc(nchashsize, M_CACHE, M_WAITOK); | |
222 | for (nchash = 1; nchash <= nchashsize / sizeof *nchp; nchash <<= 1) | |
223 | /* void */; | |
224 | nchash = (nchash >> 1) - 1; | |
225 | for (nchp = &nchashtbl[nchash]; nchp >= nchashtbl; nchp--) { | |
6f7b6c68 KM |
226 | nchp->nch_head[0] = nchp; |
227 | nchp->nch_head[1] = nchp; | |
228 | } | |
229 | } | |
230 | ||
231 | /* | |
232 | * Cache flush, a particular vnode; called when a vnode is renamed to | |
ea5eb849 | 233 | * hide entries that would now be invalid |
6f7b6c68 KM |
234 | */ |
235 | cache_purge(vp) | |
ea5eb849 | 236 | struct vnode *vp; |
6f7b6c68 | 237 | { |
1dfa72b1 | 238 | union nchash *nhp; |
ea5eb849 | 239 | struct namecache *ncp; |
6f7b6c68 | 240 | |
ea5eb849 KM |
241 | vp->v_id = ++nextvnodeid; |
242 | if (nextvnodeid != 0) | |
243 | return; | |
1dfa72b1 KM |
244 | for (nhp = &nchashtbl[nchash]; nhp >= nchashtbl; nhp--) { |
245 | for (ncp = nhp->nch_forw; ncp != (struct namecache *)nhp; | |
246 | ncp = ncp->nc_forw) { | |
247 | ncp->nc_vpid = 0; | |
248 | ncp->nc_dvpid = 0; | |
249 | } | |
6f7b6c68 | 250 | } |
ea5eb849 | 251 | vp->v_id = ++nextvnodeid; |
6f7b6c68 KM |
252 | } |
253 | ||
254 | /* | |
255 | * Cache flush, a whole filesystem; called when filesys is umounted to | |
256 | * remove entries that would now be invalid | |
257 | * | |
258 | * The line "nxtcp = nchhead" near the end is to avoid potential problems | |
259 | * if the cache lru chain is modified while we are dumping the | |
260 | * inode. This makes the algorithm O(n^2), but do you think I care? | |
261 | */ | |
262 | cache_purgevfs(mp) | |
263 | register struct mount *mp; | |
264 | { | |
265 | register struct namecache *ncp, *nxtcp; | |
266 | ||
267 | for (ncp = nchhead; ncp; ncp = nxtcp) { | |
268 | nxtcp = ncp->nc_nxt; | |
ea5eb849 | 269 | if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) |
6f7b6c68 KM |
270 | continue; |
271 | /* free the resources we had */ | |
272 | ncp->nc_vp = NULL; | |
ea5eb849 | 273 | ncp->nc_dvp = NULL; |
6f7b6c68 KM |
274 | remque(ncp); /* remove entry from its hash chain */ |
275 | ncp->nc_forw = ncp; /* and make a dummy one */ | |
276 | ncp->nc_back = ncp; | |
277 | /* delete this entry from LRU chain */ | |
278 | *ncp->nc_prev = nxtcp; | |
279 | if (nxtcp) | |
280 | nxtcp->nc_prev = ncp->nc_prev; | |
281 | else | |
282 | nchtail = ncp->nc_prev; | |
283 | /* cause rescan of list, it may have altered */ | |
284 | nxtcp = nchhead; | |
285 | /* put the now-free entry at head of LRU */ | |
286 | ncp->nc_nxt = nxtcp; | |
287 | ncp->nc_prev = &nchhead; | |
288 | nxtcp->nc_prev = &ncp->nc_nxt; | |
289 | nchhead = ncp; | |
290 | } | |
291 | } |