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6f7b6c68 | 1 | /* |
ec54f0cc KB |
2 | * Copyright (c) 1989, 1993 |
3 | * The Regents of the University of California. All rights reserved. | |
6f7b6c68 | 4 | * |
dbf0c423 | 5 | * %sccs.include.redist.c% |
6f7b6c68 | 6 | * |
ec54f0cc | 7 | * @(#)vfs_cache.c 8.1 (Berkeley) %G% |
6f7b6c68 KM |
8 | */ |
9 | ||
38a01dbe KB |
10 | #include <sys/param.h> |
11 | #include <sys/systm.h> | |
12 | #include <sys/time.h> | |
13 | #include <sys/mount.h> | |
14 | #include <sys/vnode.h> | |
15 | #include <sys/namei.h> | |
16 | #include <sys/errno.h> | |
17 | #include <sys/malloc.h> | |
6f7b6c68 KM |
18 | |
19 | /* | |
20 | * Name caching works as follows: | |
21 | * | |
22 | * Names found by directory scans are retained in a cache | |
23 | * for future reference. It is managed LRU, so frequently | |
24 | * used names will hang around. Cache is indexed by hash value | |
ea5eb849 KM |
25 | * obtained from (vp, name) where vp refers to the directory |
26 | * containing name. | |
6f7b6c68 KM |
27 | * |
28 | * For simplicity (and economy of storage), names longer than | |
29 | * a maximum length of NCHNAMLEN are not cached; they occur | |
30 | * infrequently in any case, and are almost never of interest. | |
31 | * | |
32 | * Upon reaching the last segment of a path, if the reference | |
33 | * is for DELETE, or NOCACHE is set (rewrite), and the | |
34 | * name is located in the cache, it will be dropped. | |
35 | */ | |
36 | ||
37 | /* | |
38 | * Structures associated with name cacheing. | |
39 | */ | |
12e9ded3 | 40 | struct namecache **nchashtbl; |
1dfa72b1 KM |
41 | u_long nchash; /* size of hash table - 1 */ |
42 | long numcache; /* number of cache entries allocated */ | |
6f7b6c68 KM |
43 | struct namecache *nchhead, **nchtail; /* LRU chain pointers */ |
44 | struct nchstats nchstats; /* cache effectiveness statistics */ | |
45 | ||
ea5eb849 KM |
46 | int doingcache = 1; /* 1 => enable the cache */ |
47 | ||
6f7b6c68 KM |
48 | /* |
49 | * Look for a the name in the cache. We don't do this | |
50 | * if the segment name is long, simply so the cache can avoid | |
51 | * holding long names (which would either waste space, or | |
52 | * add greatly to the complexity). | |
ea5eb849 KM |
53 | * |
54 | * Lookup is called with ni_dvp pointing to the directory to search, | |
55 | * ni_ptr pointing to the name of the entry being sought, ni_namelen | |
56 | * tells the length of the name, and ni_hash contains a hash of | |
57 | * the name. If the lookup succeeds, the vnode is returned in ni_vp | |
58 | * and a status of -1 is returned. If the lookup determines that | |
59 | * the name does not exist (negative cacheing), a status of ENOENT | |
60 | * is returned. If the lookup fails, a status of zero is returned. | |
6f7b6c68 | 61 | */ |
cfef4373 | 62 | int |
f7c1c550 | 63 | cache_lookup(dvp, vpp, cnp) |
cfef4373 JH |
64 | struct vnode *dvp; |
65 | struct vnode **vpp; | |
66 | struct componentname *cnp; | |
6f7b6c68 | 67 | { |
12e9ded3 | 68 | register struct namecache *ncp, *ncq, **ncpp; |
6f7b6c68 | 69 | |
ea5eb849 KM |
70 | if (!doingcache) |
71 | return (0); | |
cfef4373 | 72 | if (cnp->cn_namelen > NCHNAMLEN) { |
6f7b6c68 | 73 | nchstats.ncs_long++; |
cfef4373 | 74 | cnp->cn_flags &= ~MAKEENTRY; |
6f7b6c68 KM |
75 | return (0); |
76 | } | |
12e9ded3 KM |
77 | ncpp = &nchashtbl[cnp->cn_hash & nchash]; |
78 | for (ncp = *ncpp; ncp; ncp = ncp->nc_forw) { | |
ea5eb849 KM |
79 | if (ncp->nc_dvp == dvp && |
80 | ncp->nc_dvpid == dvp->v_id && | |
cfef4373 | 81 | ncp->nc_nlen == cnp->cn_namelen && |
12e9ded3 | 82 | !bcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen)) |
6f7b6c68 KM |
83 | break; |
84 | } | |
12e9ded3 | 85 | if (ncp == NULL) { |
6f7b6c68 | 86 | nchstats.ncs_miss++; |
6f7b6c68 KM |
87 | return (0); |
88 | } | |
cfef4373 | 89 | if (!(cnp->cn_flags & MAKEENTRY)) { |
ea5eb849 KM |
90 | nchstats.ncs_badhits++; |
91 | } else if (ncp->nc_vp == NULL) { | |
f7c1c550 | 92 | if (cnp->cn_nameiop != CREATE) { |
e828c39a KM |
93 | nchstats.ncs_neghits++; |
94 | /* | |
95 | * Move this slot to end of LRU chain, | |
96 | * if not already there. | |
97 | */ | |
98 | if (ncp->nc_nxt) { | |
99 | /* remove from LRU chain */ | |
100 | *ncp->nc_prev = ncp->nc_nxt; | |
101 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
102 | /* and replace at end of it */ | |
103 | ncp->nc_nxt = NULL; | |
104 | ncp->nc_prev = nchtail; | |
105 | *nchtail = ncp; | |
106 | nchtail = &ncp->nc_nxt; | |
107 | } | |
108 | return (ENOENT); | |
6f7b6c68 | 109 | } |
ea5eb849 KM |
110 | } else if (ncp->nc_vpid != ncp->nc_vp->v_id) { |
111 | nchstats.ncs_falsehits++; | |
112 | } else { | |
6f7b6c68 | 113 | nchstats.ncs_goodhits++; |
ea5eb849 KM |
114 | /* |
115 | * move this slot to end of LRU chain, if not already there | |
116 | */ | |
117 | if (ncp->nc_nxt) { | |
118 | /* remove from LRU chain */ | |
119 | *ncp->nc_prev = ncp->nc_nxt; | |
120 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
121 | /* and replace at end of it */ | |
122 | ncp->nc_nxt = NULL; | |
123 | ncp->nc_prev = nchtail; | |
124 | *nchtail = ncp; | |
125 | nchtail = &ncp->nc_nxt; | |
126 | } | |
cfef4373 | 127 | *vpp = ncp->nc_vp; |
ea5eb849 | 128 | return (-1); |
6f7b6c68 KM |
129 | } |
130 | ||
131 | /* | |
132 | * Last component and we are renaming or deleting, | |
133 | * the cache entry is invalid, or otherwise don't | |
134 | * want cache entry to exist. | |
135 | */ | |
6f7b6c68 | 136 | /* remove from LRU chain */ |
12e9ded3 KM |
137 | if (ncq = ncp->nc_nxt) |
138 | ncq->nc_prev = ncp->nc_prev; | |
6f7b6c68 KM |
139 | else |
140 | nchtail = ncp->nc_prev; | |
12e9ded3 | 141 | *ncp->nc_prev = ncq; |
ea5eb849 | 142 | /* remove from hash chain */ |
12e9ded3 KM |
143 | if (ncq = ncp->nc_forw) |
144 | ncq->nc_back = ncp->nc_back; | |
145 | *ncp->nc_back = ncq; | |
146 | /* and make a dummy hash chain */ | |
147 | ncp->nc_forw = NULL; | |
148 | ncp->nc_back = NULL; | |
6f7b6c68 | 149 | /* insert at head of LRU list (first to grab) */ |
3d73154e KM |
150 | if (ncq = nchhead) |
151 | ncq->nc_prev = &ncp->nc_nxt; | |
152 | else | |
153 | nchtail = &ncp->nc_nxt; | |
6f7b6c68 | 154 | nchhead = ncp; |
3d73154e KM |
155 | ncp->nc_nxt = ncq; |
156 | ncp->nc_prev = &nchhead; | |
6f7b6c68 KM |
157 | return (0); |
158 | } | |
159 | ||
160 | /* | |
161 | * Add an entry to the cache | |
162 | */ | |
f7c1c550 | 163 | cache_enter(dvp, vp, cnp) |
cfef4373 JH |
164 | struct vnode *dvp; |
165 | struct vnode *vp; | |
166 | struct componentname *cnp; | |
6f7b6c68 | 167 | { |
12e9ded3 | 168 | register struct namecache *ncp, *ncq, **ncpp; |
6f7b6c68 | 169 | |
7f213083 KM |
170 | #ifdef DIAGNOSTIC |
171 | if (cnp->cn_namelen > NCHNAMLEN) | |
172 | panic("cache_enter: name too long"); | |
173 | #endif | |
ea5eb849 KM |
174 | if (!doingcache) |
175 | return; | |
6f7b6c68 KM |
176 | /* |
177 | * Free the cache slot at head of lru chain. | |
178 | */ | |
1dfa72b1 KM |
179 | if (numcache < desiredvnodes) { |
180 | ncp = (struct namecache *) | |
aacc1bff | 181 | malloc((u_long)sizeof *ncp, M_CACHE, M_WAITOK); |
1dfa72b1 KM |
182 | bzero((char *)ncp, sizeof *ncp); |
183 | numcache++; | |
184 | } else if (ncp = nchhead) { | |
6f7b6c68 | 185 | /* remove from lru chain */ |
12e9ded3 KM |
186 | if (ncq = ncp->nc_nxt) |
187 | ncq->nc_prev = ncp->nc_prev; | |
6f7b6c68 KM |
188 | else |
189 | nchtail = ncp->nc_prev; | |
12e9ded3 | 190 | *ncp->nc_prev = ncq; |
40d2c81e KM |
191 | /* remove from old hash chain, if on one */ |
192 | if (ncp->nc_back) { | |
193 | if (ncq = ncp->nc_forw) | |
194 | ncq->nc_back = ncp->nc_back; | |
195 | *ncp->nc_back = ncq; | |
196 | ncp->nc_forw = NULL; | |
197 | ncp->nc_back = NULL; | |
198 | } | |
1dfa72b1 KM |
199 | } else |
200 | return; | |
201 | /* grab the vnode we just found */ | |
cfef4373 JH |
202 | ncp->nc_vp = vp; |
203 | if (vp) | |
204 | ncp->nc_vpid = vp->v_id; | |
1dfa72b1 KM |
205 | else |
206 | ncp->nc_vpid = 0; | |
207 | /* fill in cache info */ | |
cfef4373 JH |
208 | ncp->nc_dvp = dvp; |
209 | ncp->nc_dvpid = dvp->v_id; | |
210 | ncp->nc_nlen = cnp->cn_namelen; | |
211 | bcopy(cnp->cn_nameptr, ncp->nc_name, (unsigned)ncp->nc_nlen); | |
1dfa72b1 KM |
212 | /* link at end of lru chain */ |
213 | ncp->nc_nxt = NULL; | |
214 | ncp->nc_prev = nchtail; | |
215 | *nchtail = ncp; | |
216 | nchtail = &ncp->nc_nxt; | |
217 | /* and insert on hash chain */ | |
12e9ded3 KM |
218 | ncpp = &nchashtbl[cnp->cn_hash & nchash]; |
219 | if (ncq = *ncpp) | |
220 | ncq->nc_back = &ncp->nc_forw; | |
221 | ncp->nc_forw = ncq; | |
222 | ncp->nc_back = ncpp; | |
223 | *ncpp = ncp; | |
6f7b6c68 KM |
224 | } |
225 | ||
226 | /* | |
1dfa72b1 | 227 | * Name cache initialization, from vfs_init() when we are booting |
6f7b6c68 KM |
228 | */ |
229 | nchinit() | |
230 | { | |
6f7b6c68 | 231 | |
6f7b6c68 | 232 | nchtail = &nchhead; |
12e9ded3 | 233 | nchashtbl = hashinit(desiredvnodes, M_CACHE, &nchash); |
6f7b6c68 KM |
234 | } |
235 | ||
236 | /* | |
237 | * Cache flush, a particular vnode; called when a vnode is renamed to | |
ea5eb849 | 238 | * hide entries that would now be invalid |
6f7b6c68 KM |
239 | */ |
240 | cache_purge(vp) | |
ea5eb849 | 241 | struct vnode *vp; |
6f7b6c68 | 242 | { |
12e9ded3 | 243 | struct namecache *ncp, **ncpp; |
6f7b6c68 | 244 | |
ea5eb849 KM |
245 | vp->v_id = ++nextvnodeid; |
246 | if (nextvnodeid != 0) | |
247 | return; | |
12e9ded3 KM |
248 | for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) { |
249 | for (ncp = *ncpp; ncp; ncp = ncp->nc_forw) { | |
1dfa72b1 KM |
250 | ncp->nc_vpid = 0; |
251 | ncp->nc_dvpid = 0; | |
252 | } | |
6f7b6c68 | 253 | } |
ea5eb849 | 254 | vp->v_id = ++nextvnodeid; |
6f7b6c68 KM |
255 | } |
256 | ||
257 | /* | |
258 | * Cache flush, a whole filesystem; called when filesys is umounted to | |
259 | * remove entries that would now be invalid | |
260 | * | |
261 | * The line "nxtcp = nchhead" near the end is to avoid potential problems | |
262 | * if the cache lru chain is modified while we are dumping the | |
263 | * inode. This makes the algorithm O(n^2), but do you think I care? | |
264 | */ | |
265 | cache_purgevfs(mp) | |
aacc1bff | 266 | struct mount *mp; |
6f7b6c68 KM |
267 | { |
268 | register struct namecache *ncp, *nxtcp; | |
269 | ||
270 | for (ncp = nchhead; ncp; ncp = nxtcp) { | |
12e9ded3 KM |
271 | if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) { |
272 | nxtcp = ncp->nc_nxt; | |
6f7b6c68 | 273 | continue; |
12e9ded3 | 274 | } |
6f7b6c68 KM |
275 | /* free the resources we had */ |
276 | ncp->nc_vp = NULL; | |
ea5eb849 | 277 | ncp->nc_dvp = NULL; |
40d2c81e KM |
278 | /* remove from old hash chain, if on one */ |
279 | if (ncp->nc_back) { | |
280 | if (nxtcp = ncp->nc_forw) | |
281 | nxtcp->nc_back = ncp->nc_back; | |
282 | *ncp->nc_back = nxtcp; | |
283 | ncp->nc_forw = NULL; | |
284 | ncp->nc_back = NULL; | |
285 | } | |
6f7b6c68 | 286 | /* delete this entry from LRU chain */ |
12e9ded3 | 287 | if (nxtcp = ncp->nc_nxt) |
6f7b6c68 KM |
288 | nxtcp->nc_prev = ncp->nc_prev; |
289 | else | |
290 | nchtail = ncp->nc_prev; | |
12e9ded3 | 291 | *ncp->nc_prev = nxtcp; |
6f7b6c68 | 292 | /* cause rescan of list, it may have altered */ |
3d73154e KM |
293 | /* also put the now-free entry at head of LRU */ |
294 | if (nxtcp = nchhead) | |
295 | nxtcp->nc_prev = &ncp->nc_nxt; | |
296 | else | |
297 | nchtail = &ncp->nc_nxt; | |
298 | nchhead = ncp; | |
6f7b6c68 KM |
299 | ncp->nc_nxt = nxtcp; |
300 | ncp->nc_prev = &nchhead; | |
6f7b6c68 KM |
301 | } |
302 | } |