avoid-long-windows-shell-timeouts-20040105
[openafs.git] / src / WINNT / afsd / cm_buf.c
1 /*
2  * Copyright 2000, International Business Machines Corporation and others.
3  * All Rights Reserved.
4  * 
5  * This software has been released under the terms of the IBM Public
6  * License.  For details, see the LICENSE file in the top-level source
7  * directory or online at http://www.openafs.org/dl/license10.html
8  */
9
10 /* Copyright (C) 1994 Cazamar Systems, Inc. */
11
12 #include <afs/param.h>
13 #include <afs/stds.h>
14
15 #ifndef DJGPP
16 #include <windows.h>
17 #endif
18 #include <osi.h>
19 #include <malloc.h>
20 #include <stdio.h>
21 #include <assert.h>
22
23 #include "afsd.h"
24
25 extern void afsi_log(char *pattern, ...);
26
27 /* This module implements the buffer package used by the local transaction
28  * system (cm).  It is initialized by calling cm_Init, which calls buf_Init;
29  * it must be initalized before any of its main routines are called.
30  *
31  * Each buffer is hashed into a hash table by file ID and offset, and if its
32  * reference count is zero, it is also in a free list.
33  *
34  * There are two locks involved in buffer processing.  The global lock
35  * buf_globalLock protects all of the global variables defined in this module,
36  * the reference counts and hash pointers in the actual cm_buf_t structures,
37  * and the LRU queue pointers in the buffer structures.
38  *
39  * The mutexes in the buffer structures protect the remaining fields in the
40  * buffers, as well the data itself.
41  * 
42  * The locking hierarchy here is this:
43  * 
44  * - resv multiple simul. buffers reservation
45  * - lock buffer I/O flags
46  * - lock buffer's mutex
47  * - lock buf_globalLock
48  *
49  */
50
51 /* global debugging log */
52 osi_log_t *buf_logp = NULL;
53
54 /* Global lock protecting hash tables and free lists */
55 osi_rwlock_t buf_globalLock;
56
57 /* ptr to head of the free list (most recently used) and the
58  * tail (the guy to remove first).  We use osi_Q* functions
59  * to put stuff in buf_freeListp, and maintain the end
60  * pointer manually
61  */
62 cm_buf_t *buf_freeListp;
63 cm_buf_t *buf_freeListEndp;
64
65 /* a pointer to a list of all buffers, just so that we can find them
66  * easily for debugging, and for the incr syncer.  Locked under
67  * the global lock.
68  */
69 cm_buf_t *buf_allp;
70
71 /* defaults setup; these variables may be manually assigned into
72  * before calling cm_Init, as a way of changing these defaults.
73  */
74 long buf_nbuffers = CM_BUF_BUFFERS;
75 long buf_nOrigBuffers;
76 long buf_bufferSize = CM_BUF_SIZE;
77 long buf_hashSize = CM_BUF_HASHSIZE;
78
79 #ifndef DJGPP
80 static
81 HANDLE CacheHandle;
82
83 static
84 SYSTEM_INFO sysInfo;
85 #endif /* !DJGPP */
86
87 /* buffer reservation variables */
88 long buf_reservedBufs;
89 long buf_maxReservedBufs;
90 int buf_reserveWaiting;
91
92 /* callouts for reading and writing data, etc */
93 cm_buf_ops_t *cm_buf_opsp;
94
95 /* pointer to hash table; size computed dynamically */
96 cm_buf_t **buf_hashTablepp;
97
98 /* another hash table */
99 cm_buf_t **buf_fileHashTablepp;
100
101 #ifdef DISKCACHE95
102 /* for experimental disk caching support in Win95 client */
103 cm_buf_t *buf_diskFreeListp;
104 cm_buf_t *buf_diskFreeListEndp;
105 cm_buf_t *buf_diskAllp;
106 extern int cm_diskCacheEnabled;
107 #endif /* DISKCACHE95 */
108
109 /* hold a reference to an already held buffer */
110 void buf_Hold(cm_buf_t *bp)
111 {
112         lock_ObtainWrite(&buf_globalLock);
113         bp->refCount++;
114         lock_ReleaseWrite(&buf_globalLock);
115 }
116
117 /* incremental sync daemon.  Writes 1/10th of all the buffers every 5000 ms */
118 void buf_IncrSyncer(long parm)
119 {
120         cm_buf_t *bp;                   /* buffer we're hacking on; held */
121         long i;                         /* counter */
122         long nAtOnce;                   /* how many to do at once */
123         cm_req_t req;
124
125         lock_ObtainWrite(&buf_globalLock);
126         bp = buf_allp;
127         bp->refCount++;
128         lock_ReleaseWrite(&buf_globalLock);
129         nAtOnce = buf_nbuffers / 10;
130         while (1) {
131 #ifndef DJGPP
132                 i = SleepEx(5000, 1);
133                 if (i != 0) continue;
134 #else
135                 thrd_Sleep(5000);
136 #endif /* DJGPP */
137                 
138                 /* now go through our percentage of the buffers */
139                 for(i=0; i<nAtOnce; i++) {
140                         /* don't want its identity changing while we're
141                          * messing with it, so must do all of this with
142                          * bp held.
143                          */
144
145                         /* start cleaning the buffer; don't touch log pages since
146                          * the log code counts on knowing exactly who is writing
147                          * a log page at any given instant.
148                          */
149                         cm_InitReq(&req);
150                         req.flags |= CM_REQ_NORETRY;
151                         buf_CleanAsync(bp, &req);
152
153                         /* now advance to the next buffer; the allp chain never changes,
154                          * and so can be followed even when holding no locks.
155                          */
156                         lock_ObtainWrite(&buf_globalLock);
157                         buf_LockedRelease(bp);
158                         bp = bp->allp;
159                         if (!bp) bp = buf_allp;
160                         bp->refCount++;
161                         lock_ReleaseWrite(&buf_globalLock);
162                 }       /* for loop over a bunch of buffers */
163         }               /* whole daemon's while loop */
164 }
165
166 #ifndef DJGPP
167 /* Create a security attribute structure suitable for use when the cache file
168  * is created.  What we mainly want is that only the administrator should be
169  * able to do anything with the file.  We create an ACL with only one entry,
170  * an entry that grants all rights to the administrator.
171  */
172 PSECURITY_ATTRIBUTES CreateCacheFileSA()
173 {
174         PSECURITY_ATTRIBUTES psa;
175         PSECURITY_DESCRIPTOR psd;
176         SID_IDENTIFIER_AUTHORITY authority = SECURITY_NT_AUTHORITY;
177         PSID AdminSID;
178         DWORD AdminSIDlength;
179         PACL AdminOnlyACL;
180         DWORD ACLlength;
181
182         /* Get Administrator SID */
183         AllocateAndInitializeSid(&authority, 2,
184                                  SECURITY_BUILTIN_DOMAIN_RID,
185                                  DOMAIN_ALIAS_RID_ADMINS,
186                                  0, 0, 0, 0, 0, 0,
187                                  &AdminSID);
188
189         /* Create Administrator-only ACL */
190         AdminSIDlength = GetLengthSid(AdminSID);
191         ACLlength = sizeof(ACL) + sizeof(ACCESS_ALLOWED_ACE)
192                         + AdminSIDlength - sizeof(DWORD);
193         AdminOnlyACL = GlobalAlloc(GMEM_FIXED, ACLlength);
194         InitializeAcl(AdminOnlyACL, ACLlength, ACL_REVISION);
195         AddAccessAllowedAce(AdminOnlyACL, ACL_REVISION,
196                             STANDARD_RIGHTS_ALL | SPECIFIC_RIGHTS_ALL,
197                             AdminSID);
198
199         /* Create security descriptor */
200         psd = GlobalAlloc(GMEM_FIXED, sizeof(SECURITY_DESCRIPTOR));
201         InitializeSecurityDescriptor(psd, SECURITY_DESCRIPTOR_REVISION);
202         SetSecurityDescriptorDacl(psd, TRUE, AdminOnlyACL, FALSE);
203
204         /* Create security attributes structure */
205         psa = GlobalAlloc(GMEM_FIXED, sizeof(SECURITY_ATTRIBUTES));
206         psa->nLength = sizeof(SECURITY_ATTRIBUTES);
207         psa->lpSecurityDescriptor = psd;
208         psa->bInheritHandle = TRUE;
209
210         return psa;
211 }
212 #endif /* !DJGPP */
213
214 #ifndef DJGPP
215 /* Free a security attribute structure created by CreateCacheFileSA() */
216 VOID FreeCacheFileSA(PSECURITY_ATTRIBUTES psa)
217 {
218         BOOL b1, b2;
219         PACL pAcl;
220
221         GetSecurityDescriptorDacl(psa->lpSecurityDescriptor, &b1, &pAcl, &b2);
222         GlobalFree(pAcl);
223         GlobalFree(psa->lpSecurityDescriptor);
224         GlobalFree(psa);
225 }
226 #endif /* !DJGPP */
227         
228 /* initialize the buffer package; called with no locks
229  * held during the initialization phase.
230  */
231 long buf_Init(cm_buf_ops_t *opsp)
232 {
233         static osi_once_t once;
234         cm_buf_t *bp;
235         long sectorSize;
236         thread_t phandle;
237 #ifndef DJGPP
238         HANDLE hf, hm;
239         PSECURITY_ATTRIBUTES psa;
240 #endif /* !DJGPP */
241         long i;
242         unsigned long pid;
243         char *data;
244         long cs;
245
246 #ifndef DJGPP
247         /* Get system info; all we really want is the allocation granularity */ 
248         GetSystemInfo(&sysInfo);
249 #endif /* !DJGPP */
250
251         /* Have to be able to reserve a whole chunk */
252         if (((buf_nbuffers - 3) * buf_bufferSize) < cm_chunkSize)
253                 return CM_ERROR_TOOFEWBUFS;
254
255         /* recall for callouts */
256         cm_buf_opsp = opsp;
257
258         if (osi_Once(&once)) {
259                 /* initialize global locks */
260                 lock_InitializeRWLock(&buf_globalLock, "Global buffer lock");
261
262 #ifndef DJGPP
263                 /*
264                  * Cache file mapping constrained by
265                  * system allocation granularity;
266                  * round up, assuming granularity is a power of two
267                  */
268                 cs = buf_nbuffers * buf_bufferSize;
269                 cs = (cs + (sysInfo.dwAllocationGranularity - 1))
270                         & ~(sysInfo.dwAllocationGranularity - 1);
271                 if (cs != buf_nbuffers * buf_bufferSize) {
272                         buf_nbuffers = cs / buf_bufferSize;
273                         afsi_log("Cache size rounded up to %d buffers",
274                                  buf_nbuffers);
275                 }
276 #endif /* !DJGPP */
277
278                 /* remember this for those who want to reset it */
279                 buf_nOrigBuffers = buf_nbuffers;
280
281                 /* lower hash size to a prime number */
282                 buf_hashSize = osi_PrimeLessThan(buf_hashSize);
283
284                 /* create hash table */
285                 buf_hashTablepp = malloc(buf_hashSize * sizeof(cm_buf_t *));
286                 memset((void *)buf_hashTablepp, 0,
287                         buf_hashSize * sizeof(cm_buf_t *));
288
289                 /* another hash table */
290                 buf_fileHashTablepp = malloc(buf_hashSize * sizeof(cm_buf_t *));
291                 memset((void *)buf_fileHashTablepp, 0,
292                         buf_hashSize * sizeof(cm_buf_t *));
293                 
294                 /* min value for which this works */
295                 sectorSize = 1;
296
297 #ifndef DJGPP
298                 /* Reserve buffer space by mapping cache file */
299                 psa = CreateCacheFileSA();
300                 hf = CreateFile(cm_CachePath,
301                         GENERIC_READ | GENERIC_WRITE,
302                         FILE_SHARE_READ | FILE_SHARE_WRITE,
303                         psa,
304                         OPEN_ALWAYS,
305                         FILE_ATTRIBUTE_NORMAL,
306                         NULL);
307                 if (hf == INVALID_HANDLE_VALUE) {
308                         afsi_log("create file error %d", GetLastError());
309                         return CM_ERROR_INVAL;
310                 }
311                 FreeCacheFileSA(psa);
312                 CacheHandle = hf;
313                 hm = CreateFileMapping(hf,
314                         NULL,
315                         PAGE_READWRITE,
316                         0, buf_nbuffers * buf_bufferSize,
317                         NULL);
318                 if (hm == NULL) {
319                         if (GetLastError() == ERROR_DISK_FULL) {
320                                 afsi_log("Error creating cache file mapping: disk full");
321                                 return CM_ERROR_TOOMANYBUFS;
322                         }
323                         return CM_ERROR_INVAL;
324                 }
325                 data = MapViewOfFile(hm,
326                         FILE_MAP_ALL_ACCESS,
327                         0, 0,
328                         buf_nbuffers * buf_bufferSize);
329                 if (data == NULL) {
330                         CloseHandle(hf);
331                         CloseHandle(hm);
332                         return CM_ERROR_INVAL;
333                 }
334                 CloseHandle(hm);
335 #else
336                 /* djgpp doesn't support memory mapped files */
337                 data = malloc(buf_nbuffers * buf_bufferSize);
338 #endif /* !DJGPP */
339
340                 /* create buffer headers and put in free list */
341                 bp = malloc(buf_nbuffers * sizeof(cm_buf_t));
342                 buf_allp = NULL;
343                 for(i=0; i<buf_nbuffers; i++) {
344                         /* allocate and zero some storage */
345                         memset(bp, 0, sizeof(cm_buf_t));
346
347                         /* thread on list of all buffers */
348                         bp->allp = buf_allp;
349                         buf_allp = bp;
350                         
351                         osi_QAdd((osi_queue_t **)&buf_freeListp, &bp->q);
352                         bp->flags |= CM_BUF_INLRU;
353                         lock_InitializeMutex(&bp->mx, "Buffer mutex");
354
355                         /* grab appropriate number of bytes from aligned zone */
356                         bp->datap = data;
357
358                         /* setup last buffer pointer */
359                         if (i == 0)
360                                 buf_freeListEndp = bp;
361
362                         /* next */
363                         bp++;
364                         data += buf_bufferSize;
365                 }
366                 
367                 /* none reserved at first */
368                 buf_reservedBufs = 0;
369                 
370                 /* just for safety's sake */
371                 buf_maxReservedBufs = buf_nbuffers - 3;
372                 
373                 /* init the buffer trace log */
374                 buf_logp = osi_LogCreate("buffer", 10);
375
376                 osi_EndOnce(&once);
377                 
378                 /* and create the incr-syncer */
379                 phandle = thrd_Create(0, 0,
380                                       (ThreadFunc) buf_IncrSyncer, 0, 0, &pid,
381                                       "buf_IncrSyncer");
382
383                 osi_assertx(phandle != NULL, "buf: can't create incremental sync proc");
384 #ifndef DJGPP
385                 CloseHandle(phandle);
386 #endif /* !DJGPP */
387         }
388
389         return 0;
390 }
391
392 /* add nbuffers to the buffer pool, if possible.
393  * Called with no locks held.
394  */
395 long buf_AddBuffers(long nbuffers)
396 {
397         cm_buf_t *bp;
398         int i;
399         char *data;
400 #ifndef DJGPP
401         HANDLE hm;
402         long cs;
403
404     afsi_log("%d buffers being added to the existing cache of size %d",
405               nbuffers, buf_nbuffers);
406
407         /*
408          * Cache file mapping constrained by
409          * system allocation granularity;
410          * round up, assuming granularity is a power of two;
411          * assume existing cache size is already rounded
412          */
413         cs = nbuffers * buf_bufferSize;
414         cs = (cs + (sysInfo.dwAllocationGranularity - 1))
415                 & ~(sysInfo.dwAllocationGranularity - 1);
416         if (cs != nbuffers * buf_bufferSize) {
417                 nbuffers = cs / buf_bufferSize;
418         }
419
420         /* Reserve additional buffer space by remapping cache file */
421         hm = CreateFileMapping(CacheHandle,
422                 NULL,
423                 PAGE_READWRITE,
424                 0, (buf_nbuffers + nbuffers) * buf_bufferSize,
425                 NULL);
426         if (hm == NULL) {
427                 if (GetLastError() == ERROR_DISK_FULL)
428                         return CM_ERROR_TOOMANYBUFS;
429                 else
430                         return CM_ERROR_INVAL;
431         }
432         data = MapViewOfFile(hm,
433                 FILE_MAP_ALL_ACCESS,
434                 0, buf_nbuffers * buf_bufferSize,
435                 nbuffers * buf_bufferSize);
436         if (data == NULL) {
437                 CloseHandle(hm);
438                 return CM_ERROR_INVAL;
439         }
440         CloseHandle(hm);
441 #else
442         data = malloc(buf_nbuffers * buf_bufferSize);
443 #endif /* DJGPP */
444
445         /* Create buffer headers and put in free list */
446         bp = malloc(nbuffers * sizeof(*bp));
447
448         for(i=0; i<nbuffers; i++) {
449                 memset(bp, 0, sizeof(*bp));
450         
451                 lock_InitializeMutex(&bp->mx, "cm_buf_t");
452
453                 /* grab appropriate number of bytes from aligned zone */
454                 bp->datap = data;
455
456                 bp->flags |= CM_BUF_INLRU;
457                 
458                 lock_ObtainWrite(&buf_globalLock);
459                 /* note that buf_allp chain is covered by buf_globalLock now */
460                 bp->allp = buf_allp;
461                 buf_allp = bp;
462                 osi_QAdd((osi_queue_t **) &buf_freeListp, &bp->q);
463                 if (!buf_freeListEndp) buf_freeListEndp = bp;
464                 buf_nbuffers++;
465                 lock_ReleaseWrite(&buf_globalLock);
466
467                 bp++;
468                 data += buf_bufferSize;
469         
470         }        /* for loop over all buffers */
471
472         return 0;
473 }
474
475 /* interface to set the number of buffers to an exact figure.
476  * Called with no locks held.
477  */
478 long buf_SetNBuffers(long nbuffers)
479 {
480         if (nbuffers < 10) return CM_ERROR_INVAL;
481         if (nbuffers == buf_nbuffers) return 0;
482         else if (nbuffers > buf_nbuffers)
483                 return buf_AddBuffers(nbuffers - buf_nbuffers);
484         else return CM_ERROR_INVAL;
485 }
486
487 /* release a buffer.  Buffer must be referenced, but unlocked. */
488 void buf_Release(cm_buf_t *bp)
489 {
490         lock_ObtainWrite(&buf_globalLock);
491         buf_LockedRelease(bp);
492         lock_ReleaseWrite(&buf_globalLock);
493 }
494
495 /* wait for reading or writing to clear; called with write-locked
496  * buffer, and returns with locked buffer.
497  */
498 void buf_WaitIO(cm_buf_t *bp)
499 {
500         while (1) {
501                 /* if no IO is happening, we're done */
502                 if (!(bp->flags & (CM_BUF_READING | CM_BUF_WRITING)))
503                         break;
504                 
505                 /* otherwise I/O is happening, but some other thread is waiting for
506                  * the I/O already.  Wait for that guy to figure out what happened,
507                  * and then check again.
508                  */
509                 bp->flags |= CM_BUF_WAITING;
510                 osi_SleepM((long) bp, &bp->mx);
511                 lock_ObtainMutex(&bp->mx);
512                 osi_Log1(buf_logp, "buf_WaitIO conflict wait done for 0x%x", bp);
513         }
514         
515         /* if we get here, the IO is done, but we may have to wakeup people waiting for
516          * the I/O to complete.  Do so.
517          */
518         if (bp->flags & CM_BUF_WAITING) {
519                 bp->flags &= ~CM_BUF_WAITING;
520                 osi_Wakeup((long) bp);
521         }
522         osi_Log1(buf_logp, "WaitIO finished wait for bp 0x%x", (long) bp);
523 }
524
525 /* code to drop reference count while holding buf_globalLock */
526 void buf_LockedRelease(cm_buf_t *bp)
527 {
528         /* ensure that we're in the LRU queue if our ref count is 0 */
529         osi_assert(bp->refCount > 0);
530         if (--bp->refCount == 0) {
531                 if (!(bp->flags & CM_BUF_INLRU)) {
532                         osi_QAdd((osi_queue_t **) &buf_freeListp, &bp->q);
533
534                         /* watch for transition from empty to one element */
535                         if (!buf_freeListEndp)
536                                 buf_freeListEndp = buf_freeListp;
537                         bp->flags |= CM_BUF_INLRU;
538                 }
539         }
540 }
541
542 /* find a buffer, if any, for a particular file ID and offset.  Assumes
543  * that buf_globalLock is write locked when called.
544  */
545 cm_buf_t *buf_LockedFind(struct cm_scache *scp, osi_hyper_t *offsetp)
546 {
547         long i;
548         cm_buf_t *bp;
549         
550         i = BUF_HASH(&scp->fid, offsetp);
551         for(bp = buf_hashTablepp[i]; bp; bp=bp->hashp) {
552                 if (cm_FidCmp(&scp->fid, &bp->fid) == 0
553                         && offsetp->LowPart == bp->offset.LowPart
554                         && offsetp->HighPart == bp->offset.HighPart) {
555                         bp->refCount++;
556                         break;
557                 }
558         }
559         
560         /* return whatever we found, if anything */
561         return bp;
562 }
563
564 /* find a buffer with offset *offsetp for vnode *scp.  Called
565  * with no locks held.
566  */
567 cm_buf_t *buf_Find(struct cm_scache *scp, osi_hyper_t *offsetp)
568 {
569         cm_buf_t *bp;
570
571         lock_ObtainWrite(&buf_globalLock);
572         bp = buf_LockedFind(scp, offsetp);
573         lock_ReleaseWrite(&buf_globalLock);
574
575         return bp;
576 }
577
578 /* start cleaning I/O on this buffer.  Buffer must be write locked, and is returned
579  * write-locked.
580  *
581  * Makes sure that there's only one person writing this block
582  * at any given time, and also ensures that the log is forced sufficiently far,
583  * if this buffer contains logged data.
584  */
585 void buf_LockedCleanAsync(cm_buf_t *bp, cm_req_t *reqp)
586 {
587         long code;
588
589         code = 0;
590         while ((bp->flags & (CM_BUF_WRITING | CM_BUF_DIRTY)) == CM_BUF_DIRTY) {
591                 lock_ReleaseMutex(&bp->mx);
592
593                 code = (*cm_buf_opsp->Writep)(&bp->fid, &bp->offset,
594                                                 buf_bufferSize, 0, bp->userp,
595                                                 reqp);
596                 
597                 lock_ObtainMutex(&bp->mx);
598                 if (code) break;
599
600 #ifdef DISKCACHE95
601                 /* Disk cache support */
602                 /* write buffer to disk cache (synchronous for now) */
603                 diskcache_Update(bp->dcp, bp->datap, buf_bufferSize, bp->dataVersion);
604 #endif /* DISKCACHE95 */
605         };
606
607         /* do logging after call to GetLastError, or else */
608         osi_Log2(buf_logp, "buf_CleanAsync starts I/O on 0x%x, done=%d", bp, code);
609         
610         /* if someone was waiting for the I/O that just completed or failed,
611          * wake them up.
612          */
613         if (bp->flags & CM_BUF_WAITING) {
614                 /* turn off flags and wakeup users */
615                 bp->flags &= ~CM_BUF_WAITING;
616                 osi_Wakeup((long) bp);
617         }
618 }
619
620 /* Called with a zero-ref count buffer and with the buf_globalLock write locked.
621  * recycles the buffer, and leaves it ready for reuse with a ref count of 1.
622  * The buffer must already be clean, and no I/O should be happening to it.
623  */
624 void buf_Recycle(cm_buf_t *bp)
625 {
626         int i;
627         cm_buf_t **lbpp;
628         cm_buf_t *tbp;
629         cm_buf_t *prevBp, *nextBp;
630
631         /* if we get here, we know that the buffer still has a 0 ref count,
632          * and that it is clean and has no currently pending I/O.  This is
633          * the dude to return.
634          * Remember that as long as the ref count is 0, we know that we won't
635          * have any lock conflicts, so we can grab the buffer lock out of
636          * order in the locking hierarchy.
637          */
638         osi_Log2(buf_logp,
639                 "buf_Recycle recycles 0x%x, off 0x%x",
640                 bp, bp->offset.LowPart);
641
642         osi_assert(bp->refCount == 0);
643         osi_assert(!(bp->flags & (CM_BUF_READING | CM_BUF_WRITING | CM_BUF_DIRTY)));
644         lock_AssertWrite(&buf_globalLock);
645
646         if (bp->flags & CM_BUF_INHASH) {
647                 /* Remove from hash */
648
649                 i = BUF_HASH(&bp->fid, &bp->offset);
650                 lbpp = &(buf_hashTablepp[i]);
651                 for(tbp = *lbpp; tbp; lbpp = &tbp->hashp, tbp = *lbpp) {
652                         if (tbp == bp) break;
653                 }
654
655                 /* we better find it */
656                 osi_assertx(tbp != NULL, "buf_GetNewLocked: hash table screwup");
657
658                 *lbpp = bp->hashp;      /* hash out */
659
660                 /* Remove from file hash */
661
662                 i = BUF_FILEHASH(&bp->fid);
663                 prevBp = bp->fileHashBackp;
664                 nextBp = bp->fileHashp;
665                 if (prevBp)
666                         prevBp->fileHashp = nextBp;
667                 else
668                         buf_fileHashTablepp[i] = nextBp;
669                 if (nextBp)
670                         nextBp->fileHashBackp = prevBp;
671
672                 bp->flags &= ~CM_BUF_INHASH;
673         }
674                         
675         /* bump the soft reference counter now, to invalidate softRefs; no
676          * wakeup is required since people don't sleep waiting for this
677          * counter to change.
678          */
679         bp->idCounter++;
680
681         /* make the fid unrecognizable */
682         memset(&bp->fid, 0, sizeof(bp->fid));
683 }
684
685 /* recycle a buffer, removing it from the free list, hashing in its new identity
686  * and returning it write-locked so that no one can use it.  Called without
687  * any locks held, and can return an error if it loses the race condition and 
688  * finds that someone else created the desired buffer.
689  *
690  * If success is returned, the buffer is returned write-locked.
691  *
692  * May be called with null scp and offsetp, if we're just trying to reclaim some
693  * space from the buffer pool.  In that case, the buffer will be returned
694  * without being hashed into the hash table.
695  */
696 long buf_GetNewLocked(struct cm_scache *scp, osi_hyper_t *offsetp, cm_buf_t **bufpp)
697 {
698         cm_buf_t *bp;           /* buffer we're dealing with */
699         cm_buf_t *nextBp;       /* next buffer in file hash chain */
700         long i;                 /* temp */
701         cm_req_t req;
702
703         cm_InitReq(&req);       /* just in case */
704
705         while(1) {
706 retry:
707                 lock_ObtainWrite(&buf_globalLock);
708                 /* check to see if we lost the race */
709                 if (scp) {
710                         if (bp = buf_LockedFind(scp, offsetp)) {
711                                 bp->refCount--;
712                                 lock_ReleaseWrite(&buf_globalLock);
713                                 return CM_BUF_EXISTS;
714                         }
715                 }
716                 
717                 /* for debugging, assert free list isn't empty, although we
718                  * really should try waiting for a running tranasction to finish
719                  * instead of this; or better, we should have a transaction
720                  * throttler prevent us from entering this situation.
721                  */
722                 osi_assertx(buf_freeListEndp != NULL, "buf_GetNewLocked: no free buffers");
723
724                 /* look at all buffers in free list, some of which may temp.
725                  * have high refcounts and which then should be skipped,
726                  * starting cleaning I/O for those which are dirty.  If we find
727                  * a clean buffer, we rehash it, lock it and return it.
728                  */
729                 for(bp = buf_freeListEndp; bp; bp=(cm_buf_t *) osi_QPrev(&bp->q)) {
730                         /* check to see if it really has zero ref count.  This
731                          * code can bump refcounts, at least, so it may not be
732                          * zero.
733                          */
734                         if (bp->refCount > 0) continue;
735                         
736                         /* we don't have to lock buffer itself, since the ref
737                          * count is 0 and we know it will stay zero as long as
738                          * we hold the global lock.
739                          */
740
741                         /* don't recycle someone in our own chunk */
742                         if (!cm_FidCmp(&bp->fid, &scp->fid)
743                             && (bp->offset.LowPart & (-cm_chunkSize))
744                                   == (offsetp->LowPart & (-cm_chunkSize)))
745                                 continue;
746
747                         /* if this page is being filled (!) or cleaned, see if
748                          * the I/O has completed.  If not, skip it, otherwise
749                          * do the final processing for the I/O.
750                          */
751                         if (bp->flags & (CM_BUF_READING | CM_BUF_WRITING)) {
752                                 /* probably shouldn't do this much work while
753                                  * holding the big lock?  Watch for contention
754                                  * here.
755                                  */
756                                 continue;
757                         }
758                         
759                         if (bp->flags & CM_BUF_DIRTY) {
760                                 /* if the buffer is dirty, start cleaning it and
761                                  * move on to the next buffer.  We do this with
762                                  * just the lock required to minimize contention
763                                  * on the big lock.
764                                  */
765                                 bp->refCount++;
766                                 lock_ReleaseWrite(&buf_globalLock);
767
768                                 /* grab required lock and clean; this only
769                                  * starts the I/O.  By the time we're back,
770                                  * it'll still be marked dirty, but it will also
771                                  * have the WRITING flag set, so we won't get
772                                  * back here.
773                                  */
774                                 buf_CleanAsync(bp, &req);
775                                 
776                                 /* now put it back and go around again */
777                                 buf_Release(bp);
778                                 goto retry;
779                         }
780                         
781                         /* if we get here, we know that the buffer still has a 0
782                          * ref count, and that it is clean and has no currently
783                          * pending I/O.  This is the dude to return.
784                          * Remember that as long as the ref count is 0, we know
785                          * that we won't have any lock conflicts, so we can grab
786                          * the buffer lock out of order in the locking hierarchy.
787                          */
788                         buf_Recycle(bp);
789
790                         /* clean up junk flags */
791                         bp->flags &= ~(CM_BUF_EOF | CM_BUF_ERROR);
792                         bp->dataVersion = -1;   /* unknown so far */
793
794                         /* now hash in as our new buffer, and give it the
795                          * appropriate label, if requested.
796                          */
797                         if (scp) {
798                                 bp->flags |= CM_BUF_INHASH;
799                                 bp->fid = scp->fid;
800                                 bp->offset = *offsetp;
801                                 i = BUF_HASH(&scp->fid, offsetp);
802                                 bp->hashp = buf_hashTablepp[i];
803                                 buf_hashTablepp[i] = bp;
804                                 i = BUF_FILEHASH(&scp->fid);
805                                 nextBp = buf_fileHashTablepp[i];
806                                 bp->fileHashp = nextBp;
807                                 bp->fileHashBackp = NULL;
808                                 if (nextBp)
809                                         nextBp->fileHashBackp = bp;
810                                 buf_fileHashTablepp[i] = bp;
811                         }
812                         
813                         /* prepare to return it.  Start by giving it a good
814                          * refcount */
815                         bp->refCount = 1;
816                         
817                         /* and since it has a non-zero ref count, we should move
818                          * it from the lru queue.  It better be still there,
819                          * since we've held the global (big) lock since we found
820                          * it there.
821                          */
822                         osi_assertx(bp->flags & CM_BUF_INLRU,
823                                     "buf_GetNewLocked: LRU screwup");
824                         if (buf_freeListEndp == bp) {
825                                 /* we're the last guy in this queue, so maintain it */
826                                 buf_freeListEndp = (cm_buf_t *) osi_QPrev(&bp->q);
827                         }
828                         osi_QRemove((osi_queue_t **) &buf_freeListp, &bp->q);
829                         bp->flags &= ~CM_BUF_INLRU;
830                         
831                         /* finally, grab the mutex so that people don't use it
832                          * before the caller fills it with data.  Again, no one 
833                          * should have been able to get to this dude to lock it.
834                          */
835                         osi_assertx(lock_TryMutex(&bp->mx),
836                                     "buf_GetNewLocked: TryMutex failed");
837
838                         lock_ReleaseWrite(&buf_globalLock);
839                         *bufpp = bp;
840                         return 0;
841                 } /* for all buffers in lru queue */
842                 lock_ReleaseWrite(&buf_globalLock);
843         }       /* while loop over everything */
844         /* not reached */
845 } /* the proc */
846
847 /* get a page, returning it held but unlocked.  Doesn't fill in the page
848  * with I/O, since we're going to write the whole thing new.
849  */
850 long buf_GetNew(struct cm_scache *scp, osi_hyper_t *offsetp, cm_buf_t **bufpp)
851 {
852         cm_buf_t *bp;
853         long code;
854         osi_hyper_t pageOffset;
855         int created;
856
857         created = 0;
858         pageOffset.HighPart = offsetp->HighPart;
859         pageOffset.LowPart = offsetp->LowPart & ~(buf_bufferSize-1);
860         while (1) {
861                 lock_ObtainWrite(&buf_globalLock);
862                 bp = buf_LockedFind(scp, &pageOffset);
863                 lock_ReleaseWrite(&buf_globalLock);
864                 if (bp) {
865                         /* lock it and break out */
866                         lock_ObtainMutex(&bp->mx);
867                         break;
868                 }
869                 
870                 /* otherwise, we have to create a page */
871                 code = buf_GetNewLocked(scp, &pageOffset, &bp);
872
873                 /* check if the buffer was created in a race condition branch.
874                  * If so, go around so we can hold a reference to it. 
875                  */
876                 if (code == CM_BUF_EXISTS) continue;
877                 
878                 /* something else went wrong */
879                 if (code != 0) return code;
880                 
881                 /* otherwise, we have a locked buffer that we just created */
882                 created = 1;
883                 break;
884         } /* big while loop */
885         
886         /* wait for reads */
887         if (bp->flags & CM_BUF_READING)
888                 buf_WaitIO(bp);
889
890         /* once it has been read once, we can unlock it and return it, still
891          * with its refcount held.
892          */
893         lock_ReleaseMutex(&bp->mx);
894         *bufpp = bp;
895         osi_Log3(buf_logp, "buf_GetNew returning bp 0x%x for file 0x%x, offset 0x%x",
896                 bp, (long) scp, offsetp->LowPart);
897         return 0;
898 }
899
900 /* get a page, returning it held but unlocked.  Make sure it is complete */
901 long buf_Get(struct cm_scache *scp, osi_hyper_t *offsetp, cm_buf_t **bufpp)
902 {
903         cm_buf_t *bp;
904         long code;
905         osi_hyper_t pageOffset;
906         unsigned long tcount;
907         int created;
908 #ifdef DISKCACHE95
909         cm_diskcache_t *dcp;
910 #endif /* DISKCACHE95 */
911
912         created = 0;
913         pageOffset.HighPart = offsetp->HighPart;
914         pageOffset.LowPart = offsetp->LowPart & ~(buf_bufferSize-1);
915         while (1) {
916                 lock_ObtainWrite(&buf_globalLock);
917                 bp = buf_LockedFind(scp, &pageOffset);
918                 lock_ReleaseWrite(&buf_globalLock);
919                 if (bp) {
920                         /* lock it and break out */
921                         lock_ObtainMutex(&bp->mx);
922                         break;
923
924 #ifdef DISKCACHE95
925                         /* touch disk chunk to update LRU info */
926                         diskcache_Touch(bp->dcp);
927 #endif /* DISKCACHE95 */
928                 }
929                 
930                 /* otherwise, we have to create a page */
931                 code = buf_GetNewLocked(scp, &pageOffset, &bp);
932
933                 /* check if the buffer was created in a race condition branch.
934                  * If so, go around so we can hold a reference to it. 
935                  */
936                 if (code == CM_BUF_EXISTS) continue;
937                 
938                 /* something else went wrong */
939                 if (code != 0) return code;
940                 
941                 /* otherwise, we have a locked buffer that we just created */
942                 created = 1;
943                 break;
944         } /* big while loop */
945         
946         /* if we get here, we have a locked buffer that may have just been
947          * created, in which case it needs to be filled with data.
948          */
949         if (created) {
950                 /* load the page; freshly created pages should be idle */
951                 osi_assert(!(bp->flags & (CM_BUF_READING | CM_BUF_WRITING)));
952
953                 /* setup offset, event */
954 #ifndef DJGPP  /* doesn't seem to be used */
955                 bp->over.Offset = bp->offset.LowPart;
956                 bp->over.OffsetHigh = bp->offset.HighPart;
957 #endif /* !DJGPP */
958
959                 /* start the I/O; may drop lock */
960                 bp->flags |= CM_BUF_READING;
961                 code = (*cm_buf_opsp->Readp)(bp, buf_bufferSize, &tcount, NULL);
962
963 #ifdef DISKCACHE95
964                 code = diskcache_Get(&bp->fid, &bp->offset, bp->datap, buf_bufferSize, &bp->dataVersion, &tcount, &dcp);
965                 bp->dcp = dcp;    /* pointer to disk cache struct. */
966 #endif /* DISKCACHE95 */
967
968                 if (code != 0) {
969                         /* failure or queued */
970 #ifndef DJGPP   /* cm_bufRead always returns 0 */
971                         if (code != ERROR_IO_PENDING) {
972 #endif
973                                 bp->error = code;
974                                 bp->flags |= CM_BUF_ERROR;
975                                 bp->flags &= ~CM_BUF_READING;
976                                 if (bp->flags & CM_BUF_WAITING) {
977                                         bp->flags &= ~CM_BUF_WAITING;
978                                         osi_Wakeup((long) bp);
979                                 }
980                                 lock_ReleaseMutex(&bp->mx);
981                                 buf_Release(bp);
982                                 return code;
983 #ifndef DJGPP
984                         }
985 #endif
986                 } else {
987                         /* otherwise, I/O completed instantly and we're done, except
988                          * for padding the xfr out with 0s and checking for EOF
989                          */
990                         if (tcount < (unsigned long) buf_bufferSize) {
991                                 memset(bp->datap+tcount, 0, buf_bufferSize - tcount);
992                                 if (tcount == 0)
993                                         bp->flags |= CM_BUF_EOF;
994                         }
995                         bp->flags &= ~CM_BUF_READING;
996                         if (bp->flags & CM_BUF_WAITING) {
997                                 bp->flags &= ~CM_BUF_WAITING;
998                                 osi_Wakeup((long) bp);
999                         }
1000                 }
1001                         
1002         } /* if created */
1003         
1004         /* wait for reads, either that which we started above, or that someone
1005          * else started.  We don't care if we return a buffer being cleaned.
1006          */
1007         if (bp->flags & CM_BUF_READING)
1008                 buf_WaitIO(bp);
1009
1010         /* once it has been read once, we can unlock it and return it, still
1011          * with its refcount held.
1012          */
1013         lock_ReleaseMutex(&bp->mx);
1014         *bufpp = bp;
1015
1016         /* now remove from queue; will be put in at the head (farthest from
1017          * being recycled) when we're done in buf_Release.
1018          */
1019         lock_ObtainWrite(&buf_globalLock);
1020         if (bp->flags & CM_BUF_INLRU) {
1021                 if (buf_freeListEndp == bp)
1022                         buf_freeListEndp = (cm_buf_t *) osi_QPrev(&bp->q);
1023                 osi_QRemove((osi_queue_t **) &buf_freeListp, &bp->q);
1024                 bp->flags &= ~CM_BUF_INLRU;
1025         }
1026         lock_ReleaseWrite(&buf_globalLock);
1027
1028         osi_Log3(buf_logp, "buf_Get returning bp 0x%x for file 0x%x, offset 0x%x",
1029                 bp, (long) scp, offsetp->LowPart);
1030         return 0;
1031 }
1032
1033 /* count # of elements in the free list;
1034  * we don't bother doing the proper locking for accessing dataVersion or flags
1035  * since it is a pain, and this is really just an advisory call.  If you need
1036  * to do better at some point, rewrite this function.
1037  */
1038 long buf_CountFreeList(void)
1039 {
1040         long count;
1041         cm_buf_t *bufp;
1042
1043         count = 0;
1044         lock_ObtainRead(&buf_globalLock);
1045         for(bufp = buf_freeListp; bufp; bufp = (cm_buf_t *) osi_QNext(&bufp->q)) {
1046                 /* if the buffer doesn't have an identity, or if the buffer
1047                  * has been invalidate (by having its DV stomped upon), then
1048                  * count it as free, since it isn't really being utilized.
1049                  */
1050                 if (!(bufp->flags & CM_BUF_INHASH) || bufp->dataVersion <= 0)
1051                         count++;
1052         }
1053         lock_ReleaseRead(&buf_globalLock);
1054         return count;
1055 }
1056
1057 /* clean a buffer synchronously */
1058 void buf_CleanAsync(cm_buf_t *bp, cm_req_t *reqp)
1059 {
1060         lock_ObtainMutex(&bp->mx);
1061         buf_LockedCleanAsync(bp, reqp);
1062         lock_ReleaseMutex(&bp->mx);
1063 }
1064
1065 /* wait for a buffer's cleaning to finish */
1066 void buf_CleanWait(cm_buf_t *bp)
1067 {
1068         lock_ObtainMutex(&bp->mx);
1069         if (bp->flags & CM_BUF_WRITING) {
1070                 buf_WaitIO(bp);
1071         }
1072         lock_ReleaseMutex(&bp->mx);
1073 }
1074
1075 /* set the dirty flag on a buffer, and set associated write-ahead log,
1076  * if there is one.  Allow one to be added to a buffer, but not changed.
1077  *
1078  * The buffer must be locked before calling this routine.
1079  */
1080 void buf_SetDirty(cm_buf_t *bp)
1081 {
1082         osi_assert(bp->refCount > 0);
1083         
1084         osi_Log1(buf_logp, "buf_SetDirty 0x%x", bp);
1085
1086         /* set dirty bit */
1087         bp->flags |= CM_BUF_DIRTY;
1088
1089         /* and turn off EOF flag, since it has associated data now */
1090         bp->flags &= ~CM_BUF_EOF;
1091 }
1092
1093 /* clean all buffers, reset log pointers and invalidate all buffers.
1094  * Called with no locks held, and returns with same.
1095  *
1096  * This function is guaranteed to clean and remove the log ptr of all the
1097  * buffers that were dirty or had non-zero log ptrs before the call was
1098  * made.  That's sufficient to clean up any garbage left around by recovery,
1099  * which is all we're counting on this for; there may be newly created buffers
1100  * added while we're running, but that should be OK.
1101  *
1102  * In an environment where there are no transactions (artificially imposed, for
1103  * example, when switching the database to raw mode), this function is used to
1104  * make sure that all updates have been written to the disk.  In that case, we don't
1105  * really require that we forget the log association between pages and logs, but
1106  * it also doesn't hurt.  Since raw mode I/O goes through this buffer package, we don't
1107  * have to worry about invalidating data in the buffers.
1108  *
1109  * This function is used at the end of recovery as paranoia to get the recovered
1110  * database out to disk.  It removes all references to the recovery log and cleans
1111  * all buffers.
1112  */
1113 long buf_CleanAndReset(void)
1114 {
1115         long i;
1116         cm_buf_t *bp;
1117         cm_req_t req;
1118
1119         lock_ObtainWrite(&buf_globalLock);
1120         for(i=0; i<buf_hashSize; i++) {
1121                 for(bp = buf_hashTablepp[i]; bp; bp = bp->hashp) {
1122                         bp->refCount++;
1123                         lock_ReleaseWrite(&buf_globalLock);
1124                         
1125                         /* now no locks are held; clean buffer and go on */
1126                         cm_InitReq(&req);
1127                         buf_CleanAsync(bp, &req);
1128                         buf_CleanWait(bp);
1129                         
1130                         /* relock and release buffer */
1131                         lock_ObtainWrite(&buf_globalLock);
1132                         buf_LockedRelease(bp);
1133                 } /* over one bucket */
1134         }       /* for loop over all hash buckets */
1135         
1136         /* release locks */
1137         lock_ReleaseWrite(&buf_globalLock);
1138
1139         /* and we're done */
1140         return 0;
1141 }
1142
1143 /* called without global lock being held, reserves buffers for callers
1144  * that need more than one held (not locked) at once.
1145  */
1146 void buf_ReserveBuffers(long nbuffers)
1147 {
1148         lock_ObtainWrite(&buf_globalLock);
1149         while (1) {
1150                 if (buf_reservedBufs + nbuffers > buf_maxReservedBufs) {
1151                         buf_reserveWaiting = 1;
1152                         osi_Log1(buf_logp, "buf_ReserveBuffers waiting for %d bufs", nbuffers);
1153                         osi_SleepW((long) &buf_reservedBufs, &buf_globalLock);
1154                         lock_ObtainWrite(&buf_globalLock);
1155                 }
1156                 else {
1157                         buf_reservedBufs += nbuffers;
1158                         break;
1159                 }
1160         }
1161         lock_ReleaseWrite(&buf_globalLock);
1162 }
1163
1164 int buf_TryReserveBuffers(long nbuffers)
1165 {
1166         int code;
1167
1168         lock_ObtainWrite(&buf_globalLock);
1169         if (buf_reservedBufs + nbuffers > buf_maxReservedBufs) {
1170                 code = 0;
1171         }
1172         else {
1173                 buf_reservedBufs += nbuffers;
1174                 code = 1;
1175         }
1176         lock_ReleaseWrite(&buf_globalLock);
1177         return code;
1178 }
1179
1180 /* called without global lock held, releases reservation held by
1181  * buf_ReserveBuffers.
1182  */
1183 void buf_UnreserveBuffers(long nbuffers)
1184 {
1185         lock_ObtainWrite(&buf_globalLock);
1186         buf_reservedBufs -= nbuffers;
1187         if (buf_reserveWaiting) {
1188                 buf_reserveWaiting = 0;
1189                 osi_Wakeup((long) &buf_reservedBufs);
1190         }
1191         lock_ReleaseWrite(&buf_globalLock);
1192 }
1193
1194 /* truncate the buffers past sizep, zeroing out the page, if we don't
1195  * end on a page boundary.
1196  *
1197  * Requires cm_bufCreateLock to be write locked.
1198  */
1199 long buf_Truncate(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp,
1200         osi_hyper_t *sizep)
1201 {
1202         cm_buf_t *bufp;
1203         cm_buf_t *nbufp;                        /* next buffer, if didRelease */
1204         osi_hyper_t bufEnd;
1205         long code;
1206         long bufferPos;
1207         int didRelease;
1208         long i;
1209         
1210         /* assert that cm_bufCreateLock is held in write mode */
1211         lock_AssertWrite(&scp->bufCreateLock);
1212
1213         i = BUF_FILEHASH(&scp->fid);
1214
1215         lock_ObtainWrite(&buf_globalLock);
1216         bufp = buf_fileHashTablepp[i];
1217         if (bufp == NULL) {
1218                 lock_ReleaseWrite(&buf_globalLock);
1219                 return 0;
1220         }
1221
1222         bufp->refCount++;
1223         lock_ReleaseWrite(&buf_globalLock);
1224         for(; bufp; bufp = nbufp) {
1225                 didRelease = 0;
1226                 lock_ObtainMutex(&bufp->mx);
1227
1228                 bufEnd.HighPart = 0;
1229                 bufEnd.LowPart = buf_bufferSize;
1230                 bufEnd = LargeIntegerAdd(bufEnd, bufp->offset);
1231
1232                 if (cm_FidCmp(&bufp->fid, &scp->fid) == 0 &&
1233                         LargeIntegerLessThan(*sizep, bufEnd)) {
1234                         buf_WaitIO(bufp);
1235                 }
1236                 lock_ObtainMutex(&scp->mx);
1237         
1238                 /* make sure we have a callback (so we have the right value for
1239                  * the length), and wait for it to be safe to do a truncate.
1240                  */
1241                 code = cm_SyncOp(scp, bufp, userp, reqp, 0,
1242                                  CM_SCACHESYNC_NEEDCALLBACK
1243                                  | CM_SCACHESYNC_GETSTATUS
1244                                  | CM_SCACHESYNC_SETSIZE
1245                                  | CM_SCACHESYNC_BUFLOCKED);
1246                 /* if we succeeded in our locking, and this applies to the right
1247                  * file, and the truncate request overlaps the buffer either
1248                  * totally or partially, then do something.
1249                  */
1250                 if (code == 0 && cm_FidCmp(&bufp->fid, &scp->fid) == 0
1251                         && LargeIntegerLessThan(*sizep, bufEnd)) {
1252                         
1253                         lock_ObtainWrite(&buf_globalLock);
1254
1255                         /* destroy the buffer, turning off its dirty bit, if
1256                          * we're truncating the whole buffer.  Otherwise, set
1257                          * the dirty bit, and clear out the tail of the buffer
1258                          * if we just overlap some.
1259                          */
1260                         if (LargeIntegerLessThanOrEqualTo(*sizep, bufp->offset)) {
1261                                 /* truncating the entire page */
1262                                 bufp->flags &= ~CM_BUF_DIRTY;
1263                                 bufp->dataVersion = -1; /* known bad */
1264                                 bufp->dirtyCounter++;
1265                         }
1266                         else {
1267                                 /* don't set dirty, since dirty implies
1268                                  * currently up-to-date.  Don't need to do this,
1269                                  * since we'll update the length anyway.
1270                                  *
1271                                  * Zero out remainder of the page, in case we
1272                                  * seek and write past EOF, and make this data
1273                                  * visible again.
1274                                  */
1275                                 bufferPos = sizep->LowPart & (buf_bufferSize - 1);
1276                                 osi_assert(bufferPos != 0);
1277                                 memset(bufp->datap + bufferPos, 0,
1278                                         buf_bufferSize - bufferPos);
1279                         }
1280
1281                         lock_ReleaseWrite(&buf_globalLock);
1282
1283                 }
1284                 
1285                 lock_ReleaseMutex(&scp->mx);
1286                 lock_ReleaseMutex(&bufp->mx);
1287                 if (!didRelease) {
1288                         lock_ObtainWrite(&buf_globalLock);
1289                         nbufp = bufp->fileHashp;
1290                         if (nbufp) nbufp->refCount++;
1291                         buf_LockedRelease(bufp);
1292                         lock_ReleaseWrite(&buf_globalLock);
1293                 }
1294
1295                 /* bail out early if we fail */
1296                 if (code) {
1297                         /* at this point, nbufp is held; bufp has already been
1298                          * released.
1299                          */
1300                         if (nbufp) buf_Release(nbufp);
1301                         return code;
1302                 }
1303         }
1304         
1305         /* success */
1306         return 0;
1307 }
1308
1309 long buf_FlushCleanPages(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp)
1310 {
1311         long code;
1312         cm_buf_t *bp;           /* buffer we're hacking on */
1313         cm_buf_t *nbp;
1314         int didRelease;
1315         long i;
1316
1317         i = BUF_FILEHASH(&scp->fid);
1318
1319         code = 0;
1320         lock_ObtainWrite(&buf_globalLock);
1321         bp = buf_fileHashTablepp[i];
1322         if (bp) bp->refCount++;
1323         lock_ReleaseWrite(&buf_globalLock);
1324         for(; bp; bp = nbp) {
1325                 didRelease = 0; /* haven't released this buffer yet */
1326
1327                 /* clean buffer synchronously */
1328                 if (cm_FidCmp(&bp->fid, &scp->fid) == 0) {
1329                         lock_ObtainMutex(&bp->mx);
1330
1331                         /* start cleaning the buffer, and wait for it to finish */
1332                         buf_LockedCleanAsync(bp, reqp);
1333                         buf_WaitIO(bp);
1334                         lock_ReleaseMutex(&bp->mx);
1335
1336                         code = (*cm_buf_opsp->Stabilizep)(scp, userp, reqp);
1337                         if (code) goto skip;
1338
1339                         lock_ObtainWrite(&buf_globalLock);
1340                         /* actually, we only know that buffer is clean if ref
1341                          * count is 1, since we don't have buffer itself locked.
1342                          */
1343                         if (!(bp->flags & CM_BUF_DIRTY)) {
1344                                 if (bp->refCount == 1) {        /* bp is held above */
1345                                         buf_LockedRelease(bp);
1346                                         nbp = bp->fileHashp;
1347                                         if (nbp) nbp->refCount++;
1348                                         didRelease = 1;
1349                                         buf_Recycle(bp);
1350                                 }
1351                         }
1352                         lock_ReleaseWrite(&buf_globalLock);
1353
1354                         (*cm_buf_opsp->Unstabilizep)(scp, userp);
1355                 }
1356
1357 skip:
1358                 if (!didRelease) {
1359                         lock_ObtainWrite(&buf_globalLock);
1360                         if (nbp = bp->fileHashp) nbp->refCount++;
1361                         buf_LockedRelease(bp);
1362                         lock_ReleaseWrite(&buf_globalLock);
1363                 }
1364         }       /* for loop over a bunch of buffers */
1365         
1366         /* done */
1367         return code;
1368 }
1369
1370 long buf_CleanVnode(struct cm_scache *scp, cm_user_t *userp, cm_req_t *reqp)
1371 {
1372         long code;
1373         cm_buf_t *bp;           /* buffer we're hacking on */
1374         cm_buf_t *nbp;          /* next one */
1375         long i;
1376
1377         i = BUF_FILEHASH(&scp->fid);
1378
1379         code = 0;
1380         lock_ObtainWrite(&buf_globalLock);
1381         bp = buf_fileHashTablepp[i];
1382         if (bp) bp->refCount++;
1383         lock_ReleaseWrite(&buf_globalLock);
1384         for(; bp; bp = nbp) {
1385                 /* clean buffer synchronously */
1386                 if (cm_FidCmp(&bp->fid, &scp->fid) == 0) {
1387                         if (userp) {
1388                                 lock_ObtainMutex(&bp->mx);
1389                                 if (bp->userp) cm_ReleaseUser(bp->userp);
1390                                 bp->userp = userp;
1391                                 lock_ReleaseMutex(&bp->mx);
1392                                 cm_HoldUser(userp);
1393                         }
1394                         buf_CleanAsync(bp, reqp);
1395                         buf_CleanWait(bp);
1396                         lock_ObtainMutex(&bp->mx);
1397                         if (bp->flags & CM_BUF_ERROR) {
1398                                 if (code == 0 || code == -1) code = bp->error;
1399                                 if (code == 0) code = -1;
1400                         }
1401                         lock_ReleaseMutex(&bp->mx);
1402                 }
1403
1404                 lock_ObtainWrite(&buf_globalLock);
1405                 buf_LockedRelease(bp);
1406                 nbp = bp->fileHashp;
1407                 if (nbp) nbp->refCount++;
1408                 lock_ReleaseWrite(&buf_globalLock);
1409         }       /* for loop over a bunch of buffers */
1410         
1411         /* done */
1412         return code;
1413 }
1414
1415 /* dump the contents of the buf_hashTablepp. */
1416 int cm_DumpBufHashTable(FILE *outputFile, char *cookie)
1417 {
1418     int zilch;
1419     cm_buf_t *bp;
1420     char output[1024];
1421     int i;
1422   
1423     lock_ObtainRead(&buf_globalLock);
1424   
1425     sprintf(output, "%s - dumping buf_HashTable - buf_hashSize=%d\n", cookie, buf_hashSize);
1426     WriteFile(outputFile, output, strlen(output), &zilch, NULL);
1427   
1428     for (i = 0; i < buf_hashSize; i++)
1429     {
1430         for(bp = buf_hashTablepp[i]; bp; bp=bp->hashp) 
1431         {
1432             if (bp->refCount)
1433             {
1434                 sprintf(output, "%s bp=0x%08X, hash=%d, fid (cell=%d, volume=%d,"
1435                         "vnode=%d, unique=%d), size=%d refCount=%d\n", 
1436                         cookie, (void *)bp, i, bp->fid.cell, bp->fid.volume, 
1437                         bp->fid.vnode, bp->fid.unique, bp->size, bp->refCount);
1438                 WriteFile(outputFile, output, strlen(output), &zilch, NULL);
1439             }
1440         }
1441     }
1442   
1443     sprintf(output, "%s - Done dumping buf_HashTable.\n", cookie);
1444     WriteFile(outputFile, output, strlen(output), &zilch, NULL);
1445
1446     lock_ReleaseRead(&buf_globalLock);
1447     return 0;
1448 }
1449