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  * Copyright (c) 1992, 1993, 1995
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software donated to Berkeley by
    6  * Jan-Simon Pendry.
    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_vfsops.c       8.2 (Berkeley) 1/21/94
   33  *
   34  * @(#)lofs_vfsops.c    1.2 (Berkeley) 6/18/92
   35  * $FreeBSD: releng/6.0/sys/fs/nullfs/null_vfsops.c 151669 2005-10-25 20:33:59Z kris $
   36  */
   37 
   38 /*
   39  * Null Layer
   40  * (See null_vnops.c for a description of what this does.)
   41  */
   42 
   43 #include <sys/param.h>
   44 #include <sys/systm.h>
   45 #include <sys/kdb.h>
   46 #include <sys/kernel.h>
   47 #include <sys/lock.h>
   48 #include <sys/malloc.h>
   49 #include <sys/mount.h>
   50 #include <sys/namei.h>
   51 #include <sys/proc.h>
   52 #include <sys/vnode.h>
   53 
   54 #include <fs/nullfs/null.h>
   55 
   56 static MALLOC_DEFINE(M_NULLFSMNT, "NULLFS mount", "NULLFS mount structure");
   57 
   58 static vfs_fhtovp_t     nullfs_fhtovp;
   59 static vfs_checkexp_t   nullfs_checkexp;
   60 static vfs_mount_t      nullfs_mount;
   61 static vfs_quotactl_t   nullfs_quotactl;
   62 static vfs_root_t       nullfs_root;
   63 static vfs_sync_t       nullfs_sync;
   64 static vfs_statfs_t     nullfs_statfs;
   65 static vfs_unmount_t    nullfs_unmount;
   66 static vfs_vget_t       nullfs_vget;
   67 static vfs_vptofh_t     nullfs_vptofh;
   68 static vfs_extattrctl_t nullfs_extattrctl;
   69 
   70 /*
   71  * Mount null layer
   72  */
   73 static int
   74 nullfs_mount(struct mount *mp, struct thread *td)
   75 {
   76         int error = 0;
   77         struct vnode *lowerrootvp, *vp;
   78         struct vnode *nullm_rootvp;
   79         struct null_mount *xmp;
   80         char *target;
   81         int isvnunlocked = 0, len;
   82         struct nameidata nd, *ndp = &nd;
   83 
   84         NULLFSDEBUG("nullfs_mount(mp = %p)\n", (void *)mp);
   85 
   86         if (mp->mnt_flag & MNT_ROOTFS)
   87                 return (EOPNOTSUPP);
   88         /*
   89          * Update is a no-op
   90          */
   91         if (mp->mnt_flag & MNT_UPDATE) {
   92                 return (EOPNOTSUPP);
   93                 /* return VFS_MOUNT(MOUNTTONULLMOUNT(mp)->nullm_vfs, path, data, ndp, td);*/
   94         }
   95 
   96         /*
   97          * Get argument
   98          */
   99         error = vfs_getopt(mp->mnt_optnew, "target", (void **)&target, &len);
  100         if (error || target[len - 1] != '\0')
  101                 return (EINVAL);
  102 
  103         /*
  104          * Unlock lower node to avoid deadlock.
  105          * (XXX) VOP_ISLOCKED is needed?
  106          */
  107         if ((mp->mnt_vnodecovered->v_op == &null_vnodeops) &&
  108                 VOP_ISLOCKED(mp->mnt_vnodecovered, NULL)) {
  109                 VOP_UNLOCK(mp->mnt_vnodecovered, 0, td);
  110                 isvnunlocked = 1;
  111         }
  112         /*
  113          * Find lower node
  114          */
  115         NDINIT(ndp, LOOKUP, FOLLOW|WANTPARENT|LOCKLEAF,
  116                 UIO_SYSSPACE, target, td);
  117         error = namei(ndp);
  118         /*
  119          * Re-lock vnode.
  120          */
  121         if (isvnunlocked && !VOP_ISLOCKED(mp->mnt_vnodecovered, NULL))
  122                 vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY, td);
  123 
  124         if (error)
  125                 return (error);
  126         NDFREE(ndp, NDF_ONLY_PNBUF);
  127 
  128         /*
  129          * Sanity check on lower vnode
  130          */
  131         lowerrootvp = ndp->ni_vp;
  132 
  133         vrele(ndp->ni_dvp);
  134         ndp->ni_dvp = NULLVP;
  135 
  136         /*
  137          * Check multi null mount to avoid `lock against myself' panic.
  138          */
  139         if (lowerrootvp == VTONULL(mp->mnt_vnodecovered)->null_lowervp) {
  140                 NULLFSDEBUG("nullfs_mount: multi null mount?\n");
  141                 vput(lowerrootvp);
  142                 return (EDEADLK);
  143         }
  144 
  145         xmp = (struct null_mount *) malloc(sizeof(struct null_mount),
  146                                 M_NULLFSMNT, M_WAITOK); /* XXX */
  147 
  148         /*
  149          * Save reference to underlying FS
  150          */
  151         xmp->nullm_vfs = lowerrootvp->v_mount;
  152 
  153         /*
  154          * Save reference.  Each mount also holds
  155          * a reference on the root vnode.
  156          */
  157         error = null_nodeget(mp, lowerrootvp, &vp);
  158         /*
  159          * Make sure the node alias worked
  160          */
  161         if (error) {
  162                 VOP_UNLOCK(vp, 0, td);
  163                 vrele(lowerrootvp);
  164                 free(xmp, M_NULLFSMNT); /* XXX */
  165                 return (error);
  166         }
  167 
  168         /*
  169          * Keep a held reference to the root vnode.
  170          * It is vrele'd in nullfs_unmount.
  171          */
  172         nullm_rootvp = vp;
  173         nullm_rootvp->v_vflag |= VV_ROOT;
  174         xmp->nullm_rootvp = nullm_rootvp;
  175 
  176         /*
  177          * Unlock the node (either the lower or the alias)
  178          */
  179         VOP_UNLOCK(vp, 0, td);
  180 
  181         if (NULLVPTOLOWERVP(nullm_rootvp)->v_mount->mnt_flag & MNT_LOCAL)
  182                 mp->mnt_flag |= MNT_LOCAL;
  183         mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag | MNTK_MPSAFE;
  184         mp->mnt_data = (qaddr_t) xmp;
  185         vfs_getnewfsid(mp);
  186 
  187         vfs_mountedfrom(mp, target);
  188 
  189         NULLFSDEBUG("nullfs_mount: lower %s, alias at %s\n",
  190                 mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname);
  191         return (0);
  192 }
  193 
  194 /*
  195  * Free reference to null layer
  196  */
  197 static int
  198 nullfs_unmount(mp, mntflags, td)
  199         struct mount *mp;
  200         int mntflags;
  201         struct thread *td;
  202 {
  203         void *mntdata;
  204         int error;
  205         int flags = 0;
  206 
  207         NULLFSDEBUG("nullfs_unmount: mp = %p\n", (void *)mp);
  208 
  209         if (mntflags & MNT_FORCE)
  210                 flags |= FORCECLOSE;
  211 
  212         /* There is 1 extra root vnode reference (nullm_rootvp). */
  213         error = vflush(mp, 1, flags, td);
  214         if (error)
  215                 return (error);
  216 
  217         /*
  218          * Finally, throw away the null_mount structure
  219          */
  220         mntdata = mp->mnt_data;
  221         mp->mnt_data = 0;
  222         free(mntdata, M_NULLFSMNT);
  223         return 0;
  224 }
  225 
  226 static int
  227 nullfs_root(mp, flags, vpp, td)
  228         struct mount *mp;
  229         int flags;
  230         struct vnode **vpp;
  231         struct thread *td;
  232 {
  233         struct vnode *vp;
  234 
  235         NULLFSDEBUG("nullfs_root(mp = %p, vp = %p->%p)\n", (void *)mp,
  236             (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp,
  237             (void *)NULLVPTOLOWERVP(MOUNTTONULLMOUNT(mp)->nullm_rootvp));
  238 
  239         /*
  240          * Return locked reference to root.
  241          */
  242         vp = MOUNTTONULLMOUNT(mp)->nullm_rootvp;
  243         VREF(vp);
  244 
  245 #ifdef NULLFS_DEBUG
  246         if (VOP_ISLOCKED(vp, NULL)) {
  247                 kdb_enter("root vnode is locked.\n");
  248                 vrele(vp);
  249                 return (EDEADLK);
  250         }
  251 #endif
  252         vn_lock(vp, flags | LK_RETRY, td);
  253         *vpp = vp;
  254         return 0;
  255 }
  256 
  257 static int
  258 nullfs_quotactl(mp, cmd, uid, arg, td)
  259         struct mount *mp;
  260         int cmd;
  261         uid_t uid;
  262         caddr_t arg;
  263         struct thread *td;
  264 {
  265         return VFS_QUOTACTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, uid, arg, td);
  266 }
  267 
  268 static int
  269 nullfs_statfs(mp, sbp, td)
  270         struct mount *mp;
  271         struct statfs *sbp;
  272         struct thread *td;
  273 {
  274         int error;
  275         struct statfs mstat;
  276 
  277         NULLFSDEBUG("nullfs_statfs(mp = %p, vp = %p->%p)\n", (void *)mp,
  278             (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp,
  279             (void *)NULLVPTOLOWERVP(MOUNTTONULLMOUNT(mp)->nullm_rootvp));
  280 
  281         bzero(&mstat, sizeof(mstat));
  282 
  283         error = VFS_STATFS(MOUNTTONULLMOUNT(mp)->nullm_vfs, &mstat, td);
  284         if (error)
  285                 return (error);
  286 
  287         /* now copy across the "interesting" information and fake the rest */
  288         sbp->f_type = mstat.f_type;
  289         sbp->f_flags = mstat.f_flags;
  290         sbp->f_bsize = mstat.f_bsize;
  291         sbp->f_iosize = mstat.f_iosize;
  292         sbp->f_blocks = mstat.f_blocks;
  293         sbp->f_bfree = mstat.f_bfree;
  294         sbp->f_bavail = mstat.f_bavail;
  295         sbp->f_files = mstat.f_files;
  296         sbp->f_ffree = mstat.f_ffree;
  297         return (0);
  298 }
  299 
  300 static int
  301 nullfs_sync(mp, waitfor, td)
  302         struct mount *mp;
  303         int waitfor;
  304         struct thread *td;
  305 {
  306         /*
  307          * XXX - Assumes no data cached at null layer.
  308          */
  309         return (0);
  310 }
  311 
  312 static int
  313 nullfs_vget(mp, ino, flags, vpp)
  314         struct mount *mp;
  315         ino_t ino;
  316         int flags;
  317         struct vnode **vpp;
  318 {
  319         int error;
  320         error = VFS_VGET(MOUNTTONULLMOUNT(mp)->nullm_vfs, ino, flags, vpp);
  321         if (error)
  322                 return (error);
  323 
  324         return (null_nodeget(mp, *vpp, vpp));
  325 }
  326 
  327 static int
  328 nullfs_fhtovp(mp, fidp, vpp)
  329         struct mount *mp;
  330         struct fid *fidp;
  331         struct vnode **vpp;
  332 {
  333         int error;
  334         error = VFS_FHTOVP(MOUNTTONULLMOUNT(mp)->nullm_vfs, fidp, vpp);
  335         if (error)
  336                 return (error);
  337 
  338         return (null_nodeget(mp, *vpp, vpp));
  339 }
  340 
  341 static int
  342 nullfs_checkexp(mp, nam, extflagsp, credanonp)
  343         struct mount *mp;
  344         struct sockaddr *nam;
  345         int *extflagsp; 
  346         struct ucred **credanonp;
  347 {
  348 
  349         return VFS_CHECKEXP(MOUNTTONULLMOUNT(mp)->nullm_vfs, nam, 
  350                 extflagsp, credanonp);
  351 }
  352 
  353 static int
  354 nullfs_vptofh(vp, fhp)
  355         struct vnode *vp;
  356         struct fid *fhp;
  357 {
  358         struct vnode *lvp;
  359 
  360         lvp = NULLVPTOLOWERVP(vp);
  361         return VFS_VPTOFH(lvp, fhp);
  362 }
  363 
  364 static int                        
  365 nullfs_extattrctl(mp, cmd, filename_vp, namespace, attrname, td)
  366         struct mount *mp;
  367         int cmd;
  368         struct vnode *filename_vp;
  369         int namespace;
  370         const char *attrname;
  371         struct thread *td;            
  372 {
  373         return VFS_EXTATTRCTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, filename_vp,
  374             namespace, attrname, td);
  375 }
  376 
  377 
  378 static struct vfsops null_vfsops = {
  379         .vfs_checkexp =         nullfs_checkexp,
  380         .vfs_extattrctl =       nullfs_extattrctl,
  381         .vfs_fhtovp =           nullfs_fhtovp,
  382         .vfs_init =             nullfs_init,
  383         .vfs_mount =            nullfs_mount,
  384         .vfs_quotactl =         nullfs_quotactl,
  385         .vfs_root =             nullfs_root,
  386         .vfs_statfs =           nullfs_statfs,
  387         .vfs_sync =             nullfs_sync,
  388         .vfs_uninit =           nullfs_uninit,
  389         .vfs_unmount =          nullfs_unmount,
  390         .vfs_vget =             nullfs_vget,
  391         .vfs_vptofh =           nullfs_vptofh,
  392 };
  393 
  394 VFS_SET(null_vfsops, nullfs, VFCF_LOOPBACK);

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