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


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

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    1 /*-
    2  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1992, 1993, 1995
    5  *      The Regents of the University of California.  All rights reserved.
    6  *
    7  * This code is derived from software donated to Berkeley by
    8  * Jan-Simon Pendry.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 3. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      @(#)null_vfsops.c       8.2 (Berkeley) 1/21/94
   35  *
   36  * @(#)lofs_vfsops.c    1.2 (Berkeley) 6/18/92
   37  * $FreeBSD: releng/12.0/sys/fs/nullfs/null_vfsops.c 333263 2018-05-04 20:54:27Z jamie $
   38  */
   39 
   40 /*
   41  * Null Layer
   42  * (See null_vnops.c for a description of what this does.)
   43  */
   44 
   45 #include <sys/param.h>
   46 #include <sys/systm.h>
   47 #include <sys/fcntl.h>
   48 #include <sys/kernel.h>
   49 #include <sys/lock.h>
   50 #include <sys/malloc.h>
   51 #include <sys/mount.h>
   52 #include <sys/namei.h>
   53 #include <sys/proc.h>
   54 #include <sys/vnode.h>
   55 #include <sys/jail.h>
   56 
   57 #include <fs/nullfs/null.h>
   58 
   59 static MALLOC_DEFINE(M_NULLFSMNT, "nullfs_mount", "NULLFS mount structure");
   60 
   61 static vfs_fhtovp_t     nullfs_fhtovp;
   62 static vfs_mount_t      nullfs_mount;
   63 static vfs_quotactl_t   nullfs_quotactl;
   64 static vfs_root_t       nullfs_root;
   65 static vfs_sync_t       nullfs_sync;
   66 static vfs_statfs_t     nullfs_statfs;
   67 static vfs_unmount_t    nullfs_unmount;
   68 static vfs_vget_t       nullfs_vget;
   69 static vfs_extattrctl_t nullfs_extattrctl;
   70 
   71 /*
   72  * Mount null layer
   73  */
   74 static int
   75 nullfs_mount(struct mount *mp)
   76 {
   77         int error = 0;
   78         struct vnode *lowerrootvp, *vp;
   79         struct vnode *nullm_rootvp;
   80         struct null_mount *xmp;
   81         char *target;
   82         int isvnunlocked = 0, len;
   83         struct nameidata nd, *ndp = &nd;
   84 
   85         NULLFSDEBUG("nullfs_mount(mp = %p)\n", (void *)mp);
   86 
   87         if (mp->mnt_flag & MNT_ROOTFS)
   88                 return (EOPNOTSUPP);
   89 
   90         /*
   91          * Update is a no-op
   92          */
   93         if (mp->mnt_flag & MNT_UPDATE) {
   94                 /*
   95                  * Only support update mounts for NFS export.
   96                  */
   97                 if (vfs_flagopt(mp->mnt_optnew, "export", NULL, 0))
   98                         return (0);
   99                 else
  100                         return (EOPNOTSUPP);
  101         }
  102 
  103         /*
  104          * Get argument
  105          */
  106         error = vfs_getopt(mp->mnt_optnew, "target", (void **)&target, &len);
  107         if (error || target[len - 1] != '\0')
  108                 return (EINVAL);
  109 
  110         /*
  111          * Unlock lower node to avoid possible deadlock.
  112          */
  113         if ((mp->mnt_vnodecovered->v_op == &null_vnodeops) &&
  114             VOP_ISLOCKED(mp->mnt_vnodecovered) == LK_EXCLUSIVE) {
  115                 VOP_UNLOCK(mp->mnt_vnodecovered, 0);
  116                 isvnunlocked = 1;
  117         }
  118         /*
  119          * Find lower node
  120          */
  121         NDINIT(ndp, LOOKUP, FOLLOW|LOCKLEAF, UIO_SYSSPACE, target, curthread);
  122         error = namei(ndp);
  123 
  124         /*
  125          * Re-lock vnode.
  126          * XXXKIB This is deadlock-prone as well.
  127          */
  128         if (isvnunlocked)
  129                 vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY);
  130 
  131         if (error)
  132                 return (error);
  133         NDFREE(ndp, NDF_ONLY_PNBUF);
  134 
  135         /*
  136          * Sanity check on lower vnode
  137          */
  138         lowerrootvp = ndp->ni_vp;
  139 
  140         /*
  141          * Check multi null mount to avoid `lock against myself' panic.
  142          */
  143         if (lowerrootvp == VTONULL(mp->mnt_vnodecovered)->null_lowervp) {
  144                 NULLFSDEBUG("nullfs_mount: multi null mount?\n");
  145                 vput(lowerrootvp);
  146                 return (EDEADLK);
  147         }
  148 
  149         xmp = (struct null_mount *) malloc(sizeof(struct null_mount),
  150             M_NULLFSMNT, M_WAITOK | M_ZERO);
  151 
  152         /*
  153          * Save reference to underlying FS
  154          */
  155         xmp->nullm_vfs = lowerrootvp->v_mount;
  156 
  157         /*
  158          * Save reference.  Each mount also holds
  159          * a reference on the root vnode.
  160          */
  161         error = null_nodeget(mp, lowerrootvp, &vp);
  162         /*
  163          * Make sure the node alias worked
  164          */
  165         if (error) {
  166                 free(xmp, M_NULLFSMNT);
  167                 return (error);
  168         }
  169 
  170         /*
  171          * Keep a held reference to the root vnode.
  172          * It is vrele'd in nullfs_unmount.
  173          */
  174         nullm_rootvp = vp;
  175         nullm_rootvp->v_vflag |= VV_ROOT;
  176         xmp->nullm_rootvp = nullm_rootvp;
  177 
  178         /*
  179          * Unlock the node (either the lower or the alias)
  180          */
  181         VOP_UNLOCK(vp, 0);
  182 
  183         if (NULLVPTOLOWERVP(nullm_rootvp)->v_mount->mnt_flag & MNT_LOCAL) {
  184                 MNT_ILOCK(mp);
  185                 mp->mnt_flag |= MNT_LOCAL;
  186                 MNT_IUNLOCK(mp);
  187         }
  188 
  189         xmp->nullm_flags |= NULLM_CACHE;
  190         if (vfs_getopt(mp->mnt_optnew, "nocache", NULL, NULL) == 0 ||
  191             (xmp->nullm_vfs->mnt_kern_flag & MNTK_NULL_NOCACHE) != 0)
  192                 xmp->nullm_flags &= ~NULLM_CACHE;
  193 
  194         MNT_ILOCK(mp);
  195         if ((xmp->nullm_flags & NULLM_CACHE) != 0) {
  196                 mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag &
  197                     (MNTK_SHARED_WRITES | MNTK_LOOKUP_SHARED |
  198                     MNTK_EXTENDED_SHARED);
  199         }
  200         mp->mnt_kern_flag |= MNTK_LOOKUP_EXCL_DOTDOT;
  201         mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag &
  202             (MNTK_USES_BCACHE | MNTK_NO_IOPF | MNTK_UNMAPPED_BUFS);
  203         MNT_IUNLOCK(mp);
  204         mp->mnt_data = xmp;
  205         vfs_getnewfsid(mp);
  206         if ((xmp->nullm_flags & NULLM_CACHE) != 0) {
  207                 MNT_ILOCK(xmp->nullm_vfs);
  208                 TAILQ_INSERT_TAIL(&xmp->nullm_vfs->mnt_uppers, mp,
  209                     mnt_upper_link);
  210                 MNT_IUNLOCK(xmp->nullm_vfs);
  211         }
  212 
  213         vfs_mountedfrom(mp, target);
  214 
  215         NULLFSDEBUG("nullfs_mount: lower %s, alias at %s\n",
  216                 mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname);
  217         return (0);
  218 }
  219 
  220 /*
  221  * Free reference to null layer
  222  */
  223 static int
  224 nullfs_unmount(mp, mntflags)
  225         struct mount *mp;
  226         int mntflags;
  227 {
  228         struct null_mount *mntdata;
  229         struct mount *ump;
  230         int error, flags;
  231 
  232         NULLFSDEBUG("nullfs_unmount: mp = %p\n", (void *)mp);
  233 
  234         if (mntflags & MNT_FORCE)
  235                 flags = FORCECLOSE;
  236         else
  237                 flags = 0;
  238 
  239         /* There is 1 extra root vnode reference (nullm_rootvp). */
  240         error = vflush(mp, 1, flags, curthread);
  241         if (error)
  242                 return (error);
  243 
  244         /*
  245          * Finally, throw away the null_mount structure
  246          */
  247         mntdata = mp->mnt_data;
  248         ump = mntdata->nullm_vfs;
  249         if ((mntdata->nullm_flags & NULLM_CACHE) != 0) {
  250                 MNT_ILOCK(ump);
  251                 while ((ump->mnt_kern_flag & MNTK_VGONE_UPPER) != 0) {
  252                         ump->mnt_kern_flag |= MNTK_VGONE_WAITER;
  253                         msleep(&ump->mnt_uppers, &ump->mnt_mtx, 0, "vgnupw", 0);
  254                 }
  255                 TAILQ_REMOVE(&ump->mnt_uppers, mp, mnt_upper_link);
  256                 MNT_IUNLOCK(ump);
  257         }
  258         mp->mnt_data = NULL;
  259         free(mntdata, M_NULLFSMNT);
  260         return (0);
  261 }
  262 
  263 static int
  264 nullfs_root(mp, flags, vpp)
  265         struct mount *mp;
  266         int flags;
  267         struct vnode **vpp;
  268 {
  269         struct vnode *vp;
  270 
  271         NULLFSDEBUG("nullfs_root(mp = %p, vp = %p->%p)\n", (void *)mp,
  272             (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp,
  273             (void *)NULLVPTOLOWERVP(MOUNTTONULLMOUNT(mp)->nullm_rootvp));
  274 
  275         /*
  276          * Return locked reference to root.
  277          */
  278         vp = MOUNTTONULLMOUNT(mp)->nullm_rootvp;
  279         VREF(vp);
  280 
  281         ASSERT_VOP_UNLOCKED(vp, "root vnode is locked");
  282         vn_lock(vp, flags | LK_RETRY);
  283         *vpp = vp;
  284         return 0;
  285 }
  286 
  287 static int
  288 nullfs_quotactl(mp, cmd, uid, arg)
  289         struct mount *mp;
  290         int cmd;
  291         uid_t uid;
  292         void *arg;
  293 {
  294         return VFS_QUOTACTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, uid, arg);
  295 }
  296 
  297 static int
  298 nullfs_statfs(mp, sbp)
  299         struct mount *mp;
  300         struct statfs *sbp;
  301 {
  302         int error;
  303         struct statfs *mstat;
  304 
  305         NULLFSDEBUG("nullfs_statfs(mp = %p, vp = %p->%p)\n", (void *)mp,
  306             (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp,
  307             (void *)NULLVPTOLOWERVP(MOUNTTONULLMOUNT(mp)->nullm_rootvp));
  308 
  309         mstat = malloc(sizeof(struct statfs), M_STATFS, M_WAITOK | M_ZERO);
  310 
  311         error = VFS_STATFS(MOUNTTONULLMOUNT(mp)->nullm_vfs, mstat);
  312         if (error) {
  313                 free(mstat, M_STATFS);
  314                 return (error);
  315         }
  316 
  317         /* now copy across the "interesting" information and fake the rest */
  318         sbp->f_type = mstat->f_type;
  319         sbp->f_flags = (sbp->f_flags & (MNT_RDONLY | MNT_NOEXEC | MNT_NOSUID |
  320             MNT_UNION | MNT_NOSYMFOLLOW | MNT_AUTOMOUNTED)) |
  321             (mstat->f_flags & ~(MNT_ROOTFS | MNT_AUTOMOUNTED));
  322         sbp->f_bsize = mstat->f_bsize;
  323         sbp->f_iosize = mstat->f_iosize;
  324         sbp->f_blocks = mstat->f_blocks;
  325         sbp->f_bfree = mstat->f_bfree;
  326         sbp->f_bavail = mstat->f_bavail;
  327         sbp->f_files = mstat->f_files;
  328         sbp->f_ffree = mstat->f_ffree;
  329 
  330         free(mstat, M_STATFS);
  331         return (0);
  332 }
  333 
  334 static int
  335 nullfs_sync(mp, waitfor)
  336         struct mount *mp;
  337         int waitfor;
  338 {
  339         /*
  340          * XXX - Assumes no data cached at null layer.
  341          */
  342         return (0);
  343 }
  344 
  345 static int
  346 nullfs_vget(mp, ino, flags, vpp)
  347         struct mount *mp;
  348         ino_t ino;
  349         int flags;
  350         struct vnode **vpp;
  351 {
  352         int error;
  353 
  354         KASSERT((flags & LK_TYPE_MASK) != 0,
  355             ("nullfs_vget: no lock requested"));
  356 
  357         error = VFS_VGET(MOUNTTONULLMOUNT(mp)->nullm_vfs, ino, flags, vpp);
  358         if (error != 0)
  359                 return (error);
  360         return (null_nodeget(mp, *vpp, vpp));
  361 }
  362 
  363 static int
  364 nullfs_fhtovp(mp, fidp, flags, vpp)
  365         struct mount *mp;
  366         struct fid *fidp;
  367         int flags;
  368         struct vnode **vpp;
  369 {
  370         int error;
  371 
  372         error = VFS_FHTOVP(MOUNTTONULLMOUNT(mp)->nullm_vfs, fidp, flags,
  373             vpp);
  374         if (error != 0)
  375                 return (error);
  376         return (null_nodeget(mp, *vpp, vpp));
  377 }
  378 
  379 static int                        
  380 nullfs_extattrctl(mp, cmd, filename_vp, namespace, attrname)
  381         struct mount *mp;
  382         int cmd;
  383         struct vnode *filename_vp;
  384         int namespace;
  385         const char *attrname;
  386 {
  387 
  388         return (VFS_EXTATTRCTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd,
  389             filename_vp, namespace, attrname));
  390 }
  391 
  392 static void
  393 nullfs_reclaim_lowervp(struct mount *mp, struct vnode *lowervp)
  394 {
  395         struct vnode *vp;
  396 
  397         vp = null_hashget(mp, lowervp);
  398         if (vp == NULL)
  399                 return;
  400         VTONULL(vp)->null_flags |= NULLV_NOUNLOCK;
  401         vgone(vp);
  402         vput(vp);
  403 }
  404 
  405 static void
  406 nullfs_unlink_lowervp(struct mount *mp, struct vnode *lowervp)
  407 {
  408         struct vnode *vp;
  409         struct null_node *xp;
  410 
  411         vp = null_hashget(mp, lowervp);
  412         if (vp == NULL)
  413                 return;
  414         xp = VTONULL(vp);
  415         xp->null_flags |= NULLV_DROP | NULLV_NOUNLOCK;
  416         vhold(vp);
  417         vunref(vp);
  418 
  419         if (vp->v_usecount == 0) {
  420                 /*
  421                  * If vunref() dropped the last use reference on the
  422                  * nullfs vnode, it must be reclaimed, and its lock
  423                  * was split from the lower vnode lock.  Need to do
  424                  * extra unlock before allowing the final vdrop() to
  425                  * free the vnode.
  426                  */
  427                 KASSERT((vp->v_iflag & VI_DOOMED) != 0,
  428                     ("not reclaimed nullfs vnode %p", vp));
  429                 VOP_UNLOCK(vp, 0);
  430         } else {
  431                 /*
  432                  * Otherwise, the nullfs vnode still shares the lock
  433                  * with the lower vnode, and must not be unlocked.
  434                  * Also clear the NULLV_NOUNLOCK, the flag is not
  435                  * relevant for future reclamations.
  436                  */
  437                 ASSERT_VOP_ELOCKED(vp, "unlink_lowervp");
  438                 KASSERT((vp->v_iflag & VI_DOOMED) == 0,
  439                     ("reclaimed nullfs vnode %p", vp));
  440                 xp->null_flags &= ~NULLV_NOUNLOCK;
  441         }
  442         vdrop(vp);
  443 }
  444 
  445 static struct vfsops null_vfsops = {
  446         .vfs_extattrctl =       nullfs_extattrctl,
  447         .vfs_fhtovp =           nullfs_fhtovp,
  448         .vfs_init =             nullfs_init,
  449         .vfs_mount =            nullfs_mount,
  450         .vfs_quotactl =         nullfs_quotactl,
  451         .vfs_root =             nullfs_root,
  452         .vfs_statfs =           nullfs_statfs,
  453         .vfs_sync =             nullfs_sync,
  454         .vfs_uninit =           nullfs_uninit,
  455         .vfs_unmount =          nullfs_unmount,
  456         .vfs_vget =             nullfs_vget,
  457         .vfs_reclaim_lowervp =  nullfs_reclaim_lowervp,
  458         .vfs_unlink_lowervp =   nullfs_unlink_lowervp,
  459 };
  460 
  461 VFS_SET(null_vfsops, nullfs, VFCF_LOOPBACK | VFCF_JAIL);

Cache object: 2034f469914e7e484491fefc9e6721b9


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