/*
 * Copyright 2000, International Business Machines Corporation and others.
 * All Rights Reserved.
 *
 * This software has been released under the terms of the IBM Public
 * License.  For details, see the LICENSE file in the top-level source
 * directory or online at http://www.openafs.org/dl/license10.html
 */

/* Copyright (C) 1994 Cazamar Systems, Inc. */

#include <afsconfig.h>
#include <afs/param.h>
#include <roken.h>

#include <afs/stds.h>

#include <windows.h>
#include <osi.h>
#include <stdio.h>
#include <strsafe.h>
#include <math.h>
#include <hcrypto\md5.h>

#include "afsd.h"
#include "cm_memmap.h"

#ifdef DEBUG
#define TRACE_BUFFER 1
#endif

extern void afsi_log(char *pattern, ...);

/* This module implements the buffer package used by the local transaction
 * system (cm).  It is initialized by calling cm_Init, which calls buf_Init;
 * it must be initalized before any of its main routines are called.
 *
 * Each buffer is hashed into a hash table by file ID and offset, and if its
 * reference count is zero, it is also in a free list.
 *
 * There are two locks involved in buffer processing.  The global lock
 * buf_globalLock protects all of the global variables defined in this module,
 * the reference counts and hash pointers in the actual cm_buf_t structures,
 * and the LRU queue pointers in the buffer structures.
 *
 * The mutexes in the buffer structures protect the remaining fields in the
 * buffers, as well the data itself.
 *
 * The locking hierarchy here is this:
 *
 * - resv multiple simul. buffers reservation
 * - lock buffer I/O flags
 * - lock buffer's mutex
 * - lock buf_globalLock
 *
 */

/* global debugging log */
osi_log_t *buf_logp = NULL;

/* Global lock protecting hash tables and free lists */
osi_rwlock_t buf_globalLock;

/* Global lock used to limit the number of RDR Release
 * Extents requests to one. */
osi_mutex_t buf_rdrReleaseExtentsLock;

/* ptr to head of the free list (most recently used) and the
 * tail (the guy to remove first).  We use osi_Q* functions
 * to put stuff in buf_freeListp, and maintain the end
 * pointer manually
 */

/* a pointer to a list of all buffers, just so that we can find them
 * easily for debugging, and for the incr syncer.  Locked under
 * the global lock.
 */

/* defaults setup; these variables may be manually assigned into
 * before calling cm_Init, as a way of changing these defaults.
 */

/* callouts for reading and writing data, etc */
cm_buf_ops_t *cm_buf_opsp;

#ifdef DISKCACHE95
/* for experimental disk caching support in Win95 client */
cm_buf_t *buf_diskFreeListp;
cm_buf_t *buf_diskFreeListEndp;
cm_buf_t *buf_diskAllp;
extern int cm_diskCacheEnabled;
#endif /* DISKCACHE95 */

/* set this to 1 when we are terminating to prevent access attempts */
static int buf_ShutdownFlag = 0;

#ifdef DEBUG_REFCOUNT
void buf_HoldLockedDbg(cm_buf_t *bp, char *file, long line)
#else
void buf_HoldLocked(cm_buf_t *bp)
#endif
{
    afs_int32 refCount;

    osi_assertx(bp->magic == CM_BUF_MAGIC,"incorrect cm_buf_t magic");
    refCount = InterlockedIncrement(&bp->refCount);
#ifdef DEBUG_REFCOUNT
    osi_Log2(afsd_logp,"buf_HoldLocked bp 0x%p ref %d",bp, refCount);
    afsi_log("%s:%d buf_HoldLocked bp 0x%p, ref %d", file, line, bp, refCount);
#endif
}

/* hold a reference to an already held buffer */
#ifdef DEBUG_REFCOUNT
void buf_HoldDbg(cm_buf_t *bp, char *file, long line)
#else
void buf_Hold(cm_buf_t *bp)
#endif
{
    afs_int32 refCount;

    lock_ObtainRead(&buf_globalLock);
    osi_assertx(bp->magic == CM_BUF_MAGIC,"incorrect cm_buf_t magic");
    refCount = InterlockedIncrement(&bp->refCount);
#ifdef DEBUG_REFCOUNT
    osi_Log2(afsd_logp,"buf_Hold bp 0x%p ref %d",bp, refCount);
    afsi_log("%s:%d buf_Hold bp 0x%p, ref %d", file, line, bp, refCount);
#endif
    lock_ReleaseRead(&buf_globalLock);
}

/* code to drop reference count while holding buf_globalLock */
#ifdef DEBUG_REFCOUNT
void buf_ReleaseLockedDbg(cm_buf_t *bp, afs_uint32 writeLocked, char *file, long line)
#else
void buf_ReleaseLocked(cm_buf_t *bp, afs_uint32 writeLocked)
#endif
{
    afs_int32 refCount;

    if (writeLocked)
        lock_AssertWrite(&buf_globalLock);
    else
        lock_AssertRead(&buf_globalLock);

    /* ensure that we're in the LRU queue if our ref count is 0 */
    osi_assertx(bp->magic == CM_BUF_MAGIC,"incorrect cm_buf_t magic");

    refCount = InterlockedDecrement(&bp->refCount);
#ifdef DEBUG_REFCOUNT
    osi_Log3(afsd_logp,"buf_ReleaseLocked %s bp 0x%p ref %d",writeLocked?"write":"read", bp, refCount);
    afsi_log("%s:%d buf_ReleaseLocked %s bp 0x%p, ref %d", file, line, writeLocked?"write":"read", bp, refCount);
#endif
#ifdef DEBUG
    if (refCount < 0)
	osi_panic("buf refcount 0",__FILE__,__LINE__);;
#else
    osi_assertx(refCount >= 0, "cm_buf_t refCount == 0");
#endif
    if (refCount == 0) {
        /*
         * If we are read locked there could be a race condition
         * with buf_Find() so we must obtain a write lock and
         * double check that the refCount is actually zero
         * before we remove the buffer from the LRU queue.
         */
        if (!writeLocked)
            lock_ConvertRToW(&buf_globalLock);

        if (bp->refCount == 0 &&
            !(bp->qFlags & (CM_BUF_QINLRU|CM_BUF_QREDIR))) {
            osi_QAddH( (osi_queue_t **) &cm_data.buf_freeListp,
                       (osi_queue_t **) &cm_data.buf_freeListEndp,
                       &bp->q);
            _InterlockedOr(&bp->qFlags, CM_BUF_QINLRU);
            buf_IncrementFreeCount();
        }

        if (!writeLocked)
            lock_ConvertWToR(&buf_globalLock);
    }
}

/* release a buffer.  Buffer must be referenced, but unlocked. */
#ifdef DEBUG_REFCOUNT
void buf_ReleaseDbg(cm_buf_t *bp, char *file, long line)
#else
void buf_Release(cm_buf_t *bp)
#endif
{
    lock_ObtainRead(&buf_globalLock);
    buf_ReleaseLocked(bp, FALSE);
    lock_ReleaseRead(&buf_globalLock);
}

long
buf_Sync(int quitOnShutdown)
{
    cm_buf_t **bpp, *bp, *prevbp;
    afs_uint32 wasDirty = 0;
    cm_req_t req;

    /* go through all of the dirty buffers */
    lock_ObtainRead(&buf_globalLock);
    for (bpp = &cm_data.buf_dirtyListp, prevbp = NULL; bp = *bpp; ) {
        if (quitOnShutdown && buf_ShutdownFlag)
            break;

        /*
         * If the buffer is held be the redirector we must fetch
         * it back in order to determine whether or not it is in
         * fact dirty.
         */
        if (bp->qFlags & CM_BUF_QREDIR) {
            osi_Log1(buf_logp,"buf_Sync buffer held by redirector bp 0x%p", bp);

            /* Request single buffer from the redirector */
            buf_RDRShakeAnExtentFree(bp, &req);
        }

        lock_ReleaseRead(&buf_globalLock);
        /*
         * all dirty buffers are held when they are added to the
         * dirty list.  No need for an additional hold.
         */
        lock_ObtainMutex(&bp->mx);

        if ((bp->flags & CM_BUF_DIRTY)) {
            /* start cleaning the buffer; don't touch log pages since
             * the log code counts on knowing exactly who is writing
             * a log page at any given instant.
             *
             * only attempt to write the buffer if the volume might
             * be online.
             */
            afs_uint32 dirty;
            cm_volume_t * volp;

	    volp = cm_FindVolumeByFID(&bp->fid, bp->userp, &req);
            switch (cm_GetVolumeStatus(volp, bp->fid.volume)) {
            case vl_online:
            case vl_unknown:
                cm_InitReq(&req);
                req.flags |= CM_REQ_NORETRY;
                buf_CleanLocked(NULL, bp, &req, 0, &dirty);
                wasDirty |= dirty;
            }
            cm_PutVolume(volp);
        }

        /* the buffer may or may not have been dirty
        * and if dirty may or may not have been cleaned
        * successfully.  check the dirty flag again.
        */
        if (!(bp->flags & CM_BUF_DIRTY)) {
            /* remove the buffer from the dirty list */
            lock_ObtainWrite(&buf_globalLock);
#ifdef DEBUG_REFCOUNT
            if (bp->dirtyp == NULL && bp != cm_data.buf_dirtyListEndp) {
                osi_Log1(afsd_logp,"buf_Sync bp 0x%p list corruption",bp);
                afsi_log("buf_Sync bp 0x%p list corruption", bp);
            }
#endif
            *bpp = bp->dirtyp;
            bp->dirtyp = NULL;
            _InterlockedAnd(&bp->qFlags, ~CM_BUF_QINDL);
            if (cm_data.buf_dirtyListp == NULL)
                cm_data.buf_dirtyListEndp = NULL;
            else if (cm_data.buf_dirtyListEndp == bp)
                cm_data.buf_dirtyListEndp = prevbp;
            buf_ReleaseLocked(bp, TRUE);
            lock_ConvertWToR(&buf_globalLock);
        } else {
            if (buf_ShutdownFlag) {
                cm_cell_t *cellp;
                cm_volume_t *volp;
                char volstr[VL_MAXNAMELEN+12]="";
                char *ext = "";

		volp = cm_GetVolumeByFID(&bp->fid);
                if (volp) {
                    cellp = volp->cellp;
                    if (bp->fid.volume == volp->vol[RWVOL].ID)
                        ext = "";
                    else if (bp->fid.volume == volp->vol[ROVOL].ID)
                        ext = ".readonly";
                    else if (bp->fid.volume == volp->vol[BACKVOL].ID)
                        ext = ".backup";
                    else
                        ext = ".nomatch";
                    snprintf(volstr, sizeof(volstr), "%s%s", volp->namep, ext);
                } else {
                    cellp = cm_FindCellByID(bp->fid.cell, CM_FLAG_NOPROBE);
                    snprintf(volstr, sizeof(volstr), "%u", bp->fid.volume);
                }

                LogEvent(EVENTLOG_INFORMATION_TYPE, MSG_DIRTY_BUFFER_AT_SHUTDOWN,
                         cellp->name, volstr, bp->fid.vnode, bp->fid.unique,
                         bp->offset.QuadPart+bp->dirty_offset, bp->dirty_length);
            }

            /* advance the pointer so we don't loop forever */
            lock_ObtainRead(&buf_globalLock);
            bpp = &bp->dirtyp;
            prevbp = bp;
        }
        lock_ReleaseMutex(&bp->mx);
    }	/* for loop over a bunch of buffers */
    lock_ReleaseRead(&buf_globalLock);

    return wasDirty;
}

/* incremental sync daemon.  Writes all dirty buffers every 5000 ms */
static void *
buf_IncrSyncer(void * parm)
{
    long wasDirty = 0;
    long i;

    while (buf_ShutdownFlag == 0) {
        if (!wasDirty) {
	    i = SleepEx(5000, 1);
	    if (i != 0)
                continue;
	} else {
            Sleep(50);
        }

        wasDirty = buf_Sync(1);
    } /* whole daemon's while loop */

    pthread_exit(NULL);
    return NULL;
}

long
buf_ValidateBuffers(void)
{
    cm_buf_t * bp, *bpf, *bpa, *bpb;
    afs_uint64 countb = 0, countf = 0, counta = 0, countr = 0;

    if (cm_data.buf_freeListp == NULL && cm_data.buf_freeListEndp != NULL ||
         cm_data.buf_freeListp != NULL && cm_data.buf_freeListEndp == NULL) {
        afsi_log("cm_ValidateBuffers failure: inconsistent free list pointers");
        fprintf(stderr, "cm_ValidateBuffers failure: inconsistent free list pointers\n");
        return -9;
    }

    for (bp = cm_data.buf_freeListEndp; bp; bp=(cm_buf_t *) osi_QPrev(&bp->q)) {

	if ( bp < (cm_buf_t *)cm_data.bufHeaderBaseAddress ||
	     bp >= (cm_buf_t *)cm_data.bufDataBaseAddress) {
	    afsi_log("cm_ValidateBuffers failure: out of range cm_buf_t pointers");
	    fprintf(stderr, "cm_ValidateBuffers failure: out of range cm_buf_t pointers\n");
	    return -11;
	}

        if (bp->magic != CM_BUF_MAGIC) {
            afsi_log("cm_ValidateBuffers failure: bp->magic != CM_BUF_MAGIC");
            fprintf(stderr, "cm_ValidateBuffers failure: bp->magic != CM_BUF_MAGIC\n");
            return -1;
        }
        countb++;
        bpb = bp;

        if (countb > cm_data.buf_nbuffers) {
            afsi_log("cm_ValidateBuffers failure: countb > cm_data.buf_nbuffers");
            fprintf(stderr, "cm_ValidateBuffers failure: countb > cm_data.buf_nbuffers\n");
            return -6;
        }
    }

    for (bp = cm_data.buf_freeListp; bp; bp=(cm_buf_t *) osi_QNext(&bp->q)) {

	if ( bp < (cm_buf_t *)cm_data.bufHeaderBaseAddress ||
	     bp >= (cm_buf_t *)cm_data.bufDataBaseAddress) {
	    afsi_log("cm_ValidateBuffers failure: out of range cm_buf_t pointers");
	    fprintf(stderr, "cm_ValidateBuffers failure: out of range cm_buf_t pointers\n");
	    return -12;
	}

        if (bp->magic != CM_BUF_MAGIC) {
            afsi_log("cm_ValidateBuffers failure: bp->magic != CM_BUF_MAGIC");
            fprintf(stderr, "cm_ValidateBuffers failure: bp->magic != CM_BUF_MAGIC\n");
            return -2;
        }
        countf++;
        bpf = bp;

        if (countf > cm_data.buf_nbuffers) {
            afsi_log("cm_ValidateBuffers failure: countf > cm_data.buf_nbuffers");
            fprintf(stderr, "cm_ValidateBuffers failure: countf > cm_data.buf_nbuffers\n");
            return -7;
        }
    }

    for ( bp = cm_data.buf_redirListp; bp; bp = (cm_buf_t *) osi_QNext(&bp->q)) {

	if ( bp < (cm_buf_t *)cm_data.bufHeaderBaseAddress ||
	     bp >= (cm_buf_t *)cm_data.bufDataBaseAddress) {
	    afsi_log("cm_ValidateBuffers failure: out of range cm_buf_t pointers");
	    fprintf(stderr, "cm_ValidateBuffers failure: out of range cm_buf_t pointers\n");
	    return -13;
	}

        if (!(bp->qFlags & CM_BUF_QREDIR)) {
            afsi_log("CM_BUF_QREDIR not set on cm_buf_t in buf_redirListp");
            fprintf(stderr, "CM_BUF_QREDIR not set on cm_buf_t in buf_redirListp");
            return -9;
        }
        countr++;
        if (countr > cm_data.buf_nbuffers) {
            afsi_log("cm_ValidateBuffers failure: countr > cm_data.buf_nbuffers");
            fprintf(stderr, "cm_ValidateBuffers failure: countr > cm_data.buf_nbuffers\n");
            return -10;
        }
    }

    for (bp = cm_data.buf_allp; bp; bp=bp->allp) {

	if ( bp < (cm_buf_t *)cm_data.bufHeaderBaseAddress ||
	     bp >= (cm_buf_t *)cm_data.bufDataBaseAddress) {
	    afsi_log("cm_ValidateBuffers failure: out of range cm_buf_t pointers");
	    fprintf(stderr, "cm_ValidateBuffers failure: out of range cm_buf_t pointers\n");
	    return -14;
	}

        if (bp->magic != CM_BUF_MAGIC) {
            afsi_log("cm_ValidateBuffers failure: bp->magic != CM_BUF_MAGIC");
            fprintf(stderr, "cm_ValidateBuffers failure: bp->magic != CM_BUF_MAGIC\n");
            return -3;
        }

	if ( bp->datap < cm_data.bufDataBaseAddress ||
	     bp->datap >= cm_data.bufEndOfData) {
	    afsi_log("cm_ValidateBuffers failure: out of range data pointers");
	    fprintf(stderr, "cm_ValidateBuffers failure: out of range data pointers\n");
	    return -15;
	}

        counta++;
        bpa = bp;

        if (counta > cm_data.buf_nbuffers) {
            afsi_log("cm_ValidateBuffers failure: counta > cm_data.buf_nbuffers");
            fprintf(stderr, "cm_ValidateBuffers failure: counta > cm_data.buf_nbuffers\n");
            return -8;
        }
    }

    if (countb != countf) {
        afsi_log("cm_ValidateBuffers failure: countb != countf");
        fprintf(stderr, "cm_ValidateBuffers failure: countb != countf\n");
        return -4;
    }

    if (counta != cm_data.buf_nbuffers) {
        afsi_log("cm_ValidateBuffers failure: counta != cm_data.buf_nbuffers");
        fprintf(stderr, "cm_ValidateBuffers failure: counta != cm_data.buf_nbuffers\n");
        return -5;
    }

    return 0;
}

void buf_Shutdown(void)
{
    /* disable the buf_IncrSyncer() threads */
    buf_ShutdownFlag = 1;

    /* then force all dirty buffers to the file servers */
    buf_Sync(0);
}

/* initialize the buffer package; called with no locks
 * held during the initialization phase.
 */
long buf_Init(int newFile, cm_buf_ops_t *opsp, afs_uint64 nbuffers)
{
    static osi_once_t once;
    cm_buf_t *bp;
    pthread_t phandle;
    pthread_attr_t tattr;
    int pstatus;
    long i;
    char *data;

    if ( newFile ) {
        if (nbuffers)
            cm_data.buf_nbuffers = nbuffers;

        /* Have to be able to reserve a whole chunk */
        if (((cm_data.buf_nbuffers - 3) * cm_data.buf_blockSize) < cm_chunkSize)
            return CM_ERROR_TOOFEWBUFS;
    }

    /* recall for callouts */
    cm_buf_opsp = opsp;

    if (osi_Once(&once)) {
        /* initialize global locks */
        lock_InitializeRWLock(&buf_globalLock, "Global buffer lock", LOCK_HIERARCHY_BUF_GLOBAL);
        lock_InitializeMutex(&buf_rdrReleaseExtentsLock, "RDR Release Extents lock", LOCK_HIERARCHY_RDR_EXTENTS);

        if ( newFile ) {
            /* remember this for those who want to reset it */
            cm_data.buf_nOrigBuffers = cm_data.buf_nbuffers;

            /* lower hash size to a prime number */
	    cm_data.buf_hashSize = cm_NextHighestPowerOf2((afs_uint32)(cm_data.buf_nbuffers/7));

            /* create hash table */
            memset((void *)cm_data.buf_scacheHashTablepp, 0, cm_data.buf_hashSize * sizeof(cm_buf_t *));

            /* another hash table */
            memset((void *)cm_data.buf_fileHashTablepp, 0, cm_data.buf_hashSize * sizeof(cm_buf_t *));

            /* create buffer headers and put in free list */
            bp = cm_data.bufHeaderBaseAddress;
            data = cm_data.bufDataBaseAddress;
            cm_data.buf_allp = NULL;

            for (i=0; i<cm_data.buf_nbuffers; i++) {
                osi_assertx(bp >= cm_data.bufHeaderBaseAddress && bp < (cm_buf_t *)cm_data.bufDataBaseAddress,
                            "invalid cm_buf_t address");
                osi_assertx(data >= cm_data.bufDataBaseAddress && data < cm_data.bufEndOfData,
                            "invalid cm_buf_t data address");

                /* allocate and zero some storage */
                memset(bp, 0, sizeof(cm_buf_t));
                bp->magic = CM_BUF_MAGIC;
                /* thread on list of all buffers */
                bp->allp = cm_data.buf_allp;
                cm_data.buf_allp = bp;

                osi_QAddH( (osi_queue_t **) &cm_data.buf_freeListp,
                           (osi_queue_t **) &cm_data.buf_freeListEndp,
                           &bp->q);
                _InterlockedOr(&bp->qFlags, CM_BUF_QINLRU);
                buf_IncrementFreeCount();
                lock_InitializeMutex(&bp->mx, "Buffer mutex", LOCK_HIERARCHY_BUFFER);

                /* grab appropriate number of bytes from aligned zone */
                bp->datap = data;

                /* next */
                bp++;
                data += cm_data.buf_blockSize;
            }

            /* none reserved at first */
            cm_data.buf_reservedBufs = 0;

            /* just for safety's sake */
            cm_data.buf_maxReservedBufs = cm_data.buf_nbuffers - 3;
        } else {
            bp = cm_data.bufHeaderBaseAddress;
            data = cm_data.bufDataBaseAddress;

            lock_ObtainWrite(&buf_globalLock);
            for (i=0; i<cm_data.buf_nbuffers; i++) {
                lock_InitializeMutex(&bp->mx, "Buffer mutex", LOCK_HIERARCHY_BUFFER);
                bp->userp = NULL;
                bp->waitCount = 0;
                bp->waitRequests = 0;
                _InterlockedAnd(&bp->flags, ~CM_BUF_WAITING);
                bp->error = 0;
                if (bp->qFlags & CM_BUF_QREDIR) {
                    /*
                     * extent was not returned by the file system driver.
                     * clean up the mess.
                     */
                    buf_RemoveFromRedirQueue(NULL, bp);
                    bp->dataVersion = CM_BUF_VERSION_BAD;
                    bp->redirq.nextp = bp->redirq.prevp = NULL;
                    bp->redirLastAccess = 0;
                    bp->redirReleaseRequested = 0;
                    buf_ReleaseLocked(bp, TRUE);
                    buf_DecrementUsedCount();
                }
                bp++;
            }

            /*
             * There should be nothing left in cm_data.buf_redirListp
             * but double check just to be sure.
             */
            for ( bp = cm_data.buf_redirListp;
                  bp;
                  bp = cm_data.buf_redirListp)
            {
                /*
                 * extent was not returned by the file system driver.
                 * clean up the mess.
                 */
                buf_RemoveFromRedirQueue(NULL, bp);
                bp->dataVersion = CM_BUF_VERSION_BAD;
                bp->redirq.nextp = bp->redirq.prevp = NULL;
                bp->redirLastAccess = 0;
                bp->redirReleaseRequested = 0;
                buf_ReleaseLocked(bp, TRUE);
                buf_DecrementUsedCount();
            }
            lock_ReleaseWrite(&buf_globalLock);
        }

#ifdef TESTING
        buf_ValidateBufQueues();
#endif /* TESTING */

#ifdef TRACE_BUFFER
        /* init the buffer trace log */
        buf_logp = osi_LogCreate("buffer", 1000);
        osi_LogEnable(buf_logp);
#endif

        osi_EndOnce(&once);

        /* and create the incr-syncer */
        pthread_attr_init(&tattr);
        pthread_attr_setdetachstate(&tattr, PTHREAD_CREATE_DETACHED);

        pstatus = pthread_create(&phandle, &tattr, buf_IncrSyncer, 0);
        osi_assertx(pstatus == 0, "buf: can't create incremental sync proc");

        pthread_attr_destroy(&tattr);
    }

#ifdef TESTING
    buf_ValidateBufQueues();
#endif /* TESTING */
    return 0;
}

/* add nbuffers to the buffer pool, if possible.
 * Called with no locks held.
 */
long buf_AddBuffers(afs_uint64 nbuffers)
{
    /* The size of a virtual cache cannot be changed after it has
     * been created.  Subsequent calls to MapViewofFile() with
     * an existing mapping object name would not allow the
     * object to be resized.  Return failure immediately.
     *
     * A similar problem now occurs with the persistent cache
     * given that the memory mapped file now contains a complex
     * data structure.
     */
    afsi_log("request to add %d buffers to the existing cache of size %d denied",
              nbuffers, cm_data.buf_nbuffers);

    return CM_ERROR_INVAL;
}

/* interface to set the number of buffers to an exact figure.
 * Called with no locks held.
 */
long buf_SetNBuffers(afs_uint64 nbuffers)
{
    if (nbuffers < 10)
        return CM_ERROR_INVAL;
    if (nbuffers == cm_data.buf_nbuffers)
        return 0;
    else if (nbuffers > cm_data.buf_nbuffers)
        return buf_AddBuffers(nbuffers - cm_data.buf_nbuffers);
    else
        return CM_ERROR_INVAL;
}

/* wait for reading or writing to clear; called with write-locked
 * buffer and unlocked scp and returns with locked buffer.
 */
void buf_WaitIO(cm_scache_t * scp, cm_buf_t *bp)
{
    int release = 0;

    if (scp)
        osi_assertx(scp->magic == CM_SCACHE_MAGIC, "invalid cm_scache_t magic");
    osi_assertx(bp->magic == CM_BUF_MAGIC, "invalid cm_buf_t magic");

    while (1) {
        /* if no IO is happening, we're done */
        if (!(bp->flags & (CM_BUF_READING | CM_BUF_WRITING)))
            break;

        /* otherwise I/O is happening, but some other thread is waiting for
         * the I/O already.  Wait for that guy to figure out what happened,
         * and then check again.
         */
        if ( bp->flags & CM_BUF_WAITING ) {
            bp->waitCount++;
            bp->waitRequests++;
            osi_Log1(buf_logp, "buf_WaitIO CM_BUF_WAITING already set for 0x%p", bp);
        } else {
            osi_Log1(buf_logp, "buf_WaitIO CM_BUF_WAITING set for 0x%p", bp);
            _InterlockedOr(&bp->flags, CM_BUF_WAITING);
            bp->waitCount = bp->waitRequests = 1;
        }
        osi_SleepM((LONG_PTR)bp, &bp->mx);

	cm_UpdateServerPriority();

        lock_ObtainMutex(&bp->mx);
        osi_Log1(buf_logp, "buf_WaitIO conflict wait done for 0x%p", bp);
        bp->waitCount--;
        if (bp->waitCount == 0) {
            osi_Log1(buf_logp, "buf_WaitIO CM_BUF_WAITING reset for 0x%p", bp);
            _InterlockedAnd(&bp->flags, ~CM_BUF_WAITING);
            bp->waitRequests = 0;
        }

        if ( !scp ) {
            if (scp = cm_FindSCache(&bp->fid))
		 release = 1;
        }
        if ( scp ) {
            lock_ObtainRead(&scp->rw);
            if (!osi_QIsEmpty(&scp->waitQueueH)) {
                osi_Log1(buf_logp, "buf_WaitIO waking scp 0x%p", scp);
                osi_Wakeup((LONG_PTR)&scp->flags);
            }
	    lock_ReleaseRead(&scp->rw);
        }
    }

    /* if we get here, the IO is done, but we may have to wakeup people waiting for
     * the I/O to complete.  Do so.
     */
    if (bp->flags & CM_BUF_WAITING) {
        osi_Log1(buf_logp, "buf_WaitIO Waking bp 0x%p", bp);
        osi_Wakeup((LONG_PTR) bp);
    }
    osi_Log1(buf_logp, "WaitIO finished wait for bp 0x%p", bp);

    if (scp && release)
	cm_ReleaseSCache(scp);
}

/* find a buffer, if any, for a particular file ID and offset.  Assumes
 * that buf_globalLock is write locked when called.
 */
cm_buf_t *buf_FindLocked(struct cm_fid *fidp, osi_hyper_t *offsetp)
{
    afs_uint32 i;
    cm_buf_t *bp;

    lock_AssertAny(&buf_globalLock);

    i = BUF_HASH(fidp, offsetp);
    for(bp = cm_data.buf_scacheHashTablepp[i]; bp; bp=bp->hashp) {
        if (cm_FidCmp(fidp, &bp->fid) == 0
             && offsetp->LowPart == bp->offset.LowPart
             && offsetp->HighPart == bp->offset.HighPart) {
            buf_HoldLocked(bp);
            break;
        }
    }

    /* return whatever we found, if anything */
    return bp;
}

/* find a buffer with offset *offsetp for vnode *scp.  Called
 * with no locks held.
 */
cm_buf_t *buf_Find(struct cm_fid *fidp, osi_hyper_t *offsetp)
{
    cm_buf_t *bp;

    lock_ObtainRead(&buf_globalLock);
    bp = buf_FindLocked(fidp, offsetp);
    lock_ReleaseRead(&buf_globalLock);

    return bp;
}

/* find a buffer, if any, for a particular file ID and offset.  Assumes
 * that buf_globalLock is write locked when called.  Uses the all buffer
 * list.
 */
cm_buf_t *buf_FindAllLocked(struct cm_fid *fidp, osi_hyper_t *offsetp, afs_uint32 flags)
{
    cm_buf_t *bp;

    if (flags == 0) {
        for(bp = cm_data.buf_allp; bp; bp=bp->allp) {
            if (cm_FidCmp(fidp, &bp->fid) == 0
                 && offsetp->LowPart == bp->offset.LowPart
                 && offsetp->HighPart == bp->offset.HighPart) {
                buf_HoldLocked(bp);
                break;
            }
        }
    } else {
        for(bp = cm_data.buf_allp; bp; bp=bp->allp) {
            if (cm_FidCmp(fidp, &bp->fid) == 0) {
                char * fileOffset;

                fileOffset = offsetp->QuadPart + cm_data.baseAddress;
                if (fileOffset == bp->datap) {
                    buf_HoldLocked(bp);
                    break;
                }
            }
        }
    }
    /* return whatever we found, if anything */
    return bp;
}

/* find a buffer with offset *offsetp for vnode *scp.  Called
 * with no locks held.  Use the all buffer list.
 */
cm_buf_t *buf_FindAll(struct cm_fid *fidp, osi_hyper_t *offsetp, afs_uint32 flags)
{
    cm_buf_t *bp;

    lock_ObtainRead(&buf_globalLock);
    bp = buf_FindAllLocked(fidp, offsetp, flags);
    lock_ReleaseRead(&buf_globalLock);

    return bp;
}

/* start cleaning I/O on this buffer.  Buffer must be write locked, and is returned
 * write-locked.
 *
 * Makes sure that there's only one person writing this block
 * at any given time, and also ensures that the log is forced sufficiently far,
 * if this buffer contains logged data.
 *
 * Returns non-zero if the buffer was dirty.
 *
 * 'scp' may or may not be NULL.  If it is not NULL, the FID for both cm_scache_t
 * and cm_buf_t must match.
 */
afs_uint32 buf_CleanLocked(cm_scache_t *scp, cm_buf_t *bp, cm_req_t *reqp,
                                afs_uint32 flags, afs_uint32 *pisdirty)
{
    afs_uint32 code = 0;
    afs_uint32 isdirty = 0;
    osi_hyper_t offset;
    int release_scp = 0;

    osi_assertx(bp->magic == CM_BUF_MAGIC, "invalid cm_buf_t magic");
    osi_assertx(scp == NULL || cm_FidCmp(&scp->fid, &bp->fid) == 0, "scp fid != bp fid");

    /*
     * If the matching cm_scache_t was not provided as a parameter
     * we must either find one or allocate a new one.  It is possible
     * that the cm_scache_t was recycled out of the cache even though
     * a cm_buf_t with the same FID is in the cache.
     */
    if (scp == NULL &&
        cm_GetSCache(&bp->fid, NULL, &scp,
                     bp->userp ? bp->userp : cm_rootUserp,
                     reqp) == 0)
    {
        release_scp = 1;

	if (scp->flags & CM_SCACHEFLAG_DELETED) {
	    code = CM_ERROR_NOSUCHFILE;
	} else {
	    lock_ObtainWrite(&scp->rw);
	    code = cm_SyncOp(scp, NULL, bp->userp ? bp->userp : cm_rootUserp, reqp, 0,
			    CM_SCACHESYNC_NEEDCALLBACK | CM_SCACHESYNC_GETSTATUS);
	    if (code == 0) {
		cm_SyncOpDone(scp, NULL, CM_SCACHESYNC_NEEDCALLBACK | CM_SCACHESYNC_GETSTATUS);
	    }
	    lock_ReleaseWrite(&scp->rw);
        }
    }

    if (scp && (scp->flags & CM_SCACHEFLAG_DELETED)) {
        _InterlockedAnd(&bp->flags, ~CM_BUF_DIRTY);
        _InterlockedOr(&bp->flags, CM_BUF_ERROR);
        bp->dirty_length = 0;
        bp->error = code;
        bp->dataVersion = CM_BUF_VERSION_BAD;
        bp->dirtyCounter++;
        buf_DecrementUsedCount();
    }

    while ((bp->flags & CM_BUF_DIRTY) == CM_BUF_DIRTY) {
        isdirty = 1;
        lock_ReleaseMutex(&bp->mx);

        if (!scp) {
            /*
             * If we didn't find a cm_scache_t object for bp->fid it means
             * that we no longer have that FID in the cache.  It does not
             * mean that the object does not exist in the cell.  That may
             * in fact be the case but we don't know that until we attempt
             * a FetchStatus on the FID.
             */
            osi_Log1(buf_logp, "buf_CleanLocked unable to start I/O - scp not found buf 0x%p", bp);
            code = CM_ERROR_NOSUCHFILE;
        } else {
            osi_Log2(buf_logp, "buf_CleanLocked starts I/O on scp 0x%p buf 0x%p", scp, bp);

            offset = bp->offset;
            LargeIntegerAdd(offset, ConvertLongToLargeInteger(bp->dirty_offset));
            /*
             * Only specify the dirty length of the current buffer in the call
             * to cm_BufWrite().  It is the responsibility of cm_BufWrite()
             * to determine if it is appropriate to fill a full chunk of data
             * when storing to the file server.
             */
            code = (*cm_buf_opsp->Writep)(scp, &offset, bp->dirty_length, flags,
                                          bp->userp ? bp->userp : cm_rootUserp, reqp);
            osi_Log3(buf_logp, "buf_CleanLocked I/O on scp 0x%p buf 0x%p, done=%d", scp, bp, code);
        }
        lock_ObtainMutex(&bp->mx);
	/* if the Write routine returns No Such File, clear the dirty flag
	 * because we aren't going to be able to write this data to the file
	 * server.
	 */
	if (code == CM_ERROR_NOSUCHFILE || code == CM_ERROR_BADFD || code == CM_ERROR_NOACCESS ||
            code == CM_ERROR_QUOTA || code == CM_ERROR_SPACE || code == CM_ERROR_TOOBIG ||
            code == CM_ERROR_READONLY || code == CM_ERROR_NOSUCHPATH || code == EIO ||
            code == CM_ERROR_INVAL || code == CM_ERROR_INVAL_NET_RESP || code == CM_ERROR_UNKNOWN){
	    _InterlockedAnd(&bp->flags, ~CM_BUF_DIRTY);
	    _InterlockedOr(&bp->flags, CM_BUF_ERROR);
            bp->dirty_length = 0;
	    bp->error = code;
	    bp->dataVersion = CM_BUF_VERSION_BAD;
	    bp->dirtyCounter++;
            buf_DecrementUsedCount();
            break;
	}

#ifdef DISKCACHE95
        /* Disk cache support */
        /* write buffer to disk cache (synchronous for now) */
        diskcache_Update(bp->dcp, bp->datap, cm_data.buf_blockSize, bp->dataVersion);
#endif /* DISKCACHE95 */

	/* if we get here and retries are not permitted
	 * then we need to exit this loop regardless of
	 * whether or not we were able to clear the dirty bit
	 */
	if (reqp->flags & CM_REQ_NORETRY)
	    break;

        /*
         * Ditto if the hardDeadTimeout or idleTimeout was reached
         * Or a fatal error is received.
         */
        if (code == CM_ERROR_TIMEDOUT || code == CM_ERROR_ALLDOWN ||
            code == CM_ERROR_ALLBUSY || code == CM_ERROR_ALLOFFLINE ||
            code == CM_ERROR_CLOCKSKEW || code == CM_ERROR_INVAL_NET_RESP ||
            code == CM_ERROR_INVAL || code == CM_ERROR_UNKNOWN || code == EIO) {
            break;
        }
    }

    if (release_scp)
        cm_ReleaseSCache(scp);

    /* if someone was waiting for the I/O that just completed or failed,
     * wake them up.
     */
    if (bp->flags & CM_BUF_WAITING) {
        /* turn off flags and wakeup users */
        osi_Log1(buf_logp, "buf_WaitIO Waking bp 0x%p", bp);
        osi_Wakeup((LONG_PTR) bp);
    }

    if (pisdirty)
        *pisdirty = isdirty;

    return code;
}

/* Called with a zero-ref count buffer and with the buf_globalLock write locked.
 * recycles the buffer, and leaves it ready for reuse with a ref count of 0.
 * The buffer must already be clean, and no I/O should be happening to it.
 */
void buf_Recycle(cm_buf_t *bp)
{
    afs_uint32 i;
    cm_buf_t **lbpp;
    cm_buf_t *tbp;
    cm_buf_t *prevBp, *nextBp;

    osi_assertx(bp->magic == CM_BUF_MAGIC, "invalid cm_buf_t magic");

    osi_assertx(!(bp->qFlags & CM_BUF_QREDIR), "can't recycle redir held buffers");

    /* if we get here, we know that the buffer still has a 0 ref count,
     * and that it is clean and has no currently pending I/O.  This is
     * the dude to return.
     * Remember that as long as the ref count is 0, we know that we won't
     * have any lock conflicts, so we can grab the buffer lock out of
     * order in the locking hierarchy.
     */
    osi_Log3( buf_logp, "buf_Recycle recycles 0x%p, off 0x%x:%08x",
              bp, bp->offset.HighPart, bp->offset.LowPart);

    osi_assertx(bp->refCount == 0, "cm_buf_t refcount != 0");
    osi_assertx(!(bp->flags & (CM_BUF_READING | CM_BUF_WRITING | CM_BUF_DIRTY)),
                "incorrect cm_buf_t flags");
    lock_AssertWrite(&buf_globalLock);

    if (bp->qFlags & CM_BUF_QINHASH) {
        /* Remove from hash */

        i = BUF_HASH(&bp->fid, &bp->offset);
        lbpp = &(cm_data.buf_scacheHashTablepp[i]);
        for(tbp = *lbpp; tbp; lbpp = &tbp->hashp, tbp = tbp->hashp) {
            if (tbp == bp)
                break;
        }

        /* we better find it */
        osi_assertx(tbp != NULL, "buf_Recycle: hash table screwup");

        *lbpp = bp->hashp;	/* hash out */
        bp->hashp = NULL;

        /* Remove from file hash */

        i = BUF_FILEHASH(&bp->fid);
        prevBp = bp->fileHashBackp;
        bp->fileHashBackp = NULL;
        nextBp = bp->fileHashp;
        bp->fileHashp = NULL;
        if (prevBp)
            prevBp->fileHashp = nextBp;
        else
            cm_data.buf_fileHashTablepp[i] = nextBp;
        if (nextBp)
            nextBp->fileHashBackp = prevBp;

        _InterlockedAnd(&bp->qFlags, ~CM_BUF_QINHASH);
    }

    /* make the fid unrecognizable */
    memset(&bp->fid, 0, sizeof(cm_fid_t));

    /* clean up junk flags */
    _InterlockedAnd(&bp->flags, ~(CM_BUF_EOF | CM_BUF_ERROR));
    bp->dataVersion = CM_BUF_VERSION_BAD;	/* unknown so far */
}


/*
 * buf_RDRShakeAnExtentFree
 * called with buf_globalLock read locked
 */
afs_uint32
buf_RDRShakeAnExtentFree(cm_buf_t *rbp, cm_req_t *reqp)
{
    afs_uint32 code = 0;
    LARGE_INTEGER heldExtents = {0,0};
    AFSFileExtentCB extentList[1];
    DWORD extentCount = 0;
    BOOL locked = FALSE;

    if (!(rbp->qFlags & CM_BUF_QREDIR))
        return 0;

    lock_ReleaseRead(&buf_globalLock);

    if (!lock_TryMutex(&buf_rdrReleaseExtentsLock)) {
        osi_Log0(afsd_logp, "Waiting for prior RDR_RequestExtentRelease request to complete");
        if (reqp->flags & CM_REQ_NORETRY) {
            code = CM_ERROR_WOULDBLOCK;
            goto done;
        }

        lock_ObtainMutex(&buf_rdrReleaseExtentsLock);
    }

    extentList[0].Flags = 0;
    extentList[0].Length = cm_data.blockSize;
    extentList[0].FileOffset.QuadPart = rbp->offset.QuadPart;
    extentList[0].CacheOffset.QuadPart = rbp->datap - cm_data.baseAddress;
    extentCount = 1;

    code = RDR_RequestExtentRelease(&rbp->fid, heldExtents, extentCount, extentList);

    lock_ReleaseMutex(&buf_rdrReleaseExtentsLock);

  done:
    lock_ObtainRead(&buf_globalLock);
    return code;
}

/*
 * buf_RDRShakeFileExtentsFree
 * requests all extents held by the redirector to be returned for
 * the specified cm_scache_t.  This function is called with no
 * locks held.
 */
afs_uint32
buf_RDRShakeFileExtentsFree(cm_scache_t *rscp, cm_req_t *reqp)
{
    afs_uint32 code = 0;
    afs_uint64 n_redir = 0;

    if (!lock_TryMutex(&buf_rdrReleaseExtentsLock)) {
        osi_Log0(afsd_logp, "Waiting for prior RDR_RequestExtentRelease request to complete");
        if (reqp->flags & CM_REQ_NORETRY)
            return CM_ERROR_WOULDBLOCK;

        lock_ObtainMutex(&buf_rdrReleaseExtentsLock);
    }

    for ( code = CM_ERROR_RETRY; code == CM_ERROR_RETRY; ) {
        LARGE_INTEGER heldExtents = {0,0};
        AFSFileExtentCB extentList[1024];
        DWORD extentCount = 0;
        cm_buf_t *srbp;
        time_t now;

        /* only retry if a call to RDR_RequestExtentRelease says to */
        code = 0;
        lock_ObtainWrite(&buf_globalLock);

        if (rscp->redirBufCount == 0)
        {
            lock_ReleaseWrite(&buf_globalLock);
            break;
        }

        time(&now);
        for ( srbp = redirq_to_cm_buf_t(rscp->redirQueueT);
              srbp;
              srbp = ((code == 0 && extentCount == 0) ? redirq_to_cm_buf_t(rscp->redirQueueT) :
                       redirq_to_cm_buf_t(osi_QPrev(&srbp->redirq))))
        {
            extentList[extentCount].Flags = 0;
            extentList[extentCount].Length = cm_data.blockSize;
            extentList[extentCount].FileOffset.QuadPart = srbp->offset.QuadPart;
            extentList[extentCount].CacheOffset.QuadPart = srbp->datap - cm_data.baseAddress;
            srbp->redirReleaseRequested = now;
            extentCount++;

            if (extentCount == 1024) {
                lock_ReleaseWrite(&buf_globalLock);
                heldExtents.QuadPart = cm_data.buf_redirCount;
                code = RDR_RequestExtentRelease(&rscp->fid, heldExtents, extentCount, extentList);
                if (code) {
                    if (code == CM_ERROR_RETRY) {
                        /*
                         * The redirector either is not holding the extents or cannot let them
                         * go because they are otherwise in use.  At the moment, do nothing.
                         */
                    } else
                        break;
                }
                extentCount = 0;
                lock_ObtainWrite(&buf_globalLock);
            }
        }
        lock_ReleaseWrite(&buf_globalLock);

        if (code == 0 && extentCount > 0) {
            heldExtents.QuadPart = cm_data.buf_redirCount;
            code = RDR_RequestExtentRelease(&rscp->fid, heldExtents, extentCount, extentList);
        }

        if ((code == CM_ERROR_RETRY) && (reqp->flags & CM_REQ_NORETRY)) {
            code = CM_ERROR_WOULDBLOCK;
            break;
        }
    }
    lock_ReleaseMutex(&buf_rdrReleaseExtentsLock);
    return code;
}

afs_uint32
buf_RDRShakeSomeExtentsFree(cm_req_t *reqp, afs_uint32 oneFid, afs_uint32 minage)
{
    afs_uint32 code = 0;

    if (!lock_TryMutex(&buf_rdrReleaseExtentsLock)) {
        if (reqp->flags & CM_REQ_NORETRY)
            return CM_ERROR_WOULDBLOCK;

        osi_Log0(afsd_logp, "Waiting for prior RDR_RequestExtentRelease request to complete");
        lock_ObtainMutex(&buf_rdrReleaseExtentsLock);
    }

    for ( code = CM_ERROR_RETRY; code == CM_ERROR_RETRY; ) {
        LARGE_INTEGER heldExtents;
        AFSFileExtentCB extentList[1024];
        DWORD extentCount = 0;
        cm_buf_t *rbp, *srbp;
        cm_scache_t *rscp;
        time_t now;
        BOOL locked = FALSE;

        /* only retry if a call to RDR_RequestExtentRelease says to */
        code = 0;
        lock_ObtainWrite(&buf_globalLock);
        locked = TRUE;

        for ( rbp = cm_data.buf_redirListEndp;
              code == 0 && rbp && (!oneFid || extentCount == 0);
              rbp = (cm_buf_t *) osi_QPrev(&rbp->q))
        {
            if (!oneFid)
                extentCount = 0;

            if (rbp->redirLastAccess >= rbp->redirReleaseRequested) {
                rscp = cm_FindSCache(&rbp->fid);
                if (!rscp)
                    continue;

                time(&now);
                for ( srbp = redirq_to_cm_buf_t(rscp->redirQueueT);
                      srbp && extentCount < 1024;
                      srbp = redirq_to_cm_buf_t(osi_QPrev(&srbp->redirq)))
                {
                    /*
                     * Do not request a release if we have already done so
                     * or if the extent was delivered to windows less than
                     * 'minage' seconds ago.
                     */
                    if (srbp->redirLastAccess >= srbp->redirReleaseRequested &&
                         srbp->redirLastAccess < now - minage) {
                        extentList[extentCount].Flags = 0;
                        extentList[extentCount].Length = cm_data.blockSize;
                        extentList[extentCount].FileOffset.QuadPart = srbp->offset.QuadPart;
                        extentList[extentCount].CacheOffset.QuadPart = srbp->datap - cm_data.baseAddress;
                        srbp->redirReleaseRequested = now;
                        extentCount++;
                    }
                }
                cm_ReleaseSCache(rscp);
            }

            if ( !oneFid && extentCount > 0) {
                if (locked) {
                    lock_ReleaseWrite(&buf_globalLock);
                    locked = FALSE;
                }
                heldExtents.QuadPart = cm_data.buf_redirCount;
                code = RDR_RequestExtentRelease(&rbp->fid, heldExtents, extentCount, extentList);
            }
            if (!locked) {
                lock_ObtainWrite(&buf_globalLock);
                locked = TRUE;
            }
        }
        if (locked)
            lock_ReleaseWrite(&buf_globalLock);
        if (code == 0) {
            if (oneFid) {
                heldExtents.QuadPart = cm_data.buf_redirCount;
                if (rbp && extentCount)
                    code = RDR_RequestExtentRelease(&rbp->fid, heldExtents, extentCount, extentList);
                else
                    code = RDR_RequestExtentRelease(NULL, heldExtents, 1024, NULL);
            } else {
                code = 0;
            }
        }

        if ((code == CM_ERROR_RETRY) && (reqp->flags & CM_REQ_NORETRY)) {
            code = CM_ERROR_WOULDBLOCK;
            break;
        }
    }
    lock_ReleaseMutex(&buf_rdrReleaseExtentsLock);
    return code;
}

/* returns 0 if the buffer does not exist, and non-0 if it does */
static long
buf_ExistsLocked(struct cm_scache *scp, osi_hyper_t *offsetp)
{
    cm_buf_t *bp;

    if (bp = buf_FindLocked(&scp->fid, offsetp)) {
        /* Do not call buf_ReleaseLocked() because we
         * do not want to allow the buffer to be added
         * to the free list.
         */
        afs_int32 refCount = InterlockedDecrement(&bp->refCount);
#ifdef DEBUG_REFCOUNT
        osi_Log2(afsd_logp,"buf_ExistsLocked bp 0x%p ref %d", bp, refCount);
        afsi_log("%s:%d buf_ExistsLocked bp 0x%p, ref %d", __FILE__, __LINE__, bp, refCount);
#endif
        return CM_BUF_EXISTS;
    }

    return 0;
}

/* recycle a buffer, removing it from the free list, hashing in its new identity
 * and returning it write-locked so that no one can use it.  Called without
 * any locks held, and can return an error if it loses the race condition and
 * finds that someone else created the desired buffer.
 *
 * If success is returned, the buffer is returned write-locked.
 *
 * May be called with null scp and offsetp, if we're just trying to reclaim some
 * space from the buffer pool.  In that case, the buffer will be returned
 * without being hashed into the hash table.
 */
long buf_GetNewLocked(struct cm_scache *scp, osi_hyper_t *offsetp, cm_req_t *reqp,
                      afs_uint32 flags, cm_buf_t **bufpp)
{
    cm_buf_t *bp;	/* buffer we're dealing with */
    cm_buf_t *nextBp;	/* next buffer in file hash chain */
    afs_uint32 i;	/* temp */
    afs_uint64 n_bufs, n_nonzero, n_busy, n_dirty, n_own, n_redir;
    int bufCreateLocked = !!(flags & BUF_GET_FLAG_BUFCREATE_LOCKED);

#ifdef TESTING
    buf_ValidateBufQueues();
#endif /* TESTING */

    while(1) {
      retry:
        n_bufs = 0;
        n_nonzero = 0;
        n_own = 0;
        n_busy = 0;
        n_dirty = 0;
        n_redir = 0;

        if (!bufCreateLocked)
            lock_ObtainRead(&scp->bufCreateLock);
        lock_ObtainWrite(&buf_globalLock);
        /* check to see if we lost the race */
        if (buf_ExistsLocked(scp, offsetp)) {
            lock_ReleaseWrite(&buf_globalLock);
            if (!bufCreateLocked)
                lock_ReleaseRead(&scp->bufCreateLock);
            return CM_BUF_EXISTS;
        }

	/* does this fix the problem below?  it's a simple solution. */
	if (!cm_data.buf_freeListEndp)
	{
	    lock_ReleaseWrite(&buf_globalLock);
            if (!bufCreateLocked)
                lock_ReleaseRead(&scp->bufCreateLock);

            if ( RDR_Initialized )
                goto rdr_release;

	    osi_Log0(afsd_logp, "buf_GetNewLocked: Free Buffer List is empty - sleeping 200ms");
	    Sleep(200);
	    goto retry;
	}

        /* for debugging, assert free list isn't empty, although we
         * really should try waiting for a running tranasction to finish
         * instead of this; or better, we should have a transaction
         * throttler prevent us from entering this situation.
         */
        osi_assertx(cm_data.buf_freeListEndp != NULL, "buf_GetNewLocked: no free buffers");

        /* look at all buffers in free list, some of which may temp.
         * have high refcounts and which then should be skipped,
         * starting cleaning I/O for those which are dirty.  If we find
         * a clean buffer, we rehash it, lock it and return it.
         */
        for (bp = cm_data.buf_freeListEndp; bp; bp=(cm_buf_t *) osi_QPrev(&bp->q)) {
            int cleaned = 0;

            n_bufs++;

          retry_2:
            /* check to see if it really has zero ref count.  This
             * code can bump refcounts, at least, so it may not be
             * zero.
             */
            if (bp->refCount > 0) {
                n_nonzero++;
                continue;
            }

            /* we don't have to lock buffer itself, since the ref
             * count is 0 and we know it will stay zero as long as
             * we hold the global lock.
             */

            /* don't recycle someone in our own chunk */
            if (!cm_FidCmp(&bp->fid, &scp->fid) &&
                bp->dataVersion >= scp->bufDataVersionLow &&
                bp->dataVersion <= scp->dataVersion &&
                (bp->offset.LowPart & (-cm_chunkSize)) == (offsetp->LowPart & (-cm_chunkSize))) {
                n_own++;
                continue;
            }

            /* if this page is being filled (!) or cleaned, see if
             * the I/O has completed.  If not, skip it, otherwise
             * do the final processing for the I/O.
             */
            if (bp->flags & (CM_BUF_READING | CM_BUF_WRITING)) {
                /* probably shouldn't do this much work while
                 * holding the big lock?  Watch for contention
                 * here.
                 */
                n_busy++;
                continue;
            }

            /* leave the buffer alone if held by the redirector */
            if (bp->qFlags & CM_BUF_QREDIR) {
                n_redir++;
                continue;
            }

            if (bp->flags & CM_BUF_DIRTY) {
                n_dirty++;

                /* protect against cleaning the same buffer more than once. */
                if (cleaned)
                    continue;

                /* if the buffer is dirty, start cleaning it and
                 * move on to the next buffer.  We do this with
                 * just the lock required to minimize contention
                 * on the big lock.
                 */
                buf_HoldLocked(bp);
                lock_ReleaseWrite(&buf_globalLock);
                if (!bufCreateLocked)
                    lock_ReleaseRead(&scp->bufCreateLock);

                /*
                 * grab required lock and clean.
                 * previously the claim was that the cleaning
                 * operation was async which it is not.  It would
                 * be a good idea to use an async mechanism here
                 * but there is none at the moment other than
                 * the buf_IncrSyncer() thread.
                 */
                if (cm_FidCmp(&scp->fid, &bp->fid) == 0)
                    buf_Clean(scp, bp, reqp, 0, NULL);
                else
                    buf_Clean(NULL, bp, reqp, 0, NULL);

                /* now put it back and go around again */
                buf_Release(bp);

                /* but first obtain the locks we gave up
                 * before the buf_CleanAsync() call */
                if (!bufCreateLocked)
                    lock_ObtainRead(&scp->bufCreateLock);
                lock_ObtainWrite(&buf_globalLock);

                /*
                 * Since we dropped the locks we need to verify that
                 * another thread has not allocated the buffer for us.
                 */
                if (buf_ExistsLocked(scp, offsetp)) {
                    lock_ReleaseWrite(&buf_globalLock);
                    if (!bufCreateLocked)
                        lock_ReleaseRead(&scp->bufCreateLock);
                    return CM_BUF_EXISTS;
                }

                /*
                 * We just cleaned this buffer so we need to
                 * restart the loop with this buffer so it
                 * can be retested.  Set 'cleaned' so we
                 * do not attempt another call to buf_Clean()
                 * if the prior attempt failed.
                 */
                cleaned = 1;
                goto retry_2;
            }

            osi_Log3(afsd_logp, "buf_GetNewLocked: scp 0x%p examined %u buffers before recycling bufp 0x%p",
                     scp, n_bufs, bp);
            osi_Log4(afsd_logp, "... nonzero %u; own %u; busy %u; dirty %u", n_nonzero, n_own, n_busy, n_dirty);

            /* if we get here, we know that the buffer still has a 0
             * ref count, and that it is clean and has no currently
             * pending I/O.  This is the dude to return.
             * Remember that as long as the ref count is 0, we know
             * that we won't have any lock conflicts, so we can grab
             * the buffer lock out of order in the locking hierarchy.
             */
            buf_Recycle(bp);

            /* now hash in as our new buffer, and give it the
             * appropriate label, if requested.
             */
            if (scp) {
                lock_AssertWrite(&buf_globalLock);

                _InterlockedOr(&bp->qFlags, CM_BUF_QINHASH);
                bp->fid = scp->fid;
#ifdef DEBUG
		bp->scp = scp;
#endif
                bp->offset = *offsetp;
                i = BUF_HASH(&scp->fid, offsetp);
                bp->hashp = cm_data.buf_scacheHashTablepp[i];
                cm_data.buf_scacheHashTablepp[i] = bp;
                i = BUF_FILEHASH(&scp->fid);
                nextBp = cm_data.buf_fileHashTablepp[i];
                bp->fileHashp = nextBp;
                bp->fileHashBackp = NULL;
                if (nextBp)
                    nextBp->fileHashBackp = bp;
                cm_data.buf_fileHashTablepp[i] = bp;
            }

            /* we should remove it from the lru queue.  It better still be there,
             * since we've held the global (big) lock since we found it there.
             */
            osi_assertx(bp->qFlags & CM_BUF_QINLRU,
                         "buf_GetNewLocked: LRU screwup");

            osi_QRemoveHT( (osi_queue_t **) &cm_data.buf_freeListp,
                           (osi_queue_t **) &cm_data.buf_freeListEndp,
                           &bp->q);
            _InterlockedAnd(&bp->qFlags, ~CM_BUF_QINLRU);
            buf_DecrementFreeCount();

            /* prepare to return it.  Give it a refcount */
            InterlockedIncrement(&bp->refCount);
#ifdef DEBUG_REFCOUNT
            osi_Log2(afsd_logp,"buf_GetNewLocked bp 0x%p ref %d", bp, 1);
            afsi_log("%s:%d buf_GetNewLocked bp 0x%p, ref %d", __FILE__, __LINE__, bp, 1);
#endif
            /* grab the mutex so that people don't use it
             * before the caller fills it with data.  Again, no one
             * should have been able to get to this dude to lock it.
             */
	    if (!lock_TryMutex(&bp->mx)) {
	    	osi_Log2(afsd_logp, "buf_GetNewLocked bp 0x%p cannot be mutex locked.  refCount %d should be 0",
                         bp, bp->refCount);
		osi_panic("buf_GetNewLocked: TryMutex failed",__FILE__,__LINE__);
	    }

            if ( cm_data.buf_usedCount < cm_data.buf_nbuffers)
                buf_IncrementUsedCount();

            lock_ReleaseWrite(&buf_globalLock);
            if (!bufCreateLocked)
                lock_ReleaseRead(&scp->bufCreateLock);

            *bufpp = bp;

#ifdef TESTING
            buf_ValidateBufQueues();
#endif /* TESTING */
            return 0;
        } /* for all buffers in lru queue */
        lock_ReleaseWrite(&buf_globalLock);
        if (!bufCreateLocked)
            lock_ReleaseRead(&scp->bufCreateLock);

	osi_Log2(afsd_logp, "buf_GetNewLocked: Free Buffer List has %u buffers none free; redir %u", n_bufs, n_redir);
        osi_Log4(afsd_logp, "... nonzero %u; own %u; busy %u; dirty %u", n_nonzero, n_own, n_busy, n_dirty);

        if (RDR_Initialized) {
            afs_uint32 code;
          rdr_release:
            code = buf_RDRShakeSomeExtentsFree(reqp, TRUE, 2 /* seconds */);
            switch (code) {
            case CM_ERROR_RETRY:
            case 0:
                goto retry;
            case CM_ERROR_WOULDBLOCK:
                return CM_ERROR_WOULDBLOCK;
            }
        }

	Sleep(100);		/* give some time for a buffer to be freed */
    }	/* while loop over everything */
    /* not reached */
} /* the proc */

/*
 * get a page, returning it held but unlocked.  the page may or may not
 * contain valid data.
 *
 * The scp must be unlocked when passed in unlocked.
 */
long buf_Get(struct cm_scache *scp, osi_hyper_t *offsetp, cm_req_t *reqp, afs_uint32 flags, cm_buf_t **bufpp)
{
    cm_buf_t *bp;
    long code;
    osi_hyper_t pageOffset;
    unsigned long tcount;
    int created;
    long lcount = 0;
#ifdef DISKCACHE95
    cm_diskcache_t *dcp;
#endif /* DISKCACHE95 */

    created = 0;
    pageOffset.HighPart = offsetp->HighPart;
    pageOffset.LowPart = offsetp->LowPart & ~(cm_data.buf_blockSize-1);
    while (!created) {
        lcount++;
#ifdef TESTING
        buf_ValidateBufQueues();
#endif /* TESTING */

        bp = buf_Find(&scp->fid, &pageOffset);
        if (bp) {
            /* lock it and break out */
            lock_ObtainMutex(&bp->mx);

#ifdef DISKCACHE95
            /* touch disk chunk to update LRU info */
            diskcache_Touch(bp->dcp);
#endif /* DISKCACHE95 */
            break;
        }

        /* otherwise, we have to create a page */
        code = buf_GetNewLocked(scp, &pageOffset, reqp, flags, &bp);
        switch (code) {
        case 0:
            /* the requested buffer was created */
            created = 1;
            break;
        case CM_BUF_EXISTS:
            /*
             * the requested buffer existed by the time the
             * scp->bufCreateLock and buf_globalLock could be obtained.
             * loop again and permit buf_Find() to obtain a reference.
             */
            break;
        default:
            /*
             * the requested buffer could not be created.
             * return the error to the caller.
             */
#ifdef TESTING
            buf_ValidateBufQueues();
#endif /* TESTING */
            return code;
        }
    } /* big while loop */

    /* if we get here, we have a locked buffer that may have just been
     * created, in which case it needs to be filled with data.
     */
    if (created) {
        /* load the page; freshly created pages should be idle */
        osi_assertx(!(bp->flags & (CM_BUF_READING | CM_BUF_WRITING)), "incorrect cm_buf_t flags");

        /*
         * start the I/O; may drop lock.  as of this writing, the only
         * implementation of Readp is cm_BufRead() which simply sets
         * tcount to 0 and returns success.
         */
        _InterlockedOr(&bp->flags, CM_BUF_READING);
        code = (*cm_buf_opsp->Readp)(bp, cm_data.buf_blockSize, &tcount, NULL);

#ifdef DISKCACHE95
        code = diskcache_Get(&bp->fid, &bp->offset, bp->datap, cm_data.buf_blockSize, &bp->dataVersion, &tcount, &dcp);
        bp->dcp = dcp;    /* pointer to disk cache struct. */
#endif /* DISKCACHE95 */

        if (code != 0) {
            /* failure or queued */

            /* unless cm_BufRead() is altered, this path cannot be hit */
            if (code != ERROR_IO_PENDING) {
                bp->error = code;
                _InterlockedOr(&bp->flags, CM_BUF_ERROR);
                _InterlockedAnd(&bp->flags, ~CM_BUF_READING);
                if (bp->flags & CM_BUF_WAITING) {
                    osi_Log1(buf_logp, "buf_Get Waking bp 0x%p", bp);
                    osi_Wakeup((LONG_PTR) bp);
                }
                lock_ReleaseMutex(&bp->mx);
                buf_Release(bp);
#ifdef TESTING
                buf_ValidateBufQueues();
#endif /* TESTING */
                return code;
            }
        } else {
            /*
             * otherwise, I/O completed instantly and we're done, except
             * for padding the xfr out with 0s and checking for EOF
             */
            if (tcount < (unsigned long) cm_data.buf_blockSize) {
                memset(bp->datap+tcount, 0, cm_data.buf_blockSize - tcount);
                if (tcount == 0)
                    _InterlockedOr(&bp->flags, CM_BUF_EOF);
            }
            _InterlockedAnd(&bp->flags, ~CM_BUF_READING);
            if (bp->flags & CM_BUF_WAITING) {
                osi_Log1(buf_logp, "buf_Get Waking bp 0x%p", bp);
                osi_Wakeup((LONG_PTR) bp);
            }
        }
    } /* if created */

    /* wait for reads, either that which we started above, or that someone
     * else started.  We don't care if we return a buffer being cleaned.
     */
    if (bp->flags & CM_BUF_READING)
        buf_WaitIO(scp, bp);

    /* once it has been read once, we can unlock it and return it, still
     * with its refcount held.
     */
    lock_ReleaseMutex(&bp->mx);
    *bufpp = bp;

    /* now remove from queue; will be put in at the head (farthest from
     * being recycled) when we're done in buf_Release.
     */
    lock_ObtainWrite(&buf_globalLock);
    if (bp->qFlags & CM_BUF_QINLRU) {
        osi_QRemoveHT( (osi_queue_t **) &cm_data.buf_freeListp,
                       (osi_queue_t **) &cm_data.buf_freeListEndp,
                       &bp->q);
        _InterlockedAnd(&bp->qFlags, ~CM_BUF_QINLRU);
        buf_DecrementFreeCount();
    }
    lock_ReleaseWrite(&buf_globalLock);

    osi_Log4(buf_logp, "buf_Get returning bp 0x%p for scp 0x%p, offset 0x%x:%08x",
              bp, scp, offsetp->HighPart, offsetp->LowPart);
#ifdef TESTING
    buf_ValidateBufQueues();
#endif /* TESTING */
    return 0;
}

/* clean a buffer synchronously */
afs_uint32 buf_Clean(cm_scache_t *scp, cm_buf_t *bp, cm_req_t *reqp, afs_uint32 flags, afs_uint32 *pisdirty)
{
    long code;
    osi_assertx(bp->magic == CM_BUF_MAGIC, "invalid cm_buf_t magic");
    osi_assertx(!(flags & CM_BUF_WRITE_SCP_LOCKED), "scp->rw must not be held when calling buf_CleanAsync");

    lock_ObtainMutex(&bp->mx);
    code = buf_CleanLocked(scp, bp, reqp, flags, pisdirty);
    lock_ReleaseMutex(&bp->mx);

    return code;
}

/* wait for a buffer's cleaning to finish */
void buf_CleanWait(cm_scache_t * scp, cm_buf_t *bp, afs_uint32 locked)
{
    osi_assertx(bp->magic == CM_BUF_MAGIC, "invalid cm_buf_t magic");

    if (!locked)
        lock_ObtainMutex(&bp->mx);
    if (bp->flags & CM_BUF_WRITING) {
        buf_WaitIO(scp, bp);
    }
    if (!locked)
        lock_ReleaseMutex(&bp->mx);
}

/* set the dirty flag on a buffer, and set associated write-ahead log,
 * if there is one.  Allow one to be added to a buffer, but not changed.
 *
 * The buffer must be locked before calling this routine.
 */
void buf_SetDirty(cm_buf_t *bp, cm_req_t *reqp, afs_uint32 offset, afs_uint32 length, cm_user_t *userp)
{
    osi_assertx(bp->magic == CM_BUF_MAGIC, "invalid cm_buf_t magic");
    osi_assertx(bp->refCount > 0, "cm_buf_t refcount 0");
    osi_assertx(userp != NULL, "userp is NULL");

    if (length == 0)
        return;

    if (bp->flags & CM_BUF_DIRTY) {

	osi_Log1(buf_logp, "buf_SetDirty 0x%p already dirty", bp);

        if (bp->dirty_offset <= offset) {
            if (bp->dirty_offset + bp->dirty_length >= offset + length) {
                /* dirty_length remains the same */
            } else {
                bp->dirty_length = offset + length - bp->dirty_offset;
            }
        } else /* bp->dirty_offset > offset */ {
            if (bp->dirty_offset + bp->dirty_length >= offset + length) {
                bp->dirty_length = bp->dirty_offset + bp->dirty_length - offset;
            } else {
                bp->dirty_length = length;
            }
            bp->dirty_offset = offset;
        }
    } else {
	osi_Log1(buf_logp, "buf_SetDirty 0x%p", bp);

        /* set dirty bit */
        _InterlockedOr(&bp->flags, CM_BUF_DIRTY);

        /* and turn off EOF flag, since it has associated data now */
        _InterlockedAnd(&bp->flags, ~CM_BUF_EOF);

        bp->dirty_offset = offset;
        bp->dirty_length = length;

        /*
         * if the request is not from the afs redirector,
         * add to the dirty list.  The redirector interface ensures
         * that a background store operation is queued for each and
         * every dirty extent that is released.  Therefore, the
         * buf_IncrSyncer thread is not required to ensure that
         * dirty buffers are written to the file server.
         *
         * we obtain a hold on the buffer for as long as it remains
         * in the list.  buffers are only removed from the list by
         * the buf_IncrSyncer function regardless of when else the
         * dirty flag might be cleared.
         *
         * This should never happen but just in case there is a bug
         * elsewhere, never add to the dirty list if the buffer is
         * already there.
         */
        if (!(reqp->flags & CM_REQ_SOURCE_REDIR)) {
            lock_ObtainWrite(&buf_globalLock);
            if (!(bp->qFlags & CM_BUF_QINDL)) {
                buf_HoldLocked(bp);
                if (!cm_data.buf_dirtyListp) {
                    cm_data.buf_dirtyListp = cm_data.buf_dirtyListEndp = bp;
                } else {
                    cm_data.buf_dirtyListEndp->dirtyp = bp;
                    cm_data.buf_dirtyListEndp = bp;
                }
                bp->dirtyp = NULL;
                _InterlockedOr(&bp->qFlags, CM_BUF_QINDL);
            }
            lock_ReleaseWrite(&buf_globalLock);
        }
    }

    /* and record the last writer */
    if (bp->userp != userp) {
        cm_HoldUser(userp);
        if (bp->userp)
            cm_ReleaseUser(bp->userp);
        bp->userp = userp;
    }
}

/* clean all buffers, reset log pointers and invalidate all buffers.
 * Called with no locks held, and returns with same.
 *
 * This function is guaranteed to clean and remove the log ptr of all the
 * buffers that were dirty or had non-zero log ptrs before the call was
 * made.  That's sufficient to clean up any garbage left around by recovery,
 * which is all we're counting on this for; there may be newly created buffers
 * added while we're running, but that should be OK.
 *
 * In an environment where there are no transactions (artificially imposed, for
 * example, when switching the database to raw mode), this function is used to
 * make sure that all updates have been written to the disk.  In that case, we don't
 * really require that we forget the log association between pages and logs, but
 * it also doesn't hurt.  Since raw mode I/O goes through this buffer package, we don't
 * have to worry about invalidating data in the buffers.
 *
 * This function is used at the end of recovery as paranoia to get the recovered
 * database out to disk.  It removes all references to the recovery log and cleans
 * all buffers.
 */
long buf_CleanAndReset(void)
{
    afs_uint32 i;
    cm_buf_t *bp;
    cm_req_t req;

    lock_ObtainRead(&buf_globalLock);
    for(i=0; i<cm_data.buf_hashSize; i++) {
        for(bp = cm_data.buf_scacheHashTablepp[i]; bp; bp = bp->hashp) {
            if (bp->qFlags & CM_BUF_QREDIR) {
                osi_Log1(buf_logp,"buf_CleanAndReset buffer held by redirector bp 0x%p", bp);

                /* Request single extent from the redirector */
                buf_RDRShakeAnExtentFree(bp, &req);
            }

            if ((bp->flags & CM_BUF_DIRTY) == CM_BUF_DIRTY) {
                buf_HoldLocked(bp);
                lock_ReleaseRead(&buf_globalLock);

                /* now no locks are held; clean buffer and go on */
                cm_InitReq(&req);
		req.flags |= CM_REQ_NORETRY;

		buf_Clean(NULL, bp, &req, 0, NULL);
		buf_CleanWait(NULL, bp, FALSE);

                /* relock and release buffer */
                lock_ObtainRead(&buf_globalLock);
                buf_ReleaseLocked(bp, FALSE);
            } /* dirty */
        } /* over one bucket */
    }	/* for loop over all hash buckets */

    /* release locks */
    lock_ReleaseRead(&buf_globalLock);

#ifdef TESTING
    buf_ValidateBufQueues();
#endif /* TESTING */

    /* and we're done */
    return 0;
}

/* called without global lock being held, reserves buffers for callers
 * that need more than one held (not locked) at once.
 */
void buf_ReserveBuffers(afs_uint64 nbuffers)
{
    lock_ObtainWrite(&buf_globalLock);
    while (1) {
        if (cm_data.buf_reservedBufs + nbuffers > cm_data.buf_maxReservedBufs) {
            cm_data.buf_reserveWaiting = 1;
            osi_Log1(buf_logp, "buf_ReserveBuffers waiting for %d bufs", nbuffers);
            osi_SleepW((LONG_PTR) &cm_data.buf_reservedBufs, &buf_globalLock);
            lock_ObtainWrite(&buf_globalLock);
        }
        else {
            cm_data.buf_reservedBufs += nbuffers;
            break;
        }
    }
    lock_ReleaseWrite(&buf_globalLock);
}

afs_uint64
buf_TryReserveBuffers(afs_uint64 nbuffers)
{
    afs_uint64 reserved;

    lock_ObtainWrite(&buf_globalLock);
    if (cm_data.buf_reservedBufs + nbuffers > cm_data.buf_maxReservedBufs) {
        reserved = 0;
    }
    else {
        cm_data.buf_reservedBufs += nbuffers;
        reserved = nbuffers;
    }
    lock_ReleaseWrite(&buf_globalLock);
    return reserved;
}

/* called without global lock held, releases reservation held by
 * buf_ReserveBuffers.
 */
void buf_UnreserveBuffers(afs_uint64 nbuffers)
{
    lock_ObtainWrite(&buf_globalLock);
    cm_data.buf_reservedBufs -= nbuffers;
    if (cm_data.buf_reserveWaiting) {
        cm_data.buf_reserveWaiting = 0;
        osi_Wakeup((LONG_PTR) &cm_data.buf_reservedBufs);
    }
    lock_ReleaseWrite(&buf_globalLock);
}

/* truncate the buffers past sizep, zeroing out the page, if we don't
 * end on a page boundary.
 *
 * Requires cm_bufCreateLock to be write locked.
 */
long buf_Truncate(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp,
                   osi_hyper_t *sizep)
{
    cm_buf_t *bufp;
    cm_buf_t *nbufp;			/* next buffer, if didRelease */
    osi_hyper_t bufEnd;
    long code;
    long bufferPos;
    afs_uint32 i;
    afs_uint32 invalidate = 0;

    /* assert that cm_bufCreateLock is held in write mode */
    lock_AssertWrite(&scp->bufCreateLock);

    i = BUF_FILEHASH(&scp->fid);

    lock_ObtainRead(&buf_globalLock);
    bufp = cm_data.buf_fileHashTablepp[i];
    if (bufp == NULL) {
        lock_ReleaseRead(&buf_globalLock);
        return 0;
    }

    buf_HoldLocked(bufp);
    lock_ReleaseRead(&buf_globalLock);

    while (bufp) {
        lock_ObtainMutex(&bufp->mx);

        bufEnd.HighPart = 0;
        bufEnd.LowPart = cm_data.buf_blockSize;
        bufEnd = LargeIntegerAdd(bufEnd, bufp->offset);

        if (cm_FidCmp(&bufp->fid, &scp->fid) == 0 &&
             LargeIntegerLessThan(*sizep, bufEnd)) {
            buf_WaitIO(scp, bufp);
        }
        lock_ObtainWrite(&scp->rw);

        /* make sure we have a callback (so we have the right value for
         * the length), and wait for it to be safe to do a truncate.
         */
        code = cm_SyncOp(scp, bufp, userp, reqp, 0,
                          CM_SCACHESYNC_NEEDCALLBACK
                          | CM_SCACHESYNC_GETSTATUS
                          | CM_SCACHESYNC_SETSIZE
                          | CM_SCACHESYNC_BUFLOCKED);


	/* if we succeeded in our locking, and this applies to the right
         * file, and the truncate request overlaps the buffer either
         * totally or partially, then do something.
         */
        if (code == 0 && cm_FidCmp(&bufp->fid, &scp->fid) == 0
             && LargeIntegerLessThan(*sizep, bufEnd)) {


            /* destroy the buffer, turning off its dirty bit, if
             * we're truncating the whole buffer.  Otherwise, set
             * the dirty bit, and clear out the tail of the buffer
             * if we just overlap some.
             */
            if (LargeIntegerLessThanOrEqualTo(*sizep, bufp->offset)) {
                /* truncating the entire page */
                if (reqp->flags & CM_REQ_SOURCE_REDIR) {
                    /*
                     * Implicitly clear the redirector flag
                     * and release the matching hold.
                     */
                    if (bufp->qFlags & CM_BUF_QREDIR) {
                        osi_Log4(buf_logp,"buf_Truncate taking from file system bufp 0x%p vno 0x%x foffset 0x%x:%x",
                                 bufp, bufp->fid.vnode, bufp->offset.HighPart, bufp->offset.LowPart);
                        lock_ObtainWrite(&buf_globalLock);
                        if (bufp->qFlags & CM_BUF_QREDIR) {
                            buf_RemoveFromRedirQueue(scp, bufp);
                            buf_ReleaseLocked(bufp, TRUE);
                        }
                        lock_ReleaseWrite(&buf_globalLock);
                    }
                } else {
                    invalidate = 1;
                }
                _InterlockedAnd(&bufp->flags, ~CM_BUF_DIRTY);
                bufp->error = 0;
                bufp->dirty_length = 0;
                bufp->dataVersion = CM_BUF_VERSION_BAD;	/* known bad */
                bufp->dirtyCounter++;
                buf_DecrementUsedCount();
            }
            else {
                /* don't set dirty, since dirty implies
                 * currently up-to-date.  Don't need to do this,
                 * since we'll update the length anyway.
                 *
                 * Zero out remainder of the page, in case we
                 * seek and write past EOF, and make this data
                 * visible again.
                 */
                bufferPos = sizep->LowPart & (cm_data.buf_blockSize - 1);
                osi_assertx(bufferPos != 0, "non-zero bufferPos");
                memset(bufp->datap + bufferPos, 0,
                        cm_data.buf_blockSize - bufferPos);
            }
        }

	cm_SyncOpDone( scp, bufp,
		       CM_SCACHESYNC_NEEDCALLBACK | CM_SCACHESYNC_GETSTATUS
		       | CM_SCACHESYNC_SETSIZE | CM_SCACHESYNC_BUFLOCKED);

        lock_ReleaseWrite(&scp->rw);
        lock_ReleaseMutex(&bufp->mx);

	if (!code) {
	    nbufp = bufp->fileHashp;
	    if (nbufp)
		buf_Hold(nbufp);
	} else {
	    /* This forces the loop to end and the error code
	     * to be returned. */
	    nbufp = NULL;
	}
	buf_Release(bufp);
	bufp = nbufp;
    }

#ifdef TESTING
    buf_ValidateBufQueues();
#endif /* TESTING */

    if (invalidate && RDR_Initialized)
        RDR_InvalidateObject(scp->fid.cell, scp->fid.volume, scp->fid.vnode,
                             scp->fid.unique, scp->fid.hash,
                             scp->fileType, AFS_INVALIDATE_SMB);

    /* done */
    return code;
}

long buf_FlushCleanPages(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp)
{
    long code;
    cm_buf_t *bp;		/* buffer we're hacking on */
    cm_buf_t *nbp;
    int didRelease;
    afs_uint32 i;
    afs_uint32 stable = 0;

    i = BUF_FILEHASH(&scp->fid);

    code = 0;
    lock_ObtainRead(&buf_globalLock);
    bp = cm_data.buf_fileHashTablepp[i];
    if (bp)
        buf_HoldLocked(bp);
    lock_ReleaseRead(&buf_globalLock);

    for (; bp; bp = nbp) {
        didRelease = 0;	/* haven't released this buffer yet */

        /* clean buffer synchronously */
        if (cm_FidCmp(&bp->fid, &scp->fid) == 0) {

            if (code == 0 && !stable && (bp->flags & CM_BUF_DIRTY)) {
                /*
                 * we must stabilize the object to ensure that buffer
                 * changes cannot occur while the flush is performed.
                 * However, we do not want to Stabilize if we do not
                 * need to because Stabilize obtains a callback.
                 */
                code = (*cm_buf_opsp->Stabilizep)(scp, userp, reqp);
                stable = (code == 0);
            }

            if (code == CM_ERROR_BADFD) {
                /* if the scp's FID is bad its because we received VNOVNODE
                 * when attempting to FetchStatus before the write.  This
                 * page therefore contains data that can no longer be stored.
                 */
                lock_ObtainMutex(&bp->mx);
                _InterlockedAnd(&bp->flags, ~CM_BUF_DIRTY);
                _InterlockedOr(&bp->flags, CM_BUF_ERROR);
                bp->error = CM_ERROR_BADFD;
                bp->dirty_length = 0;
                bp->dataVersion = CM_BUF_VERSION_BAD;	/* known bad */
                bp->dirtyCounter++;
                lock_ReleaseMutex(&bp->mx);
                buf_DecrementUsedCount();
            } else if (!(scp->flags & CM_SCACHEFLAG_RO)) {
                if (code) {
                    goto skip;
                }

                lock_ObtainMutex(&bp->mx);

                /* start cleaning the buffer, and wait for it to finish */
                buf_CleanLocked(scp, bp, reqp, 0, NULL);
                buf_WaitIO(scp, bp);

                lock_ReleaseMutex(&bp->mx);
            }

            /* actually, we only know that buffer is clean if ref
             * count is 1, since we don't have buffer itself locked.
             */
            if (!(bp->flags & CM_BUF_DIRTY) && !(bp->qFlags & CM_BUF_QREDIR)) {
                lock_ObtainWrite(&buf_globalLock);
                if (!(bp->flags & CM_BUF_DIRTY) && !(bp->qFlags & CM_BUF_QREDIR)) {
                    if (bp->refCount == 1) {	/* bp is held above */
                        nbp = bp->fileHashp;
                        if (nbp)
                            buf_HoldLocked(nbp);
                        buf_ReleaseLocked(bp, TRUE);
                        didRelease = 1;
                        if (bp->dataVersion != CM_BUF_VERSION_BAD)
                            buf_DecrementUsedCount();
                        buf_Recycle(bp);
                    }
                }
                lock_ReleaseWrite(&buf_globalLock);
            }
        }

      skip:
        if (!didRelease) {
            lock_ObtainRead(&buf_globalLock);
            nbp = bp->fileHashp;
	    if (nbp)
                buf_HoldLocked(nbp);
            buf_ReleaseLocked(bp, FALSE);
            lock_ReleaseRead(&buf_globalLock);
        }
    }	/* for loop over a bunch of buffers */

    if (stable)
        (*cm_buf_opsp->Unstabilizep)(scp, userp);

#ifdef TESTING
    buf_ValidateBufQueues();
#endif /* TESTING */

    /* done */
    return code;
}

/* Must be called with scp->rw held */
long buf_InvalidateBuffers(cm_scache_t * scp)
{
    cm_buf_t * bp;
    afs_uint32 i;
    int found = 0;

    lock_AssertAny(&scp->rw);

    i = BUF_FILEHASH(&scp->fid);

    lock_ObtainRead(&buf_globalLock);

    for (bp = cm_data.buf_fileHashTablepp[i]; bp; bp = bp->fileHashp) {
        if (cm_FidCmp(&bp->fid, &scp->fid) == 0) {
            bp->dataVersion = CM_BUF_VERSION_BAD;
            buf_DecrementUsedCount();
            found = 1;
        }
    }
    lock_ReleaseRead(&buf_globalLock);

    if (found)
        return 0;
    else
        return ENOENT;
}

/* Must be called with scp->rw held */
long buf_ForceDataVersion(cm_scache_t * scp, afs_uint64 fromVersion, afs_uint64 toVersion)
{
    cm_buf_t * bp;
    afs_uint32 i;
    int found = 0;

    lock_AssertAny(&scp->rw);

    i = BUF_FILEHASH(&scp->fid);

    lock_ObtainRead(&buf_globalLock);

    for (bp = cm_data.buf_fileHashTablepp[i]; bp; bp = bp->fileHashp) {
        if (cm_FidCmp(&bp->fid, &scp->fid) == 0) {
            if (bp->dataVersion == fromVersion) {
                bp->dataVersion = toVersion;
                found = 1;
            }
        }
    }
    lock_ReleaseRead(&buf_globalLock);

    if (found)
        return 0;
    else
        return ENOENT;
}

long buf_CleanVnode(struct cm_scache *scp, cm_user_t *userp, cm_req_t *reqp)
{
    long code = 0;
    long wasDirty = 0;
    cm_buf_t *bp;		/* buffer we're hacking on */
    cm_buf_t *nbp;		/* next one */
    afs_uint32 i;

    if (RDR_Initialized && scp->redirBufCount > 0) {
        /* Retrieve all extents for this file from the redirector */
        buf_RDRShakeFileExtentsFree(scp, reqp);
    }

    i = BUF_FILEHASH(&scp->fid);

    lock_ObtainRead(&buf_globalLock);
    bp = cm_data.buf_fileHashTablepp[i];
    if (bp)
        buf_HoldLocked(bp);
    lock_ReleaseRead(&buf_globalLock);
    for (; bp; bp = nbp) {
        /* clean buffer synchronously */
        if (cm_FidCmp(&bp->fid, &scp->fid) == 0) {
            /*
             * If the buffer is held by the redirector we must fetch
             * it back in order to determine whether or not it is in
             * fact dirty.
             */
            if (bp->qFlags & CM_BUF_QREDIR) {
                lock_ObtainRead(&buf_globalLock);
                if (bp->qFlags & CM_BUF_QREDIR) {
                    osi_Log1(buf_logp,"buf_CleanVnode buffer held by redirector bp 0x%p", bp);

                    /* Retrieve single extent from the redirector */
                    buf_RDRShakeAnExtentFree(bp, reqp);
                }
                lock_ReleaseRead(&buf_globalLock);
            }

            lock_ObtainMutex(&bp->mx);
            if ((bp->flags & CM_BUF_DIRTY)) {
                if (userp && userp != bp->userp) {
                    cm_HoldUser(userp);
                    if (bp->userp)
                        cm_ReleaseUser(bp->userp);
                    bp->userp = userp;
                }

                switch (code) {
                case CM_ERROR_NOSUCHFILE:
                case CM_ERROR_INVAL:
                case CM_ERROR_BADFD:
                case CM_ERROR_NOACCESS:
                case CM_ERROR_QUOTA:
                case CM_ERROR_SPACE:
                case CM_ERROR_TOOBIG:
                case CM_ERROR_READONLY:
                case CM_ERROR_NOSUCHPATH:
                case EIO:
                case CM_ERROR_INVAL_NET_RESP:
                case CM_ERROR_UNKNOWN:
                    /*
                     * Apply the previous fatal error to this buffer.
                     * Do not waste the time attempting to store to
                     * the file server when we know it will fail.
                     */
                    _InterlockedAnd(&bp->flags, ~CM_BUF_DIRTY);
                    _InterlockedOr(&bp->flags, CM_BUF_ERROR);
                    bp->dirty_length = 0;
                    bp->error = code;
                    bp->dataVersion = CM_BUF_VERSION_BAD;
                    bp->dirtyCounter++;
                    buf_DecrementUsedCount();
                    break;
                case CM_ERROR_TIMEDOUT:
                case CM_ERROR_ALLDOWN:
                case CM_ERROR_ALLBUSY:
                case CM_ERROR_ALLOFFLINE:
                case CM_ERROR_CLOCKSKEW:
                    /* do not mark the buffer in error state but do
                     * not attempt to complete the rest either.
                     */
                    break;
                default:
                    code = buf_CleanLocked(scp, bp, reqp, 0, &wasDirty);
                    if (bp->flags & CM_BUF_ERROR) {
                        code = bp->error;
                        if (code == 0)
                            code = -1;
                    }
                }
                buf_CleanWait(scp, bp, TRUE);
            }
            lock_ReleaseMutex(&bp->mx);
        }

        lock_ObtainRead(&buf_globalLock);
        nbp = bp->fileHashp;
        if (nbp)
            buf_HoldLocked(nbp);
        buf_ReleaseLocked(bp, FALSE);
        lock_ReleaseRead(&buf_globalLock);
    }	/* for loop over a bunch of buffers */

#ifdef TESTING
    buf_ValidateBufQueues();
#endif /* TESTING */

    /* done */
    return code;
}

#ifdef TESTING
void
buf_ValidateBufQueues(void)
{
    cm_buf_t * bp, *bpb, *bpf, *bpa;
    afs_uint32 countf=0, countb=0, counta=0;

    lock_ObtainRead(&buf_globalLock);
    for (bp = cm_data.buf_freeListEndp; bp; bp=(cm_buf_t *) osi_QPrev(&bp->q)) {
        if (bp->magic != CM_BUF_MAGIC)
            osi_panic("buf magic error",__FILE__,__LINE__);
        countb++;
        bpb = bp;
    }

    for (bp = cm_data.buf_freeListp; bp; bp=(cm_buf_t *) osi_QNext(&bp->q)) {
        if (bp->magic != CM_BUF_MAGIC)
            osi_panic("buf magic error",__FILE__,__LINE__);
        countf++;
        bpf = bp;
    }

    for (bp = cm_data.buf_allp; bp; bp=bp->allp) {
        if (bp->magic != CM_BUF_MAGIC)
            osi_panic("buf magic error",__FILE__,__LINE__);
        counta++;
        bpa = bp;
    }
    lock_ReleaseRead(&buf_globalLock);

    if (countb != countf)
	osi_panic("buf magic error",__FILE__,__LINE__);

    if (counta != cm_data.buf_nbuffers)
	osi_panic("buf magic error",__FILE__,__LINE__);
}
#endif /* TESTING */

/* dump the contents of the buf_scacheHashTablepp. */
int cm_DumpBufHashTable(FILE *outputFile, char *cookie, int lock)
{
    int zilch;
    cm_buf_t *bp;
    char output[1024];
    afs_uint32 i;

    if (cm_data.buf_scacheHashTablepp == NULL)
        return -1;

    if (lock)
        lock_ObtainRead(&buf_globalLock);

    StringCbPrintfA(output, sizeof(output), "%s - dumping buf_HashTable - buf_hashSize=%d\r\n",
                    cookie, cm_data.buf_hashSize);
    WriteFile(outputFile, output, (DWORD)strlen(output), &zilch, NULL);

    for (i = 0; i < cm_data.buf_hashSize; i++)
    {
        for (bp = cm_data.buf_scacheHashTablepp[i]; bp; bp=bp->hashp)
        {
	    StringCbPrintfA(output, sizeof(output),
			    "%s bp=0x%08X, hash=%d, fid (cell=%d, volume=%d, "
			    "vnode=%d, unique=%d), offset=%x:%08x, dv=%I64d, "
			    "flags=0x%x, qFlags=0x%x cmFlags=0x%x, error=0x%x, refCount=%d\r\n",
			     cookie, (void *)bp, i, bp->fid.cell, bp->fid.volume,
			     bp->fid.vnode, bp->fid.unique, bp->offset.HighPart,
			     bp->offset.LowPart, bp->dataVersion, bp->flags, bp->qFlags,
			     bp->cmFlags, bp->error, bp->refCount);
	    WriteFile(outputFile, output, (DWORD)strlen(output), &zilch, NULL);
        }
    }

    StringCbPrintfA(output, sizeof(output), "%s - Done dumping buf_HashTable.\r\n", cookie);
    WriteFile(outputFile, output, (DWORD)strlen(output), &zilch, NULL);

    StringCbPrintfA(output, sizeof(output), "%s - dumping buf_freeListEndp\r\n", cookie);
    WriteFile(outputFile, output, (DWORD)strlen(output), &zilch, NULL);
    for(bp = cm_data.buf_freeListEndp; bp; bp=(cm_buf_t *) osi_QPrev(&bp->q)) {
	StringCbPrintfA(output, sizeof(output),
			 "%s bp=0x%08X, fid (cell=%d, volume=%d, "
			 "vnode=%d, unique=%d), offset=%x:%08x, dv=%I64d, "
			 "flags=0x%x, qFlags=0x%x, cmFlags=0x%x, error=0x%x, refCount=%d\r\n",
			 cookie, (void *)bp, bp->fid.cell, bp->fid.volume,
			 bp->fid.vnode, bp->fid.unique, bp->offset.HighPart,
			 bp->offset.LowPart, bp->dataVersion, bp->flags, bp->qFlags,
			 bp->cmFlags, bp->error, bp->refCount);
	WriteFile(outputFile, output, (DWORD)strlen(output), &zilch, NULL);
    }
    StringCbPrintfA(output, sizeof(output), "%s - Done dumping buf_FreeListEndp.\r\n", cookie);
    WriteFile(outputFile, output, (DWORD)strlen(output), &zilch, NULL);

    StringCbPrintfA(output, sizeof(output), "%s - dumping buf_dirtyListp\r\n", cookie);
    WriteFile(outputFile, output, (DWORD)strlen(output), &zilch, NULL);
    for(bp = cm_data.buf_dirtyListp; bp; bp=bp->dirtyp) {
	StringCbPrintfA(output, sizeof(output),
			 "%s bp=0x%08X, fid (cell=%d, volume=%d, "
			 "vnode=%d, unique=%d), offset=%x:%08x, dv=%I64d, "
			 "flags=0x%x, qFlags=0x%x, cmFlags=0x%x, error=0x%x, refCount=%d\r\n",
			 cookie, (void *)bp, bp->fid.cell, bp->fid.volume,
			 bp->fid.vnode, bp->fid.unique, bp->offset.HighPart,
			 bp->offset.LowPart, bp->dataVersion, bp->flags, bp->qFlags,
			 bp->cmFlags, bp->error, bp->refCount);
	WriteFile(outputFile, output, (DWORD)strlen(output), &zilch, NULL);
    }
    StringCbPrintfA(output, sizeof(output), "%s - Done dumping buf_dirtyListp.\r\n", cookie);
    WriteFile(outputFile, output, (DWORD)strlen(output), &zilch, NULL);

    if (lock)
        lock_ReleaseRead(&buf_globalLock);
    return 0;
}

void buf_ForceTrace(BOOL flush)
{
    HANDLE handle;
    int len;
    char buf[256];

    if (!buf_logp)
        return;

    len = GetTempPath(sizeof(buf)-10, buf);
    StringCbCopyA(&buf[len], sizeof(buf)-len, "/afs-buffer.log");
    handle = CreateFile(buf, GENERIC_WRITE, FILE_SHARE_READ,
			    NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
    if (handle == INVALID_HANDLE_VALUE) {
        osi_panic("Cannot create log file", __FILE__, __LINE__);
    }
    osi_LogPrint(buf_logp, handle);
    if (flush)
        FlushFileBuffers(handle);
    CloseHandle(handle);
}

long buf_DirtyBuffersExist(cm_fid_t *fidp)
{
    cm_buf_t *bp;
    afs_uint32 bcount = 0;
    afs_uint32 i;
    long found = 0;

    i = BUF_FILEHASH(fidp);

    lock_ObtainRead(&buf_globalLock);
    for (bp = cm_data.buf_fileHashTablepp[i]; bp; bp=bp->fileHashp, bcount++) {
	if (!cm_FidCmp(fidp, &bp->fid) && (bp->flags & CM_BUF_DIRTY)) {
	    found = 1;
            break;
        }
    }
    lock_ReleaseRead(&buf_globalLock);
    return found;
}

long buf_RDRBuffersExist(cm_fid_t *fidp)
{
    cm_buf_t *bp;
    afs_uint32 bcount = 0;
    afs_uint32 i;
    long found = 0;

    if (!RDR_Initialized || cm_directIO)
        return 0;

    i = BUF_FILEHASH(fidp);

    lock_ObtainRead(&buf_globalLock);
    for (bp = cm_data.buf_fileHashTablepp[i]; bp; bp=bp->fileHashp, bcount++) {
	if (!cm_FidCmp(fidp, &bp->fid) && (bp->qFlags & CM_BUF_QREDIR)) {
	    found = 1;
            break;
        }
    }
    lock_ReleaseRead(&buf_globalLock);
    return 0;
}

long buf_ClearRDRFlag(cm_scache_t *scp, char *reason)
{
    cm_fid_t *fidp = &scp->fid;
    cm_buf_t *bp;
    afs_uint32 bcount = 0;
    afs_uint32 i;

    if (!RDR_Initialized || cm_directIO)
        return 0;

    i = BUF_FILEHASH(fidp);

    lock_ObtainWrite(&scp->rw);
    lock_ObtainRead(&buf_globalLock);
    for (bp = cm_data.buf_fileHashTablepp[i]; bp; bp=bp->fileHashp, bcount++) {
	if (!cm_FidCmp(fidp, &bp->fid) && (bp->qFlags & CM_BUF_QREDIR)) {
            lock_ConvertRToW(&buf_globalLock);
            if (bp->qFlags & CM_BUF_QREDIR) {
                osi_Log4(buf_logp,"buf_ClearRDRFlag taking from file system bp 0x%p vno 0x%x foffset 0x%x:%x",
                          bp, bp->fid.vnode, bp->offset.HighPart, bp->offset.LowPart);
                buf_RemoveFromRedirQueue(scp, bp);
                buf_ReleaseLocked(bp, TRUE);
            }
            lock_ConvertWToR(&buf_globalLock);
        }
    }

    /* Confirm that there are none left */
    lock_ConvertRToW(&buf_globalLock);
    for ( bp = redirq_to_cm_buf_t(scp->redirQueueT);
          bp;
          bp = redirq_to_cm_buf_t(scp->redirQueueT))
    {
        if (bp->qFlags & CM_BUF_QREDIR) {
            osi_Log4(buf_logp,"buf_ClearRDRFlag taking from file system bufp 0x%p vno 0x%x foffset 0x%x:%x",
                      bp, bp->fid.vnode, bp->offset.HighPart, bp->offset.LowPart);
            buf_RemoveFromRedirQueue(scp, bp);
            buf_ReleaseLocked(bp, TRUE);
        }

    }
    lock_ReleaseWrite(&buf_globalLock);
    lock_ReleaseWrite(&scp->rw);
    return 0;
}

/*
 * The following routines will not be used on a
 * regular basis but are very useful in a variety
 * of scenarios when debugging data corruption.
 */
const char *
buf_HexCheckSum(cm_buf_t * bp)
{
    int i, k;
    static char buf[33];
    static char tr[16] = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};

    for (i=0;i<16;i++) {
        k = bp->md5cksum[i];

        buf[i*2] = tr[k / 16];
        buf[i*2+1] = tr[k % 16];
    }
    buf[32] = '\0';

    return buf;
}

void
buf_ComputeCheckSum(cm_buf_t * bp)
{
    MD5_CTX md5;

    MD5_Init(&md5);
    MD5_Update(&md5, bp->datap, cm_data.blockSize);
    MD5_Final(bp->md5cksum, &md5);

    osi_Log4(buf_logp, "CheckSum bp 0x%p md5 %s, dirty: offset %u length %u",
             bp, osi_LogSaveString(buf_logp, buf_HexCheckSum(bp)),
             bp->dirty_offset, bp->dirty_length);
}

int
buf_ValidateCheckSum(cm_buf_t * bp)
{
    MD5_CTX md5;
    unsigned char tmp[16];

    MD5_Init(&md5);
    MD5_Update(&md5, bp->datap, cm_data.blockSize);
    MD5_Final(tmp, &md5);

    if (memcmp(tmp, bp->md5cksum, 16) == 0)
        return 1;
    return 0;
}

void
buf_InsertToRedirQueue(cm_scache_t *scp, cm_buf_t *bufp)
{
    lock_AssertWrite(&buf_globalLock);

    if (scp) {
        lock_ObtainMutex(&scp->redirMx);
    }

    if (bufp->qFlags & CM_BUF_QINLRU) {
        _InterlockedAnd(&bufp->qFlags, ~CM_BUF_QINLRU);
        osi_QRemoveHT( (osi_queue_t **) &cm_data.buf_freeListp,
                       (osi_queue_t **) &cm_data.buf_freeListEndp,
                       &bufp->q);
        buf_DecrementFreeCount();
    }
    _InterlockedOr(&bufp->qFlags, CM_BUF_QREDIR);
    osi_QAddH( (osi_queue_t **) &cm_data.buf_redirListp,
               (osi_queue_t **) &cm_data.buf_redirListEndp,
               &bufp->q);
    buf_IncrementRedirCount();
    bufp->redirLastAccess = time(NULL);
    if (scp) {
        osi_QAddH( (osi_queue_t **) &scp->redirQueueH,
                   (osi_queue_t **) &scp->redirQueueT,
                   &bufp->redirq);
        scp->redirLastAccess = bufp->redirLastAccess;
        InterlockedIncrement(&scp->redirBufCount);

        lock_ReleaseMutex(&scp->redirMx);
    }
}

void
buf_RemoveFromRedirQueue(cm_scache_t *scp, cm_buf_t *bufp)
{
    lock_AssertWrite(&buf_globalLock);

    if (!(bufp->qFlags & CM_BUF_QREDIR))
        return;

    if (scp) {
        lock_ObtainMutex(&scp->redirMx);
    }

    _InterlockedAnd(&bufp->qFlags, ~CM_BUF_QREDIR);
    osi_QRemoveHT( (osi_queue_t **) &cm_data.buf_redirListp,
                   (osi_queue_t **) &cm_data.buf_redirListEndp,
                   &bufp->q);
    buf_DecrementRedirCount();

    if (scp) {
        osi_QRemoveHT( (osi_queue_t **) &scp->redirQueueH,
                       (osi_queue_t **) &scp->redirQueueT,
                       &bufp->redirq);

        InterlockedDecrement(&scp->redirBufCount);
        lock_ReleaseMutex(&scp->redirMx);
    }
}

void
buf_MoveToHeadOfRedirQueue(cm_scache_t *scp, cm_buf_t *bufp)
{
    lock_AssertWrite(&buf_globalLock);
    if (!(bufp->qFlags & CM_BUF_QREDIR))
        return;

    if (scp) {
        lock_ObtainMutex(&scp->redirMx);
    }

    osi_QRemoveHT( (osi_queue_t **) &cm_data.buf_redirListp,
                   (osi_queue_t **) &cm_data.buf_redirListEndp,
                   &bufp->q);
    osi_QAddH( (osi_queue_t **) &cm_data.buf_redirListp,
               (osi_queue_t **) &cm_data.buf_redirListEndp,
               &bufp->q);
    bufp->redirLastAccess = time(NULL);
    if (scp) {
        osi_QRemoveHT( (osi_queue_t **) &scp->redirQueueH,
                       (osi_queue_t **) &scp->redirQueueT,
                       &bufp->redirq);
        osi_QAddH( (osi_queue_t **) &scp->redirQueueH,
                   (osi_queue_t **) &scp->redirQueueT,
                   &bufp->redirq);
        scp->redirLastAccess = bufp->redirLastAccess;

        lock_ReleaseMutex(&scp->redirMx);
    }
}
