BSD 4_4_Lite2 release

[unix-history] / usr / src / sys / ufs / ufs / ufs_quota.c

/*
* Copyright (c) 1982, 1986, 1990, 1993, 1995
*      The Regents of the University of California.  All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Robert Elz at The University of Melbourne.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
*    must display the following acknowledgement:
*      This product includes software developed by the University of
*      California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*      @(#)ufs_quota.c 8.5 (Berkeley) 5/20/95
*/
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/namei.h>
#include <sys/malloc.h>
#include <sys/file.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/mount.h>

#include <ufs/ufs/quota.h>
#include <ufs/ufs/inode.h>
#include <ufs/ufs/ufsmount.h>
#include <ufs/ufs/ufs_extern.h>

/*
* Quota name to error message mapping.
*/
static char *quotatypes[] = INITQFNAMES;

/*
* Set up the quotas for an inode.
*
* This routine completely defines the semantics of quotas.
* If other criterion want to be used to establish quotas, the
* MAXQUOTAS value in quotas.h should be increased, and the
* additional dquots set up here.
*/
int
getinoquota(ip)
       register struct inode *ip;
{
       struct ufsmount *ump;
       struct vnode *vp = ITOV(ip);
       int error;

       ump = VFSTOUFS(vp->v_mount);
       /*
        * Set up the user quota based on file uid.
        * EINVAL means that quotas are not enabled.
        */
       if (ip->i_dquot[USRQUOTA] == NODQUOT &&
           (error =
               dqget(vp, ip->i_uid, ump, USRQUOTA, &ip->i_dquot[USRQUOTA])) &&
           error != EINVAL)
               return (error);
       /*
        * Set up the group quota based on file gid.
        * EINVAL means that quotas are not enabled.
        */
       if (ip->i_dquot[GRPQUOTA] == NODQUOT &&
           (error =
               dqget(vp, ip->i_gid, ump, GRPQUOTA, &ip->i_dquot[GRPQUOTA])) &&
           error != EINVAL)
               return (error);
       return (0);
}

/*
* Update disk usage, and take corrective action.
*/
int
chkdq(ip, change, cred, flags)
       register struct inode *ip;
       long change;
       struct ucred *cred;
       int flags;
{
       register struct dquot *dq;
       register int i;
       int ncurblocks, error;

#ifdef DIAGNOSTIC
       if ((flags & CHOWN) == 0)
               chkdquot(ip);
#endif
       if (change == 0)
               return (0);
       if (change < 0) {
               for (i = 0; i < MAXQUOTAS; i++) {
                       if ((dq = ip->i_dquot[i]) == NODQUOT)
                               continue;
                       while (dq->dq_flags & DQ_LOCK) {
                               dq->dq_flags |= DQ_WANT;
                               sleep((caddr_t)dq, PINOD+1);
                       }
                       ncurblocks = dq->dq_curblocks + change;
                       if (ncurblocks >= 0)
                               dq->dq_curblocks = ncurblocks;
                       else
                               dq->dq_curblocks = 0;
                       dq->dq_flags &= ~DQ_BLKS;
                       dq->dq_flags |= DQ_MOD;
               }
               return (0);
       }
       if ((flags & FORCE) == 0 && cred->cr_uid != 0) {
               for (i = 0; i < MAXQUOTAS; i++) {
                       if ((dq = ip->i_dquot[i]) == NODQUOT)
                               continue;
                       if (error = chkdqchg(ip, change, cred, i))
                               return (error);
               }
       }
       for (i = 0; i < MAXQUOTAS; i++) {
               if ((dq = ip->i_dquot[i]) == NODQUOT)
                       continue;
               while (dq->dq_flags & DQ_LOCK) {
                       dq->dq_flags |= DQ_WANT;
                       sleep((caddr_t)dq, PINOD+1);
               }
               dq->dq_curblocks += change;
               dq->dq_flags |= DQ_MOD;
       }
       return (0);
}

/*
* Check for a valid change to a users allocation.
* Issue an error message if appropriate.
*/
int
chkdqchg(ip, change, cred, type)
       struct inode *ip;
       long change;
       struct ucred *cred;
       int type;
{
       register struct dquot *dq = ip->i_dquot[type];
       long ncurblocks = dq->dq_curblocks + change;

       /*
        * If user would exceed their hard limit, disallow space allocation.
        */
       if (ncurblocks >= dq->dq_bhardlimit && dq->dq_bhardlimit) {
               if ((dq->dq_flags & DQ_BLKS) == 0 &&
                   ip->i_uid == cred->cr_uid) {
                       uprintf("\n%s: write failed, %s disk limit reached\n",
                           ITOV(ip)->v_mount->mnt_stat.f_mntonname,
                           quotatypes[type]);
                       dq->dq_flags |= DQ_BLKS;
               }
               return (EDQUOT);
       }
       /*
        * If user is over their soft limit for too long, disallow space
        * allocation. Reset time limit as they cross their soft limit.
        */
       if (ncurblocks >= dq->dq_bsoftlimit && dq->dq_bsoftlimit) {
               if (dq->dq_curblocks < dq->dq_bsoftlimit) {
                       dq->dq_btime = time.tv_sec +
                           VFSTOUFS(ITOV(ip)->v_mount)->um_btime[type];
                       if (ip->i_uid == cred->cr_uid)
                               uprintf("\n%s: warning, %s %s\n",
                                   ITOV(ip)->v_mount->mnt_stat.f_mntonname,
                                   quotatypes[type], "disk quota exceeded");
                       return (0);
               }
               if (time.tv_sec > dq->dq_btime) {
                       if ((dq->dq_flags & DQ_BLKS) == 0 &&
                           ip->i_uid == cred->cr_uid) {
                               uprintf("\n%s: write failed, %s %s\n",
                                   ITOV(ip)->v_mount->mnt_stat.f_mntonname,
                                   quotatypes[type],
                                   "disk quota exceeded for too long");
                               dq->dq_flags |= DQ_BLKS;
                       }
                       return (EDQUOT);
               }
       }
       return (0);
}

/*
* Check the inode limit, applying corrective action.
*/
int
chkiq(ip, change, cred, flags)
       register struct inode *ip;
       long change;
       struct ucred *cred;
       int flags;
{
       register struct dquot *dq;
       register int i;
       int ncurinodes, error;

#ifdef DIAGNOSTIC
       if ((flags & CHOWN) == 0)
               chkdquot(ip);
#endif
       if (change == 0)
               return (0);
       if (change < 0) {
               for (i = 0; i < MAXQUOTAS; i++) {
                       if ((dq = ip->i_dquot[i]) == NODQUOT)
                               continue;
                       while (dq->dq_flags & DQ_LOCK) {
                               dq->dq_flags |= DQ_WANT;
                               sleep((caddr_t)dq, PINOD+1);
                       }
                       ncurinodes = dq->dq_curinodes + change;
                       if (ncurinodes >= 0)
                               dq->dq_curinodes = ncurinodes;
                       else
                               dq->dq_curinodes = 0;
                       dq->dq_flags &= ~DQ_INODS;
                       dq->dq_flags |= DQ_MOD;
               }
               return (0);
       }
       if ((flags & FORCE) == 0 && cred->cr_uid != 0) {
               for (i = 0; i < MAXQUOTAS; i++) {
                       if ((dq = ip->i_dquot[i]) == NODQUOT)
                               continue;
                       if (error = chkiqchg(ip, change, cred, i))
                               return (error);
               }
       }
       for (i = 0; i < MAXQUOTAS; i++) {
               if ((dq = ip->i_dquot[i]) == NODQUOT)
                       continue;
               while (dq->dq_flags & DQ_LOCK) {
                       dq->dq_flags |= DQ_WANT;
                       sleep((caddr_t)dq, PINOD+1);
               }
               dq->dq_curinodes += change;
               dq->dq_flags |= DQ_MOD;
       }
       return (0);
}

/*
* Check for a valid change to a users allocation.
* Issue an error message if appropriate.
*/
int
chkiqchg(ip, change, cred, type)
       struct inode *ip;
       long change;
       struct ucred *cred;
       int type;
{
       register struct dquot *dq = ip->i_dquot[type];
       long ncurinodes = dq->dq_curinodes + change;

       /*
        * If user would exceed their hard limit, disallow inode allocation.
        */
       if (ncurinodes >= dq->dq_ihardlimit && dq->dq_ihardlimit) {
               if ((dq->dq_flags & DQ_INODS) == 0 &&
                   ip->i_uid == cred->cr_uid) {
                       uprintf("\n%s: write failed, %s inode limit reached\n",
                           ITOV(ip)->v_mount->mnt_stat.f_mntonname,
                           quotatypes[type]);
                       dq->dq_flags |= DQ_INODS;
               }
               return (EDQUOT);
       }
       /*
        * If user is over their soft limit for too long, disallow inode
        * allocation. Reset time limit as they cross their soft limit.
        */
       if (ncurinodes >= dq->dq_isoftlimit && dq->dq_isoftlimit) {
               if (dq->dq_curinodes < dq->dq_isoftlimit) {
                       dq->dq_itime = time.tv_sec +
                           VFSTOUFS(ITOV(ip)->v_mount)->um_itime[type];
                       if (ip->i_uid == cred->cr_uid)
                               uprintf("\n%s: warning, %s %s\n",
                                   ITOV(ip)->v_mount->mnt_stat.f_mntonname,
                                   quotatypes[type], "inode quota exceeded");
                       return (0);
               }
               if (time.tv_sec > dq->dq_itime) {
                       if ((dq->dq_flags & DQ_INODS) == 0 &&
                           ip->i_uid == cred->cr_uid) {
                               uprintf("\n%s: write failed, %s %s\n",
                                   ITOV(ip)->v_mount->mnt_stat.f_mntonname,
                                   quotatypes[type],
                                   "inode quota exceeded for too long");
                               dq->dq_flags |= DQ_INODS;
                       }
                       return (EDQUOT);
               }
       }
       return (0);
}

#ifdef DIAGNOSTIC
/*
* On filesystems with quotas enabled, it is an error for a file to change
* size and not to have a dquot structure associated with it.
*/
void
chkdquot(ip)
       register struct inode *ip;
{
       struct ufsmount *ump = VFSTOUFS(ITOV(ip)->v_mount);
       register int i;

       for (i = 0; i < MAXQUOTAS; i++) {
               if (ump->um_quotas[i] == NULLVP ||
                   (ump->um_qflags[i] & (QTF_OPENING|QTF_CLOSING)))
                       continue;
               if (ip->i_dquot[i] == NODQUOT) {
                       vprint("chkdquot: missing dquot", ITOV(ip));
                       panic("missing dquot");
               }
       }
}
#endif

/*
* Code to process quotactl commands.
*/

/*
* Q_QUOTAON - set up a quota file for a particular file system.
*/
int
quotaon(p, mp, type, fname)
       struct proc *p;
       struct mount *mp;
       register int type;
       caddr_t fname;
{
       struct ufsmount *ump = VFSTOUFS(mp);
       struct vnode *vp, **vpp;
       struct vnode *nextvp;
       struct dquot *dq;
       int error;
       struct nameidata nd;

       vpp = &ump->um_quotas[type];
       NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, fname, p);
       if (error = vn_open(&nd, FREAD|FWRITE, 0))
               return (error);
       vp = nd.ni_vp;
       VOP_UNLOCK(vp, 0, p);
       if (vp->v_type != VREG) {
               (void) vn_close(vp, FREAD|FWRITE, p->p_ucred, p);
               return (EACCES);
       }
       if (*vpp != vp)
               quotaoff(p, mp, type);
       ump->um_qflags[type] |= QTF_OPENING;
       mp->mnt_flag |= MNT_QUOTA;
       vp->v_flag |= VSYSTEM;
       *vpp = vp;
       /*
        * Save the credential of the process that turned on quotas.
        * Set up the time limits for this quota.
        */
       crhold(p->p_ucred);
       ump->um_cred[type] = p->p_ucred;
       ump->um_btime[type] = MAX_DQ_TIME;
       ump->um_itime[type] = MAX_IQ_TIME;
       if (dqget(NULLVP, 0, ump, type, &dq) == 0) {
               if (dq->dq_btime > 0)
                       ump->um_btime[type] = dq->dq_btime;
               if (dq->dq_itime > 0)
                       ump->um_itime[type] = dq->dq_itime;
               dqrele(NULLVP, dq);
       }
       /*
        * Search vnodes associated with this mount point,
        * adding references to quota file being opened.
        * NB: only need to add dquot's for inodes being modified.
        */
again:
       for (vp = mp->mnt_vnodelist.lh_first; vp != NULL; vp = nextvp) {
               nextvp = vp->v_mntvnodes.le_next;
               if (vp->v_writecount == 0)
                       continue;
               if (vget(vp, LK_EXCLUSIVE, p))
                       goto again;
               if (error = getinoquota(VTOI(vp))) {
                       vput(vp);
                       break;
               }
               vput(vp);
               if (vp->v_mntvnodes.le_next != nextvp || vp->v_mount != mp)
                       goto again;
       }
       ump->um_qflags[type] &= ~QTF_OPENING;
       if (error)
               quotaoff(p, mp, type);
       return (error);
}

/*
* Q_QUOTAOFF - turn off disk quotas for a filesystem.
*/
int
quotaoff(p, mp, type)
       struct proc *p;
       struct mount *mp;
       register int type;
{
       struct vnode *vp;
       struct vnode *qvp, *nextvp;
       struct ufsmount *ump = VFSTOUFS(mp);
       struct dquot *dq;
       struct inode *ip;
       int error;
       
       if ((qvp = ump->um_quotas[type]) == NULLVP)
               return (0);
       ump->um_qflags[type] |= QTF_CLOSING;
       /*
        * Search vnodes associated with this mount point,
        * deleting any references to quota file being closed.
        */
again:
       for (vp = mp->mnt_vnodelist.lh_first; vp != NULL; vp = nextvp) {
               nextvp = vp->v_mntvnodes.le_next;
               if (vget(vp, LK_EXCLUSIVE, p))
                       goto again;
               ip = VTOI(vp);
               dq = ip->i_dquot[type];
               ip->i_dquot[type] = NODQUOT;
               dqrele(vp, dq);
               vput(vp);
               if (vp->v_mntvnodes.le_next != nextvp || vp->v_mount != mp)
                       goto again;
       }
       dqflush(qvp);
       qvp->v_flag &= ~VSYSTEM;
       error = vn_close(qvp, FREAD|FWRITE, p->p_ucred, p);
       ump->um_quotas[type] = NULLVP;
       crfree(ump->um_cred[type]);
       ump->um_cred[type] = NOCRED;
       ump->um_qflags[type] &= ~QTF_CLOSING;
       for (type = 0; type < MAXQUOTAS; type++)
               if (ump->um_quotas[type] != NULLVP)
                       break;
       if (type == MAXQUOTAS)
               mp->mnt_flag &= ~MNT_QUOTA;
       return (error);
}

/*
* Q_GETQUOTA - return current values in a dqblk structure.
*/
int
getquota(mp, id, type, addr)
       struct mount *mp;
       u_long id;
       int type;
       caddr_t addr;
{
       struct dquot *dq;
       int error;

       if (error = dqget(NULLVP, id, VFSTOUFS(mp), type, &dq))
               return (error);
       error = copyout((caddr_t)&dq->dq_dqb, addr, sizeof (struct dqblk));
       dqrele(NULLVP, dq);
       return (error);
}

/*
* Q_SETQUOTA - assign an entire dqblk structure.
*/
int
setquota(mp, id, type, addr)
       struct mount *mp;
       u_long id;
       int type;
       caddr_t addr;
{
       register struct dquot *dq;
       struct dquot *ndq;
       struct ufsmount *ump = VFSTOUFS(mp);
       struct dqblk newlim;
       int error;

       if (error = copyin(addr, (caddr_t)&newlim, sizeof (struct dqblk)))
               return (error);
       if (error = dqget(NULLVP, id, ump, type, &ndq))
               return (error);
       dq = ndq;
       while (dq->dq_flags & DQ_LOCK) {
               dq->dq_flags |= DQ_WANT;
               sleep((caddr_t)dq, PINOD+1);
       }
       /*
        * Copy all but the current values.
        * Reset time limit if previously had no soft limit or were
        * under it, but now have a soft limit and are over it.
        */
       newlim.dqb_curblocks = dq->dq_curblocks;
       newlim.dqb_curinodes = dq->dq_curinodes;
       if (dq->dq_id != 0) {
               newlim.dqb_btime = dq->dq_btime;
               newlim.dqb_itime = dq->dq_itime;
       }
       if (newlim.dqb_bsoftlimit &&
           dq->dq_curblocks >= newlim.dqb_bsoftlimit &&
           (dq->dq_bsoftlimit == 0 || dq->dq_curblocks < dq->dq_bsoftlimit))
               newlim.dqb_btime = time.tv_sec + ump->um_btime[type];
       if (newlim.dqb_isoftlimit &&
           dq->dq_curinodes >= newlim.dqb_isoftlimit &&
           (dq->dq_isoftlimit == 0 || dq->dq_curinodes < dq->dq_isoftlimit))
               newlim.dqb_itime = time.tv_sec + ump->um_itime[type];
       dq->dq_dqb = newlim;
       if (dq->dq_curblocks < dq->dq_bsoftlimit)
               dq->dq_flags &= ~DQ_BLKS;
       if (dq->dq_curinodes < dq->dq_isoftlimit)
               dq->dq_flags &= ~DQ_INODS;
       if (dq->dq_isoftlimit == 0 && dq->dq_bsoftlimit == 0 &&
           dq->dq_ihardlimit == 0 && dq->dq_bhardlimit == 0)
               dq->dq_flags |= DQ_FAKE;
       else
               dq->dq_flags &= ~DQ_FAKE;
       dq->dq_flags |= DQ_MOD;
       dqrele(NULLVP, dq);
       return (0);
}

/*
* Q_SETUSE - set current inode and block usage.
*/
int
setuse(mp, id, type, addr)
       struct mount *mp;
       u_long id;
       int type;
       caddr_t addr;
{
       register struct dquot *dq;
       struct ufsmount *ump = VFSTOUFS(mp);
       struct dquot *ndq;
       struct dqblk usage;
       int error;

       if (error = copyin(addr, (caddr_t)&usage, sizeof (struct dqblk)))
               return (error);
       if (error = dqget(NULLVP, id, ump, type, &ndq))
               return (error);
       dq = ndq;
       while (dq->dq_flags & DQ_LOCK) {
               dq->dq_flags |= DQ_WANT;
               sleep((caddr_t)dq, PINOD+1);
       }
       /*
        * Reset time limit if have a soft limit and were
        * previously under it, but are now over it.
        */
       if (dq->dq_bsoftlimit && dq->dq_curblocks < dq->dq_bsoftlimit &&
           usage.dqb_curblocks >= dq->dq_bsoftlimit)
               dq->dq_btime = time.tv_sec + ump->um_btime[type];
       if (dq->dq_isoftlimit && dq->dq_curinodes < dq->dq_isoftlimit &&
           usage.dqb_curinodes >= dq->dq_isoftlimit)
               dq->dq_itime = time.tv_sec + ump->um_itime[type];
       dq->dq_curblocks = usage.dqb_curblocks;
       dq->dq_curinodes = usage.dqb_curinodes;
       if (dq->dq_curblocks < dq->dq_bsoftlimit)
               dq->dq_flags &= ~DQ_BLKS;
       if (dq->dq_curinodes < dq->dq_isoftlimit)
               dq->dq_flags &= ~DQ_INODS;
       dq->dq_flags |= DQ_MOD;
       dqrele(NULLVP, dq);
       return (0);
}

/*
* Q_SYNC - sync quota files to disk.
*/
int
qsync(mp)
       struct mount *mp;
{
       struct ufsmount *ump = VFSTOUFS(mp);
       struct proc *p = curproc;               /* XXX */
       struct vnode *vp, *nextvp;
       struct dquot *dq;
       int i, error;

       /*
        * Check if the mount point has any quotas.
        * If not, simply return.
        */
       for (i = 0; i < MAXQUOTAS; i++)
               if (ump->um_quotas[i] != NULLVP)
                       break;
       if (i == MAXQUOTAS)
               return (0);
       /*
        * Search vnodes associated with this mount point,
        * synchronizing any modified dquot structures.
        */
       simple_lock(&mntvnode_slock);
again:
       for (vp = mp->mnt_vnodelist.lh_first; vp != NULL; vp = nextvp) {
               if (vp->v_mount != mp)
                       goto again;
               nextvp = vp->v_mntvnodes.le_next;
               simple_lock(&vp->v_interlock);
               simple_unlock(&mntvnode_slock);
               error = vget(vp, LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK, p);
               if (error) {
                       simple_lock(&mntvnode_slock);
                       if (error == ENOENT)
                               goto again;
                       continue;
               }
               for (i = 0; i < MAXQUOTAS; i++) {
                       dq = VTOI(vp)->i_dquot[i];
                       if (dq != NODQUOT && (dq->dq_flags & DQ_MOD))
                               dqsync(vp, dq);
               }
               vput(vp);
               simple_lock(&mntvnode_slock);
               if (vp->v_mntvnodes.le_next != nextvp)
                       goto again;
       }
       simple_unlock(&mntvnode_slock);
       return (0);
}

/*
* Code pertaining to management of the in-core dquot data structures.
*/
#define DQHASH(dqvp, id) \
       (&dqhashtbl[((((int)(dqvp)) >> 8) + id) & dqhash])
LIST_HEAD(dqhash, dquot) *dqhashtbl;
u_long dqhash;

/*
* Dquot free list.
*/
#define DQUOTINC        5       /* minimum free dquots desired */
TAILQ_HEAD(dqfreelist, dquot) dqfreelist;
long numdquot, desireddquot = DQUOTINC;

/*
* Initialize the quota system.
*/
void
dqinit()
{

       dqhashtbl = hashinit(desiredvnodes, M_DQUOT, &dqhash);
       TAILQ_INIT(&dqfreelist);
}

/*
* Obtain a dquot structure for the specified identifier and quota file
* reading the information from the file if necessary.
*/
int
dqget(vp, id, ump, type, dqp)
       struct vnode *vp;
       u_long id;
       register struct ufsmount *ump;
       register int type;
       struct dquot **dqp;
{
       struct proc *p = curproc;               /* XXX */
       struct dquot *dq;
       struct dqhash *dqh;
       struct vnode *dqvp;
       struct iovec aiov;
       struct uio auio;
       int error;

       dqvp = ump->um_quotas[type];
       if (dqvp == NULLVP || (ump->um_qflags[type] & QTF_CLOSING)) {
               *dqp = NODQUOT;
               return (EINVAL);
       }
       /*
        * Check the cache first.
        */
       dqh = DQHASH(dqvp, id);
       for (dq = dqh->lh_first; dq; dq = dq->dq_hash.le_next) {
               if (dq->dq_id != id ||
                   dq->dq_ump->um_quotas[dq->dq_type] != dqvp)
                       continue;
               /*
                * Cache hit with no references.  Take
                * the structure off the free list.
                */
               if (dq->dq_cnt == 0)
                       TAILQ_REMOVE(&dqfreelist, dq, dq_freelist);
               DQREF(dq);
               *dqp = dq;
               return (0);
       }
       /*
        * Not in cache, allocate a new one.
        */
       if (dqfreelist.tqh_first == NODQUOT &&
           numdquot < MAXQUOTAS * desiredvnodes)
               desireddquot += DQUOTINC;
       if (numdquot < desireddquot) {
               dq = (struct dquot *)malloc(sizeof *dq, M_DQUOT, M_WAITOK);
               bzero((char *)dq, sizeof *dq);
               numdquot++;
       } else {
               if ((dq = dqfreelist.tqh_first) == NULL) {
                       tablefull("dquot");
                       *dqp = NODQUOT;
                       return (EUSERS);
               }
               if (dq->dq_cnt || (dq->dq_flags & DQ_MOD))
                       panic("free dquot isn't");
               TAILQ_REMOVE(&dqfreelist, dq, dq_freelist);
               LIST_REMOVE(dq, dq_hash);
       }
       /*
        * Initialize the contents of the dquot structure.
        */
       if (vp != dqvp)
               vn_lock(dqvp, LK_EXCLUSIVE | LK_RETRY, p);
       LIST_INSERT_HEAD(dqh, dq, dq_hash);
       DQREF(dq);
       dq->dq_flags = DQ_LOCK;
       dq->dq_id = id;
       dq->dq_ump = ump;
       dq->dq_type = type;
       auio.uio_iov = &aiov;
       auio.uio_iovcnt = 1;
       aiov.iov_base = (caddr_t)&dq->dq_dqb;
       aiov.iov_len = sizeof (struct dqblk);
       auio.uio_resid = sizeof (struct dqblk);
       auio.uio_offset = (off_t)(id * sizeof (struct dqblk));
       auio.uio_segflg = UIO_SYSSPACE;
       auio.uio_rw = UIO_READ;
       auio.uio_procp = (struct proc *)0;
       error = VOP_READ(dqvp, &auio, 0, ump->um_cred[type]);
       if (auio.uio_resid == sizeof(struct dqblk) && error == 0)
               bzero((caddr_t)&dq->dq_dqb, sizeof(struct dqblk));
       if (vp != dqvp)
               VOP_UNLOCK(dqvp, 0, p);
       if (dq->dq_flags & DQ_WANT)
               wakeup((caddr_t)dq);
       dq->dq_flags = 0;
       /*
        * I/O error in reading quota file, release
        * quota structure and reflect problem to caller.
        */
       if (error) {
               LIST_REMOVE(dq, dq_hash);
               dqrele(vp, dq);
               *dqp = NODQUOT;
               return (error);
       }
       /*
        * Check for no limit to enforce.
        * Initialize time values if necessary.
        */
       if (dq->dq_isoftlimit == 0 && dq->dq_bsoftlimit == 0 &&
           dq->dq_ihardlimit == 0 && dq->dq_bhardlimit == 0)
               dq->dq_flags |= DQ_FAKE;
       if (dq->dq_id != 0) {
               if (dq->dq_btime == 0)
                       dq->dq_btime = time.tv_sec + ump->um_btime[type];
               if (dq->dq_itime == 0)
                       dq->dq_itime = time.tv_sec + ump->um_itime[type];
       }
       *dqp = dq;
       return (0);
}

/*
* Obtain a reference to a dquot.
*/
void
dqref(dq)
       struct dquot *dq;
{

       dq->dq_cnt++;
}

/*
* Release a reference to a dquot.
*/
void
dqrele(vp, dq)
       struct vnode *vp;
       register struct dquot *dq;
{

       if (dq == NODQUOT)
               return;
       if (dq->dq_cnt > 1) {
               dq->dq_cnt--;
               return;
       }
       if (dq->dq_flags & DQ_MOD)
               (void) dqsync(vp, dq);
       if (--dq->dq_cnt > 0)
               return;
       TAILQ_INSERT_TAIL(&dqfreelist, dq, dq_freelist);
}

/*
* Update the disk quota in the quota file.
*/
int
dqsync(vp, dq)
       struct vnode *vp;
       struct dquot *dq;
{
       struct proc *p = curproc;               /* XXX */
       struct vnode *dqvp;
       struct iovec aiov;
       struct uio auio;
       int error;

       if (dq == NODQUOT)
               panic("dqsync: dquot");
       if ((dq->dq_flags & DQ_MOD) == 0)
               return (0);
       if ((dqvp = dq->dq_ump->um_quotas[dq->dq_type]) == NULLVP)
               panic("dqsync: file");
       if (vp != dqvp)
               vn_lock(dqvp, LK_EXCLUSIVE | LK_RETRY, p);
       while (dq->dq_flags & DQ_LOCK) {
               dq->dq_flags |= DQ_WANT;
               sleep((caddr_t)dq, PINOD+2);
               if ((dq->dq_flags & DQ_MOD) == 0) {
                       if (vp != dqvp)
                               VOP_UNLOCK(dqvp, 0, p);
                       return (0);
               }
       }
       dq->dq_flags |= DQ_LOCK;
       auio.uio_iov = &aiov;
       auio.uio_iovcnt = 1;
       aiov.iov_base = (caddr_t)&dq->dq_dqb;
       aiov.iov_len = sizeof (struct dqblk);
       auio.uio_resid = sizeof (struct dqblk);
       auio.uio_offset = (off_t)(dq->dq_id * sizeof (struct dqblk));
       auio.uio_segflg = UIO_SYSSPACE;
       auio.uio_rw = UIO_WRITE;
       auio.uio_procp = (struct proc *)0;
       error = VOP_WRITE(dqvp, &auio, 0, dq->dq_ump->um_cred[dq->dq_type]);
       if (auio.uio_resid && error == 0)
               error = EIO;
       if (dq->dq_flags & DQ_WANT)
               wakeup((caddr_t)dq);
       dq->dq_flags &= ~(DQ_MOD|DQ_LOCK|DQ_WANT);
       if (vp != dqvp)
               VOP_UNLOCK(dqvp, 0, p);
       return (error);
}

/*
* Flush all entries from the cache for a particular vnode.
*/
void
dqflush(vp)
       register struct vnode *vp;
{
       register struct dquot *dq, *nextdq;
       struct dqhash *dqh;

       /*
        * Move all dquot's that used to refer to this quota
        * file off their hash chains (they will eventually
        * fall off the head of the free list and be re-used).
        */
       for (dqh = &dqhashtbl[dqhash]; dqh >= dqhashtbl; dqh--) {
               for (dq = dqh->lh_first; dq; dq = nextdq) {
                       nextdq = dq->dq_hash.le_next;
                       if (dq->dq_ump->um_quotas[dq->dq_type] != vp)
                               continue;
                       if (dq->dq_cnt)
                               panic("dqflush: stray dquot");
                       LIST_REMOVE(dq, dq_hash);
                       dq->dq_ump = (struct ufsmount *)0;
               }
       }
}