/*
 * 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
 */

#include <afs/param.h>
#include <afs/stds.h>

#include <windows.h>
#include <winsock2.h>
#include <malloc.h>
#include <string.h>
#include <stdlib.h>
#include <nb30.h>
#include <osi.h>

#include "afsd.h"

osi_mutex_t cm_bufGetMutex;

/* functions called back from the buffer package when reading or writing data,
 * or when holding or releasing a vnode pointer.
 */
long cm_BufWrite(void *vfidp, osi_hyper_t *offsetp, long length, long flags,
	cm_user_t *userp, cm_req_t *reqp)
{
	/* store the data back from this buffer; the buffer is locked and held,
	 * but the vnode involved isn't locked, yet.  It is held by its
	 * reference from the buffer, which won't change until the buffer is
	 * released by our caller.  Thus, we don't have to worry about holding
	 * bufp->scp.
         */
	long code;
	cm_fid_t *fidp = vfidp;
        cm_scache_t *scp;
        long nbytes;
        long temp;
        AFSFetchStatus outStatus;
        AFSStoreStatus inStatus;
        osi_hyper_t thyper;
        AFSVolSync volSync;
        AFSFid tfid;
        struct rx_call *callp;
        osi_queueData_t *qdp;
        cm_buf_t *bufp;
        long wbytes;
        char *bufferp;
        cm_conn_t *connp;
        long truncPos;
        cm_bulkIO_t biod;		/* bulk IO descriptor */

        osi_assert(userp != NULL);

        /* now, the buffer may or may not be filled with good data (buf_GetNew
         * drops lots of locks, and may indeed return a properly initialized
         * buffer, although more likely it will just return a new, empty, buffer.
         */
	scp = cm_FindSCache(fidp);
	if (scp == NULL)
		return CM_ERROR_NOSUCHFILE;	/* shouldn't happen */

	cm_AFSFidFromFid(&tfid, fidp);

	lock_ObtainMutex(&scp->mx);
        
        code = cm_SetupStoreBIOD(scp, offsetp, length, &biod, userp, reqp);
        if (code) {
		osi_Log1(afsd_logp, "cm_SetupStoreBIOD code %x", code);
		lock_ReleaseMutex(&scp->mx);
		cm_ReleaseSCache(scp);
                return code;
        }

	if (biod.length == 0) {
		osi_Log0(afsd_logp, "cm_SetupStoreBIOD length 0");
		lock_ReleaseMutex(&scp->mx);
		cm_ReleaseBIOD(&biod, 1);	/* should be a NOOP */
		cm_ReleaseSCache(scp);
        	return 0;
	}

	/* Serialize StoreData RPC's; for rationale see cm_scache.c */
	(void) cm_SyncOp(scp, NULL, userp, reqp, 0, CM_SCACHESYNC_STOREDATA_EXCL);

	/* prepare the output status for the store */
	scp->mask |= CM_SCACHEMASK_CLIENTMODTIME;
        cm_StatusFromAttr(&inStatus, scp, NULL);
        truncPos = scp->length.LowPart;
        if ((scp->mask & CM_SCACHEMASK_TRUNCPOS)
               	&& scp->truncPos.LowPart < (unsigned long) truncPos)
                       	truncPos = scp->truncPos.LowPart;
	scp->mask &= ~CM_SCACHEMASK_TRUNCPOS;
                
	/* compute how many bytes to write from this buffer */
        thyper = LargeIntegerSubtract(scp->length, biod.offset);
        if (LargeIntegerLessThanZero(thyper)) {
		/* entire buffer is past EOF */
		nbytes = 0;
        }
        else {
		/* otherwise write out part of buffer before EOF, but not
                 * more than bufferSize bytes.
                 */
		nbytes = thyper.LowPart;
                if (nbytes > biod.length) nbytes = biod.length;
        }

	lock_ReleaseMutex(&scp->mx);
        
        /* now we're ready to do the store operation */
        do {
		code = cm_Conn(&scp->fid, userp, reqp, &connp);
                if (code) continue;
		
		callp = rx_NewCall(connp->callp);

		osi_Log3(afsd_logp, "CALL StoreData vp %x, off 0x%x, size 0x%x",
                	(long) scp, biod.offset.LowPart, nbytes);

                code = StartRXAFS_StoreData(callp, &tfid, &inStatus,
			biod.offset.LowPart, nbytes, truncPos);

		if (code == 0) {
                	/* write the data from the the list of buffers */
                        qdp = NULL;
			while(nbytes > 0) {
				if (qdp == NULL)
		 			qdp = biod.bufListEndp;
				else
					qdp = (osi_queueData_t *) osi_QPrev(&qdp->q);
				osi_assert(qdp != NULL);
	                        bufp = osi_GetQData(qdp);
                                bufferp = bufp->datap;
	                        wbytes = nbytes;
	                        if (wbytes > buf_bufferSize) wbytes = buf_bufferSize;

                                /* write out wbytes of data from bufferp */
	                        temp = rx_Write(callp, bufferp, wbytes);
	                        if (temp != wbytes) {
                                	code = -1;
					break;
				}
                                nbytes -= wbytes;
                        }	/* while more bytes to write */
		}		/* if RPC started successfully */

		if (code == 0)
			code = EndRXAFS_StoreData(callp, &outStatus, &volSync);
                code = rx_EndCall(callp, code);
                osi_Log0(afsd_logp, "CALL StoreData DONE");
                
	} while (cm_Analyze(connp, userp, reqp, &scp->fid, &volSync, NULL, code));
        code = cm_MapRPCError(code, reqp);
        
        /* now, clean up our state */
        lock_ObtainMutex(&scp->mx);

	cm_SyncOpDone(scp, NULL, CM_SCACHESYNC_STOREDATA_EXCL);

	if (code == 0) {
		/* now, here's something a little tricky: in AFS 3, a dirty
		 * length can't be directly stored, instead, a dirty chunk is
		 * stored that sets the file's size (by writing and by using
		 * the truncate-first option in the store call).
		 *
                 * At this point, we've just finished a store, and so the trunc
		 * pos field is clean.  If the file's size at the server is at
		 * least as big as we think it should be, then we turn off the
		 * length dirty bit, since all the other dirty buffers must
		 * precede this one in the file.
                 *
                 * The file's desired size shouldn't be smaller than what's
		 * stored at the server now, since we just did the trunc pos
		 * store.
                 *
                 * We have to turn off the length dirty bit as soon as we can,
		 * so that we see updates made by other machines.
                 */
		if (outStatus.Length >= scp->length.LowPart)
                	scp->mask &= ~CM_SCACHEMASK_LENGTH;
		cm_MergeStatus(scp, &outStatus, &volSync, userp, 0);
	} else {
		if (code == CM_ERROR_SPACE)
			scp->flags |= CM_SCACHEFLAG_OUTOFSPACE;
		else if (code == CM_ERROR_QUOTA)
			scp->flags |= CM_SCACHEFLAG_OVERQUOTA;
	}
        lock_ReleaseMutex(&scp->mx);
        cm_ReleaseBIOD(&biod, 1);
	cm_ReleaseSCache(scp);

        return code;
}

/*
 * Truncate the file, by sending a StoreData RPC with zero length.
 *
 * Called with scp locked.  Releases and re-obtains the lock.
 */
long cm_StoreMini(cm_scache_t *scp, cm_user_t *userp, cm_req_t *reqp)
{
        AFSFetchStatus outStatus;
        AFSStoreStatus inStatus;
        AFSVolSync volSync;
        AFSFid tfid;
	long code;
	long truncPos;
	cm_conn_t *connp;
        struct rx_call *callp;

	/* Serialize StoreData RPC's; for rationale see cm_scache.c */
	(void) cm_SyncOp(scp, NULL, userp, reqp, 0,
			 CM_SCACHESYNC_STOREDATA_EXCL);

	/* prepare the output status for the store */
	inStatus.Mask = AFS_SETMODTIME;
	inStatus.ClientModTime = scp->clientModTime;
	scp->mask &= ~CM_SCACHEMASK_CLIENTMODTIME;

	/* calculate truncation position */
        truncPos = scp->length.LowPart;
        if ((scp->mask & CM_SCACHEMASK_TRUNCPOS)
               	&& scp->truncPos.LowPart < (unsigned long) truncPos)
                       	truncPos = scp->truncPos.LowPart;
	scp->mask &= ~CM_SCACHEMASK_TRUNCPOS;
                
	lock_ReleaseMutex(&scp->mx);

	cm_AFSFidFromFid(&tfid, &scp->fid);

        /* now we're ready to do the store operation */
        do {
		code = cm_Conn(&scp->fid, userp, reqp, &connp);
                if (code) continue;
		
		callp = rx_NewCall(connp->callp);

                code = StartRXAFS_StoreData(callp, &tfid, &inStatus,
			0, 0, truncPos);

		if (code == 0)
			code = EndRXAFS_StoreData(callp, &outStatus, &volSync);
                code = rx_EndCall(callp, code);
                
	} while (cm_Analyze(connp, userp, reqp, &scp->fid, &volSync, NULL, code));
        code = cm_MapRPCError(code, reqp);
        
        /* now, clean up our state */
        lock_ObtainMutex(&scp->mx);

	cm_SyncOpDone(scp, NULL, CM_SCACHESYNC_STOREDATA_EXCL);

	if (code == 0) {
		/*
		 * For explanation of handling of CM_SCACHEMASK_LENGTH,
		 * see cm_BufWrite().
		 */
		if (outStatus.Length >= scp->length.LowPart)
                	scp->mask &= ~CM_SCACHEMASK_LENGTH;
		cm_MergeStatus(scp, &outStatus, &volSync, userp, 0);
	}

	return code;
}

long cm_BufRead(cm_buf_t *bufp, long nbytes, long *bytesReadp, cm_user_t *userp)
{
	*bytesReadp = buf_bufferSize;

	/* now return a code that means that I/O is done */
        return 0;
}

/* stabilize scache entry, and return with it locked so 
 * it stays stable.
 */
long cm_BufStabilize(void *parmp, cm_user_t *userp, cm_req_t *reqp)
{
	cm_scache_t *scp;
        long code;

        scp = parmp;
        
	lock_ObtainMutex(&scp->mx);
        code = cm_SyncOp(scp, NULL, userp, reqp,
			 0, CM_SCACHESYNC_NEEDCALLBACK
				| CM_SCACHESYNC_GETSTATUS
        			| CM_SCACHESYNC_SETSIZE);
	if (code) {
		lock_ReleaseMutex(&scp->mx);
        	return code;
	}
        
        return 0;
}

/* undoes the work that cm_BufStabilize does: releases lock so things can change again */
long cm_BufUnstabilize(void *parmp, cm_user_t *userp)
{
	cm_scache_t *scp;
        
        scp = parmp;
        
        lock_ReleaseMutex(&scp->mx);
        
	/* always succeeds */
        return 0;
}

cm_buf_ops_t cm_bufOps = {
	cm_BufWrite,
        cm_BufRead,
        cm_BufStabilize,
        cm_BufUnstabilize
};

int cm_InitDCache(long chunkSize, long nbuffers)
{
	lock_InitializeMutex(&cm_bufGetMutex, "buf_Get mutex");
	if (nbuffers) buf_nbuffers = nbuffers;
	return buf_Init(&cm_bufOps);
}

/* check to see if we have an up-to-date buffer.  The buffer must have
 * previously been obtained by calling buf_Get.
 *
 * Make sure we have a callback, and that the dataversion matches.
 *
 * Scp must be locked.
 *
 * Bufp *may* be locked.
 */
int cm_HaveBuffer(cm_scache_t *scp, cm_buf_t *bufp, int isBufLocked)
{
	int code;
	if (!cm_HaveCallback(scp))
		return 0;
	if ((bufp->cmFlags
	     & (CM_BUF_CMFETCHING | CM_BUF_CMFULLYFETCHED))
		== (CM_BUF_CMFETCHING | CM_BUF_CMFULLYFETCHED))
		return 1;
       	if (bufp->dataVersion == scp->dataVersion)
        	return 1;
	if (!isBufLocked) {
		code = lock_TryMutex(&bufp->mx);
                if (code == 0) {
			/* don't have the lock, and can't lock it, then
                         * return failure.
                         */
                         return 0;
                }
        }

	/* remember dirty flag for later */
	code = bufp->flags & CM_BUF_DIRTY;

	/* release lock if we obtained it here */
	if (!isBufLocked) lock_ReleaseMutex(&bufp->mx);

	/* if buffer was dirty, buffer is acceptable for use */
        if (code) return 1;
        else return 0;
}

/* used when deciding whether to do a prefetch or not */
long cm_CheckFetchRange(cm_scache_t *scp, osi_hyper_t *startBasep, long length,
	cm_user_t *up, cm_req_t *reqp, osi_hyper_t *realBasep)
{
	osi_hyper_t toffset;
        osi_hyper_t tbase;
        long code;
        cm_buf_t *bp;
        int stop;
        
        /* now scan all buffers in the range, looking for any that look like
         * they need work.
         */
	tbase = *startBasep;
	stop = 0;
	lock_ObtainMutex(&scp->mx);
        while(length > 0) {
		/* get callback so we can do a meaningful dataVersion comparison */
	        code = cm_SyncOp(scp, NULL, up, reqp, 0,
				 CM_SCACHESYNC_NEEDCALLBACK
                       		 | CM_SCACHESYNC_GETSTATUS);
		if (code) {
			scp->flags &= ~CM_SCACHEFLAG_PREFETCHING;
			lock_ReleaseMutex(&scp->mx);
                        return code;
                }
                
                if (LargeIntegerGreaterThanOrEqualTo(tbase, scp->length)) {
			/* we're past the end of file */
                        break;
                }

		bp = buf_Find(scp, &tbase);
		/* We cheat slightly by not locking the bp mutex. */
                if (bp) {
                        if ((bp->cmFlags
			      & (CM_BUF_CMFETCHING | CM_BUF_CMSTORING)) == 0
                        	&& bp->dataVersion != scp->dataVersion)
                                	stop = 1;
	                buf_Release(bp);
		}
                else stop = 1;

		/* if this buffer is essentially guaranteed to require a fetch,
                 * break out here and return this position.
                 */
                if (stop) break;
                
                toffset.LowPart = buf_bufferSize;
                toffset.HighPart = 0;
                tbase = LargeIntegerAdd(toffset, tbase);
                length -= buf_bufferSize;
        }
        
        /* if we get here, either everything is fine or stop stopped us at a
	 * particular buffer in the range that definitely needs to be fetched.
         */
        if (stop == 0) {
		/* return non-zero code since realBasep won't be valid */
		scp->flags &= ~CM_SCACHEFLAG_PREFETCHING;
		code = -1;
        }
        else {
		/* successfully found a page that will need fetching */
		*realBasep = tbase;
                code = 0;
        }
        lock_ReleaseMutex(&scp->mx);
        return code;
}

void cm_BkgStore(cm_scache_t *scp, long p1, long p2, long p3, long p4,
	cm_user_t *userp)
{
	osi_hyper_t toffset;
        long length;
	cm_req_t req;

	cm_InitReq(&req);
	req.flags |= CM_REQ_NORETRY;

        toffset.LowPart = p1;
        toffset.HighPart = p2;
        length = p3;

	osi_Log2(afsd_logp, "Starting BKG store vp 0x%x, base 0x%x", scp, p1);

	cm_BufWrite(&scp->fid, &toffset, length, /* flags */ 0, userp, &req);

	lock_ObtainMutex(&scp->mx);
	cm_SyncOpDone(scp, NULL, CM_SCACHESYNC_ASYNCSTORE);
        lock_ReleaseMutex(&scp->mx);
}

void cm_ClearPrefetchFlag(long code, cm_scache_t *scp, osi_hyper_t *base)
{
	osi_hyper_t thyper;

	if (code == 0) {
		thyper.LowPart = cm_chunkSize;
		thyper.HighPart = 0;
		thyper =  LargeIntegerAdd(*base, thyper);
		thyper.LowPart &= (-cm_chunkSize);
		if (LargeIntegerGreaterThan(*base, scp->prefetch.base))
	                scp->prefetch.base = *base;
		if (LargeIntegerGreaterThan(thyper, scp->prefetch.end))
	                scp->prefetch.end = thyper;
	}
	scp->flags &= ~CM_SCACHEFLAG_PREFETCHING;
}

/* do the prefetch */
void cm_BkgPrefetch(cm_scache_t *scp, long p1, long p2, long p3, long p4,
	cm_user_t *userp)
{
	long length;
        osi_hyper_t base;
        long code;
        cm_buf_t *bp;
	int cpff = 0;			/* cleared prefetch flag */
	cm_req_t req;

	cm_InitReq(&req);
	req.flags |= CM_REQ_NORETRY;
        
	base.LowPart = p1;
        base.HighPart = p2;
        length = p3;
        
	osi_Log2(afsd_logp, "Starting BKG prefetch vp 0x%x, base 0x%x", scp, p1);

        code = buf_Get(scp, &base, &bp);

	lock_ObtainMutex(&scp->mx);

        if (code || (bp->cmFlags & CM_BUF_CMFETCHING)) {
		scp->flags &= ~CM_SCACHEFLAG_PREFETCHING;
		lock_ReleaseMutex(&scp->mx);
		return;
	}

        code = cm_GetBuffer(scp, bp, &cpff, userp, &req);
	if (!cpff) cm_ClearPrefetchFlag(code, scp, &base);
	lock_ReleaseMutex(&scp->mx);
        buf_Release(bp);
        return;
}

/* a read was issued to offsetp, and we have to determine whether we should
 * do a prefetch.
 */
void cm_ConsiderPrefetch(cm_scache_t *scp, osi_hyper_t *offsetp,
	cm_user_t *userp, cm_req_t *reqp)
{
	long code;
        osi_hyper_t realBase;
        osi_hyper_t readBase;
        
        readBase = *offsetp;
	/* round up to chunk boundary */
	readBase.LowPart += (cm_chunkSize-1);
	readBase.LowPart &= (-cm_chunkSize);

	lock_ObtainMutex(&scp->mx);
	if ((scp->flags & CM_SCACHEFLAG_PREFETCHING)
	      || LargeIntegerLessThanOrEqualTo(readBase, scp->prefetch.base)) {
		lock_ReleaseMutex(&scp->mx);
        	return;
	}
	scp->flags |= CM_SCACHEFLAG_PREFETCHING;

	/* start the scan at the latter of the end of this read or
         * the end of the last fetched region.
         */
	if (LargeIntegerGreaterThan(scp->prefetch.end, readBase))
        	readBase = scp->prefetch.end;

        lock_ReleaseMutex(&scp->mx);


        code = cm_CheckFetchRange(scp, &readBase, cm_chunkSize, userp, reqp,
        	&realBase);
	if (code) return;	/* can't find something to prefetch */

        osi_Log2(afsd_logp, "BKG Prefetch request vp 0x%x, base 0x%x",
		 scp, realBase.LowPart);

        cm_QueueBKGRequest(scp, cm_BkgPrefetch, realBase.LowPart,
		realBase.HighPart, cm_chunkSize, 0, userp);
}

/* scp must be locked; temporarily unlocked during processing.
 * If returns 0, returns buffers held in biop, and with
 * CM_BUF_CMSTORING set.
 *
 * Caller *must* set CM_BUF_WRITING and reset the over.hEvent field if the
 * buffer is ever unlocked before CM_BUF_DIRTY is cleared.  And if
 * CM_BUF_WRITING is ever viewed by anyone, then it must be cleared, sleepers
 * must be woken, and the event must be set when the I/O is done.  All of this
 * is required so that buf_WaitIO synchronizes properly with the buffer as it
 * is being written out.
 */
long cm_SetupStoreBIOD(cm_scache_t *scp, osi_hyper_t *inOffsetp, long inSize,
	cm_bulkIO_t *biop, cm_user_t *userp, cm_req_t *reqp)
{
        cm_buf_t *bufp;
        osi_queueData_t *qdp;
        osi_hyper_t thyper;
        osi_hyper_t tbase;
        osi_hyper_t scanStart;		/* where to start scan for dirty pages */
        osi_hyper_t scanEnd;		/* where to stop scan for dirty pages */
        osi_hyper_t firstModOffset;	/* offset of first modified page in range */
        long temp;
        long code;
        long flags;			/* flags to cm_SyncOp */
        
	/* clear things out */
	biop->scp = scp;		/* don't hold */
        biop->offset = *inOffsetp;
        biop->length = 0;
        biop->bufListp = NULL;
        biop->bufListEndp = NULL;
	biop->reserved = 0;

	/* reserve a chunk's worth of buffers */
	lock_ReleaseMutex(&scp->mx);
	buf_ReserveBuffers(cm_chunkSize / buf_bufferSize);
	lock_ObtainMutex(&scp->mx);

        bufp = NULL;
        for(temp = 0; temp < inSize; temp += buf_bufferSize, bufp = NULL) {
		thyper.HighPart = 0;
		thyper.LowPart = temp;
                tbase = LargeIntegerAdd(*inOffsetp, thyper);
                
                bufp = buf_Find(scp, &tbase);
                if (bufp) {
			/* get buffer mutex and scp mutex safely */
			lock_ReleaseMutex(&scp->mx);
			lock_ObtainMutex(&bufp->mx);
			lock_ObtainMutex(&scp->mx);

			flags = CM_SCACHESYNC_NEEDCALLBACK
                        	| CM_SCACHESYNC_GETSTATUS
                                | CM_SCACHESYNC_STOREDATA
                                | CM_SCACHESYNC_BUFLOCKED;
			code = cm_SyncOp(scp, bufp, userp, reqp, 0, flags); 
                        if (code) {
				lock_ReleaseMutex(&bufp->mx);
                                buf_Release(bufp);
				buf_UnreserveBuffers(cm_chunkSize
							/ buf_bufferSize);
                                return code;
                        }
                        
			/* if the buffer is dirty, we're done */
                        if (bufp->flags & CM_BUF_DIRTY) {
                        	osi_assertx(!(bufp->flags & CM_BUF_WRITING),
                                	"WRITING w/o CMSTORING in SetupStoreBIOD");
				bufp->flags |= CM_BUF_WRITING;
				break;
                        }

			/* this buffer is clean, so there's no reason to process it */
			cm_SyncOpDone(scp, bufp, flags);
			lock_ReleaseMutex(&bufp->mx);
			buf_Release(bufp);
                }
        }

	biop->reserved = 1;
        
        /* if we get here, if bufp is null, we didn't find any dirty buffers
	 * that weren't already being stored back, so we just quit now.
         */
        if (!bufp) {
        	return 0;
	}

	/* don't need buffer mutex any more */
	lock_ReleaseMutex(&bufp->mx);
        
	/* put this element in the list */
        qdp = osi_QDAlloc();
        osi_SetQData(qdp, bufp);
	/* don't have to hold bufp, since held by buf_Find above */
        osi_QAddH((osi_queue_t **) &biop->bufListp,
		  (osi_queue_t **) &biop->bufListEndp,
		  &qdp->q);
        biop->length = buf_bufferSize;
        firstModOffset = bufp->offset;
        biop->offset = firstModOffset;

	/* compute the window surrounding *inOffsetp of size cm_chunkSize */
	scanStart = *inOffsetp;
        scanStart.LowPart &= (-cm_chunkSize);
	thyper.LowPart = cm_chunkSize;
        thyper.HighPart = 0;
	scanEnd = LargeIntegerAdd(scanStart, thyper);

	flags = CM_SCACHESYNC_NEEDCALLBACK
		| CM_SCACHESYNC_GETSTATUS
                | CM_SCACHESYNC_STOREDATA
                | CM_SCACHESYNC_BUFLOCKED
                | CM_SCACHESYNC_NOWAIT;

	/* start by looking backwards until scanStart */
	thyper.HighPart = 0;		/* hyper version of buf_bufferSize */
        thyper.LowPart = buf_bufferSize;
	tbase = LargeIntegerSubtract(firstModOffset, thyper);
        while(LargeIntegerGreaterThanOrEqualTo(tbase, scanStart)) {
		/* see if we can find the buffer */
		bufp = buf_Find(scp, &tbase);
                if (!bufp) break;

		/* try to lock it, and quit if we can't (simplifies locking) */
                code = lock_TryMutex(&bufp->mx);
                if (code == 0) {
			buf_Release(bufp);
                        break;
                }
                
                code = cm_SyncOp(scp, bufp, userp, reqp, 0, flags);
                if (code) {
			lock_ReleaseMutex(&bufp->mx);
			buf_Release(bufp);
                        break;
                }
                
		if (!(bufp->flags & CM_BUF_DIRTY)) {
			/* buffer is clean, so we shouldn't add it */
			cm_SyncOpDone(scp, bufp, flags);
			lock_ReleaseMutex(&bufp->mx);
			buf_Release(bufp);
                        break;
                }

		/* don't need buffer mutex any more */
		lock_ReleaseMutex(&bufp->mx);

                /* we have a dirty buffer ready for storing.  Add it to the tail
                 * of the list, since it immediately precedes all of the disk
                 * addresses we've already collected.
                 */
		qdp = osi_QDAlloc();
                osi_SetQData(qdp, bufp);
                /* no buf_hold necessary, since we have it held from buf_Find */
                osi_QAddT((osi_queue_t **) &biop->bufListp,
			  (osi_queue_t **) &biop->bufListEndp,
                	  &qdp->q);

		/* update biod info describing the transfer */
                biop->offset = LargeIntegerSubtract(biop->offset, thyper);
                biop->length += buf_bufferSize;
                
                /* update loop pointer */
                tbase = LargeIntegerSubtract(tbase, thyper);
        }	/* while loop looking for pages preceding the one we found */

	/* now, find later dirty, contiguous pages, and add them to the list */
	thyper.HighPart = 0;		/* hyper version of buf_bufferSize */
        thyper.LowPart = buf_bufferSize;
	tbase = LargeIntegerAdd(firstModOffset, thyper);
        while(LargeIntegerLessThan(tbase, scanEnd)) {
		/* see if we can find the buffer */
		bufp = buf_Find(scp, &tbase);
                if (!bufp) break;

		/* try to lock it, and quit if we can't (simplifies locking) */
                code = lock_TryMutex(&bufp->mx);
                if (code == 0) {
			buf_Release(bufp);
                        break;
                }
                
                code = cm_SyncOp(scp, bufp, userp, reqp, 0, flags);
                if (code) {
			lock_ReleaseMutex(&bufp->mx);
			buf_Release(bufp);
                        break;
                }
                
		if (!(bufp->flags & CM_BUF_DIRTY)) {
			/* buffer is clean, so we shouldn't add it */
			cm_SyncOpDone(scp, bufp, flags);
			lock_ReleaseMutex(&bufp->mx);
			buf_Release(bufp);
                        break;
                }

		/* don't need buffer mutex any more */
		lock_ReleaseMutex(&bufp->mx);

                /* we have a dirty buffer ready for storing.  Add it to the head
                 * of the list, since it immediately follows all of the disk
                 * addresses we've already collected.
                 */
		qdp = osi_QDAlloc();
                osi_SetQData(qdp, bufp);
                /* no buf_hold necessary, since we have it held from buf_Find */
                osi_QAddH((osi_queue_t **) &biop->bufListp,
			  (osi_queue_t **) &biop->bufListEndp,
                	  &qdp->q);

		/* update biod info describing the transfer */
                biop->length += buf_bufferSize;
                
                /* update loop pointer */
                tbase = LargeIntegerAdd(tbase, thyper);
        }	/* while loop looking for pages following the first page we found */
	
        /* finally, we're done */
        return 0;
}

/* scp must be locked; temporarily unlocked during processing.
 * If returns 0, returns buffers held in biop, and with
 * CM_BUF_CMFETCHING flags set.
 * If an error is returned, we don't return any buffers.
 */
long cm_SetupFetchBIOD(cm_scache_t *scp, osi_hyper_t *offsetp,
			cm_bulkIO_t *biop, cm_user_t *up, cm_req_t *reqp)
{
	long code;
        cm_buf_t *tbp;
        osi_hyper_t toffset;		/* a long long temp variable */
        osi_hyper_t pageBase;		/* base offset we're looking at */
        osi_queueData_t *qdp;		/* one temp queue structure */
        osi_queueData_t *tqdp;		/* another temp queue structure */
        long collected;			/* how many bytes have been collected */
        int isFirst;
        long flags;
        osi_hyper_t fileSize;		/* the # of bytes in the file */
        osi_queueData_t *heldBufListp;	/* we hold all buffers in this list */
        osi_queueData_t *heldBufListEndp;	/* first one */
	int reserving;
        
        biop->scp = scp;
        biop->offset = *offsetp;
	/* null out the list of buffers */
        biop->bufListp = biop->bufListEndp = NULL;
	biop->reserved = 0;

	/* first lookup the file's length, so we know when to stop */
        code = cm_SyncOp(scp, NULL, up, reqp, 0, CM_SCACHESYNC_NEEDCALLBACK
						 | CM_SCACHESYNC_GETSTATUS);
        if (code) return code;
        
	/* copy out size, since it may change */
        fileSize = scp->serverLength;
        
        lock_ReleaseMutex(&scp->mx);

	pageBase = *offsetp;
        collected = pageBase.LowPart & (cm_chunkSize - 1);
        heldBufListp = NULL;
        heldBufListEndp = NULL;

	/*
	 * Obtaining buffers can cause dirty buffers to be recycled, which
	 * can cause a storeback, so cannot be done while we have buffers
	 * reserved.
	 *
	 * To get around this, we get buffers twice.  Before reserving buffers,
	 * we obtain and release each one individually.  After reserving
	 * buffers, we try to obtain them again, but only by lookup, not by
	 * recycling.  If a buffer has gone away while we were waiting for
	 * the others, we just use whatever buffers we already have.
	 *
	 * On entry to this function, we are already holding a buffer, so we
	 * can't wait for reservation.  So we call buf_TryReserveBuffers()
	 * instead.  Not only that, we can't really even call buf_Get(), for
	 * the same reason.  We can't avoid that, though.  To avoid deadlock
	 * we allow only one thread to be executing the buf_Get()-buf_Release()
	 * sequence at a time.
	 */

	/* first hold all buffers, since we can't hold any locks in buf_Get */
        while (1) {
		/* stop at chunk boundary */
		if (collected >= cm_chunkSize) break;
                
                /* see if the next page would be past EOF */
                if (LargeIntegerGreaterThanOrEqualTo(pageBase, fileSize)) break;

		lock_ObtainMutex(&cm_bufGetMutex);

		code = buf_Get(scp, &pageBase, &tbp);
                if (code) {
			lock_ReleaseMutex(&cm_bufGetMutex);
			lock_ObtainMutex(&scp->mx);
			return code;
		}
                
		buf_Release(tbp);

		lock_ReleaseMutex(&cm_bufGetMutex);

                toffset.HighPart = 0;
                toffset.LowPart = buf_bufferSize;
                pageBase = LargeIntegerAdd(toffset, pageBase);
		collected += buf_bufferSize;
        }

        /* reserve a chunk's worth of buffers if possible */
	reserving = buf_TryReserveBuffers(cm_chunkSize / buf_bufferSize);

	pageBase = *offsetp;
        collected = pageBase.LowPart & (cm_chunkSize - 1);

	/* now hold all buffers, if they are still there */
        while (1) {
		/* stop at chunk boundary */
		if (collected >= cm_chunkSize) break;
                
                /* see if the next page would be past EOF */
                if (LargeIntegerGreaterThanOrEqualTo(pageBase, fileSize)) break;

                tbp = buf_Find(scp, &pageBase);
		if (!tbp) break;

                /* add the buffer to the list */
		qdp = osi_QDAlloc();
                osi_SetQData(qdp, tbp);
                osi_QAdd((osi_queue_t **)&heldBufListp, &qdp->q);
                if (!heldBufListEndp) heldBufListEndp = qdp;
		/* leave tbp held (from buf_Get) */

		if (!reserving) break;

                collected += buf_bufferSize;
                toffset.HighPart = 0;
                toffset.LowPart = buf_bufferSize;
                pageBase = LargeIntegerAdd(toffset, pageBase);
        }

        /* look at each buffer, adding it into the list if it looks idle and
	 * filled with old data.  One special case: wait for idle if it is the
	 * first buffer since we really need that one for our caller to make
	 * any progress.
         */
        isFirst = 1;
        collected = 0;		/* now count how many we'll really use */
	for(tqdp = heldBufListEndp;
	    tqdp;
	    tqdp = (osi_queueData_t *) osi_QPrev(&tqdp->q)) {
		/* get a ptr to the held buffer */
		tbp = osi_GetQData(tqdp);
                pageBase = tbp->offset;

		/* now lock the buffer lock */
		lock_ObtainMutex(&tbp->mx);
		lock_ObtainMutex(&scp->mx);

		/* don't bother fetching over data that is already current */
		if (tbp->dataVersion == scp->dataVersion) {
			/* we don't need this buffer, since it is current */
			lock_ReleaseMutex(&scp->mx);
                        lock_ReleaseMutex(&tbp->mx);
                        break;
                }

		flags = CM_SCACHESYNC_NEEDCALLBACK | CM_SCACHESYNC_FETCHDATA
                	| CM_SCACHESYNC_BUFLOCKED;
		if (!isFirst) flags |= CM_SCACHESYNC_NOWAIT;

		/* wait for the buffer to serialize, if required.  Doesn't
		 * release the scp or buffer lock(s) if NOWAIT is specified.
                 */
		code = cm_SyncOp(scp, tbp, up, reqp, 0, flags);
                if (code) {
			lock_ReleaseMutex(&scp->mx);
			lock_ReleaseMutex(&tbp->mx);
                	break;
		}
                
		/* don't fetch over dirty buffers */
                if (tbp->flags & CM_BUF_DIRTY) {
			cm_SyncOpDone(scp, tbp, flags);
			lock_ReleaseMutex(&scp->mx);
                        lock_ReleaseMutex(&tbp->mx);
                        break;
		}

		/* Release locks */
		lock_ReleaseMutex(&scp->mx);
		lock_ReleaseMutex(&tbp->mx);

                /* add the buffer to the list */
		qdp = osi_QDAlloc();
                osi_SetQData(qdp, tbp);
                osi_QAdd((osi_queue_t **)&biop->bufListp, &qdp->q);
                if (!biop->bufListEndp) biop->bufListEndp = qdp;
		buf_Hold(tbp);

		/* from now on, a failure just stops our collection process, but
                 * we still do the I/O to whatever we've already managed to collect.
                 */
        	isFirst = 0;
                collected += buf_bufferSize;
        }
        
        /* now, we've held in biop->bufListp all the buffer's we're really
	 * interested in.  We also have holds left from heldBufListp, and we
	 * now release those holds on the buffers.
         */
	for(qdp = heldBufListp; qdp; qdp = tqdp) {
		tqdp = (osi_queueData_t *) osi_QNext(&qdp->q);
		tbp = osi_GetQData(qdp);
                osi_QDFree(qdp);
                buf_Release(tbp);
        }

	/* Caller expects this */
	lock_ObtainMutex(&scp->mx);
 
	/* if we got a failure setting up the first buffer, then we don't have
         * any side effects yet, and we also have failed an operation that the
         * caller requires to make any progress.  Give up now.
         */
        if (code && isFirst) {
		buf_UnreserveBuffers(cm_chunkSize / buf_bufferSize);
		return code;
	}
        
        /* otherwise, we're still OK, and should just return the I/O setup we've
         * got.
         */
	biop->length = collected;
	biop->reserved = reserving;
        return 0;
}

/* release a bulk I/O structure that was setup by cm_SetupFetchBIOD or by
 * cm_SetupStoreBIOD
 */
void cm_ReleaseBIOD(cm_bulkIO_t *biop, int isStore)
{
	cm_scache_t *scp;
        cm_buf_t *bufp;
        osi_queueData_t *qdp;
        osi_queueData_t *nqdp;
        int flags;

	/* Give back reserved buffers */
	if (biop->reserved)
		buf_UnreserveBuffers(cm_chunkSize / buf_bufferSize);
        
	flags = CM_SCACHESYNC_NEEDCALLBACK;
        if (isStore)
        	flags |= CM_SCACHESYNC_STOREDATA;
	else
		flags |= CM_SCACHESYNC_FETCHDATA;

	scp = biop->scp;
        for(qdp = biop->bufListp; qdp; qdp = nqdp) {
		/* lookup next guy first, since we're going to free this one */
		nqdp = (osi_queueData_t *) osi_QNext(&qdp->q);
                
		/* extract buffer and free queue data */
                bufp = osi_GetQData(qdp);
                osi_QDFree(qdp);
                
                /* now, mark I/O as done, unlock the buffer and release it */
		lock_ObtainMutex(&bufp->mx);
		lock_ObtainMutex(&scp->mx);
                cm_SyncOpDone(scp, bufp, flags);
		lock_ReleaseMutex(&scp->mx);
                
		/* turn off writing and wakeup users */
                if (isStore) {
                	if (bufp->flags & CM_BUF_WAITING) {
				osi_Wakeup((long) bufp);
                        }
			bufp->flags &= ~(CM_BUF_WAITING | CM_BUF_WRITING
					  | CM_BUF_DIRTY);
                }

                lock_ReleaseMutex(&bufp->mx);
                buf_Release(bufp);
        }
        
        /* clean things out */
        biop->bufListp = NULL;
        biop->bufListEndp = NULL;
}

/* Fetch a buffer.  Called with scp locked.
 * The scp is locked on return.
 */
long cm_GetBuffer(cm_scache_t *scp, cm_buf_t *bufp, int *cpffp, cm_user_t *up,
	cm_req_t *reqp)
{
	long code;
        long nbytes;			/* bytes in transfer */
        long rbytes;			/* bytes in rx_Read call */
        long temp;
        AFSFetchStatus afsStatus;
        AFSCallBack callback;
        AFSVolSync volSync;
        char *bufferp;
        cm_buf_t *tbufp;		/* buf we're filling */
        osi_queueData_t *qdp;		/* q element we're scanning */
        AFSFid tfid;
        struct rx_call *callp;
        cm_bulkIO_t biod;		/* bulk IO descriptor */
        cm_conn_t *connp;

        /* now, the buffer may or may not be filled with good data (buf_GetNew
         * drops lots of locks, and may indeed return a properly initialized
         * buffer, although more likely it will just return a new, empty, buffer.
         */
	cm_AFSFidFromFid(&tfid, &scp->fid);

	code = cm_SetupFetchBIOD(scp, &bufp->offset, &biod, up, reqp);
	if (code) {
		/* couldn't even get the first page setup properly */
		osi_Log1(afsd_logp, "SetupFetchBIOD failure code %d", code);
        	return code;
	}

        /* once we get here, we have the callback in place, we know that no one
	 * is fetching the data now.  Check one last time that we still have
	 * the wrong data, and then fetch it if we're still wrong.
	 *
         * We can lose a race condition and end up with biod.length zero, in
	 * which case we just retry.
         */
        if (bufp->dataVersion == scp->dataVersion || biod.length == 0) {
		osi_Log3(afsd_logp, "Bad DVs %d, %d or length 0x%x",
			 bufp->dataVersion, scp->dataVersion, biod.length);
		if ((bufp->dataVersion == -1
		     || bufp->dataVersion < scp->dataVersion)
		    && LargeIntegerGreaterThanOrEqualTo(bufp->offset,
							scp->serverLength)) {
			if (bufp->dataVersion == -1)
				memset(bufp->datap, 0, buf_bufferSize);
			bufp->dataVersion = scp->dataVersion;
		}
		lock_ReleaseMutex(&scp->mx);
		cm_ReleaseBIOD(&biod, 0);
		lock_ObtainMutex(&scp->mx);
                return 0;
        }
        
        lock_ReleaseMutex(&scp->mx);

	/* now make the call */
        do {
		code = cm_Conn(&scp->fid, up, reqp, &connp);
                if (code) continue;
		
		callp = rx_NewCall(connp->callp);

		osi_Log3(afsd_logp, "CALL FetchData vp %x, off 0x%x, size 0x%x",
                	(long) scp, biod.offset.LowPart, biod.length);

                code = StartRXAFS_FetchData(callp, &tfid, biod.offset.LowPart,
                	biod.length);

		/* now copy the data out of the pipe and put it in the buffer */
		temp  = rx_Read(callp, &nbytes, 4);
		if (temp == 4) {
			nbytes = ntohl(nbytes);
                        if (nbytes > biod.length) code = -1;
                }
                else code = -1;

		if (code == 0) {
                        qdp = biod.bufListEndp;
                        if (qdp) {
				tbufp = osi_GetQData(qdp);
                                bufferp = tbufp->datap;
                        }
                        else bufferp = NULL;
			/* fill nbytes of data from the pipe into the pages.
			 * When we stop, qdp will point at the last page we're
			 * dealing with, and bufferp will tell us where we
			 * stopped.  We'll need this info below when we clear
			 * the remainder of the last page out (and potentially
                         * clear later pages out, if we fetch past EOF).
                         */
	                while(nbytes > 0) {
				/* assert that there are still more buffers;
				 * our check above for nbytes being less than
				 * biod.length should ensure this.
                                 */
				osi_assert(bufferp != NULL);

				/* read rbytes of data */
                                rbytes = (nbytes > buf_bufferSize? buf_bufferSize : nbytes);
                                temp = rx_Read(callp, bufferp, rbytes);
                                if (temp < rbytes) {
                                	code = -1;
                                        break;
				}

				/* allow read-while-fetching.
				 * if this is the last buffer, clear the
				 * PREFETCHING flag, so the reader waiting for
				 * this buffer will start a prefetch.
				 */
				tbufp->cmFlags |= CM_BUF_CMFULLYFETCHED;
				lock_ObtainMutex(&scp->mx);
				if (scp->flags & CM_SCACHEFLAG_WAITING) {
					scp->flags &= ~CM_SCACHEFLAG_WAITING;
					osi_Wakeup((long) &scp->flags);
				}
				if (cpffp && !*cpffp && !osi_QPrev(&qdp->q)) {
					*cpffp = 1;
					cm_ClearPrefetchFlag(0, scp,
							     &biod.offset);
				}
				lock_ReleaseMutex(&scp->mx);

				/* and adjust counters */
                                nbytes -= temp;
                                
                                /* and move to the next buffer */
				if (nbytes != 0) {
	                                qdp = (osi_queueData_t *) osi_QPrev(&qdp->q);
	                                if (qdp) {
						tbufp = osi_GetQData(qdp);
	                                        bufferp = tbufp->datap;
	                                }
	                                else bufferp = NULL;
				} else bufferp += temp;
	                }

                        /* zero out remainder of last pages, in case we are
			 * fetching past EOF.  We were fetching an integral #
			 * of pages, but stopped, potentially in the middle of
			 * a page.  Zero the remainder of that page, and then
			 * all of the rest of the pages.
                         */
			/* bytes fetched */
                       	rbytes = bufferp - tbufp->datap;
			/* bytes left to zero */
                        rbytes = buf_bufferSize - rbytes;
                        while(qdp) {
                                if (rbytes != 0)
					memset(bufferp, 0, rbytes);
                                qdp = (osi_queueData_t *) osi_QPrev(&qdp->q);
				if (qdp == NULL) break;
				tbufp = osi_GetQData(qdp);
                                bufferp = tbufp->datap;
				/* bytes to clear in this page */
				rbytes = buf_bufferSize;
                        }
		}

		if (code == 0)
			code = EndRXAFS_FetchData(callp, &afsStatus, &callback, &volSync);
                code = rx_EndCall(callp, code);
                osi_Log0(afsd_logp, "CALL FetchData DONE");
                
	} while (cm_Analyze(connp, up, reqp, &scp->fid, &volSync, NULL, code));
        code = cm_MapRPCError(code, reqp);

        lock_ObtainMutex(&scp->mx);
	/* we know that no one else has changed the buffer, since we still have
	 * the fetching flag on the buffers, and we have the scp locked again.
	 * Copy in the version # into the buffer if we got code 0 back from the
	 * read.
         */
	if (code == 0) {
		for(qdp = biod.bufListp;
		    qdp;
		    qdp = (osi_queueData_t *) osi_QNext(&qdp->q)) {
			tbufp = osi_GetQData(qdp);
                        tbufp->dataVersion = afsStatus.DataVersion;
                }
        }

	/* release scatter/gather I/O structure (buffers, locks) */
	lock_ReleaseMutex(&scp->mx);
	cm_ReleaseBIOD(&biod, 0);
	lock_ObtainMutex(&scp->mx);

        if (code == 0) cm_MergeStatus(scp, &afsStatus, &volSync, up, 0);
	return code;
}
