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coda_namecache.c revision 1.29
      1 /*	$NetBSD: coda_namecache.c,v 1.29 2024/02/09 22:08:34 andvar Exp $	*/
      2 
      3 /*
      4  *
      5  *             Coda: an Experimental Distributed File System
      6  *                              Release 3.1
      7  *
      8  *           Copyright (c) 1987-1998 Carnegie Mellon University
      9  *                          All Rights Reserved
     10  *
     11  * Permission  to  use, copy, modify and distribute this software and its
     12  * documentation is hereby granted,  provided  that  both  the  copyright
     13  * notice  and  this  permission  notice  appear  in  all  copies  of the
     14  * software, derivative works or  modified  versions,  and  any  portions
     15  * thereof, and that both notices appear in supporting documentation, and
     16  * that credit is given to Carnegie Mellon University  in  all  documents
     17  * and publicity pertaining to direct or indirect use of this code or its
     18  * derivatives.
     19  *
     20  * CODA IS AN EXPERIMENTAL SOFTWARE SYSTEM AND IS  KNOWN  TO  HAVE  BUGS,
     21  * SOME  OF  WHICH MAY HAVE SERIOUS CONSEQUENCES.  CARNEGIE MELLON ALLOWS
     22  * FREE USE OF THIS SOFTWARE IN ITS "AS IS" CONDITION.   CARNEGIE  MELLON
     23  * DISCLAIMS  ANY  LIABILITY  OF  ANY  KIND  FOR  ANY  DAMAGES WHATSOEVER
     24  * RESULTING DIRECTLY OR INDIRECTLY FROM THE USE OF THIS SOFTWARE  OR  OF
     25  * ANY DERIVATIVE WORK.
     26  *
     27  * Carnegie  Mellon  encourages  users  of  this  software  to return any
     28  * improvements or extensions that  they  make,  and  to  grant  Carnegie
     29  * Mellon the rights to redistribute these changes without encumbrance.
     30  *
     31  * 	@(#) coda/coda_namecache.c,v 1.1.1.1 1998/08/29 21:26:45 rvb Exp $
     32  */
     33 
     34 /*
     35  * Mach Operating System
     36  * Copyright (c) 1990 Carnegie-Mellon University
     37  * Copyright (c) 1989 Carnegie-Mellon University
     38  * All rights reserved.  The CMU software License Agreement specifies
     39  * the terms and conditions for use and redistribution.
     40  */
     41 
     42 /*
     43  * This code was written for the Coda file system at Carnegie Mellon University.
     44  * Contributers include David Steere, James Kistler, and M. Satyanarayanan.
     45  */
     46 
     47 /*
     48  * This module contains the routines to implement the CODA name cache. The
     49  * purpose of this cache is to reduce the cost of translating pathnames
     50  * into Vice FIDs. Each entry in the cache contains the name of the file,
     51  * the vnode (FID) of the parent directory, and the cred structure of the
     52  * user accessing the file.
     53  *
     54  * The first time a file is accessed, it is looked up by the local Venus
     55  * which first insures that the user has access to the file. In addition
     56  * we are guaranteed that Venus will invalidate any name cache entries in
     57  * case the user no longer should be able to access the file. For these
     58  * reasons we do not need to keep access list information as well as a
     59  * cred structure for each entry.
     60  *
     61  * The table can be accessed through the routines cnc_init(), cnc_enter(),
     62  * cnc_lookup(), cnc_rmfidcred(), cnc_rmfid(), cnc_rmcred(), and cnc_purge().
     63  * There are several other routines which aid in the implementation of the
     64  * hash table.
     65  */
     66 
     67 /*
     68  * NOTES: rvb@cs
     69  * 1.	The name cache holds a reference to every vnode in it.  Hence files can not be
     70  *	 closed or made inactive until they are released.
     71  * 2.	coda_nc_name(cp) was added to get a name for a cnode pointer for debugging.
     72  * 3.	coda_nc_find() has debug code to detect when entries are stored with different
     73  *	 credentials.  We don't understand yet, if/how entries are NOT EQ but still
     74  *	 EQUAL
     75  * 4.	I wonder if this name cache could be replace by the vnode name cache.
     76  *	The latter has no zapping functions, so probably not.
     77  */
     78 
     79 #include <sys/cdefs.h>
     80 __KERNEL_RCSID(0, "$NetBSD: coda_namecache.c,v 1.29 2024/02/09 22:08:34 andvar Exp $");
     81 
     82 #include <sys/param.h>
     83 #include <sys/errno.h>
     84 #include <sys/malloc.h>
     85 #include <sys/select.h>
     86 #include <sys/kauth.h>
     87 
     88 #include <coda/coda.h>
     89 #include <coda/cnode.h>
     90 #include <coda/coda_namecache.h>
     91 #include <coda/coda_subr.h>
     92 
     93 /*
     94  * Declaration of the name cache data structure.
     95  */
     96 
     97 int 	coda_nc_use = 1;			 /* Indicate use of CODA Name Cache */
     98 
     99 int	coda_nc_size = CODA_NC_CACHESIZE;	 /* size of the cache */
    100 int	coda_nc_hashsize = CODA_NC_HASHSIZE; /* size of the primary hash */
    101 
    102 struct 	coda_cache *coda_nc_heap;	/* pointer to the cache entries */
    103 struct	coda_hash  *coda_nc_hash;	/* hash table of cfscache pointers */
    104 struct	coda_lru   coda_nc_lru;		/* head of lru chain */
    105 
    106 struct coda_nc_statistics coda_nc_stat;	/* Keep various stats */
    107 
    108 /*
    109  * for testing purposes
    110  */
    111 int coda_nc_debug = 0;
    112 
    113 /*
    114  * Entry points for the CODA Name Cache
    115  */
    116 static struct coda_cache *
    117 coda_nc_find(struct cnode *dcp, const char *name, int namelen,
    118 	kauth_cred_t cred, int hash);
    119 static void
    120 coda_nc_remove(struct coda_cache *cncp, enum dc_status dcstat);
    121 
    122 /*
    123  * Initialize the cache, the LRU structure and the Hash structure(s)
    124  */
    125 
    126 #define TOTAL_CACHE_SIZE 	(sizeof(struct coda_cache) * coda_nc_size)
    127 #define TOTAL_HASH_SIZE 	(sizeof(struct coda_hash)  * coda_nc_hashsize)
    128 
    129 int coda_nc_initialized = 0;      /* Initially the cache has not been initialized */
    130 
    131 void
    132 coda_nc_init(void)
    133 {
    134     int i;
    135 
    136     /* zero the statistics structure */
    137 
    138     memset(&coda_nc_stat, 0, (sizeof(struct coda_nc_statistics)));
    139 
    140 #ifdef	CODA_VERBOSE
    141     printf("CODA NAME CACHE: CACHE %d, HASH TBL %d\n", CODA_NC_CACHESIZE, CODA_NC_HASHSIZE);
    142 #endif
    143     CODA_ALLOC(coda_nc_heap, struct coda_cache *, TOTAL_CACHE_SIZE);
    144     CODA_ALLOC(coda_nc_hash, struct coda_hash *, TOTAL_HASH_SIZE);
    145 
    146     memset(coda_nc_heap, 0, TOTAL_CACHE_SIZE);
    147     memset(coda_nc_hash, 0, TOTAL_HASH_SIZE);
    148 
    149     TAILQ_INIT(&coda_nc_lru.head);
    150 
    151     for (i=0; i < coda_nc_size; i++) {	/* initialize the heap */
    152 	TAILQ_INSERT_HEAD(&coda_nc_lru.head, &coda_nc_heap[i], lru);
    153     }
    154 
    155     for (i=0; i < coda_nc_hashsize; i++) {	/* initialize the hashtable */
    156 	LIST_INIT(&coda_nc_hash[i].head);
    157     }
    158 
    159     coda_nc_initialized++;
    160 }
    161 
    162 /*
    163  * Auxiliary routines -- shouldn't be entry points
    164  */
    165 
    166 static struct coda_cache *
    167 coda_nc_find(struct cnode *dcp, const char *name, int namelen,
    168 	kauth_cred_t cred, int hash)
    169 {
    170 	/*
    171 	 * hash to find the appropriate bucket, look through the chain
    172 	 * for the right entry (especially right cred, unless cred == 0)
    173 	 */
    174 	struct coda_cache *cncp;
    175 	int count = 1;
    176 
    177 	CODA_NC_DEBUG(CODA_NC_FIND,
    178 		myprintf(("coda_nc_find(dcp %p, name %s, len %d, cred %p, hash %d\n",
    179 			dcp, name, namelen, cred, hash));)
    180 
    181 	LIST_FOREACH(cncp, &coda_nc_hash[hash].head, hash)
    182 	{
    183 
    184 	    if ((CODA_NAMEMATCH(cncp, name, namelen, dcp)) &&
    185 		((cred == 0) || (cncp->cred == cred)))
    186 	    {
    187 		/* compare cr_uid instead */
    188 		coda_nc_stat.Search_len += count;
    189 		return(cncp);
    190 	    }
    191 #ifdef	DEBUG
    192 	    else if (CODA_NAMEMATCH(cncp, name, namelen, dcp)) {
    193 	    	printf("coda_nc_find: name %s, new cred = %p, cred = %p\n",
    194 			name, cred, cncp->cred);
    195 		printf("nref %d, nuid %d, ngid %d // oref %d, ocred %d, ogid %d\n",
    196 			kauth_cred_getrefcnt(cred),
    197 			kauth_cred_geteuid(cred),
    198 			kauth_cred_getegid(cred),
    199 			kauth_cred_getrefcnt(cncp->cred),
    200 			kauth_cred_geteuid(cncp->cred),
    201 			kauth_cred_getegid(cncp->cred));
    202 		coda_print_cred(cred);
    203 		coda_print_cred(cncp->cred);
    204 	    }
    205 #endif
    206 	    count++;
    207 	}
    208 
    209 	return((struct coda_cache *)0);
    210 }
    211 
    212 /*
    213  * Enter a new (dir cnode, name) pair into the cache, updating the
    214  * LRU and Hash as needed.
    215  */
    216 void
    217 coda_nc_enter(struct cnode *dcp, const char *name, int namelen,
    218 	kauth_cred_t cred, struct cnode *cp)
    219 {
    220     struct coda_cache *cncp;
    221     int hash;
    222 
    223     if (coda_nc_use == 0)			/* Cache is off */
    224 	return;
    225 
    226     CODA_NC_DEBUG(CODA_NC_ENTER,
    227 		myprintf(("Enter: dcp %p cp %p name %s cred %p \n",
    228 		       dcp, cp, name, cred)); )
    229 
    230     if (namelen > CODA_NC_NAMELEN) {
    231 	CODA_NC_DEBUG(CODA_NC_ENTER,
    232 		    myprintf(("long name enter %s\n",name));)
    233 	    coda_nc_stat.long_name_enters++;	/* record stats */
    234 	return;
    235     }
    236 
    237     hash = CODA_NC_HASH(name, namelen, dcp);
    238     cncp = coda_nc_find(dcp, name, namelen, cred, hash);
    239     if (cncp != (struct coda_cache *) 0) {
    240 	coda_nc_stat.dbl_enters++;		/* duplicate entry */
    241 	return;
    242     }
    243 
    244     coda_nc_stat.enters++;		/* record the enters statistic */
    245 
    246     /* Grab the next element in the lru chain */
    247     cncp = TAILQ_FIRST(&coda_nc_lru.head);
    248     TAILQ_REMOVE(&coda_nc_lru.head, cncp, lru);
    249 
    250     if (CODA_NC_VALID(cncp)) {
    251 	/* Seems really ugly, but we have to decrement the appropriate
    252 	   hash bucket length here, so we have to find the hash bucket
    253 	   */
    254 	coda_nc_hash[CODA_NC_HASH(cncp->name, cncp->namelen, cncp->dcp)].length--;
    255 
    256 	coda_nc_stat.lru_rm++;	/* zapped a valid entry */
    257 	LIST_REMOVE(cncp, hash);
    258 	vrele(CTOV(cncp->dcp));
    259 	vrele(CTOV(cncp->cp));
    260 	kauth_cred_free(cncp->cred);
    261     }
    262 
    263     /*
    264      * Put a hold on the current vnodes and fill in the cache entry.
    265      */
    266     vref(CTOV(cp));
    267     vref(CTOV(dcp));
    268     kauth_cred_hold(cred);
    269     cncp->dcp = dcp;
    270     cncp->cp = cp;
    271     cncp->namelen = namelen;
    272     cncp->cred = cred;
    273 
    274     memcpy(cncp->name, name, (unsigned)namelen);
    275 
    276     /* Insert into the lru and hash chains. */
    277     TAILQ_INSERT_TAIL(&coda_nc_lru.head, cncp, lru);
    278     LIST_INSERT_HEAD(&coda_nc_hash[hash].head, cncp, hash);
    279     coda_nc_hash[hash].length++;                      /* Used for tuning */
    280 
    281     CODA_NC_DEBUG(CODA_NC_PRINTCODA_NC, print_coda_nc(); )
    282 }
    283 
    284 /*
    285  * Find the (dir cnode, name) pair in the cache, if its cred
    286  * matches the input, return it, otherwise return 0
    287  */
    288 struct cnode *
    289 coda_nc_lookup(struct cnode *dcp, const char *name, int namelen,
    290 	kauth_cred_t cred)
    291 {
    292 	int hash;
    293 	struct coda_cache *cncp;
    294 
    295 	if (coda_nc_use == 0)			/* Cache is off */
    296 		return((struct cnode *) 0);
    297 
    298 	if (namelen > CODA_NC_NAMELEN) {
    299 	        CODA_NC_DEBUG(CODA_NC_LOOKUP,
    300 			    myprintf(("long name lookup %s\n",name));)
    301 		coda_nc_stat.long_name_lookups++;		/* record stats */
    302 		return((struct cnode *) 0);
    303 	}
    304 
    305 	/* Use the hash function to locate the starting point,
    306 	   then the search routine to go down the list looking for
    307 	   the correct cred.
    308  	 */
    309 
    310 	hash = CODA_NC_HASH(name, namelen, dcp);
    311 	cncp = coda_nc_find(dcp, name, namelen, cred, hash);
    312 	if (cncp == (struct coda_cache *) 0) {
    313 		coda_nc_stat.misses++;			/* record miss */
    314 		return((struct cnode *) 0);
    315 	}
    316 
    317 	coda_nc_stat.hits++;
    318 
    319 	/* put this entry at the end of the LRU */
    320 	TAILQ_REMOVE(&coda_nc_lru.head, cncp, lru);
    321 	TAILQ_INSERT_TAIL(&coda_nc_lru.head, cncp, lru);
    322 
    323 	/* move it to the front of the hash chain */
    324 	/* don't need to change the hash bucket length */
    325 	LIST_REMOVE(cncp, hash);
    326 	LIST_INSERT_HEAD(&coda_nc_hash[hash].head, cncp, hash);
    327 
    328 	CODA_NC_DEBUG(CODA_NC_LOOKUP,
    329 		printf("lookup: dcp %p, name %s, cred %p = cp %p\n",
    330 			dcp, name, cred, cncp->cp); )
    331 
    332 	return(cncp->cp);
    333 }
    334 
    335 static void
    336 coda_nc_remove(struct coda_cache *cncp, enum dc_status dcstat)
    337 {
    338 	/*
    339 	 * remove an entry -- vrele(cncp->dcp, cp), crfree(cred),
    340 	 * remove it from its hash chain, and
    341 	 * place it at the head of the lru list.
    342 	 */
    343         CODA_NC_DEBUG(CODA_NC_REMOVE,
    344 		    myprintf(("coda_nc_remove %s from parent %s\n",
    345 			      cncp->name, coda_f2s(&cncp->dcp->c_fid))); )
    346 
    347 
    348 	LIST_REMOVE(cncp, hash);
    349 	memset(&cncp->hash, 0, sizeof(cncp->hash));
    350 
    351 	if ((dcstat == IS_DOWNCALL) && (vrefcnt(CTOV(cncp->dcp)) == 1)) {
    352 		cncp->dcp->c_flags |= C_PURGING;
    353 	}
    354 	vrele(CTOV(cncp->dcp));
    355 
    356 	if ((dcstat == IS_DOWNCALL) && (vrefcnt(CTOV(cncp->cp)) == 1)) {
    357 		cncp->cp->c_flags |= C_PURGING;
    358 	}
    359 	vrele(CTOV(cncp->cp));
    360 
    361 	kauth_cred_free(cncp->cred);
    362 	memset(DATA_PART(cncp), 0, DATA_SIZE);
    363 
    364 	/* move the null entry to the front for reuse */
    365 	TAILQ_REMOVE(&coda_nc_lru.head, cncp, lru);
    366 	TAILQ_INSERT_HEAD(&coda_nc_lru.head, cncp, lru);
    367 }
    368 
    369 /*
    370  * Remove all entries with a parent which has the input fid.
    371  */
    372 void
    373 coda_nc_zapParentfid(CodaFid *fid, enum dc_status dcstat)
    374 {
    375 	/* To get to a specific fid, we might either have another hashing
    376 	   function or do a sequential search through the cache for the
    377 	   appropriate entries. The later may be acceptable since I don't
    378 	   think callbacks or whatever Case 1 covers are frequent occurrences.
    379 	 */
    380 	struct coda_cache *cncp, *ncncp;
    381 	int i;
    382 
    383 	if (coda_nc_use == 0)			/* Cache is off */
    384 		return;
    385 
    386 	CODA_NC_DEBUG(CODA_NC_ZAPPFID,
    387 		myprintf(("ZapParent: fid %s\n", coda_f2s(fid))); )
    388 
    389 	coda_nc_stat.zapPfids++;
    390 
    391 	for (i = 0; i < coda_nc_hashsize; i++) {
    392 
    393 		/*
    394 		 * Need to save the hash_next pointer in case we remove the
    395 		 * entry. remove causes hash_next to point to itself.
    396 		 */
    397 
    398 		ncncp = LIST_FIRST(&coda_nc_hash[i].head);
    399 		while ((cncp = ncncp) != NULL) {
    400 			ncncp = LIST_NEXT(cncp, hash);
    401 
    402 			if (coda_fid_eq(&(cncp->dcp->c_fid), fid)) {
    403 			        coda_nc_hash[i].length--;      /* Used for tuning */
    404 				coda_nc_remove(cncp, dcstat);
    405 			}
    406 		}
    407 	}
    408 }
    409 
    410 /*
    411  * Remove all entries which have the same fid as the input
    412  */
    413 void
    414 coda_nc_zapfid(CodaFid *fid, enum dc_status dcstat)
    415 {
    416 	/* See comment for zapParentfid. This routine will be used
    417 	   if attributes are being cached.
    418 	 */
    419 	struct coda_cache *cncp, *ncncp;
    420 	int i;
    421 
    422 	if (coda_nc_use == 0)			/* Cache is off */
    423 		return;
    424 
    425 	CODA_NC_DEBUG(CODA_NC_ZAPFID,
    426 		myprintf(("Zapfid: fid %s\n", coda_f2s(fid))); )
    427 
    428 	coda_nc_stat.zapFids++;
    429 
    430 	for (i = 0; i < coda_nc_hashsize; i++) {
    431 
    432 		ncncp = LIST_FIRST(&coda_nc_hash[i].head);
    433 		while ((cncp = ncncp) != NULL) {
    434 			ncncp = LIST_NEXT(cncp, hash);
    435 
    436 			if (coda_fid_eq(&cncp->cp->c_fid, fid)) {
    437 			        coda_nc_hash[i].length--;     /* Used for tuning */
    438 				coda_nc_remove(cncp, dcstat);
    439 			}
    440 		}
    441 	}
    442 }
    443 
    444 /*
    445  * Remove all entries which match the fid and the cred
    446  */
    447 void
    448 coda_nc_zapvnode(CodaFid *fid, kauth_cred_t cred,
    449     enum dc_status dcstat)
    450 {
    451 	/* See comment for zapfid. I don't think that one would ever
    452 	   want to zap a file with a specific cred from the kernel.
    453 	   We'll leave this one unimplemented.
    454 	 */
    455 	if (coda_nc_use == 0)			/* Cache is off */
    456 		return;
    457 
    458 	CODA_NC_DEBUG(CODA_NC_ZAPVNODE,
    459 		myprintf(("Zapvnode: fid %s cred %p\n",
    460 			  coda_f2s(fid), cred)); )
    461 }
    462 
    463 /*
    464  * Remove all entries which have the (dir vnode, name) pair
    465  */
    466 void
    467 coda_nc_zapfile(struct cnode *dcp, const char *name, int namelen)
    468 {
    469 	/* use the hash function to locate the file, then zap all
    470  	   entries of it regardless of the cred.
    471 	 */
    472 	struct coda_cache *cncp;
    473 	int hash;
    474 
    475 	if (coda_nc_use == 0)			/* Cache is off */
    476 		return;
    477 
    478 	CODA_NC_DEBUG(CODA_NC_ZAPFILE,
    479 		myprintf(("Zapfile: dcp %p name %s \n",
    480 			  dcp, name)); )
    481 
    482 	if (namelen > CODA_NC_NAMELEN) {
    483 		coda_nc_stat.long_remove++;		/* record stats */
    484 		return;
    485 	}
    486 
    487 	coda_nc_stat.zapFile++;
    488 
    489 	hash = CODA_NC_HASH(name, namelen, dcp);
    490 	cncp = coda_nc_find(dcp, name, namelen, 0, hash);
    491 
    492 	while (cncp) {
    493 	  coda_nc_hash[hash].length--;                 /* Used for tuning */
    494 /* 1.3 */
    495 	  coda_nc_remove(cncp, NOT_DOWNCALL);
    496 	  cncp = coda_nc_find(dcp, name, namelen, 0, hash);
    497 	}
    498 }
    499 
    500 /*
    501  * Remove all the entries for a particular user. Used when tokens expire.
    502  * A user is determined by his/her effective user id (id_uid).
    503  */
    504 void
    505 coda_nc_purge_user(uid_t uid, enum dc_status dcstat)
    506 {
    507 	/*
    508 	 * I think the best approach is to go through the entire cache
    509 	 * via HASH or whatever and zap all entries which match the
    510 	 * input cred. Or just flush the whole cache.  It might be
    511 	 * best to go through on basis of LRU since cache will almost
    512 	 * always be full and LRU is more straightforward.
    513 	 */
    514 
    515 	struct coda_cache *cncp, *ncncp;
    516 	int hash;
    517 
    518 	if (coda_nc_use == 0)			/* Cache is off */
    519 		return;
    520 
    521 	CODA_NC_DEBUG(CODA_NC_PURGEUSER,
    522 		myprintf(("ZapDude: uid %x\n", uid)); )
    523 	coda_nc_stat.zapUsers++;
    524 
    525 	ncncp = TAILQ_FIRST(&coda_nc_lru.head);
    526 	while ((cncp = ncncp) != NULL) {
    527 		ncncp = TAILQ_NEXT(cncp, lru);
    528 
    529 		if ((CODA_NC_VALID(cncp)) &&
    530 		   (kauth_cred_geteuid(cncp->cred) == uid)) {
    531 		        /* Seems really ugly, but we have to decrement the appropriate
    532 			   hash bucket length here, so we have to find the hash bucket
    533 			   */
    534 		        hash = CODA_NC_HASH(cncp->name, cncp->namelen, cncp->dcp);
    535 			coda_nc_hash[hash].length--;     /* For performance tuning */
    536 
    537 			coda_nc_remove(cncp, dcstat);
    538 		}
    539 	}
    540 }
    541 
    542 /*
    543  * Flush the entire name cache. In response to a flush of the Venus cache.
    544  */
    545 void
    546 coda_nc_flush(enum dc_status dcstat)
    547 {
    548 	/* One option is to deallocate the current name cache and
    549 	   call init to start again. Or just deallocate, then rebuild.
    550 	   Or again, we could just go through the array and zero the
    551 	   appropriate fields.
    552 	 */
    553 
    554 	/*
    555 	 * Go through the whole lru chain and kill everything as we go.
    556 	 * I don't use remove since that would rebuild the lru chain
    557 	 * as it went and that seemed unnecessary.
    558 	 */
    559 	struct coda_cache *cncp;
    560 	int i;
    561 
    562 	if (coda_nc_use == 0)			/* Cache is off */
    563 		return;
    564 
    565 	coda_nc_stat.Flushes++;
    566 
    567 	TAILQ_FOREACH(cncp, &coda_nc_lru.head, lru) {
    568 		if (CODA_NC_VALID(cncp)) {	/* only zero valid nodes */
    569 			LIST_REMOVE(cncp, hash);
    570 			memset(&cncp->hash, 0, sizeof(cncp->hash));
    571 
    572 			if ((dcstat == IS_DOWNCALL)
    573 			    && (vrefcnt(CTOV(cncp->dcp)) == 1))
    574 			{
    575 				cncp->dcp->c_flags |= C_PURGING;
    576 			}
    577 			vrele(CTOV(cncp->dcp));
    578 
    579 			if (CTOV(cncp->cp)->v_iflag & VI_TEXT) {
    580 			    if (coda_vmflush(cncp->cp))
    581 				CODADEBUG(CODA_FLUSH,
    582 					myprintf(("coda_nc_flush: %s busy\n",
    583 						coda_f2s(&cncp->cp->c_fid))); )
    584 			}
    585 
    586 			if ((dcstat == IS_DOWNCALL)
    587 			    && (vrefcnt(CTOV(cncp->cp)) == 1))
    588 			{
    589 				cncp->cp->c_flags |= C_PURGING;
    590 			}
    591 			vrele(CTOV(cncp->cp));
    592 
    593 			kauth_cred_free(cncp->cred);
    594 			memset(DATA_PART(cncp), 0, DATA_SIZE);
    595 		}
    596 	}
    597 
    598 	for (i = 0; i < coda_nc_hashsize; i++)
    599 	  coda_nc_hash[i].length = 0;
    600 }
    601 
    602 /*
    603  * Debugging routines
    604  */
    605 
    606 /*
    607  * This routine should print out all the hash chains to the console.
    608  */
    609 void
    610 print_coda_nc(void)
    611 {
    612 	int hash;
    613 	struct coda_cache *cncp;
    614 
    615 	for (hash = 0; hash < coda_nc_hashsize; hash++) {
    616 		myprintf(("\nhash %d\n",hash));
    617 
    618 		LIST_FOREACH(cncp, &coda_nc_hash[hash].head, hash) {
    619 			myprintf(("cp %p dcp %p cred %p name %s\n",
    620 				  cncp->cp, cncp->dcp,
    621 				  cncp->cred, cncp->name));
    622 		     }
    623 	}
    624 }
    625 
    626 void
    627 coda_nc_gather_stats(void)
    628 {
    629     int i, xmax = 0, sum = 0, temp, zeros = 0, ave, n;
    630 
    631 	for (i = 0; i < coda_nc_hashsize; i++) {
    632 	  if (coda_nc_hash[i].length) {
    633 	    sum += coda_nc_hash[i].length;
    634 	  } else {
    635 	    zeros++;
    636 	  }
    637 
    638 	  if (coda_nc_hash[i].length > xmax)
    639 	    xmax = coda_nc_hash[i].length;
    640 	}
    641 
    642 	/*
    643 	 * When computing the Arithmetic mean, only count slots which
    644 	 * are not empty in the distribution.
    645 	 */
    646         coda_nc_stat.Sum_bucket_len = sum;
    647         coda_nc_stat.Num_zero_len = zeros;
    648         coda_nc_stat.Max_bucket_len = xmax;
    649 
    650 	if ((n = coda_nc_hashsize - zeros) > 0)
    651 	  ave = sum / n;
    652 	else
    653 	  ave = 0;
    654 
    655 	sum = 0;
    656 	for (i = 0; i < coda_nc_hashsize; i++) {
    657 	  if (coda_nc_hash[i].length) {
    658 	    temp = coda_nc_hash[i].length - ave;
    659 	    sum += temp * temp;
    660 	  }
    661 	}
    662         coda_nc_stat.Sum2_bucket_len = sum;
    663 }
    664 
    665 /*
    666  * The purpose of this routine is to allow the hash and cache sizes to be
    667  * changed dynamically. This should only be used in controlled environments,
    668  * it makes no effort to lock other users from accessing the cache while it
    669  * is in an improper state (except by turning the cache off).
    670  */
    671 int
    672 coda_nc_resize(int hashsize, int heapsize, enum dc_status dcstat)
    673 {
    674     if ((hashsize % 2) || (heapsize % 2)) { /* Illegal hash or cache sizes */
    675 	return(EINVAL);
    676     }
    677 
    678     coda_nc_use = 0;                       /* Turn the cache off */
    679 
    680     coda_nc_flush(dcstat);                 /* free any cnodes in the cache */
    681 
    682     /* WARNING: free must happen *before* size is reset */
    683     CODA_FREE(coda_nc_heap,TOTAL_CACHE_SIZE);
    684     CODA_FREE(coda_nc_hash,TOTAL_HASH_SIZE);
    685 
    686     coda_nc_hashsize = hashsize;
    687     coda_nc_size = heapsize;
    688 
    689     coda_nc_init();                        /* Set up a cache with the new size */
    690 
    691     coda_nc_use = 1;                       /* Turn the cache back on */
    692     return(0);
    693 }
    694 
    695 char coda_nc_name_buf[CODA_MAXNAMLEN+1];
    696 
    697 void
    698 coda_nc_name(struct cnode *cp)
    699 {
    700 	struct coda_cache *cncp;
    701 	int i;
    702 
    703 	if (coda_nc_use == 0)			/* Cache is off */
    704 		return;
    705 
    706 	for (i = 0; i < coda_nc_hashsize; i++) {
    707 
    708 		LIST_FOREACH(cncp, &coda_nc_hash[i].head, hash) {
    709 			if (cncp->cp == cp) {
    710 				memcpy(coda_nc_name_buf, cncp->name, cncp->namelen);
    711 				coda_nc_name_buf[cncp->namelen] = 0;
    712 				printf(" is %s (%p,%p)@%p",
    713 					coda_nc_name_buf, cncp->cp, cncp->dcp, cncp);
    714 			}
    715 
    716 		}
    717 	}
    718 }
    719