Commit | Line | Data |
---|---|---|
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 | * |
f7c1c550 | 7 | * @(#)vfs_cache.c 7.10 (Berkeley) %G% |
6f7b6c68 KM |
8 | */ |
9 | ||
10 | #include "param.h" | |
11 | #include "systm.h" | |
12 | #include "time.h" | |
aacc1bff | 13 | #include "mount.h" |
6f7b6c68 | 14 | #include "vnode.h" |
6f7b6c68 | 15 | #include "namei.h" |
ea5eb849 | 16 | #include "errno.h" |
1dfa72b1 | 17 | #include "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 | */ | |
6f7b6c68 KM |
40 | union nchash { |
41 | union nchash *nch_head[2]; | |
42 | struct namecache *nch_chain[2]; | |
1dfa72b1 | 43 | } *nchashtbl; |
6f7b6c68 KM |
44 | #define nch_forw nch_chain[0] |
45 | #define nch_back nch_chain[1] | |
46 | ||
1dfa72b1 KM |
47 | u_long nchash; /* size of hash table - 1 */ |
48 | long numcache; /* number of cache entries allocated */ | |
6f7b6c68 KM |
49 | struct namecache *nchhead, **nchtail; /* LRU chain pointers */ |
50 | struct nchstats nchstats; /* cache effectiveness statistics */ | |
51 | ||
ea5eb849 KM |
52 | int doingcache = 1; /* 1 => enable the cache */ |
53 | ||
6f7b6c68 KM |
54 | /* |
55 | * Look for a the name in the cache. We don't do this | |
56 | * if the segment name is long, simply so the cache can avoid | |
57 | * holding long names (which would either waste space, or | |
58 | * add greatly to the complexity). | |
ea5eb849 KM |
59 | * |
60 | * Lookup is called with ni_dvp pointing to the directory to search, | |
61 | * ni_ptr pointing to the name of the entry being sought, ni_namelen | |
62 | * tells the length of the name, and ni_hash contains a hash of | |
63 | * the name. If the lookup succeeds, the vnode is returned in ni_vp | |
64 | * and a status of -1 is returned. If the lookup determines that | |
65 | * the name does not exist (negative cacheing), a status of ENOENT | |
66 | * is returned. If the lookup fails, a status of zero is returned. | |
6f7b6c68 | 67 | */ |
cfef4373 | 68 | int |
f7c1c550 | 69 | cache_lookup(dvp, vpp, cnp) |
cfef4373 JH |
70 | struct vnode *dvp; |
71 | struct vnode **vpp; | |
72 | struct componentname *cnp; | |
6f7b6c68 | 73 | { |
6f7b6c68 KM |
74 | register struct namecache *ncp; |
75 | union nchash *nhp; | |
76 | ||
ea5eb849 KM |
77 | if (!doingcache) |
78 | return (0); | |
cfef4373 | 79 | if (cnp->cn_namelen > NCHNAMLEN) { |
6f7b6c68 | 80 | nchstats.ncs_long++; |
cfef4373 | 81 | cnp->cn_flags &= ~MAKEENTRY; |
6f7b6c68 KM |
82 | return (0); |
83 | } | |
cfef4373 | 84 | nhp = &nchashtbl[cnp->cn_hash & nchash]; |
6f7b6c68 KM |
85 | for (ncp = nhp->nch_forw; ncp != (struct namecache *)nhp; |
86 | ncp = ncp->nc_forw) { | |
ea5eb849 KM |
87 | if (ncp->nc_dvp == dvp && |
88 | ncp->nc_dvpid == dvp->v_id && | |
cfef4373 JH |
89 | ncp->nc_nlen == cnp->cn_namelen && |
90 | !bcmp(ncp->nc_name, cnp->cn_nameptr, (unsigned)ncp->nc_nlen)) | |
6f7b6c68 KM |
91 | break; |
92 | } | |
93 | if (ncp == (struct namecache *)nhp) { | |
94 | nchstats.ncs_miss++; | |
6f7b6c68 KM |
95 | return (0); |
96 | } | |
cfef4373 | 97 | if (!(cnp->cn_flags & MAKEENTRY)) { |
ea5eb849 KM |
98 | nchstats.ncs_badhits++; |
99 | } else if (ncp->nc_vp == NULL) { | |
f7c1c550 | 100 | if (cnp->cn_nameiop != CREATE) { |
e828c39a KM |
101 | nchstats.ncs_neghits++; |
102 | /* | |
103 | * Move this slot to end of LRU chain, | |
104 | * if not already there. | |
105 | */ | |
106 | if (ncp->nc_nxt) { | |
107 | /* remove from LRU chain */ | |
108 | *ncp->nc_prev = ncp->nc_nxt; | |
109 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
110 | /* and replace at end of it */ | |
111 | ncp->nc_nxt = NULL; | |
112 | ncp->nc_prev = nchtail; | |
113 | *nchtail = ncp; | |
114 | nchtail = &ncp->nc_nxt; | |
115 | } | |
116 | return (ENOENT); | |
6f7b6c68 | 117 | } |
ea5eb849 KM |
118 | } else if (ncp->nc_vpid != ncp->nc_vp->v_id) { |
119 | nchstats.ncs_falsehits++; | |
120 | } else { | |
6f7b6c68 | 121 | nchstats.ncs_goodhits++; |
ea5eb849 KM |
122 | /* |
123 | * move this slot to end of LRU chain, if not already there | |
124 | */ | |
125 | if (ncp->nc_nxt) { | |
126 | /* remove from LRU chain */ | |
127 | *ncp->nc_prev = ncp->nc_nxt; | |
128 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
129 | /* and replace at end of it */ | |
130 | ncp->nc_nxt = NULL; | |
131 | ncp->nc_prev = nchtail; | |
132 | *nchtail = ncp; | |
133 | nchtail = &ncp->nc_nxt; | |
134 | } | |
cfef4373 | 135 | *vpp = ncp->nc_vp; |
ea5eb849 | 136 | return (-1); |
6f7b6c68 KM |
137 | } |
138 | ||
139 | /* | |
140 | * Last component and we are renaming or deleting, | |
141 | * the cache entry is invalid, or otherwise don't | |
142 | * want cache entry to exist. | |
143 | */ | |
6f7b6c68 KM |
144 | /* remove from LRU chain */ |
145 | *ncp->nc_prev = ncp->nc_nxt; | |
146 | if (ncp->nc_nxt) | |
147 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
148 | else | |
149 | nchtail = ncp->nc_prev; | |
ea5eb849 KM |
150 | /* remove from hash chain */ |
151 | remque(ncp); | |
6f7b6c68 KM |
152 | /* insert at head of LRU list (first to grab) */ |
153 | ncp->nc_nxt = nchhead; | |
154 | ncp->nc_prev = &nchhead; | |
155 | nchhead->nc_prev = &ncp->nc_nxt; | |
156 | nchhead = ncp; | |
157 | /* and make a dummy hash chain */ | |
158 | ncp->nc_forw = ncp; | |
159 | ncp->nc_back = ncp; | |
6f7b6c68 KM |
160 | return (0); |
161 | } | |
162 | ||
163 | /* | |
164 | * Add an entry to the cache | |
165 | */ | |
f7c1c550 | 166 | cache_enter(dvp, vp, cnp) |
cfef4373 JH |
167 | struct vnode *dvp; |
168 | struct vnode *vp; | |
169 | struct componentname *cnp; | |
6f7b6c68 KM |
170 | { |
171 | register struct namecache *ncp; | |
172 | union nchash *nhp; | |
173 | ||
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 KM |
185 | /* remove from lru chain */ |
186 | *ncp->nc_prev = ncp->nc_nxt; | |
187 | if (ncp->nc_nxt) | |
188 | ncp->nc_nxt->nc_prev = ncp->nc_prev; | |
189 | else | |
190 | nchtail = ncp->nc_prev; | |
ea5eb849 KM |
191 | /* remove from old hash chain */ |
192 | remque(ncp); | |
1dfa72b1 KM |
193 | } else |
194 | return; | |
195 | /* grab the vnode we just found */ | |
cfef4373 JH |
196 | ncp->nc_vp = vp; |
197 | if (vp) | |
198 | ncp->nc_vpid = vp->v_id; | |
1dfa72b1 KM |
199 | else |
200 | ncp->nc_vpid = 0; | |
201 | /* fill in cache info */ | |
cfef4373 JH |
202 | ncp->nc_dvp = dvp; |
203 | ncp->nc_dvpid = dvp->v_id; | |
204 | ncp->nc_nlen = cnp->cn_namelen; | |
205 | bcopy(cnp->cn_nameptr, ncp->nc_name, (unsigned)ncp->nc_nlen); | |
1dfa72b1 KM |
206 | /* link at end of lru chain */ |
207 | ncp->nc_nxt = NULL; | |
208 | ncp->nc_prev = nchtail; | |
209 | *nchtail = ncp; | |
210 | nchtail = &ncp->nc_nxt; | |
211 | /* and insert on hash chain */ | |
cfef4373 | 212 | nhp = &nchashtbl[cnp->cn_hash & nchash]; |
1dfa72b1 | 213 | insque(ncp, nhp); |
6f7b6c68 KM |
214 | } |
215 | ||
216 | /* | |
1dfa72b1 | 217 | * Name cache initialization, from vfs_init() when we are booting |
6f7b6c68 KM |
218 | */ |
219 | nchinit() | |
220 | { | |
221 | register union nchash *nchp; | |
1dfa72b1 | 222 | long nchashsize; |
6f7b6c68 KM |
223 | |
224 | nchhead = 0; | |
225 | nchtail = &nchhead; | |
1dfa72b1 KM |
226 | nchashsize = roundup((desiredvnodes + 1) * sizeof *nchp / 2, |
227 | NBPG * CLSIZE); | |
aacc1bff KM |
228 | nchashtbl = (union nchash *)malloc((u_long)nchashsize, |
229 | M_CACHE, M_WAITOK); | |
1dfa72b1 KM |
230 | for (nchash = 1; nchash <= nchashsize / sizeof *nchp; nchash <<= 1) |
231 | /* void */; | |
232 | nchash = (nchash >> 1) - 1; | |
233 | for (nchp = &nchashtbl[nchash]; nchp >= nchashtbl; nchp--) { | |
6f7b6c68 KM |
234 | nchp->nch_head[0] = nchp; |
235 | nchp->nch_head[1] = nchp; | |
236 | } | |
237 | } | |
238 | ||
239 | /* | |
240 | * Cache flush, a particular vnode; called when a vnode is renamed to | |
ea5eb849 | 241 | * hide entries that would now be invalid |
6f7b6c68 KM |
242 | */ |
243 | cache_purge(vp) | |
ea5eb849 | 244 | struct vnode *vp; |
6f7b6c68 | 245 | { |
1dfa72b1 | 246 | union nchash *nhp; |
ea5eb849 | 247 | struct namecache *ncp; |
6f7b6c68 | 248 | |
ea5eb849 KM |
249 | vp->v_id = ++nextvnodeid; |
250 | if (nextvnodeid != 0) | |
251 | return; | |
1dfa72b1 KM |
252 | for (nhp = &nchashtbl[nchash]; nhp >= nchashtbl; nhp--) { |
253 | for (ncp = nhp->nch_forw; ncp != (struct namecache *)nhp; | |
254 | ncp = ncp->nc_forw) { | |
255 | ncp->nc_vpid = 0; | |
256 | ncp->nc_dvpid = 0; | |
257 | } | |
6f7b6c68 | 258 | } |
ea5eb849 | 259 | vp->v_id = ++nextvnodeid; |
6f7b6c68 KM |
260 | } |
261 | ||
262 | /* | |
263 | * Cache flush, a whole filesystem; called when filesys is umounted to | |
264 | * remove entries that would now be invalid | |
265 | * | |
266 | * The line "nxtcp = nchhead" near the end is to avoid potential problems | |
267 | * if the cache lru chain is modified while we are dumping the | |
268 | * inode. This makes the algorithm O(n^2), but do you think I care? | |
269 | */ | |
270 | cache_purgevfs(mp) | |
aacc1bff | 271 | struct mount *mp; |
6f7b6c68 KM |
272 | { |
273 | register struct namecache *ncp, *nxtcp; | |
274 | ||
275 | for (ncp = nchhead; ncp; ncp = nxtcp) { | |
276 | nxtcp = ncp->nc_nxt; | |
ea5eb849 | 277 | if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) |
6f7b6c68 KM |
278 | continue; |
279 | /* free the resources we had */ | |
280 | ncp->nc_vp = NULL; | |
ea5eb849 | 281 | ncp->nc_dvp = NULL; |
6f7b6c68 KM |
282 | remque(ncp); /* remove entry from its hash chain */ |
283 | ncp->nc_forw = ncp; /* and make a dummy one */ | |
284 | ncp->nc_back = ncp; | |
285 | /* delete this entry from LRU chain */ | |
286 | *ncp->nc_prev = nxtcp; | |
287 | if (nxtcp) | |
288 | nxtcp->nc_prev = ncp->nc_prev; | |
289 | else | |
290 | nchtail = ncp->nc_prev; | |
291 | /* cause rescan of list, it may have altered */ | |
292 | nxtcp = nchhead; | |
293 | /* put the now-free entry at head of LRU */ | |
294 | ncp->nc_nxt = nxtcp; | |
295 | ncp->nc_prev = &nchhead; | |
296 | nxtcp->nc_prev = &ncp->nc_nxt; | |
297 | nchhead = ncp; | |
298 | } | |
299 | } |