The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

FreeBSD/Linux Kernel Cross Reference
sys/fs/nullfs/null_vnops.c

Version: -  FREEBSD  -  FREEBSD-13-STABLE  -  FREEBSD-13-0  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  l41  -  OPENBSD  -  linux-2.6  -  MK84  -  PLAN9  -  xnu-8792 
SearchContext: -  none  -  3  -  10 

    1 /*-
    2  * Copyright (c) 1992, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software contributed to Berkeley by
    6  * John Heidemann of the UCLA Ficus project.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 4. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  *      @(#)null_vnops.c        8.6 (Berkeley) 5/27/95
   33  *
   34  * Ancestors:
   35  *      @(#)lofs_vnops.c        1.2 (Berkeley) 6/18/92
   36  *      ...and...
   37  *      @(#)null_vnodeops.c 1.20 92/07/07 UCLA Ficus project
   38  *
   39  * $FreeBSD: releng/8.0/sys/fs/nullfs/null_vnops.c 194601 2009-06-21 19:21:01Z kib $
   40  */
   41 
   42 /*
   43  * Null Layer
   44  *
   45  * (See mount_nullfs(8) for more information.)
   46  *
   47  * The null layer duplicates a portion of the filesystem
   48  * name space under a new name.  In this respect, it is
   49  * similar to the loopback filesystem.  It differs from
   50  * the loopback fs in two respects:  it is implemented using
   51  * a stackable layers techniques, and its "null-node"s stack above
   52  * all lower-layer vnodes, not just over directory vnodes.
   53  *
   54  * The null layer has two purposes.  First, it serves as a demonstration
   55  * of layering by proving a layer which does nothing.  (It actually
   56  * does everything the loopback filesystem does, which is slightly
   57  * more than nothing.)  Second, the null layer can serve as a prototype
   58  * layer.  Since it provides all necessary layer framework,
   59  * new filesystem layers can be created very easily be starting
   60  * with a null layer.
   61  *
   62  * The remainder of this man page examines the null layer as a basis
   63  * for constructing new layers.
   64  *
   65  *
   66  * INSTANTIATING NEW NULL LAYERS
   67  *
   68  * New null layers are created with mount_nullfs(8).
   69  * Mount_nullfs(8) takes two arguments, the pathname
   70  * of the lower vfs (target-pn) and the pathname where the null
   71  * layer will appear in the namespace (alias-pn).  After
   72  * the null layer is put into place, the contents
   73  * of target-pn subtree will be aliased under alias-pn.
   74  *
   75  *
   76  * OPERATION OF A NULL LAYER
   77  *
   78  * The null layer is the minimum filesystem layer,
   79  * simply bypassing all possible operations to the lower layer
   80  * for processing there.  The majority of its activity centers
   81  * on the bypass routine, through which nearly all vnode operations
   82  * pass.
   83  *
   84  * The bypass routine accepts arbitrary vnode operations for
   85  * handling by the lower layer.  It begins by examing vnode
   86  * operation arguments and replacing any null-nodes by their
   87  * lower-layer equivlants.  It then invokes the operation
   88  * on the lower layer.  Finally, it replaces the null-nodes
   89  * in the arguments and, if a vnode is return by the operation,
   90  * stacks a null-node on top of the returned vnode.
   91  *
   92  * Although bypass handles most operations, vop_getattr, vop_lock,
   93  * vop_unlock, vop_inactive, vop_reclaim, and vop_print are not
   94  * bypassed. Vop_getattr must change the fsid being returned.
   95  * Vop_lock and vop_unlock must handle any locking for the
   96  * current vnode as well as pass the lock request down.
   97  * Vop_inactive and vop_reclaim are not bypassed so that
   98  * they can handle freeing null-layer specific data. Vop_print
   99  * is not bypassed to avoid excessive debugging information.
  100  * Also, certain vnode operations change the locking state within
  101  * the operation (create, mknod, remove, link, rename, mkdir, rmdir,
  102  * and symlink). Ideally these operations should not change the
  103  * lock state, but should be changed to let the caller of the
  104  * function unlock them. Otherwise all intermediate vnode layers
  105  * (such as union, umapfs, etc) must catch these functions to do
  106  * the necessary locking at their layer.
  107  *
  108  *
  109  * INSTANTIATING VNODE STACKS
  110  *
  111  * Mounting associates the null layer with a lower layer,
  112  * effect stacking two VFSes.  Vnode stacks are instead
  113  * created on demand as files are accessed.
  114  *
  115  * The initial mount creates a single vnode stack for the
  116  * root of the new null layer.  All other vnode stacks
  117  * are created as a result of vnode operations on
  118  * this or other null vnode stacks.
  119  *
  120  * New vnode stacks come into existance as a result of
  121  * an operation which returns a vnode.
  122  * The bypass routine stacks a null-node above the new
  123  * vnode before returning it to the caller.
  124  *
  125  * For example, imagine mounting a null layer with
  126  * "mount_nullfs /usr/include /dev/layer/null".
  127  * Changing directory to /dev/layer/null will assign
  128  * the root null-node (which was created when the null layer was mounted).
  129  * Now consider opening "sys".  A vop_lookup would be
  130  * done on the root null-node.  This operation would bypass through
  131  * to the lower layer which would return a vnode representing
  132  * the UFS "sys".  Null_bypass then builds a null-node
  133  * aliasing the UFS "sys" and returns this to the caller.
  134  * Later operations on the null-node "sys" will repeat this
  135  * process when constructing other vnode stacks.
  136  *
  137  *
  138  * CREATING OTHER FILE SYSTEM LAYERS
  139  *
  140  * One of the easiest ways to construct new filesystem layers is to make
  141  * a copy of the null layer, rename all files and variables, and
  142  * then begin modifing the copy.  Sed can be used to easily rename
  143  * all variables.
  144  *
  145  * The umap layer is an example of a layer descended from the
  146  * null layer.
  147  *
  148  *
  149  * INVOKING OPERATIONS ON LOWER LAYERS
  150  *
  151  * There are two techniques to invoke operations on a lower layer
  152  * when the operation cannot be completely bypassed.  Each method
  153  * is appropriate in different situations.  In both cases,
  154  * it is the responsibility of the aliasing layer to make
  155  * the operation arguments "correct" for the lower layer
  156  * by mapping a vnode arguments to the lower layer.
  157  *
  158  * The first approach is to call the aliasing layer's bypass routine.
  159  * This method is most suitable when you wish to invoke the operation
  160  * currently being handled on the lower layer.  It has the advantage
  161  * that the bypass routine already must do argument mapping.
  162  * An example of this is null_getattrs in the null layer.
  163  *
  164  * A second approach is to directly invoke vnode operations on
  165  * the lower layer with the VOP_OPERATIONNAME interface.
  166  * The advantage of this method is that it is easy to invoke
  167  * arbitrary operations on the lower layer.  The disadvantage
  168  * is that vnode arguments must be manualy mapped.
  169  *
  170  */
  171 
  172 #include <sys/param.h>
  173 #include <sys/systm.h>
  174 #include <sys/conf.h>
  175 #include <sys/kernel.h>
  176 #include <sys/lock.h>
  177 #include <sys/malloc.h>
  178 #include <sys/mount.h>
  179 #include <sys/mutex.h>
  180 #include <sys/namei.h>
  181 #include <sys/sysctl.h>
  182 #include <sys/vnode.h>
  183 
  184 #include <fs/nullfs/null.h>
  185 
  186 #include <vm/vm.h>
  187 #include <vm/vm_extern.h>
  188 #include <vm/vm_object.h>
  189 #include <vm/vnode_pager.h>
  190 
  191 static int null_bug_bypass = 0;   /* for debugging: enables bypass printf'ing */
  192 SYSCTL_INT(_debug, OID_AUTO, nullfs_bug_bypass, CTLFLAG_RW, 
  193         &null_bug_bypass, 0, "");
  194 
  195 /*
  196  * This is the 10-Apr-92 bypass routine.
  197  *    This version has been optimized for speed, throwing away some
  198  * safety checks.  It should still always work, but it's not as
  199  * robust to programmer errors.
  200  *
  201  * In general, we map all vnodes going down and unmap them on the way back.
  202  * As an exception to this, vnodes can be marked "unmapped" by setting
  203  * the Nth bit in operation's vdesc_flags.
  204  *
  205  * Also, some BSD vnode operations have the side effect of vrele'ing
  206  * their arguments.  With stacking, the reference counts are held
  207  * by the upper node, not the lower one, so we must handle these
  208  * side-effects here.  This is not of concern in Sun-derived systems
  209  * since there are no such side-effects.
  210  *
  211  * This makes the following assumptions:
  212  * - only one returned vpp
  213  * - no INOUT vpp's (Sun's vop_open has one of these)
  214  * - the vnode operation vector of the first vnode should be used
  215  *   to determine what implementation of the op should be invoked
  216  * - all mapped vnodes are of our vnode-type (NEEDSWORK:
  217  *   problems on rmdir'ing mount points and renaming?)
  218  */
  219 int
  220 null_bypass(struct vop_generic_args *ap)
  221 {
  222         struct vnode **this_vp_p;
  223         int error;
  224         struct vnode *old_vps[VDESC_MAX_VPS];
  225         struct vnode **vps_p[VDESC_MAX_VPS];
  226         struct vnode ***vppp;
  227         struct vnodeop_desc *descp = ap->a_desc;
  228         int reles, i;
  229 
  230         if (null_bug_bypass)
  231                 printf ("null_bypass: %s\n", descp->vdesc_name);
  232 
  233 #ifdef DIAGNOSTIC
  234         /*
  235          * We require at least one vp.
  236          */
  237         if (descp->vdesc_vp_offsets == NULL ||
  238             descp->vdesc_vp_offsets[0] == VDESC_NO_OFFSET)
  239                 panic ("null_bypass: no vp's in map");
  240 #endif
  241 
  242         /*
  243          * Map the vnodes going in.
  244          * Later, we'll invoke the operation based on
  245          * the first mapped vnode's operation vector.
  246          */
  247         reles = descp->vdesc_flags;
  248         for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) {
  249                 if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET)
  250                         break;   /* bail out at end of list */
  251                 vps_p[i] = this_vp_p =
  252                         VOPARG_OFFSETTO(struct vnode**,descp->vdesc_vp_offsets[i],ap);
  253                 /*
  254                  * We're not guaranteed that any but the first vnode
  255                  * are of our type.  Check for and don't map any
  256                  * that aren't.  (We must always map first vp or vclean fails.)
  257                  */
  258                 if (i && (*this_vp_p == NULLVP ||
  259                     (*this_vp_p)->v_op != &null_vnodeops)) {
  260                         old_vps[i] = NULLVP;
  261                 } else {
  262                         old_vps[i] = *this_vp_p;
  263                         *(vps_p[i]) = NULLVPTOLOWERVP(*this_vp_p);
  264                         /*
  265                          * XXX - Several operations have the side effect
  266                          * of vrele'ing their vp's.  We must account for
  267                          * that.  (This should go away in the future.)
  268                          */
  269                         if (reles & VDESC_VP0_WILLRELE)
  270                                 VREF(*this_vp_p);
  271                 }
  272 
  273         }
  274 
  275         /*
  276          * Call the operation on the lower layer
  277          * with the modified argument structure.
  278          */
  279         if (vps_p[0] && *vps_p[0])
  280                 error = VCALL(ap);
  281         else {
  282                 printf("null_bypass: no map for %s\n", descp->vdesc_name);
  283                 error = EINVAL;
  284         }
  285 
  286         /*
  287          * Maintain the illusion of call-by-value
  288          * by restoring vnodes in the argument structure
  289          * to their original value.
  290          */
  291         reles = descp->vdesc_flags;
  292         for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) {
  293                 if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET)
  294                         break;   /* bail out at end of list */
  295                 if (old_vps[i]) {
  296                         *(vps_p[i]) = old_vps[i];
  297 #if 0
  298                         if (reles & VDESC_VP0_WILLUNLOCK)
  299                                 VOP_UNLOCK(*(vps_p[i]), 0);
  300 #endif
  301                         if (reles & VDESC_VP0_WILLRELE)
  302                                 vrele(*(vps_p[i]));
  303                 }
  304         }
  305 
  306         /*
  307          * Map the possible out-going vpp
  308          * (Assumes that the lower layer always returns
  309          * a VREF'ed vpp unless it gets an error.)
  310          */
  311         if (descp->vdesc_vpp_offset != VDESC_NO_OFFSET &&
  312             !(descp->vdesc_flags & VDESC_NOMAP_VPP) &&
  313             !error) {
  314                 /*
  315                  * XXX - even though some ops have vpp returned vp's,
  316                  * several ops actually vrele this before returning.
  317                  * We must avoid these ops.
  318                  * (This should go away when these ops are regularized.)
  319                  */
  320                 if (descp->vdesc_flags & VDESC_VPP_WILLRELE)
  321                         goto out;
  322                 vppp = VOPARG_OFFSETTO(struct vnode***,
  323                                  descp->vdesc_vpp_offset,ap);
  324                 if (*vppp)
  325                         error = null_nodeget(old_vps[0]->v_mount, **vppp, *vppp);
  326         }
  327 
  328  out:
  329         return (error);
  330 }
  331 
  332 /*
  333  * We have to carry on the locking protocol on the null layer vnodes
  334  * as we progress through the tree. We also have to enforce read-only
  335  * if this layer is mounted read-only.
  336  */
  337 static int
  338 null_lookup(struct vop_lookup_args *ap)
  339 {
  340         struct componentname *cnp = ap->a_cnp;
  341         struct vnode *dvp = ap->a_dvp;
  342         int flags = cnp->cn_flags;
  343         struct vnode *vp, *ldvp, *lvp;
  344         int error;
  345 
  346         if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
  347             (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
  348                 return (EROFS);
  349         /*
  350          * Although it is possible to call null_bypass(), we'll do
  351          * a direct call to reduce overhead
  352          */
  353         ldvp = NULLVPTOLOWERVP(dvp);
  354         vp = lvp = NULL;
  355         error = VOP_LOOKUP(ldvp, &lvp, cnp);
  356         if (error == EJUSTRETURN && (flags & ISLASTCN) &&
  357             (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
  358             (cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME))
  359                 error = EROFS;
  360 
  361         if ((error == 0 || error == EJUSTRETURN) && lvp != NULL) {
  362                 if (ldvp == lvp) {
  363                         *ap->a_vpp = dvp;
  364                         VREF(dvp);
  365                         vrele(lvp);
  366                 } else {
  367                         error = null_nodeget(dvp->v_mount, lvp, &vp);
  368                         if (error)
  369                                 vput(lvp);
  370                         else
  371                                 *ap->a_vpp = vp;
  372                 }
  373         }
  374         return (error);
  375 }
  376 
  377 static int
  378 null_open(struct vop_open_args *ap)
  379 {
  380         int retval;
  381         struct vnode *vp, *ldvp;
  382 
  383         vp = ap->a_vp;
  384         ldvp = NULLVPTOLOWERVP(vp);
  385         retval = null_bypass(&ap->a_gen);
  386         if (retval == 0)
  387                 vp->v_object = ldvp->v_object;
  388         return (retval);
  389 }
  390 
  391 /*
  392  * Setattr call. Disallow write attempts if the layer is mounted read-only.
  393  */
  394 static int
  395 null_setattr(struct vop_setattr_args *ap)
  396 {
  397         struct vnode *vp = ap->a_vp;
  398         struct vattr *vap = ap->a_vap;
  399 
  400         if ((vap->va_flags != VNOVAL || vap->va_uid != (uid_t)VNOVAL ||
  401             vap->va_gid != (gid_t)VNOVAL || vap->va_atime.tv_sec != VNOVAL ||
  402             vap->va_mtime.tv_sec != VNOVAL || vap->va_mode != (mode_t)VNOVAL) &&
  403             (vp->v_mount->mnt_flag & MNT_RDONLY))
  404                 return (EROFS);
  405         if (vap->va_size != VNOVAL) {
  406                 switch (vp->v_type) {
  407                 case VDIR:
  408                         return (EISDIR);
  409                 case VCHR:
  410                 case VBLK:
  411                 case VSOCK:
  412                 case VFIFO:
  413                         if (vap->va_flags != VNOVAL)
  414                                 return (EOPNOTSUPP);
  415                         return (0);
  416                 case VREG:
  417                 case VLNK:
  418                 default:
  419                         /*
  420                          * Disallow write attempts if the filesystem is
  421                          * mounted read-only.
  422                          */
  423                         if (vp->v_mount->mnt_flag & MNT_RDONLY)
  424                                 return (EROFS);
  425                 }
  426         }
  427 
  428         return (null_bypass((struct vop_generic_args *)ap));
  429 }
  430 
  431 /*
  432  *  We handle getattr only to change the fsid.
  433  */
  434 static int
  435 null_getattr(struct vop_getattr_args *ap)
  436 {
  437         int error;
  438 
  439         if ((error = null_bypass((struct vop_generic_args *)ap)) != 0)
  440                 return (error);
  441 
  442         ap->a_vap->va_fsid = ap->a_vp->v_mount->mnt_stat.f_fsid.val[0];
  443         return (0);
  444 }
  445 
  446 /*
  447  * Handle to disallow write access if mounted read-only.
  448  */
  449 static int
  450 null_access(struct vop_access_args *ap)
  451 {
  452         struct vnode *vp = ap->a_vp;
  453         accmode_t accmode = ap->a_accmode;
  454 
  455         /*
  456          * Disallow write attempts on read-only layers;
  457          * unless the file is a socket, fifo, or a block or
  458          * character device resident on the filesystem.
  459          */
  460         if (accmode & VWRITE) {
  461                 switch (vp->v_type) {
  462                 case VDIR:
  463                 case VLNK:
  464                 case VREG:
  465                         if (vp->v_mount->mnt_flag & MNT_RDONLY)
  466                                 return (EROFS);
  467                         break;
  468                 default:
  469                         break;
  470                 }
  471         }
  472         return (null_bypass((struct vop_generic_args *)ap));
  473 }
  474 
  475 static int
  476 null_accessx(struct vop_accessx_args *ap)
  477 {
  478         struct vnode *vp = ap->a_vp;
  479         accmode_t accmode = ap->a_accmode;
  480 
  481         /*
  482          * Disallow write attempts on read-only layers;
  483          * unless the file is a socket, fifo, or a block or
  484          * character device resident on the filesystem.
  485          */
  486         if (accmode & VWRITE) {
  487                 switch (vp->v_type) {
  488                 case VDIR:
  489                 case VLNK:
  490                 case VREG:
  491                         if (vp->v_mount->mnt_flag & MNT_RDONLY)
  492                                 return (EROFS);
  493                         break;
  494                 default:
  495                         break;
  496                 }
  497         }
  498         return (null_bypass((struct vop_generic_args *)ap));
  499 }
  500 
  501 /*
  502  * We handle this to eliminate null FS to lower FS
  503  * file moving. Don't know why we don't allow this,
  504  * possibly we should.
  505  */
  506 static int
  507 null_rename(struct vop_rename_args *ap)
  508 {
  509         struct vnode *tdvp = ap->a_tdvp;
  510         struct vnode *fvp = ap->a_fvp;
  511         struct vnode *fdvp = ap->a_fdvp;
  512         struct vnode *tvp = ap->a_tvp;
  513 
  514         /* Check for cross-device rename. */
  515         if ((fvp->v_mount != tdvp->v_mount) ||
  516             (tvp && (fvp->v_mount != tvp->v_mount))) {
  517                 if (tdvp == tvp)
  518                         vrele(tdvp);
  519                 else
  520                         vput(tdvp);
  521                 if (tvp)
  522                         vput(tvp);
  523                 vrele(fdvp);
  524                 vrele(fvp);
  525                 return (EXDEV);
  526         }
  527         
  528         return (null_bypass((struct vop_generic_args *)ap));
  529 }
  530 
  531 /*
  532  * We need to process our own vnode lock and then clear the
  533  * interlock flag as it applies only to our vnode, not the
  534  * vnodes below us on the stack.
  535  */
  536 static int
  537 null_lock(struct vop_lock1_args *ap)
  538 {
  539         struct vnode *vp = ap->a_vp;
  540         int flags = ap->a_flags;
  541         struct null_node *nn;
  542         struct vnode *lvp;
  543         int error;
  544 
  545 
  546         if ((flags & LK_INTERLOCK) == 0) {
  547                 VI_LOCK(vp);
  548                 ap->a_flags = flags |= LK_INTERLOCK;
  549         }
  550         nn = VTONULL(vp);
  551         /*
  552          * If we're still active we must ask the lower layer to
  553          * lock as ffs has special lock considerations in it's
  554          * vop lock.
  555          */
  556         if (nn != NULL && (lvp = NULLVPTOLOWERVP(vp)) != NULL) {
  557                 VI_LOCK_FLAGS(lvp, MTX_DUPOK);
  558                 VI_UNLOCK(vp);
  559                 /*
  560                  * We have to hold the vnode here to solve a potential
  561                  * reclaim race.  If we're forcibly vgone'd while we
  562                  * still have refs, a thread could be sleeping inside
  563                  * the lowervp's vop_lock routine.  When we vgone we will
  564                  * drop our last ref to the lowervp, which would allow it
  565                  * to be reclaimed.  The lowervp could then be recycled,
  566                  * in which case it is not legal to be sleeping in it's VOP.
  567                  * We prevent it from being recycled by holding the vnode
  568                  * here.
  569                  */
  570                 vholdl(lvp);
  571                 error = VOP_LOCK(lvp, flags);
  572 
  573                 /*
  574                  * We might have slept to get the lock and someone might have
  575                  * clean our vnode already, switching vnode lock from one in
  576                  * lowervp to v_lock in our own vnode structure.  Handle this
  577                  * case by reacquiring correct lock in requested mode.
  578                  */
  579                 if (VTONULL(vp) == NULL && error == 0) {
  580                         ap->a_flags &= ~(LK_TYPE_MASK | LK_INTERLOCK);
  581                         switch (flags & LK_TYPE_MASK) {
  582                         case LK_SHARED:
  583                                 ap->a_flags |= LK_SHARED;
  584                                 break;
  585                         case LK_UPGRADE:
  586                         case LK_EXCLUSIVE:
  587                                 ap->a_flags |= LK_EXCLUSIVE;
  588                                 break;
  589                         default:
  590                                 panic("Unsupported lock request %d\n",
  591                                     ap->a_flags);
  592                         }
  593                         VOP_UNLOCK(lvp, 0);
  594                         error = vop_stdlock(ap);
  595                 }
  596                 vdrop(lvp);
  597         } else
  598                 error = vop_stdlock(ap);
  599 
  600         return (error);
  601 }
  602 
  603 /*
  604  * We need to process our own vnode unlock and then clear the
  605  * interlock flag as it applies only to our vnode, not the
  606  * vnodes below us on the stack.
  607  */
  608 static int
  609 null_unlock(struct vop_unlock_args *ap)
  610 {
  611         struct vnode *vp = ap->a_vp;
  612         int flags = ap->a_flags;
  613         int mtxlkflag = 0;
  614         struct null_node *nn;
  615         struct vnode *lvp;
  616         int error;
  617 
  618         if ((flags & LK_INTERLOCK) != 0)
  619                 mtxlkflag = 1;
  620         else if (mtx_owned(VI_MTX(vp)) == 0) {
  621                 VI_LOCK(vp);
  622                 mtxlkflag = 2;
  623         }
  624         nn = VTONULL(vp);
  625         if (nn != NULL && (lvp = NULLVPTOLOWERVP(vp)) != NULL) {
  626                 VI_LOCK_FLAGS(lvp, MTX_DUPOK);
  627                 flags |= LK_INTERLOCK;
  628                 vholdl(lvp);
  629                 VI_UNLOCK(vp);
  630                 error = VOP_UNLOCK(lvp, flags);
  631                 vdrop(lvp);
  632                 if (mtxlkflag == 0)
  633                         VI_LOCK(vp);
  634         } else {
  635                 if (mtxlkflag == 2)
  636                         VI_UNLOCK(vp);
  637                 error = vop_stdunlock(ap);
  638         }
  639 
  640         return (error);
  641 }
  642 
  643 /*
  644  * There is no way to tell that someone issued remove/rmdir operation
  645  * on the underlying filesystem. For now we just have to release lowervp
  646  * as soon as possible.
  647  *
  648  * Note, we can't release any resources nor remove vnode from hash before 
  649  * appropriate VXLOCK stuff is is done because other process can find this
  650  * vnode in hash during inactivation and may be sitting in vget() and waiting
  651  * for null_inactive to unlock vnode. Thus we will do all those in VOP_RECLAIM.
  652  */
  653 static int
  654 null_inactive(struct vop_inactive_args *ap)
  655 {
  656         struct vnode *vp = ap->a_vp;
  657         struct thread *td = ap->a_td;
  658 
  659         vp->v_object = NULL;
  660 
  661         /*
  662          * If this is the last reference, then free up the vnode
  663          * so as not to tie up the lower vnodes.
  664          */
  665         vrecycle(vp, td);
  666 
  667         return (0);
  668 }
  669 
  670 /*
  671  * Now, the VXLOCK is in force and we're free to destroy the null vnode.
  672  */
  673 static int
  674 null_reclaim(struct vop_reclaim_args *ap)
  675 {
  676         struct vnode *vp = ap->a_vp;
  677         struct null_node *xp = VTONULL(vp);
  678         struct vnode *lowervp = xp->null_lowervp;
  679 
  680         if (lowervp)
  681                 null_hashrem(xp);
  682         /*
  683          * Use the interlock to protect the clearing of v_data to
  684          * prevent faults in null_lock().
  685          */
  686         lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
  687         VI_LOCK(vp);
  688         vp->v_data = NULL;
  689         vp->v_object = NULL;
  690         vp->v_vnlock = &vp->v_lock;
  691         VI_UNLOCK(vp);
  692         if (lowervp)
  693                 vput(lowervp);
  694         else
  695                 panic("null_reclaim: reclaiming a node with no lowervp");
  696         free(xp, M_NULLFSNODE);
  697 
  698         return (0);
  699 }
  700 
  701 static int
  702 null_print(struct vop_print_args *ap)
  703 {
  704         struct vnode *vp = ap->a_vp;
  705 
  706         printf("\tvp=%p, lowervp=%p\n", vp, NULLVPTOLOWERVP(vp));
  707         return (0);
  708 }
  709 
  710 /* ARGSUSED */
  711 static int
  712 null_getwritemount(struct vop_getwritemount_args *ap)
  713 {
  714         struct null_node *xp;
  715         struct vnode *lowervp;
  716         struct vnode *vp;
  717 
  718         vp = ap->a_vp;
  719         VI_LOCK(vp);
  720         xp = VTONULL(vp);
  721         if (xp && (lowervp = xp->null_lowervp)) {
  722                 VI_LOCK_FLAGS(lowervp, MTX_DUPOK);
  723                 VI_UNLOCK(vp);
  724                 vholdl(lowervp);
  725                 VI_UNLOCK(lowervp);
  726                 VOP_GETWRITEMOUNT(lowervp, ap->a_mpp);
  727                 vdrop(lowervp);
  728         } else {
  729                 VI_UNLOCK(vp);
  730                 *(ap->a_mpp) = NULL;
  731         }
  732         return (0);
  733 }
  734 
  735 static int
  736 null_vptofh(struct vop_vptofh_args *ap)
  737 {
  738         struct vnode *lvp;
  739 
  740         lvp = NULLVPTOLOWERVP(ap->a_vp);
  741         return VOP_VPTOFH(lvp, ap->a_fhp);
  742 }
  743 
  744 static int
  745 null_vptocnp(struct vop_vptocnp_args *ap)
  746 {
  747         struct vnode *vp = ap->a_vp;
  748         struct vnode **dvp = ap->a_vpp;
  749         struct vnode *lvp, *ldvp;
  750         struct ucred *cred = ap->a_cred;
  751         int error, locked;
  752 
  753         if (vp->v_type == VDIR)
  754                 return (vop_stdvptocnp(ap));
  755 
  756         locked = VOP_ISLOCKED(vp);
  757         lvp = NULLVPTOLOWERVP(vp);
  758         vhold(lvp);
  759         VOP_UNLOCK(vp, 0); /* vp is held by vn_vptocnp_locked that called us */
  760         ldvp = lvp;
  761         error = vn_vptocnp(&ldvp, cred, ap->a_buf, ap->a_buflen);
  762         vdrop(lvp);
  763         if (error != 0) {
  764                 vn_lock(vp, locked | LK_RETRY);
  765                 return (ENOENT);
  766         }
  767 
  768         /*
  769          * Exclusive lock is required by insmntque1 call in
  770          * null_nodeget()
  771          */
  772         error = vn_lock(ldvp, LK_EXCLUSIVE);
  773         if (error != 0) {
  774                 vn_lock(vp, locked | LK_RETRY);
  775                 vdrop(ldvp);
  776                 return (ENOENT);
  777         }
  778         vref(ldvp);
  779         vdrop(ldvp);
  780         error = null_nodeget(vp->v_mount, ldvp, dvp);
  781         if (error == 0) {
  782 #ifdef DIAGNOSTIC
  783                 NULLVPTOLOWERVP(*dvp);
  784 #endif
  785                 vhold(*dvp);
  786                 vput(*dvp);
  787         } else
  788                 vput(ldvp);
  789 
  790         vn_lock(vp, locked | LK_RETRY);
  791         return (error);
  792 }
  793 
  794 /*
  795  * Global vfs data structures
  796  */
  797 struct vop_vector null_vnodeops = {
  798         .vop_bypass =           null_bypass,
  799         .vop_access =           null_access,
  800         .vop_accessx =          null_accessx,
  801         .vop_bmap =             VOP_EOPNOTSUPP,
  802         .vop_getattr =          null_getattr,
  803         .vop_getwritemount =    null_getwritemount,
  804         .vop_inactive =         null_inactive,
  805         .vop_islocked =         vop_stdislocked,
  806         .vop_lock1 =            null_lock,
  807         .vop_lookup =           null_lookup,
  808         .vop_open =             null_open,
  809         .vop_print =            null_print,
  810         .vop_reclaim =          null_reclaim,
  811         .vop_rename =           null_rename,
  812         .vop_setattr =          null_setattr,
  813         .vop_strategy =         VOP_EOPNOTSUPP,
  814         .vop_unlock =           null_unlock,
  815         .vop_vptocnp =          null_vptocnp,
  816         .vop_vptofh =           null_vptofh,
  817 };

Cache object: 9b080faae065897b8627c4bd271daed4


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.