union_vfsops.c

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    1 /*
    2  * Copyright (c) 1994, 1995 The Regents of the University of California.
    3  * Copyright (c) 1994, 1995 Jan-Simon Pendry.
    4  * All rights reserved.
    5  *
    6  * This code is derived from software donated to Berkeley by
    7  * Jan-Simon Pendry.
    8  *
    9  * Redistribution and use in source and binary forms, with or without
   10  * modification, are permitted provided that the following conditions
   11  * are met:
   12  * 1. Redistributions of source code must retain the above copyright
   13  *    notice, this list of conditions and the following disclaimer.
   14  * 2. Redistributions in binary form must reproduce the above copyright
   15  *    notice, this list of conditions and the following disclaimer in the
   16  *    documentation and/or other materials provided with the distribution.
   17  * 3. All advertising materials mentioning features or use of this software
   18  *    must display the following acknowledgement:
   19  *      This product includes software developed by the University of
   20  *      California, Berkeley and its contributors.
   21  * 4. Neither the name of the University nor the names of its contributors
   22  *    may be used to endorse or promote products derived from this software
   23  *    without specific prior written permission.
   24  *
   25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   35  * SUCH DAMAGE.
   36  *
   37  *      @(#)union_vfsops.c      8.20 (Berkeley) 5/20/95
   38  * $FreeBSD$
   39  */
   40 
   41 /*
   42  * Union Layer
   43  */
   44 
   45 #include <sys/param.h>
   46 #include <sys/systm.h>
   47 #include <sys/kernel.h>
   48 #include <sys/proc.h>
   49 #include <sys/vnode.h>
   50 #include <sys/mount.h>
   51 #include <sys/namei.h>
   52 #include <sys/malloc.h>
   53 #include <sys/filedesc.h>
   54 #include <miscfs/union/union.h>
   55 
   56 static MALLOC_DEFINE(M_UNIONFSMNT, "UNION mount", "UNION mount structure");
   57 
   58 extern int      union_init __P((struct vfsconf *));
   59 
   60 extern int      union_fhtovp __P((struct mount *mp, struct fid *fidp,
   61                                   struct mbuf *nam, struct vnode **vpp,
   62                                   int *exflagsp, struct ucred **credanonp));
   63 static int      union_mount __P((struct mount *mp, char *path, caddr_t data,
   64                                  struct nameidata *ndp, struct proc *p));
   65 extern int      union_quotactl __P((struct mount *mp, int cmd, uid_t uid,
   66                                     caddr_t arg, struct proc *p));
   67 static int      union_root __P((struct mount *mp, struct vnode **vpp));
   68 static int      union_start __P((struct mount *mp, int flags, struct proc *p));
   69 static int      union_statfs __P((struct mount *mp, struct statfs *sbp,
   70                                   struct proc *p));
   71 extern int      union_sync __P((struct mount *mp, int waitfor,
   72                                 struct ucred *cred, struct proc *p));
   73 static int      union_unmount __P((struct mount *mp, int mntflags,
   74                                    struct proc *p));
   75 extern int      union_vget __P((struct mount *mp, ino_t ino,
   76                                 struct vnode **vpp));
   77 extern int      union_vptofh __P((struct vnode *vp, struct fid *fhp));
   78 
   79 /*
   80  * Mount union filesystem
   81  */
   82 static int
   83 union_mount(mp, path, data, ndp, p)
   84         struct mount *mp;
   85         char *path;
   86         caddr_t data;
   87         struct nameidata *ndp;
   88         struct proc *p;
   89 {
   90         int error = 0;
   91         struct union_args args;
   92         struct vnode *lowerrootvp = NULLVP;
   93         struct vnode *upperrootvp = NULLVP;
   94         struct union_mount *um = 0;
   95         struct ucred *cred = 0;
   96         char *cp = 0;
   97         int len;
   98         u_int size;
   99 
  100 #ifdef UNION_DIAGNOSTIC
  101         printf("union_mount(mp = %x)\n", mp);
  102 #endif
  103 
  104         /*
  105          * Disable clustered write, otherwise system becomes unstable.
  106          */
  107         mp->mnt_flag |= MNT_NOCLUSTERW;
  108 
  109         /*
  110          * Update is a no-op
  111          */
  112         if (mp->mnt_flag & MNT_UPDATE) {
  113                 /*
  114                  * Need to provide.
  115                  * 1. a way to convert between rdonly and rdwr mounts.
  116                  * 2. support for nfs exports.
  117                  */
  118                 error = EOPNOTSUPP;
  119                 goto bad;
  120         }
  121 
  122         /*
  123          * Get argument
  124          */
  125         error = copyin(data, (caddr_t)&args, sizeof(struct union_args));
  126         if (error)
  127                 goto bad;
  128 
  129         lowerrootvp = mp->mnt_vnodecovered;
  130         VREF(lowerrootvp);
  131 
  132         /*
  133          * Unlock lower node to avoid deadlock.
  134          */
  135         if (lowerrootvp->v_op == union_vnodeop_p)
  136                 VOP_UNLOCK(lowerrootvp, 0, p);
  137 
  138         /*
  139          * Find upper node.
  140          */
  141         NDINIT(ndp, LOOKUP, FOLLOW|WANTPARENT,
  142                UIO_USERSPACE, args.target, p);
  143 
  144         error = namei(ndp);
  145         if (lowerrootvp->v_op == union_vnodeop_p)
  146                 vn_lock(lowerrootvp, LK_EXCLUSIVE | LK_RETRY, p);
  147         if (error)
  148                 goto bad;
  149 
  150         upperrootvp = ndp->ni_vp;
  151         vrele(ndp->ni_dvp);
  152         ndp->ni_dvp = NULL;
  153 
  154         /*
  155          * Check multi union mount to avoid `lock myself again' panic.
  156          */
  157         if (upperrootvp == VTOUNION(lowerrootvp)->un_uppervp) {
  158 #ifdef DIAGNOSTIC
  159                 printf("union_mount: multi union mount?\n");
  160 #endif
  161                 error = EDEADLK;
  162                 goto bad;
  163         }
  164 
  165         if (upperrootvp->v_type != VDIR) {
  166                 error = EINVAL;
  167                 goto bad;
  168         }
  169 
  170         um = (struct union_mount *) malloc(sizeof(struct union_mount),
  171                                 M_UNIONFSMNT, M_WAITOK);        /* XXX */
  172 
  173         /*
  174          * Keep a held reference to the target vnodes.
  175          * They are vrele'd in union_unmount.
  176          *
  177          * Depending on the _BELOW flag, the filesystems are
  178          * viewed in a different order.  In effect, this is the
  179          * same as providing a mount under option to the mount syscall.
  180          */
  181 
  182         um->um_op = args.mntflags & UNMNT_OPMASK;
  183         switch (um->um_op) {
  184         case UNMNT_ABOVE:
  185                 um->um_lowervp = lowerrootvp;
  186                 um->um_uppervp = upperrootvp;
  187                 break;
  188 
  189         case UNMNT_BELOW:
  190                 um->um_lowervp = upperrootvp;
  191                 um->um_uppervp = lowerrootvp;
  192                 break;
  193 
  194         case UNMNT_REPLACE:
  195                 vrele(lowerrootvp);
  196                 lowerrootvp = NULLVP;
  197                 um->um_uppervp = upperrootvp;
  198                 um->um_lowervp = lowerrootvp;
  199                 break;
  200 
  201         default:
  202                 error = EINVAL;
  203                 goto bad;
  204         }
  205 
  206         /*
  207          * Unless the mount is readonly, ensure that the top layer
  208          * supports whiteout operations
  209          */
  210         if ((mp->mnt_flag & MNT_RDONLY) == 0) {
  211                 error = VOP_WHITEOUT(um->um_uppervp, (struct componentname *) 0, LOOKUP);
  212                 if (error)
  213                         goto bad;
  214         }
  215 
  216         um->um_cred = p->p_ucred;
  217         crhold(um->um_cred);
  218         um->um_cmode = UN_DIRMODE &~ p->p_fd->fd_cmask;
  219 
  220         /*
  221          * Depending on what you think the MNT_LOCAL flag might mean,
  222          * you may want the && to be || on the conditional below.
  223          * At the moment it has been defined that the filesystem is
  224          * only local if it is all local, ie the MNT_LOCAL flag implies
  225          * that the entire namespace is local.  If you think the MNT_LOCAL
  226          * flag implies that some of the files might be stored locally
  227          * then you will want to change the conditional.
  228          */
  229         if (um->um_op == UNMNT_ABOVE) {
  230                 if (((um->um_lowervp == NULLVP) ||
  231                      (um->um_lowervp->v_mount->mnt_flag & MNT_LOCAL)) &&
  232                     (um->um_uppervp->v_mount->mnt_flag & MNT_LOCAL))
  233                         mp->mnt_flag |= MNT_LOCAL;
  234         }
  235 
  236         /*
  237          * Copy in the upper layer's RDONLY flag.  This is for the benefit
  238          * of lookup() which explicitly checks the flag, rather than asking
  239          * the filesystem for its own opinion.  This means, that an update
  240          * mount of the underlying filesystem to go from rdonly to rdwr
  241          * will leave the unioned view as read-only.
  242          */
  243         mp->mnt_flag |= (um->um_uppervp->v_mount->mnt_flag & MNT_RDONLY);
  244 
  245         mp->mnt_data = (qaddr_t) um;
  246         vfs_getnewfsid(mp);
  247 
  248         (void) copyinstr(path, mp->mnt_stat.f_mntonname, MNAMELEN - 1, &size);
  249         bzero(mp->mnt_stat.f_mntonname + size, MNAMELEN - size);
  250 
  251         switch (um->um_op) {
  252         case UNMNT_ABOVE:
  253                 cp = "<above>:";
  254                 break;
  255         case UNMNT_BELOW:
  256                 cp = "<below>:";
  257                 break;
  258         case UNMNT_REPLACE:
  259                 cp = "";
  260                 break;
  261         }
  262         len = strlen(cp);
  263         bcopy(cp, mp->mnt_stat.f_mntfromname, len);
  264 
  265         cp = mp->mnt_stat.f_mntfromname + len;
  266         len = MNAMELEN - len;
  267 
  268         (void) copyinstr(args.target, cp, len - 1, &size);
  269         bzero(cp + size, len - size);
  270 
  271         (void)union_statfs(mp, &mp->mnt_stat, p);
  272 
  273 #ifdef UNION_DIAGNOSTIC
  274         printf("union_mount: from %s, on %s\n",
  275                 mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname);
  276 #endif
  277         return (0);
  278 
  279 bad:
  280         if (um)
  281                 free(um, M_UNIONFSMNT);
  282         if (cred)
  283                 crfree(cred);
  284         if (upperrootvp)
  285                 vrele(upperrootvp);
  286         if (lowerrootvp)
  287                 vrele(lowerrootvp);
  288         return (error);
  289 }
  290 
  291 /*
  292  * VFS start.  Nothing needed here - the start routine
  293  * on the underlying filesystem(s) will have been called
  294  * when that filesystem was mounted.
  295  */
  296 static int
  297 union_start(mp, flags, p)
  298         struct mount *mp;
  299         int flags;
  300         struct proc *p;
  301 {
  302 
  303         return (0);
  304 }
  305 
  306 /*
  307  * Free reference to union layer
  308  */
  309 static int
  310 union_unmount(mp, mntflags, p)
  311         struct mount *mp;
  312         int mntflags;
  313         struct proc *p;
  314 {
  315         struct union_mount *um = MOUNTTOUNIONMOUNT(mp);
  316         struct vnode *um_rootvp;
  317         int error;
  318         int freeing;
  319         int flags = 0;
  320 
  321 #ifdef UNION_DIAGNOSTIC
  322         printf("union_unmount(mp = %x)\n", mp);
  323 #endif
  324 
  325         if (mntflags & MNT_FORCE)
  326                 flags |= FORCECLOSE;
  327 
  328         if (error = union_root(mp, &um_rootvp))
  329                 return (error);
  330 
  331         /*
  332          * Keep flushing vnodes from the mount list.
  333          * This is needed because of the un_pvp held
  334          * reference to the parent vnode.
  335          * If more vnodes have been freed on a given pass,
  336          * the try again.  The loop will iterate at most
  337          * (d) times, where (d) is the maximum tree depth
  338          * in the filesystem.
  339          */
  340         for (freeing = 0; vflush(mp, um_rootvp, flags) != 0;) {
  341                 struct vnode *vp;
  342                 int n;
  343 
  344                 /* count #vnodes held on mount list */
  345                 for (n = 0, vp = mp->mnt_vnodelist.lh_first;
  346                                 vp != NULLVP;
  347                                 vp = vp->v_mntvnodes.le_next)
  348                         n++;
  349 
  350                 /* if this is unchanged then stop */
  351                 if (n == freeing)
  352                         break;
  353 
  354                 /* otherwise try once more time */
  355                 freeing = n;
  356         }
  357 
  358         /* At this point the root vnode should have a single reference */
  359         if (um_rootvp->v_usecount > 1) {
  360                 vput(um_rootvp);
  361                 return (EBUSY);
  362         }
  363 
  364 #ifdef UNION_DIAGNOSTIC
  365         vprint("union root", um_rootvp);
  366 #endif   
  367         /*
  368          * Discard references to upper and lower target vnodes.
  369          */
  370         if (um->um_lowervp)
  371                 vrele(um->um_lowervp);
  372         vrele(um->um_uppervp);
  373         crfree(um->um_cred);
  374         /*
  375          * Release reference on underlying root vnode
  376          */
  377         vput(um_rootvp);
  378         /*
  379          * And blow it away for future re-use
  380          */
  381         vgone(um_rootvp);
  382         /*
  383          * Finally, throw away the union_mount structure
  384          */
  385         free(mp->mnt_data, M_UNIONFSMNT);       /* XXX */
  386         mp->mnt_data = 0;
  387         return (0);
  388 }
  389 
  390 static int
  391 union_root(mp, vpp)
  392         struct mount *mp;
  393         struct vnode **vpp;
  394 {
  395         struct proc *p = curproc;       /* XXX */
  396         struct union_mount *um = MOUNTTOUNIONMOUNT(mp);
  397         int error;
  398         int loselock;
  399         int lockadj = 0;
  400 
  401         if (um->um_lowervp && um->um_op != UNMNT_BELOW &&
  402                 VOP_ISLOCKED(um->um_lowervp)) {
  403                 VREF(um->um_lowervp);
  404                 VOP_UNLOCK(um->um_lowervp, 0, p);
  405                 lockadj = 1;
  406         }
  407 
  408         /*
  409          * Return locked reference to root.
  410          */
  411         VREF(um->um_uppervp);
  412         if ((um->um_op == UNMNT_BELOW) &&
  413             VOP_ISLOCKED(um->um_uppervp)) {
  414                 loselock = 1;
  415         } else {
  416                 vn_lock(um->um_uppervp, LK_EXCLUSIVE | LK_RETRY, p);
  417                 loselock = 0;
  418         }
  419         if (um->um_lowervp)
  420                 VREF(um->um_lowervp);
  421         error = union_allocvp(vpp, mp,
  422                               (struct vnode *) 0,
  423                               (struct vnode *) 0,
  424                               (struct componentname *) 0,
  425                               um->um_uppervp,
  426                               um->um_lowervp,
  427                               1);
  428 
  429         if (error) {
  430                 if (loselock)
  431                         vrele(um->um_uppervp);
  432                 else
  433                         vput(um->um_uppervp);
  434                 if (um->um_lowervp)
  435                         vrele(um->um_lowervp);
  436         } else {
  437                 if (loselock)
  438                         VTOUNION(*vpp)->un_flags &= ~UN_ULOCK;
  439         }
  440         if (lockadj) {
  441                 vn_lock(um->um_lowervp, LK_EXCLUSIVE | LK_RETRY, p);
  442                 vrele(um->um_lowervp);
  443         }
  444 
  445         return (error);
  446 }
  447 
  448 static int
  449 union_statfs(mp, sbp, p)
  450         struct mount *mp;
  451         struct statfs *sbp;
  452         struct proc *p;
  453 {
  454         int error;
  455         struct union_mount *um = MOUNTTOUNIONMOUNT(mp);
  456         struct statfs mstat;
  457         int lbsize;
  458 
  459 #ifdef UNION_DIAGNOSTIC
  460         printf("union_statfs(mp = %x, lvp = %x, uvp = %x)\n", mp,
  461                         um->um_lowervp,
  462                         um->um_uppervp);
  463 #endif
  464 
  465         bzero(&mstat, sizeof(mstat));
  466 
  467         if (um->um_lowervp) {
  468                 error = VFS_STATFS(um->um_lowervp->v_mount, &mstat, p);
  469                 if (error)
  470                         return (error);
  471         }
  472 
  473         /* now copy across the "interesting" information and fake the rest */
  474 #if 0
  475         sbp->f_type = mstat.f_type;
  476         sbp->f_flags = mstat.f_flags;
  477         sbp->f_bsize = mstat.f_bsize;
  478         sbp->f_iosize = mstat.f_iosize;
  479 #endif
  480         lbsize = mstat.f_bsize;
  481         sbp->f_blocks = mstat.f_blocks;
  482         sbp->f_bfree = mstat.f_bfree;
  483         sbp->f_bavail = mstat.f_bavail;
  484         sbp->f_files = mstat.f_files;
  485         sbp->f_ffree = mstat.f_ffree;
  486 
  487         error = VFS_STATFS(um->um_uppervp->v_mount, &mstat, p);
  488         if (error)
  489                 return (error);
  490 
  491         sbp->f_flags = mstat.f_flags;
  492         sbp->f_bsize = mstat.f_bsize;
  493         sbp->f_iosize = mstat.f_iosize;
  494 
  495         /*
  496          * if the lower and upper blocksizes differ, then frig the
  497          * block counts so that the sizes reported by df make some
  498          * kind of sense.  none of this makes sense though.
  499          */
  500 
  501         if (mstat.f_bsize != lbsize)
  502                 sbp->f_blocks = ((off_t) sbp->f_blocks * lbsize) / mstat.f_bsize;
  503 
  504         /*
  505          * The "total" fields count total resources in all layers,
  506          * the "free" fields count only those resources which are
  507          * free in the upper layer (since only the upper layer
  508          * is writeable).
  509          */
  510         sbp->f_blocks += mstat.f_blocks;
  511         sbp->f_bfree = mstat.f_bfree;
  512         sbp->f_bavail = mstat.f_bavail;
  513         sbp->f_files += mstat.f_files;
  514         sbp->f_ffree = mstat.f_ffree;
  515 
  516         if (sbp != &mp->mnt_stat) {
  517                 sbp->f_type = mp->mnt_vfc->vfc_typenum;
  518                 bcopy(&mp->mnt_stat.f_fsid, &sbp->f_fsid, sizeof(sbp->f_fsid));
  519                 bcopy(mp->mnt_stat.f_mntonname, sbp->f_mntonname, MNAMELEN);
  520                 bcopy(mp->mnt_stat.f_mntfromname, sbp->f_mntfromname, MNAMELEN);
  521         }
  522         return (0);
  523 }
  524 
  525 /*
  526  * XXX - Assumes no data cached at union layer.
  527  */
  528 #define union_sync ((int (*) __P((struct mount *, int, struct ucred *, \
  529             struct proc *)))nullop)
  530 
  531 #define union_fhtovp ((int (*) __P((struct mount *, struct fid *, \
  532             struct sockaddr *, struct vnode **, int *, struct ucred **)))eopnotsupp)
  533 #define union_quotactl ((int (*) __P((struct mount *, int, uid_t, caddr_t, \
  534             struct proc *)))eopnotsupp)
  535 #define union_sysctl ((int (*) __P((int *, u_int, void *, size_t *, void *, \
  536             size_t, struct proc *)))eopnotsupp)
  537 #define union_vget ((int (*) __P((struct mount *, ino_t, struct vnode **))) \
  538             eopnotsupp)
  539 #define union_vptofh ((int (*) __P((struct vnode *, struct fid *)))eopnotsupp)
  540 
  541 static struct vfsops union_vfsops = {
  542         union_mount,
  543         union_start,
  544         union_unmount,
  545         union_root,
  546         union_quotactl,
  547         union_statfs,
  548         union_sync,
  549         union_vget,
  550         union_fhtovp,
  551         union_vptofh,
  552         union_init,
  553 };
  554 
  555 VFS_SET(union_vfsops, union, VFCF_LOOPBACK);
Cache object: e2952d967218a7d81ad4780b34564ed8
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FreeBSD/Linux Kernel Cross Reference sys/miscfs/union/union_vfsops.c

FreeBSD/Linux Kernel Cross Reference
sys/miscfs/union/union_vfsops.c
