sys/vfs/nullfs/null_vfsops.c

   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  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  *      @(#)null_vfsops.c       8.2 (Berkeley) 1/21/94
  37  *
  38  * @(#)lofs_vfsops.c    1.2 (Berkeley) 6/18/92
  39  * $FreeBSD: src/sys/miscfs/nullfs/null_vfsops.c,v 1.35.2.3 2001/07/26 20:37:11 iedowse Exp $
  40  * $DragonFly: src/sys/vfs/nullfs/null_vfsops.c,v 1.29 2006/10/27 04:56:34 dillon Exp $
  41  */
  42
  43 /*
  44  * Null Layer
  45  * (See null_vnops.c for a description of what this does.)
  46  */
  47
  48 #include <sys/param.h>
  49 #include <sys/systm.h>
  50 #include <sys/kernel.h>
  51 #include <sys/proc.h>
  52 #include <sys/malloc.h>
  53 #include <sys/vnode.h>
  54 #include <sys/mount.h>
  55 #include <sys/nlookup.h>
  56 #include "null.h"
  57
  58 extern struct vop_ops null_vnode_vops;
  59
  60 static MALLOC_DEFINE(M_NULLFSMNT, "NULLFS mount", "NULLFS mount structure");
  61
  62 static int      nullfs_root(struct mount *mp, struct vnode **vpp);
  63 static int      nullfs_statfs(struct mount *mp, struct statfs *sbp,
  64                                 struct ucred *cred);
  65
  66 /*
  67  * Mount null layer
  68  */
  69 static int
  70 nullfs_mount(struct mount *mp, char *path, caddr_t data, struct ucred *cred)
  71 {
  72         int error = 0;
  73         struct null_args args;
  74         struct vnode *rootvp;
  75         struct null_mount *xmp;
  76         u_int size;
  77         struct nlookupdata nd;
  78
  79         NULLFSDEBUG("nullfs_mount(mp = %p)\n", (void *)mp);
  80
  81         /*
  82          * Update is a no-op
  83          */
  84         if (mp->mnt_flag & MNT_UPDATE) {
  85                 return (EOPNOTSUPP);
  86         }
  87
  88         /*
  89          * Get argument
  90          */
  91         error = copyin(data, (caddr_t)&args, sizeof(struct null_args));
  92         if (error)
  93                 return (error);
  94
  95         /*
  96          * Find lower node
  97          */
  98         rootvp = NULL;
  99         error = nlookup_init(&nd, args.target, UIO_USERSPACE, NLC_FOLLOW);
 100         if (error)
 101                 goto fail1;
 102         error = nlookup(&nd);
 103         if (error)
 104                 goto fail2;
 105         error = cache_vget(&nd.nl_nch, nd.nl_cred, LK_EXCLUSIVE, &rootvp);
 106         if (error)
 107                 goto fail2;
 108
 109         xmp = (struct null_mount *) kmalloc(sizeof(struct null_mount),
 110                                 M_NULLFSMNT, M_WAITOK); /* XXX */
 111
 112         /*
 113          * Save reference to underlying FS
 114          *
 115          * As lite stacking enters the scene, the old way of doing this
 116          * -- via the vnode -- is not good enough anymore.  Use the
 117          * underlying filesystem's namecache handle as our mount point
 118          * root, adjusting the mount to point to us.
 119          *
 120          * NCF_ISMOUNTPT is normally set on the mount point, but we also
 121          * want to set it on the base directory being mounted to prevent
 122          * that directory from being destroyed out from under the nullfs
 123          * mount.
 124          */
 125         xmp->nullm_vfs = nd.nl_nch.mount;
 126         mp->mnt_ncmountpt = nd.nl_nch;
 127         cache_changemount(&mp->mnt_ncmountpt, mp);
 128         mp->mnt_ncmountpt.ncp->nc_flag |= NCF_ISMOUNTPT;
 129         cache_unlock(&mp->mnt_ncmountpt);
 130         cache_zero(&nd.nl_nch);
 131         nlookup_done(&nd);
 132
 133         vfs_add_vnodeops(mp, &null_vnode_vops, &mp->mnt_vn_norm_ops);
 134
 135         vn_unlock(rootvp);              /* leave reference intact */
 136
 137         /*
 138          * Keep a held reference to the root vnode.
 139          * It is vrele'd in nullfs_unmount.
 140          */
 141         xmp->nullm_rootvp = rootvp;
 142         /*
 143          * XXX What's the proper safety condition for querying
 144          * the underlying mount? Is this flag tuning necessary
 145          * at all?
 146          */
 147         if (xmp->nullm_vfs->mnt_flag & MNT_LOCAL)
 148                 mp->mnt_flag |= MNT_LOCAL;
 149         mp->mnt_data = (qaddr_t) xmp;
 150         vfs_getnewfsid(mp);
 151
 152         (void) copyinstr(args.target, mp->mnt_stat.f_mntfromname, MNAMELEN - 1,
 153             &size);
 154         bzero(mp->mnt_stat.f_mntfromname + size, MNAMELEN - size);
 155         (void)nullfs_statfs(mp, &mp->mnt_stat, cred);
 156         NULLFSDEBUG("nullfs_mount: lower %s, alias at %s\n",
 157                 mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntfromname);
 158
 159         /*
 160          * So unmount won't complain about namecache refs still existing
 161          */
 162         mp->mnt_kern_flag |= MNTK_NCALIASED;
 163         return (0);
 164 fail2:
 165         nlookup_done(&nd);
 166 fail1:
 167         return (error);
 168 }
 169
 170 /*
 171  * Free reference to null layer
 172  */
 173 static int
 174 nullfs_unmount(struct mount *mp, int mntflags)
 175 {
 176         struct null_mount *xmp;
 177         int flags = 0;
 178
 179         NULLFSDEBUG("nullfs_unmount: mp = %p\n", (void *)mp);
 180
 181         if (mntflags & MNT_FORCE)
 182                 flags |= FORCECLOSE;
 183
 184         /*
 185          * Finally, throw away the null_mount structure
 186          */
 187         xmp = (void *)mp->mnt_data;
 188         mp->mnt_data = 0;
 189         if (xmp->nullm_rootvp) {
 190                 vrele(xmp->nullm_rootvp);
 191                 xmp->nullm_rootvp = NULL;
 192         }
 193         kfree(xmp, M_NULLFSMNT);
 194         return 0;
 195 }
 196
 197 static int
 198 nullfs_root(struct mount *mp, struct vnode **vpp)
 199 {
 200         struct vnode *vp;
 201         int error;
 202
 203         NULLFSDEBUG("nullfs_root(mp = %p, vp = %p)\n", (void *)mp,
 204             (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp);
 205
 206         /*
 207          * Return locked reference to root.
 208          */
 209         vp = MOUNTTONULLMOUNT(mp)->nullm_rootvp;
 210         error = vget(vp, LK_EXCLUSIVE | LK_RETRY);
 211         if (error == 0)
 212                 *vpp = vp;
 213         return (error);
 214 }
 215
 216 static int
 217 nullfs_quotactl(struct mount *mp, int cmd, uid_t uid, caddr_t arg,
 218                 struct ucred *cred)
 219 {
 220         return VFS_QUOTACTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, uid, arg, cred);
 221 }
 222
 223 static int
 224 nullfs_statfs(struct mount *mp, struct statfs *sbp, struct ucred *cred)
 225 {
 226         int error;
 227         struct statfs mstat;
 228
 229         NULLFSDEBUG("nullfs_statfs(mp = %p, vp = %p)\n", (void *)mp,
 230             (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp);
 231
 232         bzero(&mstat, sizeof(mstat));
 233
 234         error = VFS_STATFS(MOUNTTONULLMOUNT(mp)->nullm_vfs, &mstat, cred);
 235         if (error)
 236                 return (error);
 237
 238         /* now copy across the "interesting" information and fake the rest */
 239         sbp->f_type = mstat.f_type;
 240         sbp->f_flags = mstat.f_flags;
 241         sbp->f_bsize = mstat.f_bsize;
 242         sbp->f_iosize = mstat.f_iosize;
 243         sbp->f_blocks = mstat.f_blocks;
 244         sbp->f_bfree = mstat.f_bfree;
 245         sbp->f_bavail = mstat.f_bavail;
 246         sbp->f_files = mstat.f_files;
 247         sbp->f_ffree = mstat.f_ffree;
 248         if (sbp != &mp->mnt_stat) {
 249                 bcopy(&mp->mnt_stat.f_fsid, &sbp->f_fsid, sizeof(sbp->f_fsid));
 250                 bcopy(mp->mnt_stat.f_mntfromname, sbp->f_mntfromname, MNAMELEN);
 251         }
 252         return (0);
 253 }
 254
 255 static int
 256 nullfs_checkexp(struct mount *mp, struct sockaddr *nam, int *extflagsp,
 257                 struct ucred **credanonp)
 258 {
 259
 260         return VFS_CHECKEXP(MOUNTTONULLMOUNT(mp)->nullm_vfs, nam,
 261                 extflagsp, credanonp);
 262 }
 263
 264 static int
 265 nullfs_extattrctl(struct mount *mp, int cmd, const char *attrname, caddr_t arg,
 266                   struct ucred *cred)
 267 {
 268         return VFS_EXTATTRCTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, attrname,
 269             arg, cred);
 270 }
 271
 272
 273 static struct vfsops null_vfsops = {
 274         .vfs_mount =            nullfs_mount,
 275         .vfs_unmount =          nullfs_unmount,
 276         .vfs_root =             nullfs_root,
 277         .vfs_quotactl =         nullfs_quotactl,
 278         .vfs_statfs =           nullfs_statfs,
 279         .vfs_sync =             vfs_stdsync,
 280         .vfs_checkexp =         nullfs_checkexp,
 281         .vfs_extattrctl =       nullfs_extattrctl
 282 };
 283
 284 VFS_SET(null_vfsops, null, VFCF_LOOPBACK);