1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
|
/*
* Copyright (c) 1992, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* John Heidemann of the UCLA Ficus project.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)null_vnops.c 8.6 (Berkeley) 5/27/95
*
* Ancestors:
* @(#)lofs_vnops.c 1.2 (Berkeley) 6/18/92
* ...and...
* @(#)null_vnodeops.c 1.20 92/07/07 UCLA Ficus project
*
* $FreeBSD$
*/
/*
* Null Layer
*
* (See mount_nullfs(8) for more information.)
*
* The null layer duplicates a portion of the filesystem
* name space under a new name. In this respect, it is
* similar to the loopback filesystem. It differs from
* the loopback fs in two respects: it is implemented using
* a stackable layers techniques, and its "null-node"s stack above
* all lower-layer vnodes, not just over directory vnodes.
*
* The null layer has two purposes. First, it serves as a demonstration
* of layering by proving a layer which does nothing. (It actually
* does everything the loopback filesystem does, which is slightly
* more than nothing.) Second, the null layer can serve as a prototype
* layer. Since it provides all necessary layer framework,
* new filesystem layers can be created very easily be starting
* with a null layer.
*
* The remainder of this man page examines the null layer as a basis
* for constructing new layers.
*
*
* INSTANTIATING NEW NULL LAYERS
*
* New null layers are created with mount_nullfs(8).
* Mount_nullfs(8) takes two arguments, the pathname
* of the lower vfs (target-pn) and the pathname where the null
* layer will appear in the namespace (alias-pn). After
* the null layer is put into place, the contents
* of target-pn subtree will be aliased under alias-pn.
*
*
* OPERATION OF A NULL LAYER
*
* The null layer is the minimum filesystem layer,
* simply bypassing all possible operations to the lower layer
* for processing there. The majority of its activity centers
* on the bypass routine, through which nearly all vnode operations
* pass.
*
* The bypass routine accepts arbitrary vnode operations for
* handling by the lower layer. It begins by examing vnode
* operation arguments and replacing any null-nodes by their
* lower-layer equivlants. It then invokes the operation
* on the lower layer. Finally, it replaces the null-nodes
* in the arguments and, if a vnode is return by the operation,
* stacks a null-node on top of the returned vnode.
*
* Although bypass handles most operations, vop_getattr, vop_lock,
* vop_unlock, vop_inactive, vop_reclaim, and vop_print are not
* bypassed. Vop_getattr must change the fsid being returned.
* Vop_lock and vop_unlock must handle any locking for the
* current vnode as well as pass the lock request down.
* Vop_inactive and vop_reclaim are not bypassed so that
* they can handle freeing null-layer specific data. Vop_print
* is not bypassed to avoid excessive debugging information.
* Also, certain vnode operations change the locking state within
* the operation (create, mknod, remove, link, rename, mkdir, rmdir,
* and symlink). Ideally these operations should not change the
* lock state, but should be changed to let the caller of the
* function unlock them. Otherwise all intermediate vnode layers
* (such as union, umapfs, etc) must catch these functions to do
* the necessary locking at their layer.
*
*
* INSTANTIATING VNODE STACKS
*
* Mounting associates the null layer with a lower layer,
* effect stacking two VFSes. Vnode stacks are instead
* created on demand as files are accessed.
*
* The initial mount creates a single vnode stack for the
* root of the new null layer. All other vnode stacks
* are created as a result of vnode operations on
* this or other null vnode stacks.
*
* New vnode stacks come into existance as a result of
* an operation which returns a vnode.
* The bypass routine stacks a null-node above the new
* vnode before returning it to the caller.
*
* For example, imagine mounting a null layer with
* "mount_nullfs /usr/include /dev/layer/null".
* Changing directory to /dev/layer/null will assign
* the root null-node (which was created when the null layer was mounted).
* Now consider opening "sys". A vop_lookup would be
* done on the root null-node. This operation would bypass through
* to the lower layer which would return a vnode representing
* the UFS "sys". Null_bypass then builds a null-node
* aliasing the UFS "sys" and returns this to the caller.
* Later operations on the null-node "sys" will repeat this
* process when constructing other vnode stacks.
*
*
* CREATING OTHER FILE SYSTEM LAYERS
*
* One of the easiest ways to construct new filesystem layers is to make
* a copy of the null layer, rename all files and variables, and
* then begin modifing the copy. Sed can be used to easily rename
* all variables.
*
* The umap layer is an example of a layer descended from the
* null layer.
*
*
* INVOKING OPERATIONS ON LOWER LAYERS
*
* There are two techniques to invoke operations on a lower layer
* when the operation cannot be completely bypassed. Each method
* is appropriate in different situations. In both cases,
* it is the responsibility of the aliasing layer to make
* the operation arguments "correct" for the lower layer
* by mapping a vnode arguments to the lower layer.
*
* The first approach is to call the aliasing layer's bypass routine.
* This method is most suitable when you wish to invoke the operation
* currently being handled on the lower layer. It has the advantage
* that the bypass routine already must do argument mapping.
* An example of this is null_getattrs in the null layer.
*
* A second approach is to directly invoke vnode operations on
* the lower layer with the VOP_OPERATIONNAME interface.
* The advantage of this method is that it is easy to invoke
* arbitrary operations on the lower layer. The disadvantage
* is that vnode arguments must be manualy mapped.
*
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/sysctl.h>
#include <sys/vnode.h>
#include <fs/nullfs/null.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_object.h>
#include <vm/vnode_pager.h>
static int null_bug_bypass = 0; /* for debugging: enables bypass printf'ing */
SYSCTL_INT(_debug, OID_AUTO, nullfs_bug_bypass, CTLFLAG_RW,
&null_bug_bypass, 0, "");
static int null_access(struct vop_access_args *ap);
static int null_createvobject(struct vop_createvobject_args *ap);
static int null_destroyvobject(struct vop_destroyvobject_args *ap);
static int null_getattr(struct vop_getattr_args *ap);
static int null_getvobject(struct vop_getvobject_args *ap);
static int null_inactive(struct vop_inactive_args *ap);
static int null_islocked(struct vop_islocked_args *ap);
static int null_lock(struct vop_lock_args *ap);
static int null_lookup(struct vop_lookup_args *ap);
static int null_open(struct vop_open_args *ap);
static int null_print(struct vop_print_args *ap);
static int null_reclaim(struct vop_reclaim_args *ap);
static int null_rename(struct vop_rename_args *ap);
static int null_setattr(struct vop_setattr_args *ap);
static int null_unlock(struct vop_unlock_args *ap);
/*
* This is the 10-Apr-92 bypass routine.
* This version has been optimized for speed, throwing away some
* safety checks. It should still always work, but it's not as
* robust to programmer errors.
*
* In general, we map all vnodes going down and unmap them on the way back.
* As an exception to this, vnodes can be marked "unmapped" by setting
* the Nth bit in operation's vdesc_flags.
*
* Also, some BSD vnode operations have the side effect of vrele'ing
* their arguments. With stacking, the reference counts are held
* by the upper node, not the lower one, so we must handle these
* side-effects here. This is not of concern in Sun-derived systems
* since there are no such side-effects.
*
* This makes the following assumptions:
* - only one returned vpp
* - no INOUT vpp's (Sun's vop_open has one of these)
* - the vnode operation vector of the first vnode should be used
* to determine what implementation of the op should be invoked
* - all mapped vnodes are of our vnode-type (NEEDSWORK:
* problems on rmdir'ing mount points and renaming?)
*/
int
null_bypass(ap)
struct vop_generic_args /* {
struct vnodeop_desc *a_desc;
<other random data follows, presumably>
} */ *ap;
{
register struct vnode **this_vp_p;
int error;
struct vnode *old_vps[VDESC_MAX_VPS];
struct vnode **vps_p[VDESC_MAX_VPS];
struct vnode ***vppp;
struct vnodeop_desc *descp = ap->a_desc;
int reles, i;
if (null_bug_bypass)
printf ("null_bypass: %s\n", descp->vdesc_name);
#ifdef DIAGNOSTIC
/*
* We require at least one vp.
*/
if (descp->vdesc_vp_offsets == NULL ||
descp->vdesc_vp_offsets[0] == VDESC_NO_OFFSET)
panic ("null_bypass: no vp's in map");
#endif
/*
* Map the vnodes going in.
* Later, we'll invoke the operation based on
* the first mapped vnode's operation vector.
*/
reles = descp->vdesc_flags;
for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) {
if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET)
break; /* bail out at end of list */
vps_p[i] = this_vp_p =
VOPARG_OFFSETTO(struct vnode**,descp->vdesc_vp_offsets[i],ap);
/*
* We're not guaranteed that any but the first vnode
* are of our type. Check for and don't map any
* that aren't. (We must always map first vp or vclean fails.)
*/
if (i && (*this_vp_p == NULLVP ||
(*this_vp_p)->v_op != null_vnodeop_p)) {
old_vps[i] = NULLVP;
} else {
old_vps[i] = *this_vp_p;
*(vps_p[i]) = NULLVPTOLOWERVP(*this_vp_p);
/*
* XXX - Several operations have the side effect
* of vrele'ing their vp's. We must account for
* that. (This should go away in the future.)
*/
if (reles & VDESC_VP0_WILLRELE)
VREF(*this_vp_p);
}
}
/*
* Call the operation on the lower layer
* with the modified argument structure.
*/
if (vps_p[0] && *vps_p[0])
error = VCALL(*(vps_p[0]), descp->vdesc_offset, ap);
else {
printf("null_bypass: no map for %s\n", descp->vdesc_name);
error = EINVAL;
}
/*
* Maintain the illusion of call-by-value
* by restoring vnodes in the argument structure
* to their original value.
*/
reles = descp->vdesc_flags;
for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) {
if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET)
break; /* bail out at end of list */
if (old_vps[i]) {
*(vps_p[i]) = old_vps[i];
#if 0
if (reles & VDESC_VP0_WILLUNLOCK)
VOP_UNLOCK(*(vps_p[i]), LK_THISLAYER, curthread);
#endif
if (reles & VDESC_VP0_WILLRELE)
vrele(*(vps_p[i]));
}
}
/*
* Map the possible out-going vpp
* (Assumes that the lower layer always returns
* a VREF'ed vpp unless it gets an error.)
*/
if (descp->vdesc_vpp_offset != VDESC_NO_OFFSET &&
!(descp->vdesc_flags & VDESC_NOMAP_VPP) &&
!error) {
/*
* XXX - even though some ops have vpp returned vp's,
* several ops actually vrele this before returning.
* We must avoid these ops.
* (This should go away when these ops are regularized.)
*/
if (descp->vdesc_flags & VDESC_VPP_WILLRELE)
goto out;
vppp = VOPARG_OFFSETTO(struct vnode***,
descp->vdesc_vpp_offset,ap);
if (*vppp)
error = null_nodeget(old_vps[0]->v_mount, **vppp, *vppp);
}
out:
return (error);
}
/*
* We have to carry on the locking protocol on the null layer vnodes
* as we progress through the tree. We also have to enforce read-only
* if this layer is mounted read-only.
*/
static int
null_lookup(ap)
struct vop_lookup_args /* {
struct vnode * a_dvp;
struct vnode ** a_vpp;
struct componentname * a_cnp;
} */ *ap;
{
struct componentname *cnp = ap->a_cnp;
struct vnode *dvp = ap->a_dvp;
struct thread *td = cnp->cn_thread;
int flags = cnp->cn_flags;
struct vnode *vp, *ldvp, *lvp;
int error;
if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
return (EROFS);
/*
* Although it is possible to call null_bypass(), we'll do
* a direct call to reduce overhead
*/
ldvp = NULLVPTOLOWERVP(dvp);
vp = lvp = NULL;
error = VOP_LOOKUP(ldvp, &lvp, cnp);
if (error == EJUSTRETURN && (flags & ISLASTCN) &&
(dvp->v_mount->mnt_flag & MNT_RDONLY) &&
(cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME))
error = EROFS;
/*
* Rely only on the PDIRUNLOCK flag which should be carefully
* tracked by underlying filesystem.
*/
if (cnp->cn_flags & PDIRUNLOCK)
VOP_UNLOCK(dvp, LK_THISLAYER, td);
if ((error == 0 || error == EJUSTRETURN) && lvp != NULL) {
if (ldvp == lvp) {
*ap->a_vpp = dvp;
VREF(dvp);
vrele(lvp);
} else {
error = null_nodeget(dvp->v_mount, lvp, &vp);
if (error) {
/* XXX Cleanup needed... */
panic("null_nodeget failed");
}
*ap->a_vpp = vp;
}
}
return (error);
}
/*
* Setattr call. Disallow write attempts if the layer is mounted read-only.
*/
static int
null_setattr(ap)
struct vop_setattr_args /* {
struct vnodeop_desc *a_desc;
struct vnode *a_vp;
struct vattr *a_vap;
struct ucred *a_cred;
struct thread *a_td;
} */ *ap;
{
struct vnode *vp = ap->a_vp;
struct vattr *vap = ap->a_vap;
if ((vap->va_flags != VNOVAL || vap->va_uid != (uid_t)VNOVAL ||
vap->va_gid != (gid_t)VNOVAL || vap->va_atime.tv_sec != VNOVAL ||
vap->va_mtime.tv_sec != VNOVAL || vap->va_mode != (mode_t)VNOVAL) &&
(vp->v_mount->mnt_flag & MNT_RDONLY))
return (EROFS);
if (vap->va_size != VNOVAL) {
switch (vp->v_type) {
case VDIR:
return (EISDIR);
case VCHR:
case VBLK:
case VSOCK:
case VFIFO:
if (vap->va_flags != VNOVAL)
return (EOPNOTSUPP);
return (0);
case VREG:
case VLNK:
default:
/*
* Disallow write attempts if the filesystem is
* mounted read-only.
*/
if (vp->v_mount->mnt_flag & MNT_RDONLY)
return (EROFS);
}
}
return (null_bypass((struct vop_generic_args *)ap));
}
/*
* We handle getattr only to change the fsid.
*/
static int
null_getattr(ap)
struct vop_getattr_args /* {
struct vnode *a_vp;
struct vattr *a_vap;
struct ucred *a_cred;
struct thread *a_td;
} */ *ap;
{
int error;
if ((error = null_bypass((struct vop_generic_args *)ap)) != 0)
return (error);
ap->a_vap->va_fsid = ap->a_vp->v_mount->mnt_stat.f_fsid.val[0];
return (0);
}
/*
* Handle to disallow write access if mounted read-only.
*/
static int
null_access(ap)
struct vop_access_args /* {
struct vnode *a_vp;
int a_mode;
struct ucred *a_cred;
struct thread *a_td;
} */ *ap;
{
struct vnode *vp = ap->a_vp;
mode_t mode = ap->a_mode;
/*
* Disallow write attempts on read-only layers;
* unless the file is a socket, fifo, or a block or
* character device resident on the filesystem.
*/
if (mode & VWRITE) {
switch (vp->v_type) {
case VDIR:
case VLNK:
case VREG:
if (vp->v_mount->mnt_flag & MNT_RDONLY)
return (EROFS);
break;
default:
break;
}
}
return (null_bypass((struct vop_generic_args *)ap));
}
/*
* We must handle open to be able to catch MNT_NODEV and friends.
*/
static int
null_open(ap)
struct vop_open_args /* {
struct vnode *a_vp;
int a_mode;
struct ucred *a_cred;
struct thread *a_td;
} */ *ap;
{
struct vnode *vp = ap->a_vp;
struct vnode *lvp = NULLVPTOLOWERVP(ap->a_vp);
if ((vp->v_mount->mnt_flag & MNT_NODEV) &&
(lvp->v_type == VBLK || lvp->v_type == VCHR))
return ENXIO;
return (null_bypass((struct vop_generic_args *)ap));
}
/*
* We handle this to eliminate null FS to lower FS
* file moving. Don't know why we don't allow this,
* possibly we should.
*/
static int
null_rename(ap)
struct vop_rename_args /* {
struct vnode *a_fdvp;
struct vnode *a_fvp;
struct componentname *a_fcnp;
struct vnode *a_tdvp;
struct vnode *a_tvp;
struct componentname *a_tcnp;
} */ *ap;
{
struct vnode *tdvp = ap->a_tdvp;
struct vnode *fvp = ap->a_fvp;
struct vnode *fdvp = ap->a_fdvp;
struct vnode *tvp = ap->a_tvp;
/* Check for cross-device rename. */
if ((fvp->v_mount != tdvp->v_mount) ||
(tvp && (fvp->v_mount != tvp->v_mount))) {
if (tdvp == tvp)
vrele(tdvp);
else
vput(tdvp);
if (tvp)
vput(tvp);
vrele(fdvp);
vrele(fvp);
return (EXDEV);
}
return (null_bypass((struct vop_generic_args *)ap));
}
/*
* We need to process our own vnode lock and then clear the
* interlock flag as it applies only to our vnode, not the
* vnodes below us on the stack.
*/
static int
null_lock(ap)
struct vop_lock_args /* {
struct vnode *a_vp;
int a_flags;
struct thread *a_td;
} */ *ap;
{
struct vnode *vp = ap->a_vp;
int flags = ap->a_flags;
struct thread *td = ap->a_td;
struct vnode *lvp;
int error;
if (flags & LK_THISLAYER) {
if (vp->v_vnlock != NULL) {
/* lock is shared across layers */
if (flags & LK_INTERLOCK)
mtx_unlock(&vp->v_interlock);
return 0;
}
error = lockmgr(&vp->v_lock, flags & ~LK_THISLAYER,
&vp->v_interlock, td);
return (error);
}
if (vp->v_vnlock != NULL) {
/*
* The lower level has exported a struct lock to us. Use
* it so that all vnodes in the stack lock and unlock
* simultaneously. Note: we don't DRAIN the lock as DRAIN
* decommissions the lock - just because our vnode is
* going away doesn't mean the struct lock below us is.
* LK_EXCLUSIVE is fine.
*/
if ((flags & LK_TYPE_MASK) == LK_DRAIN) {
NULLFSDEBUG("null_lock: avoiding LK_DRAIN\n");
return(lockmgr(vp->v_vnlock,
(flags & ~LK_TYPE_MASK) | LK_EXCLUSIVE,
&vp->v_interlock, td));
}
return(lockmgr(vp->v_vnlock, flags, &vp->v_interlock, td));
} else {
/*
* To prevent race conditions involving doing a lookup
* on "..", we have to lock the lower node, then lock our
* node. Most of the time it won't matter that we lock our
* node (as any locking would need the lower one locked
* first). But we can LK_DRAIN the upper lock as a step
* towards decomissioning it.
*/
lvp = NULLVPTOLOWERVP(vp);
if (lvp == NULL)
return (lockmgr(&vp->v_lock, flags, &vp->v_interlock, td));
if (flags & LK_INTERLOCK) {
mtx_unlock(&vp->v_interlock);
flags &= ~LK_INTERLOCK;
}
if ((flags & LK_TYPE_MASK) == LK_DRAIN) {
error = VOP_LOCK(lvp,
(flags & ~LK_TYPE_MASK) | LK_EXCLUSIVE, td);
} else
error = VOP_LOCK(lvp, flags, td);
if (error)
return (error);
error = lockmgr(&vp->v_lock, flags, &vp->v_interlock, td);
if (error)
VOP_UNLOCK(lvp, 0, td);
return (error);
}
}
/*
* We need to process our own vnode unlock and then clear the
* interlock flag as it applies only to our vnode, not the
* vnodes below us on the stack.
*/
static int
null_unlock(ap)
struct vop_unlock_args /* {
struct vnode *a_vp;
int a_flags;
struct thread *a_td;
} */ *ap;
{
struct vnode *vp = ap->a_vp;
int flags = ap->a_flags;
struct thread *td = ap->a_td;
struct vnode *lvp;
if (vp->v_vnlock != NULL) {
if (flags & LK_THISLAYER)
return 0; /* the lock is shared across layers */
flags &= ~LK_THISLAYER;
return (lockmgr(vp->v_vnlock, flags | LK_RELEASE,
&vp->v_interlock, td));
}
lvp = NULLVPTOLOWERVP(vp);
if (lvp == NULL)
return (lockmgr(&vp->v_lock, flags | LK_RELEASE, &vp->v_interlock, td));
if ((flags & LK_THISLAYER) == 0) {
if (flags & LK_INTERLOCK) {
mtx_unlock(&vp->v_interlock);
flags &= ~LK_INTERLOCK;
}
VOP_UNLOCK(lvp, flags & ~LK_INTERLOCK, td);
} else
flags &= ~LK_THISLAYER;
return (lockmgr(&vp->v_lock, flags | LK_RELEASE, &vp->v_interlock, td));
}
static int
null_islocked(ap)
struct vop_islocked_args /* {
struct vnode *a_vp;
struct thread *a_td;
} */ *ap;
{
struct vnode *vp = ap->a_vp;
struct thread *td = ap->a_td;
if (vp->v_vnlock != NULL)
return (lockstatus(vp->v_vnlock, td));
return (lockstatus(&vp->v_lock, td));
}
/*
* There is no way to tell that someone issued remove/rmdir operation
* on the underlying filesystem. For now we just have to release lowevrp
* as soon as possible.
*
* Note, we can't release any resources nor remove vnode from hash before
* appropriate VXLOCK stuff is is done because other process can find this
* vnode in hash during inactivation and may be sitting in vget() and waiting
* for null_inactive to unlock vnode. Thus we will do all those in VOP_RECLAIM.
*/
static int
null_inactive(ap)
struct vop_inactive_args /* {
struct vnode *a_vp;
struct thread *a_td;
} */ *ap;
{
struct vnode *vp = ap->a_vp;
struct thread *td = ap->a_td;
VOP_UNLOCK(vp, 0, td);
/*
* If this is the last reference, then free up the vnode
* so as not to tie up the lower vnodes.
*/
vrecycle(vp, NULL, td);
return (0);
}
/*
* Now, the VXLOCK is in force and we're free to destroy the null vnode.
*/
static int
null_reclaim(ap)
struct vop_reclaim_args /* {
struct vnode *a_vp;
struct thread *a_td;
} */ *ap;
{
struct vnode *vp = ap->a_vp;
struct null_node *xp = VTONULL(vp);
struct vnode *lowervp = xp->null_lowervp;
if (lowervp) {
null_hashrem(xp);
vrele(lowervp);
vrele(lowervp);
}
vp->v_data = NULL;
vp->v_vnlock = &vp->v_lock;
FREE(xp, M_NULLFSNODE);
return (0);
}
static int
null_print(ap)
struct vop_print_args /* {
struct vnode *a_vp;
} */ *ap;
{
register struct vnode *vp = ap->a_vp;
printf("\tvp=%p, lowervp=%p\n", vp, NULLVPTOLOWERVP(vp));
return (0);
}
/*
* Let an underlying filesystem do the work
*/
static int
null_createvobject(ap)
struct vop_createvobject_args /* {
struct vnode *vp;
struct ucred *cred;
struct thread *td;
} */ *ap;
{
struct vnode *vp = ap->a_vp;
struct vnode *lowervp = VTONULL(vp) ? NULLVPTOLOWERVP(vp) : NULL;
int error;
if (vp->v_type == VNON || lowervp == NULL)
return 0;
error = VOP_CREATEVOBJECT(lowervp, ap->a_cred, ap->a_td);
if (error)
return (error);
vp->v_vflag |= VV_OBJBUF;
return (0);
}
/*
* We have nothing to destroy and this operation shouldn't be bypassed.
*/
static int
null_destroyvobject(ap)
struct vop_destroyvobject_args /* {
struct vnode *vp;
} */ *ap;
{
struct vnode *vp = ap->a_vp;
vp->v_vflag &= ~VV_OBJBUF;
return (0);
}
static int
null_getvobject(ap)
struct vop_getvobject_args /* {
struct vnode *vp;
struct vm_object **objpp;
} */ *ap;
{
struct vnode *lvp = NULLVPTOLOWERVP(ap->a_vp);
if (lvp == NULL)
return EINVAL;
return (VOP_GETVOBJECT(lvp, ap->a_objpp));
}
/*
* Global vfs data structures
*/
vop_t **null_vnodeop_p;
static struct vnodeopv_entry_desc null_vnodeop_entries[] = {
{ &vop_default_desc, (vop_t *) null_bypass },
{ &vop_access_desc, (vop_t *) null_access },
{ &vop_bmap_desc, (vop_t *) vop_eopnotsupp },
{ &vop_createvobject_desc, (vop_t *) null_createvobject },
{ &vop_destroyvobject_desc, (vop_t *) null_destroyvobject },
{ &vop_getattr_desc, (vop_t *) null_getattr },
{ &vop_getvobject_desc, (vop_t *) null_getvobject },
{ &vop_getwritemount_desc, (vop_t *) vop_stdgetwritemount},
{ &vop_inactive_desc, (vop_t *) null_inactive },
{ &vop_islocked_desc, (vop_t *) null_islocked },
{ &vop_lock_desc, (vop_t *) null_lock },
{ &vop_lookup_desc, (vop_t *) null_lookup },
{ &vop_open_desc, (vop_t *) null_open },
{ &vop_print_desc, (vop_t *) null_print },
{ &vop_reclaim_desc, (vop_t *) null_reclaim },
{ &vop_rename_desc, (vop_t *) null_rename },
{ &vop_setattr_desc, (vop_t *) null_setattr },
{ &vop_strategy_desc, (vop_t *) vop_eopnotsupp },
{ &vop_unlock_desc, (vop_t *) null_unlock },
{ NULL, NULL }
};
static struct vnodeopv_desc null_vnodeop_opv_desc =
{ &null_vnodeop_p, null_vnodeop_entries };
VNODEOP_SET(null_vnodeop_opv_desc);
|