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 * $FreeBSD$
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
nullfs_mount(struct mount * mp)75 nullfs_mount(struct mount *mp)
76 {
77 struct vnode *lowerrootvp, *vp;
78 struct vnode *nullm_rootvp;
79 struct null_mount *xmp;
80 struct null_node *nn;
81 struct nameidata nd, *ndp;
82 char *target;
83 int error, len;
84 bool isvnunlocked;
85
86 NULLFSDEBUG("nullfs_mount(mp = %p)\n", (void *)mp);
87
88 if (mp->mnt_flag & MNT_ROOTFS)
89 return (EOPNOTSUPP);
90
91 /*
92 * Update is a no-op
93 */
94 if (mp->mnt_flag & MNT_UPDATE) {
95 /*
96 * Only support update mounts for NFS export.
97 */
98 if (vfs_flagopt(mp->mnt_optnew, "export", NULL, 0))
99 return (0);
100 else
101 return (EOPNOTSUPP);
102 }
103
104 /*
105 * Get argument
106 */
107 error = vfs_getopt(mp->mnt_optnew, "target", (void **)&target, &len);
108 if (error || target[len - 1] != '\0')
109 return (EINVAL);
110
111 /*
112 * Unlock lower node to avoid possible deadlock.
113 */
114 if (mp->mnt_vnodecovered->v_op == &null_vnodeops &&
115 VOP_ISLOCKED(mp->mnt_vnodecovered) == LK_EXCLUSIVE) {
116 VOP_UNLOCK(mp->mnt_vnodecovered, 0);
117 isvnunlocked = true;
118 } else {
119 isvnunlocked = false;
120 }
121
122 /*
123 * Find lower node
124 */
125 ndp = &nd;
126 NDINIT(ndp, LOOKUP, FOLLOW|LOCKLEAF, UIO_SYSSPACE, target, curthread);
127 error = namei(ndp);
128
129 /*
130 * Re-lock vnode.
131 * XXXKIB This is deadlock-prone as well.
132 */
133 if (isvnunlocked)
134 vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY);
135
136 if (error)
137 return (error);
138 NDFREE(ndp, NDF_ONLY_PNBUF);
139
140 /*
141 * Sanity check on lower vnode
142 */
143 lowerrootvp = ndp->ni_vp;
144
145 /*
146 * Check multi null mount to avoid `lock against myself' panic.
147 */
148 if (mp->mnt_vnodecovered->v_op == &null_vnodeops) {
149 nn = VTONULL(mp->mnt_vnodecovered);
150 if (nn == NULL || lowerrootvp == nn->null_lowervp) {
151 NULLFSDEBUG("nullfs_mount: multi null mount?\n");
152 vput(lowerrootvp);
153 return (EDEADLK);
154 }
155 }
156
157 xmp = (struct null_mount *) malloc(sizeof(struct null_mount),
158 M_NULLFSMNT, M_WAITOK | M_ZERO);
159
160 /*
161 * Save reference to underlying FS
162 */
163 xmp->nullm_vfs = lowerrootvp->v_mount;
164
165 /*
166 * Save reference. Each mount also holds
167 * a reference on the root vnode.
168 */
169 error = null_nodeget(mp, lowerrootvp, &vp);
170 /*
171 * Make sure the node alias worked
172 */
173 if (error) {
174 free(xmp, M_NULLFSMNT);
175 return (error);
176 }
177
178 /*
179 * Keep a held reference to the root vnode.
180 * It is vrele'd in nullfs_unmount.
181 */
182 nullm_rootvp = vp;
183 nullm_rootvp->v_vflag |= VV_ROOT;
184 xmp->nullm_rootvp = nullm_rootvp;
185
186 /*
187 * Unlock the node (either the lower or the alias)
188 */
189 VOP_UNLOCK(vp, 0);
190
191 if (NULLVPTOLOWERVP(nullm_rootvp)->v_mount->mnt_flag & MNT_LOCAL) {
192 MNT_ILOCK(mp);
193 mp->mnt_flag |= MNT_LOCAL;
194 MNT_IUNLOCK(mp);
195 }
196
197 xmp->nullm_flags |= NULLM_CACHE;
198 if (vfs_getopt(mp->mnt_optnew, "nocache", NULL, NULL) == 0 ||
199 (xmp->nullm_vfs->mnt_kern_flag & MNTK_NULL_NOCACHE) != 0)
200 xmp->nullm_flags &= ~NULLM_CACHE;
201
202 MNT_ILOCK(mp);
203 if ((xmp->nullm_flags & NULLM_CACHE) != 0) {
204 mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag &
205 (MNTK_SHARED_WRITES | MNTK_LOOKUP_SHARED |
206 MNTK_EXTENDED_SHARED);
207 }
208 mp->mnt_kern_flag |= MNTK_LOOKUP_EXCL_DOTDOT;
209 mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag &
210 (MNTK_USES_BCACHE | MNTK_NO_IOPF | MNTK_UNMAPPED_BUFS);
211 MNT_IUNLOCK(mp);
212 mp->mnt_data = xmp;
213 vfs_getnewfsid(mp);
214 if ((xmp->nullm_flags & NULLM_CACHE) != 0) {
215 MNT_ILOCK(xmp->nullm_vfs);
216 TAILQ_INSERT_TAIL(&xmp->nullm_vfs->mnt_uppers, mp,
217 mnt_upper_link);
218 MNT_IUNLOCK(xmp->nullm_vfs);
219 }
220
221 vfs_mountedfrom(mp, target);
222
223 NULLFSDEBUG("nullfs_mount: lower %s, alias at %s\n",
224 mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname);
225 return (0);
226 }
227
228 /*
229 * Free reference to null layer
230 */
231 static int
nullfs_unmount(mp,mntflags)232 nullfs_unmount(mp, mntflags)
233 struct mount *mp;
234 int mntflags;
235 {
236 struct null_mount *mntdata;
237 struct mount *ump;
238 int error, flags, rootrefs;
239
240 NULLFSDEBUG("nullfs_unmount: mp = %p\n", (void *)mp);
241
242 if (mntflags & MNT_FORCE)
243 flags = FORCECLOSE;
244 else
245 flags = 0;
246
247 for (rootrefs = 1;; rootrefs = 0) {
248 /* There is 1 extra root vnode reference (nullm_rootvp). */
249 error = vflush(mp, rootrefs, flags, curthread);
250 if (error)
251 return (error);
252 MNT_ILOCK(mp);
253 if (mp->mnt_nvnodelistsize == 0) {
254 MNT_IUNLOCK(mp);
255 break;
256 }
257 MNT_IUNLOCK(mp);
258 if ((mntflags & MNT_FORCE) == 0)
259 return (EBUSY);
260 }
261
262 /*
263 * Finally, throw away the null_mount structure
264 */
265 mntdata = mp->mnt_data;
266 ump = mntdata->nullm_vfs;
267 if ((mntdata->nullm_flags & NULLM_CACHE) != 0) {
268 MNT_ILOCK(ump);
269 while ((ump->mnt_kern_flag & MNTK_VGONE_UPPER) != 0) {
270 ump->mnt_kern_flag |= MNTK_VGONE_WAITER;
271 msleep(&ump->mnt_uppers, &ump->mnt_mtx, 0, "vgnupw", 0);
272 }
273 TAILQ_REMOVE(&ump->mnt_uppers, mp, mnt_upper_link);
274 MNT_IUNLOCK(ump);
275 }
276 mp->mnt_data = NULL;
277 free(mntdata, M_NULLFSMNT);
278 return (0);
279 }
280
281 static int
nullfs_root(mp,flags,vpp)282 nullfs_root(mp, flags, vpp)
283 struct mount *mp;
284 int flags;
285 struct vnode **vpp;
286 {
287 struct vnode *vp;
288
289 NULLFSDEBUG("nullfs_root(mp = %p, vp = %p->%p)\n", (void *)mp,
290 (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp,
291 (void *)NULLVPTOLOWERVP(MOUNTTONULLMOUNT(mp)->nullm_rootvp));
292
293 /*
294 * Return locked reference to root.
295 */
296 vp = MOUNTTONULLMOUNT(mp)->nullm_rootvp;
297 VREF(vp);
298
299 ASSERT_VOP_UNLOCKED(vp, "root vnode is locked");
300 vn_lock(vp, flags | LK_RETRY);
301 *vpp = vp;
302 return 0;
303 }
304
305 static int
nullfs_quotactl(mp,cmd,uid,arg)306 nullfs_quotactl(mp, cmd, uid, arg)
307 struct mount *mp;
308 int cmd;
309 uid_t uid;
310 void *arg;
311 {
312 return VFS_QUOTACTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, uid, arg);
313 }
314
315 static int
nullfs_statfs(mp,sbp)316 nullfs_statfs(mp, sbp)
317 struct mount *mp;
318 struct statfs *sbp;
319 {
320 int error;
321 struct statfs *mstat;
322
323 NULLFSDEBUG("nullfs_statfs(mp = %p, vp = %p->%p)\n", (void *)mp,
324 (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp,
325 (void *)NULLVPTOLOWERVP(MOUNTTONULLMOUNT(mp)->nullm_rootvp));
326
327 mstat = malloc(sizeof(struct statfs), M_STATFS, M_WAITOK | M_ZERO);
328
329 error = VFS_STATFS(MOUNTTONULLMOUNT(mp)->nullm_vfs, mstat);
330 if (error) {
331 free(mstat, M_STATFS);
332 return (error);
333 }
334
335 /* now copy across the "interesting" information and fake the rest */
336 sbp->f_type = mstat->f_type;
337 sbp->f_flags = (sbp->f_flags & (MNT_RDONLY | MNT_NOEXEC | MNT_NOSUID |
338 MNT_UNION | MNT_NOSYMFOLLOW | MNT_AUTOMOUNTED)) |
339 (mstat->f_flags & ~(MNT_ROOTFS | MNT_AUTOMOUNTED));
340 sbp->f_bsize = mstat->f_bsize;
341 sbp->f_iosize = mstat->f_iosize;
342 sbp->f_blocks = mstat->f_blocks;
343 sbp->f_bfree = mstat->f_bfree;
344 sbp->f_bavail = mstat->f_bavail;
345 sbp->f_files = mstat->f_files;
346 sbp->f_ffree = mstat->f_ffree;
347
348 free(mstat, M_STATFS);
349 return (0);
350 }
351
352 static int
nullfs_sync(mp,waitfor)353 nullfs_sync(mp, waitfor)
354 struct mount *mp;
355 int waitfor;
356 {
357 /*
358 * XXX - Assumes no data cached at null layer.
359 */
360 return (0);
361 }
362
363 static int
nullfs_vget(mp,ino,flags,vpp)364 nullfs_vget(mp, ino, flags, vpp)
365 struct mount *mp;
366 ino_t ino;
367 int flags;
368 struct vnode **vpp;
369 {
370 int error;
371
372 KASSERT((flags & LK_TYPE_MASK) != 0,
373 ("nullfs_vget: no lock requested"));
374
375 error = VFS_VGET(MOUNTTONULLMOUNT(mp)->nullm_vfs, ino, flags, vpp);
376 if (error != 0)
377 return (error);
378 return (null_nodeget(mp, *vpp, vpp));
379 }
380
381 static int
nullfs_fhtovp(mp,fidp,flags,vpp)382 nullfs_fhtovp(mp, fidp, flags, vpp)
383 struct mount *mp;
384 struct fid *fidp;
385 int flags;
386 struct vnode **vpp;
387 {
388 int error;
389
390 error = VFS_FHTOVP(MOUNTTONULLMOUNT(mp)->nullm_vfs, fidp, flags,
391 vpp);
392 if (error != 0)
393 return (error);
394 return (null_nodeget(mp, *vpp, vpp));
395 }
396
397 static int
nullfs_extattrctl(mp,cmd,filename_vp,namespace,attrname)398 nullfs_extattrctl(mp, cmd, filename_vp, namespace, attrname)
399 struct mount *mp;
400 int cmd;
401 struct vnode *filename_vp;
402 int namespace;
403 const char *attrname;
404 {
405
406 return (VFS_EXTATTRCTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd,
407 filename_vp, namespace, attrname));
408 }
409
410 static void
nullfs_reclaim_lowervp(struct mount * mp,struct vnode * lowervp)411 nullfs_reclaim_lowervp(struct mount *mp, struct vnode *lowervp)
412 {
413 struct vnode *vp;
414
415 vp = null_hashget(mp, lowervp);
416 if (vp == NULL)
417 return;
418 VTONULL(vp)->null_flags |= NULLV_NOUNLOCK;
419 vgone(vp);
420 vput(vp);
421 }
422
423 static void
nullfs_unlink_lowervp(struct mount * mp,struct vnode * lowervp)424 nullfs_unlink_lowervp(struct mount *mp, struct vnode *lowervp)
425 {
426 struct vnode *vp;
427 struct null_node *xp;
428
429 vp = null_hashget(mp, lowervp);
430 if (vp == NULL)
431 return;
432 xp = VTONULL(vp);
433 xp->null_flags |= NULLV_DROP | NULLV_NOUNLOCK;
434 vhold(vp);
435 vunref(vp);
436
437 if (vp->v_usecount == 0) {
438 /*
439 * If vunref() dropped the last use reference on the
440 * nullfs vnode, it must be reclaimed, and its lock
441 * was split from the lower vnode lock. Need to do
442 * extra unlock before allowing the final vdrop() to
443 * free the vnode.
444 */
445 KASSERT((vp->v_iflag & VI_DOOMED) != 0,
446 ("not reclaimed nullfs vnode %p", vp));
447 VOP_UNLOCK(vp, 0);
448 } else {
449 /*
450 * Otherwise, the nullfs vnode still shares the lock
451 * with the lower vnode, and must not be unlocked.
452 * Also clear the NULLV_NOUNLOCK, the flag is not
453 * relevant for future reclamations.
454 */
455 ASSERT_VOP_ELOCKED(vp, "unlink_lowervp");
456 KASSERT((vp->v_iflag & VI_DOOMED) == 0,
457 ("reclaimed nullfs vnode %p", vp));
458 xp->null_flags &= ~NULLV_NOUNLOCK;
459 }
460 vdrop(vp);
461 }
462
463 static struct vfsops null_vfsops = {
464 .vfs_extattrctl = nullfs_extattrctl,
465 .vfs_fhtovp = nullfs_fhtovp,
466 .vfs_init = nullfs_init,
467 .vfs_mount = nullfs_mount,
468 .vfs_quotactl = nullfs_quotactl,
469 .vfs_root = nullfs_root,
470 .vfs_statfs = nullfs_statfs,
471 .vfs_sync = nullfs_sync,
472 .vfs_uninit = nullfs_uninit,
473 .vfs_unmount = nullfs_unmount,
474 .vfs_vget = nullfs_vget,
475 .vfs_reclaim_lowervp = nullfs_reclaim_lowervp,
476 .vfs_unlink_lowervp = nullfs_unlink_lowervp,
477 };
478
479 VFS_SET(null_vfsops, nullfs, VFCF_LOOPBACK | VFCF_JAIL);
480