/*
 * 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
 */

/*
 * Implements:
 *
 */

#include "../afs/param.h"	/* Should be always first */
#include "../afs/sysincludes.h"	/* Standard vendor system headers */
#include "../afs/afsincludes.h"	/* Afs-based standard headers */
#include "../afs/afs_stats.h" /* statistics */
#include "../afs/afs_cbqueue.h"
#include "../afs/nfsclient.h"
#include "../afs/afs_osidnlc.h"

#if	defined(AFS_HPUX102_ENV)
#define AFS_FLOCK	k_flock
#else
#if	defined(AFS_SUN56_ENV)
#define AFS_FLOCK       flock64
#else
#define AFS_FLOCK	flock
#endif /* AFS_SUN65_ENV */
#endif /* AFS_HPUX102_ENV */

static int GetFlockCount(struct vcache *avc, struct vrequest *areq);

void lockIdSet(flock, slp, clid)
   int clid;  /* non-zero on SGI, OSF, SunOS */
    struct SimpleLocks *slp;
    struct AFS_FLOCK *flock;
{
#if	defined(AFS_SUN5_ENV)
    register proc_t *procp = ttoproc(curthread);    
#else
#if !defined(AFS_AIX41_ENV) && !defined(AFS_LINUX20_ENV) && !defined(AFS_SGI65_ENV)
#ifdef AFS_SGI_ENV
    struct proc *procp = OSI_GET_CURRENT_PROCP();
#else
    struct proc *procp = u.u_procp;
#endif /* AFS_SGI_ENV */
#endif
#endif
#if defined(AFS_SGI65_ENV)
    flid_t flid;
    get_current_flid(&flid);
#endif

    if (slp) {
#ifdef	AFS_AIX32_ENV
#ifdef	AFS_AIX41_ENV
	slp->sysid = 0;
	slp->pid = getpid();
#else
	slp->sysid = u.u_sysid;
	slp->pid = u.u_epid;
#endif
#else
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV)
#ifdef	AFS_SUN53_ENV
	slp->sysid = 0;
	slp->pid = procp->p_pid;
#else
	slp->sysid = procp->p_sysid;
	slp->pid = procp->p_epid;
#endif
#else
#if defined(AFS_SGI_ENV)
#ifdef AFS_SGI65_ENV
	slp->sysid = flid.fl_sysid;
#else
        slp->sysid = OSI_GET_CURRENT_SYSID();
#endif
        slp->pid = clid;
#else
#if	defined(AFS_SUN_ENV) || defined(AFS_OSF_ENV)
	slp->pid = clid;
#else
#if defined(AFS_LINUX20_ENV) || defined(AFS_HPUX_ENV)
	slp->pid = getpid();
#else
	slp->pid  = u.u_procp->p_pid;
#endif
#endif
#endif /* AFS_AIX_ENV */
#endif /* AFS_AIX32_ENV */
#endif
    } else {
#if	defined(AFS_AIX32_ENV)
#ifdef	AFS_AIX41_ENV
	flock->l_sysid = 0;
	flock->l_pid = getpid();
#else
	flock->l_sysid = u.u_sysid;
	flock->l_pid = u.u_epid;
#endif
#else
#if	defined(AFS_AIX_ENV)  || defined(AFS_SUN5_ENV)
#ifdef	AFS_SUN53_ENV
	flock->l_sysid = 0;
	flock->l_pid = procp->p_pid;
#else
	flock->l_sysid = procp->p_sysid;
	flock->l_pid = procp->p_epid;
#endif
#else
#if defined(AFS_SGI_ENV)
#ifdef AFS_SGI65_ENV
	flock->l_sysid = flid.fl_sysid;
#else
        flock->l_sysid = OSI_GET_CURRENT_SYSID();
#endif
        flock->l_pid = clid;
#else
#if	defined(AFS_SUN_ENV) || defined(AFS_OSF_ENV)
	flock->l_pid = clid;
#else
#if defined(AFS_LINUX20_ENV) || defined(AFS_HPUX_ENV)
	flock->l_pid = getpid();
#else
	flock->l_pid = u.u_procp->p_pid;
#endif
#endif
#endif
#endif /* AFS_AIX_ENV */
#endif /* AFS_AIX32_ENV */
    }	
}	

/* return 1 (true) if specified flock does not match alp (if 
 * specified), or any of the slp structs (if alp == 0) 
 */
/* I'm not sure that the comparsion of flock->pid to p_ppid
 * is correct.  Should that be a comparision of alp (or slp) ->pid  
 * to p_ppid?  Especially in the context of the lower loop, where
 * the repeated comparison doesn't make much sense...
 */
static int lockIdcmp2(flock1, vp, alp, onlymine, clid)
    struct AFS_FLOCK *flock1;
    struct vcache *vp;
    register struct SimpleLocks *alp;
    int onlymine;  /* don't match any locks which are held by my */
		   /* parent */
     int clid; /* Only Irix 6.5 for now. */
{
    register struct SimpleLocks *slp;
#if	defined(AFS_SUN5_ENV)
    register proc_t *procp = ttoproc(curthread);    
#else
#if !defined(AFS_AIX41_ENV) && !defined(AFS_LINUX20_ENV) && !defined(AFS_SGI65_ENV)
#ifdef AFS_SGI64_ENV
    struct proc *procp = curprocp;
#else /* AFS_SGI64_ENV */
    struct proc *procp = u.u_procp;
#endif /* AFS_SGI64_ENV */
#endif
#endif
    int code = 0;

    if (alp) {
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
      if (flock1->l_sysid != alp->sysid) {
	return 1;
      }
#endif
      if ((flock1->l_pid == alp->pid) || 
#if defined(AFS_AIX41_ENV) || defined(AFS_LINUX20_ENV) || defined(AFS_HPUX_ENV)
	  (!onlymine && (flock1->l_pid == getppid()))
#else
#if defined(AFS_SGI65_ENV)
	  (!onlymine && (flock1->l_pid == clid))
#else
	  (!onlymine && (flock1->l_pid == procp->p_ppid))
#endif
#endif
	  ) {
	return 0;
      }
      return 1;
    }

    for (slp = vp->slocks; slp; slp = slp->next) {
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
	if (flock1->l_sysid != slp->sysid) {
	  continue;
	}
#endif
	if (flock1->l_pid == slp->pid) {
	    return 0;
	  }
    }
    return (1); 	/* failure */
}


/* we don't send multiple read flocks to the server, but rather just count
    them up ourselves.  Of course, multiple write locks are incompatible.
    
    Note that we should always try to release a lock, even if we have
    a network problem sending the release command through, since often
    a lock is released on a close call, when the user can't retry anyway.
    
    After we remove it from our structure, the lock will no longer be
    kept alive, and the server should time it out within a few minutes.
    
    94.04.13 add "force" parameter.  If a child explicitly unlocks a
    file, I guess we'll permit it.  however, we don't want simple,
    innocent closes by children to unlock files in the parent process.
*/
HandleFlock(avc, acom, areq, clid, onlymine)
    pid_t clid;        /* non-zero on SGI, SunOS, OSF1 only */
    register struct vcache *avc;
    struct vrequest *areq;
    int onlymine; 
    int acom; {
    struct conn *tc;
    struct SimpleLocks *slp, *tlp, **slpp;
    afs_int32 code;
    struct AFSVolSync tsync;
    afs_int32 lockType;
    struct AFS_FLOCK flock;
    XSTATS_DECLS

    AFS_STATCNT(HandleFlock);
    code = 0;		/* default when we don't make any network calls */
    lockIdSet(&flock, (struct SimpleLocks *)0, clid);

#if defined(AFS_SGI_ENV)
    osi_Assert(valusema(&avc->vc_rwlock) <= 0);
    osi_Assert(OSI_GET_LOCKID() == avc->vc_rwlockid);
#endif
    ObtainWriteLock(&avc->lock,118);
    if (acom & LOCK_UN) {

/* defect 3083 */

#ifdef AFS_AIX_ENV
	/* If the lock is held exclusive, then only the owning process
         * or a child can unlock it. Use pid and ppid because they are
         * unique identifiers.
	 */
	if ((avc->flockCount < 0) && (getpid() != avc->ownslock)) {
#ifdef	AFS_AIX41_ENV
	  if (onlymine || (getppid() != avc->ownslock)) {
#else
	  if (onlymine || (u.u_procp->p_ppid != avc->ownslock)) {
#endif
	    ReleaseWriteLock(&avc->lock);
	    return 0;
	  }
	}
#endif
	if (lockIdcmp2(&flock, avc, (struct SimpleLocks *)0, onlymine, clid)) {
	  ReleaseWriteLock(&avc->lock); 	    
	  return 0;
 	} 
#ifdef AFS_AIX_ENV
	avc->ownslock = 0; 
#endif
 	if (avc->flockCount == 0) { 	    
	  ReleaseWriteLock(&avc->lock);
	  return 0		/*ENOTTY*/;
	  /* no lock held */
 	} 	
	/* unlock the lock */ 
	if (avc->flockCount > 0) {
	  slpp = &avc->slocks; 
	  for (slp = *slpp; slp;) {
	    if (!lockIdcmp2(&flock, avc, slp, onlymine, clid)) {
	      avc->flockCount--;
	      tlp = *slpp = slp->next;
	      osi_FreeSmallSpace(slp);
	      slp = tlp;
	    } else {
	      slpp = &slp->next;
	      slp = *slpp;
	    }
	  }
 	}
	else if (avc->flockCount == -1) {
	  afs_StoreAllSegments(avc, areq, AFS_ASYNC); /* fsync file early */
	  avc->flockCount = 0; 
	  /* And remove the (only) exclusive lock entry from the list... */
	  osi_FreeSmallSpace(avc->slocks);
	  avc->slocks = 0;
 	}
 	if (avc->flockCount == 0) {
 	    do {
 		tc = afs_Conn(&avc->fid, areq, SHARED_LOCK);
 		if (tc) {
 		   XSTATS_START_TIME(AFS_STATS_FS_RPCIDX_RELEASELOCK);
#ifdef RX_ENABLE_LOCKS
		   AFS_GUNLOCK();
#endif /* RX_ENABLE_LOCKS */
 		   code = RXAFS_ReleaseLock(tc->id, (struct AFSFid *)
 					    &avc->fid.Fid, &tsync);
#ifdef RX_ENABLE_LOCKS
		   AFS_GLOCK();
#endif /* RX_ENABLE_LOCKS */
		   XSTATS_END_TIME;
		}
		else code = -1;
	    } while
	      (afs_Analyze(tc, code, &avc->fid, areq, 
			   AFS_STATS_FS_RPCIDX_RELEASELOCK,
                           SHARED_LOCK, (struct cell *)0));
	}
    }
    else {
	while (1) {	    /* set a new lock */
	    /*
	     * Upgrading from shared locks to Exclusive and vice versa
             * is a bit tricky and we don't really support it yet. But
             * we try to support the common used one which is upgrade
             * a shared lock to an exclusive for the same process...
             */
	    if ((avc->flockCount > 0 && (acom & LOCK_EX)) || 
		(avc->flockCount == -1 && (acom & LOCK_SH))) {
		/*
		 * Upgrading from shared locks to an exclusive one:
		 * For now if all the shared locks belong to the
		 * same process then we unlock them on the server
		 * and proceed with the upgrade.  Unless we change the
		 * server's locking interface impl we prohibit from
		 * unlocking other processes's shared locks...
		 * Upgrading from an exclusive lock to a shared one:
		 * Again only allowed to be done by the same process.
		 */
		slpp = &avc->slocks;
		for (slp = *slpp; slp;) {
		    if (!lockIdcmp2(&flock, avc, slp, 1/*!onlymine*/, clid)) {
			if (acom & LOCK_EX)
			    avc->flockCount--;
			else
			    avc->flockCount = 0;
			tlp = *slpp = slp->next;
			osi_FreeSmallSpace(slp);
			slp = tlp;
		    } else {
			code = EWOULDBLOCK;
			slpp = &slp->next;
			slp = *slpp;
		    }
		}
	       if (!code && avc->flockCount == 0) {
		    do {
			tc = afs_Conn(&avc->fid, areq, SHARED_LOCK);
			if (tc) {
			  XSTATS_START_TIME(AFS_STATS_FS_RPCIDX_RELEASELOCK);
#ifdef RX_ENABLE_LOCKS
			  AFS_GUNLOCK();
#endif /* RX_ENABLE_LOCKS */
			  code = RXAFS_ReleaseLock(tc->id,
						   (struct AFSFid *) &avc->fid.Fid,
						   &tsync);
#ifdef RX_ENABLE_LOCKS
			  AFS_GLOCK();
#endif /* RX_ENABLE_LOCKS */
			  XSTATS_END_TIME;
			}
			else code = -1;
		    } while
		      (afs_Analyze(tc, code, &avc->fid, areq,
				   AFS_STATS_FS_RPCIDX_RELEASELOCK,
				   SHARED_LOCK, (struct cell *)0));
		}
	    } else if (avc->flockCount == -1 && (acom & LOCK_EX)) {
		if (lockIdcmp2(&flock, avc, (struct SimpleLocks *)0, 1, clid)) {
		    code = EWOULDBLOCK;
		} else
		    code = 0;
	    }
	    if (code == 0) {
		/* compatible here, decide if needs to go to file server.  If
		   we've already got the file locked (and thus read-locked, since
		   we've already checked for compatibility), we shouldn't send
		   the call through to the server again */
		if (avc->flockCount == 0) {
		    /* we're the first on our block, send the call through */
		    lockType = ((acom & LOCK_EX)? LockWrite : LockRead);
		    do {
			tc = afs_Conn(&avc->fid, areq, SHARED_LOCK);
			if (tc) {
			  XSTATS_START_TIME(AFS_STATS_FS_RPCIDX_SETLOCK);
#ifdef RX_ENABLE_LOCKS
			  AFS_GUNLOCK();
#endif /* RX_ENABLE_LOCKS */
			  code = RXAFS_SetLock(tc->id, (struct AFSFid *)
					      &avc->fid.Fid, lockType, &tsync);
#ifdef RX_ENABLE_LOCKS
			  AFS_GLOCK();
#endif /* RX_ENABLE_LOCKS */
			  XSTATS_END_TIME;
			}
			else code = -1;
		    } while
			(afs_Analyze(tc, code, &avc->fid, areq,
				     AFS_STATS_FS_RPCIDX_SETLOCK,
				     SHARED_LOCK, (struct cell *)0));
		}
		else code = 0;	/* otherwise, pretend things worked */
	    }
	    if (code == 0) {
		slp = (struct SimpleLocks *) osi_AllocSmallSpace(sizeof(struct SimpleLocks));
		if (acom & LOCK_EX) {

/* defect 3083 */

#ifdef AFS_AIX_ENV
		  /* Record unique id of process owning exclusive lock. */
		  avc->ownslock = getpid();
#endif

		    slp->type = LockWrite;
		    slp->next = (struct SimpleLocks *)0;		    
		    avc->slocks = slp;
		    avc->flockCount = -1;
		} else {
		    slp->type = LockRead;
		    slp->next = avc->slocks;
		    avc->slocks = slp;
		    avc->flockCount++;
		}

		lockIdSet(&flock, slp, clid);
		break;
	    }
	    /* now, if we got EWOULDBLOCK, and we're supposed to wait, we do */
	    if(((code == EWOULDBLOCK)||(code == EAGAIN)) && !(acom & LOCK_NB)) {
		/* sleep for a second, allowing interrupts */
		ReleaseWriteLock(&avc->lock);
#if defined(AFS_SGI_ENV)
		AFS_RWUNLOCK((vnode_t *)avc, VRWLOCK_WRITE);
#endif
		code = afs_osi_Wait(1000, (struct afs_osi_WaitHandle *) 0, 1);
#if defined(AFS_SGI_ENV)
		AFS_RWLOCK((vnode_t *)avc, VRWLOCK_WRITE);
#endif
		ObtainWriteLock(&avc->lock,120);
		if (code) {
		    code = EINTR;	/* return this if ^C typed */
		    break;
		}
	    }
	    else break;
	}	/* while loop */
    }
    ReleaseWriteLock(&avc->lock);
    code = afs_CheckCode(code, areq, 1); /* defeat a buggy AIX optimization */
    return code;
}


/* warn a user that a lock has been ignored */
afs_int32 lastWarnTime = 0;
static void DoLockWarning() {
    register afs_int32 now;
    now = osi_Time();

    AFS_STATCNT(DoLockWarning);
    /* check if we've already warned someone recently */
    if (now < lastWarnTime + 120) return;

    /* otherwise, it is time to nag the user */
    lastWarnTime = now;
    afs_warn("afs: byte-range lock/unlock ignored; make sure no one else is running this program.\n");
}


#ifdef	AFS_OSF_ENV
afs_lockctl(avc, af, flag, acred, clid, offset)
struct eflock *af;
int flag;
pid_t clid;
off_t offset;
#else
#if defined(AFS_SGI_ENV) || (defined(AFS_SUN_ENV) && !defined(AFS_SUN5_ENV))
afs_lockctl(avc, af, acmd, acred, clid)
pid_t clid;
#else
u_int clid=0;
afs_lockctl(avc, af, acmd, acred)
#endif
struct AFS_FLOCK *af;
int acmd;
#endif
struct vcache *avc;
struct AFS_UCRED *acred; {
    struct vrequest treq;
    afs_int32 code;
#ifdef	AFS_OSF_ENV
    int acmd = 0;
#endif

    AFS_STATCNT(afs_lockctl);
    if (code = afs_InitReq(&treq, acred)) return code;
#ifdef	AFS_OSF_ENV
    if (flag & VNOFLCK)	return 0;
    if (flag & CLNFLCK) {
	acmd = LOCK_UN;
    } else if ((flag & GETFLCK) || (flag & RGETFLCK)) {
	acmd = F_GETLK;
    } else if ((flag & SETFLCK) || (flag & RSETFLCK)) {
	acmd = F_SETLK;
    }
#endif
#if (defined(AFS_SUN_ENV) || defined(AFS_SGI_ENV) || defined(AFS_SUN5_ENV)) && !defined(AFS_SUN58_ENV)
    if ((acmd == F_GETLK) || (acmd == F_RGETLK)) {
#else
    if (acmd == F_GETLK) {
#endif
	if (af->l_type == F_UNLCK)
	    return 0;
#ifndef	AFS_OSF_ENV	/* getlock is a no-op for osf (for now) */
	code = HandleGetLock(avc, af, &treq, clid);
#endif
	code = afs_CheckCode(code, &treq, 2); /* defeat buggy AIX optimz */
	return code;
    }
    else if ((acmd == F_SETLK) || (acmd == F_SETLKW) 
#if (defined(AFS_SUN_ENV) || defined(AFS_SGI_ENV) || defined(AFS_SUN5_ENV)) && !defined(AFS_SUN58_ENV)
	     || (acmd == F_RSETLK)|| (acmd == F_RSETLKW)) {
#else
	) {
#endif
	/* this next check is safer when left out, but more applications work
	   with it in.  However, they fail in race conditions.  The question is
	   what to do for people who don't have source to their application;
	   this way at least, they can get work done */
	if (af->l_len == 0x7fffffff)
	    af->l_len = 0;	/* since some systems indicate it as EOF */
	/* next line makes byte range locks always succeed,
	   even when they should block */
	if (af->l_whence != 0 || af->l_start != 0 || af->l_len != 0) {
	    DoLockWarning();
	    return 0;
	}
	/* otherwise we can turn this into a whole-file flock */
	if (af->l_type == F_RDLCK) code = LOCK_SH;
	else if (af->l_type == F_WRLCK) code = LOCK_EX;
	else if (af->l_type == F_UNLCK) code = LOCK_UN;
	else return EINVAL; /* unknown lock type */
	if (((acmd == F_SETLK) 
#if 	(defined(AFS_SGI_ENV) || defined(AFS_SUN_ENV)) && !defined(AFS_SUN58_ENV)
	|| (acmd == F_RSETLK) 
#endif
	) && code != LOCK_UN)
	    code |= LOCK_NB;	/* non-blocking, s.v.p. */
#if	defined(AFS_SUN_ENV) && !defined(AFS_SUN5_ENV) || defined(AFS_OSF_ENV) 
	code = HandleFlock(avc, code, &treq, clid, 0/*!onlymine*/);
#else
#if defined(AFS_SGI_ENV)
	AFS_RWLOCK((vnode_t *)avc, VRWLOCK_WRITE);
	code = HandleFlock(avc, code, &treq, clid, 0/*!onlymine*/);
	AFS_RWUNLOCK((vnode_t *)avc, VRWLOCK_WRITE);
#else
	code = HandleFlock(avc, code, &treq, 0, 0/*!onlymine*/);
#endif
#endif
	code = afs_CheckCode(code, &treq, 3); /* defeat AIX -O bug */
	return code;
    }
    return EINVAL;
}


/*
 * Get a description of the first lock which would
 * block the lock specified.  If the specified lock
 * would succeed, fill in the lock structure with 'F_UNLCK'.
 *
 * To do that, we have to ask the server for the lock
 * count if:
 *    1. The file is not locked by this machine.
 *    2. Asking for write lock, and only the current
 *       PID has the file read locked.
 */
#ifndef	AFS_OSF_ENV	/* getlock is a no-op for osf (for now) */
HandleGetLock(avc, af, areq, clid)
    int clid;           /* not used by some OSes */
    register struct vcache *avc;
    register struct vrequest *areq;
    register struct AFS_FLOCK *af; 
{
    register afs_int32 code;
    struct AFS_FLOCK flock;

    lockIdSet(&flock, (struct SimpleLocks *)0, clid);

    ObtainWriteLock(&avc->lock,122);
    if (avc->flockCount == 0) {
	/* We don't know ourselves, so ask the server. Unfortunately, we don't know the pid.
	 * Not even the server knows the pid.  Besides, the process with the lock is on another machine
	 */
	code = GetFlockCount(avc, areq);
	if (code == 0 || (af->l_type == F_RDLCK && code > 0)) {
	    af->l_type = F_UNLCK;
	    goto unlck_leave;
	}
	if (code > 0)
	    af->l_type = F_RDLCK;
	else
	    af->l_type = F_WRLCK;

	af->l_pid = 0;
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
	af->l_sysid = 0;
#endif
	goto done;
    }

    if (af->l_type == F_RDLCK) {
	/*
	 * We want a read lock.  If there are only
	 * read locks, or we are the one with the
	 * write lock, say it is unlocked.
	 */
	if (avc->flockCount > 0 ||      /* only read locks */
	    !lockIdcmp2(&flock, avc, (struct SimpleLocks *)0, 1, clid)) {
	    af->l_type = F_UNLCK;
	    goto unlck_leave;
	}

	/* one write lock, but who? */
	af->l_type = F_WRLCK;           /* not us, so lock would block */
	if (avc->slocks) {              /* we know who, so tell */
	    af->l_pid = avc->slocks->pid;
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
	    af->l_sysid = avc->slocks->sysid;
#endif
	} else {
	    af->l_pid = 0;      /* XXX can't happen?? */
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
	    af->l_sysid = 0;
#endif
	}
	goto done;
    }

    /*
     * Ok, we want a write lock.  If there is a write lock
     * already, and it is not this process, we fail.
     */
    if (avc->flockCount < 0) {
	if (lockIdcmp2(&flock, avc, (struct SimpleLocks *)0, 1, clid)) {
	    af->l_type = F_WRLCK;
	    if (avc->slocks) {
		af->l_pid = avc->slocks->pid;
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
		af->l_sysid = avc->slocks->sysid;
#endif
	    } else {
		af->l_pid = 0;  /* XXX can't happen?? */
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
		af->l_sysid = 0;
#endif
	    }
	    goto done;
	}
       /* we are the one with the write lock */
	af->l_type = F_UNLCK;
	goto unlck_leave;
    }

    /*
     * Want a write lock, and we know there are read locks.
     * If there is more than one, or it isn't us, we cannot lock.
     */
    if ((avc->flockCount > 1)
	|| lockIdcmp2(&flock, avc, (struct SimpleLocks *)0, 1, clid)) {
	struct SimpleLocks *slp;
	
	af->l_type = F_RDLCK;
	af->l_pid = 0;
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
	af->l_sysid = 0;
#endif
	/* find a pid that isn't our own */
	for (slp = avc->slocks; slp; slp = slp->next) {
           if (lockIdcmp2(&flock, (struct vcache *)0, slp, 1, clid)) {
               af->l_pid = slp->pid;
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
               af->l_sysid = avc->slocks->sysid;
#endif
		break;
	   } 
       }
	goto done;
    }

       /*
	* Ok, we want a write lock.  If there is a write lock
	* already, and it is not this process, we fail.
	*/
	if (avc->flockCount < 0) {
	    if (lockIdcmp2(&flock, avc, (struct SimpleLocks *)0, 1, clid)) {
		af->l_type = F_WRLCK;
		if (avc->slocks) {
		    af->l_pid = avc->slocks->pid;
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
		    af->l_sysid = avc->slocks->sysid;
#endif
		} else {
		    af->l_pid = 0;  /* XXX can't happen?? */
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
		    af->l_sysid = 0;
#endif
		}
		goto done;
	    }
	    /* we are the one with the write lock */
	    af->l_type = F_UNLCK;
	    goto unlck_leave;
	}

	/*
	 * Want a write lock, and we know there are read locks.
	 * If there is more than one, or it isn't us, we cannot lock.
	 */
	if ((avc->flockCount > 1)
	    || lockIdcmp2(&flock, avc, (struct SimpleLocks *)0, 1, clid)) {
	    struct SimpleLocks *slp;
	    af->l_type = F_RDLCK;
	    af->l_pid = 0;
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
	    af->l_sysid = 0;
#endif
	    /* find a pid that isn't our own */
	    for (slp = avc->slocks; slp; slp = slp->next) {
		if (lockIdcmp2(&flock, (struct vcache *)0, slp, 1, clid)) {
		    af->l_pid = slp->pid;
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
		    af->l_sysid = avc->slocks->sysid;
#endif
		    break;
		}
	    }
	    goto done;
	}
	
	/*
	 * Want a write lock, and there is just one read lock, and it
	 * is this process with a read lock.  Ask the server if there
	 * are any more processes with the file locked.
	 */
	code = GetFlockCount(avc, areq);
	if (code == 0 || code == 1) {
	    af->l_type = F_UNLCK;
	    goto unlck_leave;
	}
	if (code > 0)
	    af->l_type = F_RDLCK;
	else
	    af->l_type = F_WRLCK;
	af->l_pid = 0;
#if	defined(AFS_AIX_ENV) || defined(AFS_SUN5_ENV) || defined(AFS_SGI_ENV)
	af->l_sysid = 0;
#endif

done:
	af->l_whence = 0;
	af->l_start = 0;
	af->l_len = 0;    /* to end of file */

unlck_leave:
	ReleaseWriteLock(&avc->lock);
	return 0;
}

/* Get the 'flock' count from the server.  This comes back in a 'spare'
 * field from a GetStatus RPC.  If we have any problems with the RPC,
 * we lie and say the file is unlocked.  If we ask any 'old' fileservers,
 * the spare field will be a zero, saying the file is unlocked.  This is
 * OK, as a further 'lock' request will do the right thing.
 */
static int GetFlockCount(struct vcache *avc, struct vrequest *areq)
{
    register struct conn *tc;
    register afs_int32 code;
    struct AFSFetchStatus OutStatus;
    struct AFSCallBack CallBack;
    struct AFSVolSync tsync;
    int temp;
    XSTATS_DECLS

    temp = areq->flags & O_NONBLOCK;
    areq->flags |= O_NONBLOCK;

    do {
	tc = afs_Conn(&avc->fid, areq, SHARED_LOCK); 
	if (tc){
          XSTATS_START_TIME(AFS_STATS_FS_RPCIDX_FETCHSTATUS);
#ifdef RX_ENABLE_LOCKS
	  AFS_GUNLOCK();
#endif /* RX_ENABLE_LOCKS */
	  code = RXAFS_FetchStatus(tc->id, (struct AFSFid *) &avc->fid.Fid,
				     &OutStatus, &CallBack, &tsync);
#ifdef RX_ENABLE_LOCKS
	  AFS_GLOCK();
#endif /* RX_ENABLE_LOCKS */
          XSTATS_END_TIME;
	} else code = -1;
    } while
      (afs_Analyze(tc, code, &avc->fid, areq,
		   AFS_STATS_FS_RPCIDX_FETCHSTATUS,
		   SHARED_LOCK, (struct cell *)0));

    if (temp)
	areq->flags &= ~O_NONBLOCK;

    if (code) {
	return(0);              /* failed, say it is 'unlocked' */
    } else {
	return((int)OutStatus.spare2);
    }
}
#endif


#if	!defined(AFS_AIX_ENV) && !defined(AFS_HPUX_ENV) && !defined(AFS_SUN5_ENV) && !defined(AFS_SGI_ENV) && !defined(UKERNEL) && !defined(AFS_LINUX20_ENV)
/* Flock not support on System V systems */
#ifdef AFS_OSF_ENV
extern struct fileops afs_fileops;
afs_xflock (p, args, retval) 
	struct proc *p;
	void *args;
	int *retval;
{
#else /* AFS_OSF_ENV */
afs_xflock () {
#endif
    int code = 0;
    struct a {
	int fd;
	int com;
    } *uap;
    struct file *fd;
    struct vrequest treq;
    struct vcache *tvc;
    int flockDone;

    AFS_STATCNT(afs_xflock);
    flockDone = 0;
#ifdef AFS_OSF_ENV
    uap = (struct a *)args;
    getf(&fd, uap->fd, FILE_FLAGS_NULL, &u.u_file_state);
#else /* AFS_OSF_ENV */
    uap = (struct a *)u.u_ap;
    fd = getf(uap->fd);
#endif
    if (!fd) return;

    if (flockDone = afs_InitReq(&treq, u.u_cred)) return flockDone;
    /* first determine whether this is any sort of vnode */
    if (fd->f_type == DTYPE_VNODE) {
	/* good, this is a vnode; next see if it is an AFS vnode */
	tvc = (struct vcache *) fd->f_data;	/* valid, given a vnode */
	if (IsAfsVnode((struct vnode *)tvc)) {
	    /* This is an AFS vnode, so do the work */
#ifdef AFS_DEC_ENV
	    /* find real vcache entry; shouldn't be null if gnode ref count
	     * is greater than 0.
	     */
	    tvc = (struct vcache *) afs_gntovn(tvc);
	    if (!tvc) {
		u.u_error = ENOENT;
		return;
	    }
#endif
	    if ((fd->f_flag & (FEXLOCK | FSHLOCK)) && !(uap->com & LOCK_UN)) {
		/* First, if fd already has lock, release it for relock path */
#if defined(AFS_SGI_ENV) || defined(AFS_OSF_ENV) || (defined(AFS_SUN_ENV) && !defined(AFS_SUN5_ENV))
		HandleFlock(tvc, LOCK_UN, &treq, u.u_procp->p_pid, 0/*!onlymine*/);
#else
		HandleFlock(tvc, LOCK_UN, &treq, 0, 0/*!onlymine*/);
#endif
		fd->f_flag &= ~(FEXLOCK | FSHLOCK);
	    }
	    /* now try the requested operation */

#if defined(AFS_SGI_ENV) || defined(AFS_OSF_ENV) || (defined(AFS_SUN_ENV) && !defined(AFS_SUN5_ENV))
	    code = HandleFlock(tvc, uap->com, &treq,
			       u.u_procp->p_pid, 0/*!onlymine*/);
#else
	    code = HandleFlock(tvc, uap->com, &treq, 0, 0/*!onlymine*/);
#endif
#ifndef AFS_OSF_ENV
	    u.u_error = code;
#endif

	    if (uap->com & LOCK_UN) {
		/* gave up lock */
		fd->f_flag &= ~(FEXLOCK | FSHLOCK);
	    }
	    else {
#ifdef AFS_OSF_ENV
		if (!code) {
#else /* AFS_OSF_ENV */
		if (!u.u_error) {
#endif
		    if (uap->com & LOCK_SH) fd->f_flag |= FSHLOCK;
		    else if (uap->com & LOCK_EX) fd->f_flag |= FEXLOCK;
		}
	    }
	    flockDone = 1;
	    fd->f_ops = &afs_fileops;
	}
    }
#ifdef	AFS_OSF_ENV
    if (!flockDone)
	code = flock(p, args, retval);
#ifdef	AFS_OSF30_ENV
    FP_UNREF_ALWAYS(fd);
#else
    FP_UNREF(fd);
#endif
    return code;
#else	/* AFS_OSF_ENV */
    if (!flockDone)
#ifdef DYNEL
	(*afs_longcall_procs.LC_flock)();
#else
    	flock();
#endif
    return;
#endif
}
#endif /* !defined(AFS_AIX_ENV) && !defined(AFS_HPUX_ENV) && !defined(AFS_SUN5_ENV) && !defined(UKERNEL)  && !defined(AFS_LINUX20_ENV) */