xref: /titanic_51/usr/src/uts/common/fs/dcfs/dc_vnops.c (revision e2c5185af3c50d9510e5df68aa37abdc6c0d3aac)
1 
2 /*
3  * CDDL HEADER START
4  *
5  * The contents of this file are subject to the terms of the
6  * Common Development and Distribution License (the "License").
7  * You may not use this file except in compliance with the License.
8  *
9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10  * or http://www.opensolaris.org/os/licensing.
11  * See the License for the specific language governing permissions
12  * and limitations under the License.
13  *
14  * When distributing Covered Code, include this CDDL HEADER in each
15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16  * If applicable, add the following below this CDDL HEADER, with the
17  * fields enclosed by brackets "[]" replaced with your own identifying
18  * information: Portions Copyright [yyyy] [name of copyright owner]
19  *
20  * CDDL HEADER END
21  */
22 /*
23  * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
24  */
25 
26 /*	Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T	*/
27 /*	  All Rights Reserved  	*/
28 
29 /*
30  * University Copyright- Copyright (c) 1982, 1986, 1988
31  * The Regents of the University of California
32  * All Rights Reserved
33  *
34  * University Acknowledgment- Portions of this document are derived from
35  * software developed by the University of California, Berkeley, and its
36  * contributors.
37  */
38 
39 #include <sys/types.h>
40 #include <sys/thread.h>
41 #include <sys/t_lock.h>
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/bitmap.h>
45 #include <sys/buf.h>
46 #include <sys/cmn_err.h>
47 #include <sys/conf.h>
48 #include <sys/ddi.h>
49 #include <sys/debug.h>
50 #include <sys/errno.h>
51 #include <sys/time.h>
52 #include <sys/fcntl.h>
53 #include <sys/flock.h>
54 #include <sys/file.h>
55 #include <sys/kmem.h>
56 #include <sys/mman.h>
57 #include <sys/vmsystm.h>
58 #include <sys/open.h>
59 #include <sys/swap.h>
60 #include <sys/sysmacros.h>
61 #include <sys/uio.h>
62 #include <sys/vfs.h>
63 #include <sys/vfs_opreg.h>
64 #include <sys/vnode.h>
65 #include <sys/stat.h>
66 #include <sys/poll.h>
67 #include <sys/zmod.h>
68 #include <sys/fs/decomp.h>
69 
70 #include <vm/hat.h>
71 #include <vm/as.h>
72 #include <vm/page.h>
73 #include <vm/pvn.h>
74 #include <vm/seg_vn.h>
75 #include <vm/seg_kmem.h>
76 #include <vm/seg_map.h>
77 
78 #include <fs/fs_subr.h>
79 
80 /*
81  * dcfs - A filesystem for automatic decompressing of fiocompressed files
82  *
83  * This filesystem is a layered filesystem that sits on top of a normal
84  * persistent filesystem and provides automatic decompression of files
85  * that have been previously compressed and stored on the host file system.
86  * This is a pseudo filesystem in that it does not persist data, rather it
87  * intercepts file lookup requests on the host filesystem and provides
88  * transparent decompression of those files. Currently the only supported
89  * host filesystem is ufs.
90  *
91  * A file is compressed via a userland utility (currently cmd/boot/fiocompress)
92  * and marked by fiocompress as a compressed file via a flag in the on-disk
93  * inode (set via a ufs ioctl() - see `ufs_vnops.c`ufs_ioctl()`_FIO_COMPRESSED
94  * ufs_lookup checks for this flag and if set, passes control to decompvp
95  * a function defined in this (dcfs) filesystem. decomvp uncompresses the file
96  * and returns a dcfs vnode to the VFS layer.
97  *
98  * dcfs is layered on top of ufs and passes requests involving persistence
99  * to the underlying ufs filesystem. The compressed files currently cannot be
100  * written to.
101  */
102 
103 
104 /*
105  * Define data structures within this file.
106  */
107 #define	DCSHFT		5
108 #define	DCTABLESIZE	16
109 
110 #if ((DCTABLESIZE & (DCTABLESIZE - 1)) == 0)
111 #define	DCHASH(vp) (((uintptr_t)(vp) >> DCSHFT) & (DCTABLESIZE - 1))
112 #else
113 #define	DCHASH(vp) (((uintptr_t)(vp) >> DCSHFT) % DTABLESIZEC)
114 #endif
115 
116 #define	DCLRUSIZE	16
117 
118 #define	DCCACHESIZE	4
119 
120 #define	rounddown(x, y)	((x) & ~((y) - 1))
121 
122 struct dcnode	*dctable[DCTABLESIZE];
123 
124 struct dcnode	*dclru;
125 static int	dclru_len;
126 
127 kmutex_t	dctable_lock;
128 
129 dev_t		dcdev;
130 struct vfs	dc_vfs;
131 
132 struct kmem_cache *dcnode_cache;
133 struct kmem_cache *dcbuf_cache[DCCACHESIZE];
134 
135 kmutex_t	dccache_lock;
136 
137 static int dcinit(int, char *);
138 
139 static struct dcnode	*dcnode_alloc(void);
140 static void		dcnode_free(struct dcnode *);
141 static void		dcnode_recycle(struct dcnode *);
142 
143 static void		dcinsert(struct dcnode *);
144 static void		dcdelete(struct dcnode *);
145 static struct dcnode	*dcfind(struct vnode *);
146 static void		dclru_add(struct dcnode *);
147 static void		dclru_sub(struct dcnode *);
148 
149 
150 /*
151  * This is the loadable module wrapper.
152  */
153 #include <sys/modctl.h>
154 
155 struct vfsops *dc_vfsops;
156 
157 static vfsdef_t vfw = {
158 	VFSDEF_VERSION,
159 	"dcfs",
160 	dcinit,
161 	VSW_ZMOUNT,
162 	NULL
163 };
164 
165 /*
166  * Module linkage information for the kernel.
167  */
168 extern struct mod_ops mod_fsops;
169 
170 static struct modlfs modlfs = {
171 	&mod_fsops, "compressed filesystem", &vfw
172 };
173 
174 static struct modlinkage modlinkage = {
175 	MODREV_1, (void *)&modlfs, NULL
176 };
177 
178 int
179 _init()
180 {
181 	return (mod_install(&modlinkage));
182 }
183 
184 int
185 _info(struct modinfo *modinfop)
186 {
187 	return (mod_info(&modlinkage, modinfop));
188 }
189 
190 
191 static int dc_open(struct vnode **, int, struct cred *, caller_context_t *);
192 static int dc_close(struct vnode *, int, int, offset_t,
193     struct cred *, caller_context_t *);
194 static int dc_read(struct vnode *, struct uio *, int, struct cred *,
195     struct caller_context *);
196 static int dc_getattr(struct vnode *, struct vattr *, int,
197     struct cred *, caller_context_t *);
198 static int dc_setattr(struct vnode *, struct vattr *, int, struct cred *,
199     struct caller_context *);
200 static int dc_access(struct vnode *, int, int,
201     struct cred *, caller_context_t *);
202 static int dc_fsync(struct vnode *, int, struct cred *, caller_context_t *);
203 static void dc_inactive(struct vnode *, struct cred *, caller_context_t *);
204 static int dc_fid(struct vnode *, struct fid *, caller_context_t *);
205 static int dc_seek(struct vnode *, offset_t, offset_t *, caller_context_t *);
206 static int dc_frlock(struct vnode *, int, struct flock64 *, int, offset_t,
207     struct flk_callback *, struct cred *, caller_context_t *);
208 static int dc_realvp(struct vnode *, struct vnode **, caller_context_t *);
209 static int dc_getpage(struct vnode *, offset_t, size_t, uint_t *,
210     struct page **, size_t, struct seg *, caddr_t, enum seg_rw,
211     struct cred *, caller_context_t *);
212 static int dc_putpage(struct vnode *, offset_t, size_t, int,
213     struct cred *, caller_context_t *);
214 static int dc_map(struct vnode *, offset_t, struct as *, caddr_t *, size_t,
215     uchar_t, uchar_t, uint_t, struct cred *, caller_context_t *);
216 static int dc_addmap(struct vnode *, offset_t, struct as *, caddr_t, size_t,
217     uchar_t, uchar_t, uint_t, struct cred *, caller_context_t *);
218 static int dc_delmap(struct vnode *, offset_t, struct as *, caddr_t, size_t,
219     uint_t, uint_t, uint_t, struct cred *, caller_context_t *);
220 
221 struct vnodeops *dc_vnodeops;
222 
223 const fs_operation_def_t dc_vnodeops_template[] = {
224 	VOPNAME_OPEN,			{ .vop_open = dc_open },
225 	VOPNAME_CLOSE,			{ .vop_close = dc_close },
226 	VOPNAME_READ,			{ .vop_read = dc_read },
227 	VOPNAME_GETATTR,		{ .vop_getattr =  dc_getattr },
228 	VOPNAME_SETATTR,		{ .vop_setattr = dc_setattr },
229 	VOPNAME_ACCESS,			{ .vop_access = dc_access },
230 	VOPNAME_FSYNC,			{ .vop_fsync = dc_fsync },
231 	VOPNAME_INACTIVE,		{ .vop_inactive = dc_inactive },
232 	VOPNAME_FID,			{ .vop_fid = dc_fid },
233 	VOPNAME_SEEK,			{ .vop_seek = dc_seek },
234 	VOPNAME_FRLOCK,			{ .vop_frlock = dc_frlock },
235 	VOPNAME_REALVP,			{ .vop_realvp = dc_realvp },
236 	VOPNAME_GETPAGE,		{ .vop_getpage = dc_getpage },
237 	VOPNAME_PUTPAGE,		{ .vop_putpage = dc_putpage },
238 	VOPNAME_MAP,			{ .vop_map = dc_map },
239 	VOPNAME_ADDMAP,			{ .vop_addmap = dc_addmap },
240 	VOPNAME_DELMAP,			{ .vop_delmap = dc_delmap },
241 	NULL,				NULL
242 };
243 
244 /*ARGSUSED*/
245 static int
246 dc_open(struct vnode **vpp, int flag, struct cred *cr, caller_context_t *ctp)
247 {
248 	return (0);
249 }
250 
251 /*ARGSUSED*/
252 static int
253 dc_close(struct vnode *vp, int flag, int count, offset_t off,
254     struct cred *cr, caller_context_t *ctp)
255 {
256 	(void) cleanlocks(vp, ttoproc(curthread)->p_pid, 0);
257 	cleanshares(vp, ttoproc(curthread)->p_pid);
258 	return (0);
259 }
260 
261 /*ARGSUSED*/
262 static int
263 dc_read(struct vnode *vp, struct uio *uiop, int ioflag, struct cred *cr,
264 	struct caller_context *ct)
265 {
266 	struct dcnode *dp = VTODC(vp);
267 	size_t rdsize = MAX(MAXBSIZE, dp->dc_hdr->ch_blksize);
268 	size_t fsize = dp->dc_hdr->ch_fsize;
269 	int error;
270 
271 	/*
272 	 * Loop through file with segmap, decompression will occur
273 	 * in dc_getapage
274 	 */
275 	do {
276 		caddr_t base;
277 		size_t n;
278 		offset_t mapon;
279 
280 		/*
281 		 * read to end of block or file
282 		 */
283 		mapon = uiop->uio_loffset & (rdsize - 1);
284 		n = MIN(rdsize - mapon, uiop->uio_resid);
285 		n = MIN(n, fsize - uiop->uio_loffset);
286 		if (n == 0)
287 			return (0);	/* at EOF */
288 
289 		base = segmap_getmapflt(segkmap, vp, uiop->uio_loffset, n, 1,
290 		    S_READ);
291 		error = uiomove(base + mapon, n, UIO_READ, uiop);
292 		if (!error) {
293 			uint_t flags;
294 
295 			if (n + mapon == rdsize || uiop->uio_loffset == fsize)
296 				flags = SM_DONTNEED;
297 			else
298 				flags = 0;
299 			error = segmap_release(segkmap, base, flags);
300 		} else
301 			(void) segmap_release(segkmap, base, 0);
302 	} while (!error && uiop->uio_resid);
303 
304 	return (error);
305 }
306 
307 static int
308 dc_getattr(struct vnode *vp, struct vattr *vap, int flags,
309     cred_t *cred, caller_context_t *ctp)
310 {
311 	struct dcnode *dp = VTODC(vp);
312 	struct vnode *subvp = dp->dc_subvp;
313 	int error;
314 
315 	error = VOP_GETATTR(subvp, vap, flags, cred, ctp);
316 
317 	/* substitute uncompressed size */
318 	vap->va_size = dp->dc_hdr->ch_fsize;
319 	return (error);
320 }
321 
322 static int
323 dc_setattr(struct vnode *vp, struct vattr *vap, int flags, cred_t *cred,
324     caller_context_t *ctp)
325 {
326 	struct dcnode *dp = VTODC(vp);
327 	struct vnode *subvp = dp->dc_subvp;
328 
329 	return (VOP_SETATTR(subvp, vap, flags, cred, ctp));
330 }
331 
332 static int
333 dc_access(struct vnode *vp, int mode, int flags,
334     cred_t *cred, caller_context_t *ctp)
335 {
336 	struct dcnode *dp = VTODC(vp);
337 	struct vnode *subvp = dp->dc_subvp;
338 
339 	return (VOP_ACCESS(subvp, mode, flags, cred, ctp));
340 }
341 
342 /*ARGSUSED*/
343 static int
344 dc_fsync(vnode_t *vp, int syncflag, cred_t *cred, caller_context_t *ctp)
345 {
346 	return (0);
347 }
348 
349 /*ARGSUSED*/
350 static void
351 dc_inactive(struct vnode *vp, cred_t *cr, caller_context_t *ctp)
352 {
353 	struct dcnode *dp = VTODC(vp);
354 
355 	mutex_enter(&dctable_lock);
356 	mutex_enter(&vp->v_lock);
357 	ASSERT(vp->v_count >= 1);
358 	if (--vp->v_count != 0) {
359 		/*
360 		 * Somebody accessed the dcnode before we got a chance to
361 		 * remove it.  They will remove it when they do a vn_rele.
362 		 */
363 		mutex_exit(&vp->v_lock);
364 		mutex_exit(&dctable_lock);
365 		return;
366 	}
367 	mutex_exit(&vp->v_lock);
368 
369 	dcnode_free(dp);
370 
371 	mutex_exit(&dctable_lock);
372 }
373 
374 static int
375 dc_fid(struct vnode *vp, struct fid *fidp, caller_context_t *ctp)
376 {
377 	struct dcnode *dp = VTODC(vp);
378 	struct vnode *subvp = dp->dc_subvp;
379 
380 	return (VOP_FID(subvp, fidp, ctp));
381 }
382 
383 static int
384 dc_seek(struct vnode *vp, offset_t oof, offset_t *noffp, caller_context_t *ctp)
385 {
386 	struct dcnode *dp = VTODC(vp);
387 	struct vnode *subvp = dp->dc_subvp;
388 
389 	return (VOP_SEEK(subvp, oof, noffp, ctp));
390 }
391 
392 static int
393 dc_frlock(struct vnode *vp, int cmd, struct flock64 *bfp, int flag,
394     offset_t offset, struct flk_callback *flk_cbp,
395     cred_t *cr, caller_context_t *ctp)
396 {
397 	struct dcnode *dp = VTODC(vp);
398 	int error;
399 	struct vattr vattr;
400 
401 	/*
402 	 * If file is being mapped, disallow frlock.
403 	 */
404 	vattr.va_mask = AT_MODE;
405 	if (error = VOP_GETATTR(dp->dc_subvp, &vattr, 0, cr, ctp))
406 		return (error);
407 	if (dp->dc_mapcnt > 0 && MANDLOCK(vp, vattr.va_mode))
408 		return (EAGAIN);
409 
410 	return (fs_frlock(vp, cmd, bfp, flag, offset, flk_cbp, cr, ctp));
411 }
412 
413 /*ARGSUSED*/
414 static int
415 dc_getblock_miss(struct vnode *vp, offset_t off, size_t len, struct page **ppp,
416     struct seg *seg, caddr_t addr, enum seg_rw rw, struct cred *cr)
417 {
418 	struct dcnode *dp = VTODC(vp);
419 	struct comphdr *hdr = dp->dc_hdr;
420 	struct page *pp;
421 	struct buf *bp;
422 	caddr_t saddr;
423 	off_t cblkno;
424 	size_t rdoff, rdsize, dsize;
425 	long xlen;
426 	int error, zerr;
427 
428 	ASSERT(len == hdr->ch_blksize);
429 	/*
430 	 * Get destination pages and make them addressable
431 	 */
432 	pp = page_create_va(vp, off, len, PG_WAIT, seg, addr);
433 	bp = pageio_setup(pp, len, vp, B_READ);
434 	bp_mapin(bp);
435 
436 	/*
437 	 * read compressed data from subordinate vnode
438 	 */
439 	saddr = kmem_cache_alloc(dp->dc_bufcache, KM_SLEEP);
440 	cblkno = off / len;
441 	rdoff = hdr->ch_blkmap[cblkno];
442 	rdsize = hdr->ch_blkmap[cblkno + 1] - rdoff;
443 	error = vn_rdwr(UIO_READ, dp->dc_subvp, saddr, rdsize, rdoff,
444 	    UIO_SYSSPACE, 0, 0, cr, NULL);
445 	if (error)
446 		goto cleanup;
447 
448 	/*
449 	 * Uncompress
450 	 */
451 	dsize = len;
452 	zerr = z_uncompress(bp->b_un.b_addr, &dsize, saddr, dp->dc_zmax);
453 	if (zerr != Z_OK) {
454 		error = EIO;
455 		goto cleanup;
456 	}
457 
458 	/*
459 	 * Handle EOF
460 	 */
461 	xlen = hdr->ch_fsize - off;
462 	if (xlen < len) {
463 		bzero(bp->b_un.b_addr + xlen, len - xlen);
464 		if (dsize != xlen)
465 			error = EIO;
466 	} else if (dsize != len)
467 		error = EIO;
468 
469 	/*
470 	 * Clean up
471 	 */
472 cleanup:
473 	kmem_cache_free(dp->dc_bufcache, saddr);
474 	pageio_done(bp);
475 	*ppp = pp;
476 	return (error);
477 }
478 
479 static int
480 dc_getblock(struct vnode *vp, offset_t off, size_t len, struct page **ppp,
481     struct seg *seg, caddr_t addr, enum seg_rw rw, struct cred *cr)
482 {
483 	struct page *pp, *plist = NULL;
484 	offset_t pgoff;
485 	int rdblk;
486 
487 	/*
488 	 * pvn_read_kluster() doesn't quite do what we want, since it
489 	 * thinks sub block reads are ok.  Here we always decompress
490 	 * a full block.
491 	 */
492 
493 	/*
494 	 * Check page cache
495 	 */
496 	rdblk = 0;
497 	for (pgoff = off; pgoff < off + len; pgoff += PAGESIZE) {
498 		pp = page_lookup(vp, pgoff, SE_EXCL);
499 		if (pp == NULL) {
500 			rdblk = 1;
501 			break;
502 		}
503 		page_io_lock(pp);
504 		page_add(&plist, pp);
505 		plist = plist->p_next;
506 	}
507 	if (!rdblk) {
508 		*ppp = plist;
509 		return (0);	/* all pages in cache */
510 	}
511 
512 	/*
513 	 * Undo any locks so getblock_miss has an open field
514 	 */
515 	if (plist != NULL)
516 		pvn_io_done(plist);
517 
518 	return (dc_getblock_miss(vp, off, len, ppp, seg, addr, rw, cr));
519 }
520 
521 static int
522 dc_realvp(vnode_t *vp, vnode_t **vpp, caller_context_t *ct)
523 {
524 	struct vnode *rvp;
525 
526 	vp = VTODC(vp)->dc_subvp;
527 	if (VOP_REALVP(vp, &rvp, ct) == 0)
528 		vp = rvp;
529 	*vpp = vp;
530 	return (0);
531 }
532 
533 /*ARGSUSED10*/
534 static int
535 dc_getpage(struct vnode *vp, offset_t off, size_t len, uint_t *protp,
536     struct page *pl[], size_t plsz, struct seg *seg, caddr_t addr,
537     enum seg_rw rw, struct cred *cr, caller_context_t *ctp)
538 {
539 	struct dcnode *dp = VTODC(vp);
540 	struct comphdr *hdr = dp->dc_hdr;
541 	struct page *pp, *plist = NULL;
542 	caddr_t vp_baddr;
543 	offset_t vp_boff, vp_bend;
544 	size_t bsize = hdr->ch_blksize;
545 	int nblks, error;
546 
547 	/* does not support write */
548 	if (rw == S_WRITE) {
549 		panic("write attempt on compressed file");
550 		/*NOTREACHED*/
551 	}
552 
553 	if (protp)
554 		*protp = PROT_ALL;
555 	/*
556 	 * We don't support asynchronous operation at the moment, so
557 	 * just pretend we did it.  If the pages are ever actually
558 	 * needed, they'll get brought in then.
559 	 */
560 	if (pl == NULL)
561 		return (0);
562 
563 	/*
564 	 * Calc block start and end offsets
565 	 */
566 	vp_boff = rounddown(off, bsize);
567 	vp_bend = roundup(off + len, bsize);
568 	vp_baddr = (caddr_t)rounddown((uintptr_t)addr, bsize);
569 
570 	nblks = (vp_bend - vp_boff) / bsize;
571 	while (nblks--) {
572 		error = dc_getblock(vp, vp_boff, bsize, &pp, seg, vp_baddr,
573 		    rw, cr);
574 		page_list_concat(&plist, &pp);
575 		vp_boff += bsize;
576 		vp_baddr += bsize;
577 	}
578 	if (!error)
579 		pvn_plist_init(plist, pl, plsz, off, len, rw);
580 	else
581 		pvn_read_done(plist, B_ERROR);
582 	return (error);
583 }
584 
585 /*
586  * This function should never be called. We need to have it to pass
587  * it as an argument to other functions.
588  */
589 /*ARGSUSED*/
590 static int
591 dc_putapage(struct vnode *vp, struct page *pp, u_offset_t *offp, size_t *lenp,
592     int flags, struct cred *cr)
593 {
594 	/* should never happen */
595 	cmn_err(CE_PANIC, "dcfs: dc_putapage: dirty page");
596 	/*NOTREACHED*/
597 	return (0);
598 }
599 
600 
601 /*
602  * The only flags we support are B_INVAL, B_FREE and B_DONTNEED.
603  * B_INVAL is set by:
604  *
605  *	1) the MC_SYNC command of memcntl(2) to support the MS_INVALIDATE flag.
606  *	2) the MC_ADVISE command of memcntl(2) with the MADV_DONTNEED advice
607  *	   which translates to an MC_SYNC with the MS_INVALIDATE flag.
608  *
609  * The B_FREE (as well as the B_DONTNEED) flag is set when the
610  * MADV_SEQUENTIAL advice has been used. VOP_PUTPAGE is invoked
611  * from SEGVN to release pages behind a pagefault.
612  */
613 /*ARGSUSED5*/
614 static int
615 dc_putpage(struct vnode *vp, offset_t off, size_t len, int flags,
616     struct cred *cr, caller_context_t *ctp)
617 {
618 	int error = 0;
619 
620 	if (vp->v_count == 0) {
621 		panic("dcfs_putpage: bad v_count");
622 		/*NOTREACHED*/
623 	}
624 
625 	if (vp->v_flag & VNOMAP)
626 		return (ENOSYS);
627 
628 	if (!vn_has_cached_data(vp))	/* no pages mapped */
629 		return (0);
630 
631 	if (len == 0)		/* from 'off' to EOF */
632 		error = pvn_vplist_dirty(vp, off, dc_putapage, flags, cr);
633 	else {
634 		offset_t io_off;
635 		se_t se = (flags & (B_INVAL | B_FREE)) ? SE_EXCL : SE_SHARED;
636 
637 		for (io_off = off; io_off < off + len; io_off += PAGESIZE) {
638 			page_t *pp;
639 
640 			/*
641 			 * We insist on getting the page only if we are
642 			 * about to invalidate, free or write it and
643 			 * the B_ASYNC flag is not set.
644 			 */
645 			if ((flags & B_INVAL) || ((flags & B_ASYNC) == 0))
646 				pp = page_lookup(vp, io_off, se);
647 			else
648 				pp = page_lookup_nowait(vp, io_off, se);
649 
650 			if (pp == NULL)
651 				continue;
652 			/*
653 			 * Normally pvn_getdirty() should return 0, which
654 			 * impies that it has done the job for us.
655 			 * The shouldn't-happen scenario is when it returns 1.
656 			 * This means that the page has been modified and
657 			 * needs to be put back.
658 			 * Since we can't write to a dcfs compressed file,
659 			 * we fake a failed I/O and force pvn_write_done()
660 			 * to destroy the page.
661 			 */
662 			if (pvn_getdirty(pp, flags) == 1) {
663 				cmn_err(CE_NOTE, "dc_putpage: dirty page");
664 				pvn_write_done(pp, flags |
665 				    B_ERROR | B_WRITE | B_INVAL | B_FORCE);
666 			}
667 		}
668 	}
669 	return (error);
670 }
671 
672 static int
673 dc_map(struct vnode *vp, offset_t off, struct as *as, caddr_t *addrp,
674     size_t len, uchar_t prot, uchar_t maxprot, uint_t flags,
675     struct cred *cred, caller_context_t *ctp)
676 {
677 	struct vattr vattr;
678 	struct segvn_crargs vn_a;
679 	int error;
680 
681 	if (vp->v_flag & VNOMAP)
682 		return (ENOSYS);
683 
684 	if (off < (offset_t)0 || (offset_t)(off + len) < (offset_t)0)
685 		return (ENXIO);
686 
687 	/*
688 	 * If file is being locked, disallow mapping.
689 	 */
690 	if (error = VOP_GETATTR(VTODC(vp)->dc_subvp, &vattr, 0, cred, ctp))
691 		return (error);
692 	if (vn_has_mandatory_locks(vp, vattr.va_mode))
693 		return (EAGAIN);
694 
695 	as_rangelock(as);
696 
697 	if ((flags & MAP_FIXED) == 0) {
698 		map_addr(addrp, len, off, 1, flags);
699 		if (*addrp == NULL) {
700 			as_rangeunlock(as);
701 			return (ENOMEM);
702 		}
703 	} else {
704 		/*
705 		 * User specified address - blow away any previous mappings
706 		 */
707 		(void) as_unmap(as, *addrp, len);
708 	}
709 
710 	vn_a.vp = vp;
711 	vn_a.offset = off;
712 	vn_a.type = flags & MAP_TYPE;
713 	vn_a.prot = prot;
714 	vn_a.maxprot = maxprot;
715 	vn_a.flags = flags & ~MAP_TYPE;
716 	vn_a.cred = cred;
717 	vn_a.amp = NULL;
718 	vn_a.szc = 0;
719 	vn_a.lgrp_mem_policy_flags = 0;
720 
721 	error = as_map(as, *addrp, len, segvn_create, &vn_a);
722 	as_rangeunlock(as);
723 	return (error);
724 }
725 
726 /*ARGSUSED*/
727 static int
728 dc_addmap(struct vnode *vp, offset_t off, struct as *as, caddr_t addr,
729     size_t len, uchar_t prot, uchar_t maxprot, uint_t flags,
730     struct cred *cr, caller_context_t *ctp)
731 {
732 	struct dcnode *dp;
733 
734 	if (vp->v_flag & VNOMAP)
735 		return (ENOSYS);
736 
737 	dp = VTODC(vp);
738 	mutex_enter(&dp->dc_lock);
739 	dp->dc_mapcnt += btopr(len);
740 	mutex_exit(&dp->dc_lock);
741 	return (0);
742 }
743 
744 /*ARGSUSED*/
745 static int
746 dc_delmap(struct vnode *vp, offset_t off, struct as *as, caddr_t addr,
747     size_t len, uint_t prot, uint_t maxprot, uint_t flags,
748     struct cred *cr, caller_context_t *ctp)
749 {
750 	struct dcnode *dp;
751 
752 	if (vp->v_flag & VNOMAP)
753 		return (ENOSYS);
754 
755 	dp = VTODC(vp);
756 	mutex_enter(&dp->dc_lock);
757 	dp->dc_mapcnt -= btopr(len);
758 	ASSERT(dp->dc_mapcnt >= 0);
759 	mutex_exit(&dp->dc_lock);
760 	return (0);
761 }
762 
763 /*
764  * Constructor/destructor routines for dcnodes
765  */
766 /*ARGSUSED1*/
767 static int
768 dcnode_constructor(void *buf, void *cdrarg, int kmflags)
769 {
770 	struct dcnode *dp = buf;
771 	struct vnode *vp;
772 
773 	vp = dp->dc_vp = vn_alloc(kmflags);
774 	if (vp == NULL) {
775 		return (-1);
776 	}
777 	vp->v_data = dp;
778 	vp->v_type = VREG;
779 	vp->v_flag = VNOSWAP;
780 	vp->v_vfsp = &dc_vfs;
781 	vn_setops(vp, dc_vnodeops);
782 	vn_exists(vp);
783 
784 	mutex_init(&dp->dc_lock, NULL, MUTEX_DEFAULT, NULL);
785 	dp->dc_mapcnt = 0;
786 	dp->dc_lrunext = dp->dc_lruprev = NULL;
787 	dp->dc_hdr = NULL;
788 	dp->dc_subvp = NULL;
789 	return (0);
790 }
791 
792 /*ARGSUSED*/
793 static void
794 dcnode_destructor(void *buf, void *cdrarg)
795 {
796 	struct dcnode *dp = buf;
797 	struct vnode *vp = DCTOV(dp);
798 
799 	mutex_destroy(&dp->dc_lock);
800 
801 	VERIFY(dp->dc_hdr == NULL);
802 	VERIFY(dp->dc_subvp == NULL);
803 	vn_invalid(vp);
804 	vn_free(vp);
805 }
806 
807 static struct dcnode *
808 dcnode_alloc(void)
809 {
810 	struct dcnode *dp;
811 
812 	/*
813 	 * If the free list is above DCLRUSIZE
814 	 * re-use one from it
815 	 */
816 	mutex_enter(&dctable_lock);
817 	if (dclru_len < DCLRUSIZE) {
818 		mutex_exit(&dctable_lock);
819 		dp = kmem_cache_alloc(dcnode_cache, KM_SLEEP);
820 	} else {
821 		ASSERT(dclru != NULL);
822 		dp = dclru;
823 		dclru_sub(dp);
824 		dcdelete(dp);
825 		mutex_exit(&dctable_lock);
826 		dcnode_recycle(dp);
827 	}
828 	return (dp);
829 }
830 
831 static void
832 dcnode_free(struct dcnode *dp)
833 {
834 	struct vnode *vp = DCTOV(dp);
835 
836 	ASSERT(MUTEX_HELD(&dctable_lock));
837 
838 	/*
839 	 * If no cached pages, no need to put it on lru
840 	 */
841 	if (!vn_has_cached_data(vp)) {
842 		dcdelete(dp);
843 		dcnode_recycle(dp);
844 		kmem_cache_free(dcnode_cache, dp);
845 		return;
846 	}
847 
848 	/*
849 	 * Add to lru, if it's over the limit, free from head
850 	 */
851 	dclru_add(dp);
852 	if (dclru_len > DCLRUSIZE) {
853 		dp = dclru;
854 		dclru_sub(dp);
855 		dcdelete(dp);
856 		dcnode_recycle(dp);
857 		kmem_cache_free(dcnode_cache, dp);
858 	}
859 }
860 
861 static void
862 dcnode_recycle(struct dcnode *dp)
863 {
864 	struct vnode *vp;
865 
866 	vp = DCTOV(dp);
867 
868 	VN_RELE(dp->dc_subvp);
869 	dp->dc_subvp = NULL;
870 	(void) pvn_vplist_dirty(vp, 0, dc_putapage, B_INVAL, NULL);
871 	kmem_free(dp->dc_hdr, dp->dc_hdrsize);
872 	dp->dc_hdr = NULL;
873 	dp->dc_hdrsize = dp->dc_zmax = 0;
874 	dp->dc_bufcache = NULL;
875 	dp->dc_mapcnt = 0;
876 	vn_reinit(vp);
877 	vp->v_type = VREG;
878 	vp->v_flag = VNOSWAP;
879 	vp->v_vfsp = &dc_vfs;
880 }
881 
882 static int
883 dcinit(int fstype, char *name)
884 {
885 	static const fs_operation_def_t dc_vfsops_template[] = {
886 		NULL, NULL
887 	};
888 	int error;
889 	major_t dev;
890 
891 	error = vfs_setfsops(fstype, dc_vfsops_template, &dc_vfsops);
892 	if (error) {
893 		cmn_err(CE_WARN, "dcinit: bad vfs ops template");
894 		return (error);
895 	}
896 	VFS_INIT(&dc_vfs, dc_vfsops, NULL);
897 	dc_vfs.vfs_flag = VFS_RDONLY;
898 	dc_vfs.vfs_fstype = fstype;
899 	if ((dev = getudev()) == (major_t)-1)
900 		dev = 0;
901 	dcdev = makedevice(dev, 0);
902 	dc_vfs.vfs_dev = dcdev;
903 
904 	error = vn_make_ops(name, dc_vnodeops_template, &dc_vnodeops);
905 	if (error != 0) {
906 		(void) vfs_freevfsops_by_type(fstype);
907 		cmn_err(CE_WARN, "dcinit: bad vnode ops template");
908 		return (error);
909 	}
910 
911 	mutex_init(&dctable_lock, NULL, MUTEX_DEFAULT, NULL);
912 	mutex_init(&dccache_lock, NULL, MUTEX_DEFAULT, NULL);
913 	dcnode_cache = kmem_cache_create("dcnode_cache", sizeof (struct dcnode),
914 	    0, dcnode_constructor, dcnode_destructor, NULL, NULL, NULL, 0);
915 
916 	return (0);
917 }
918 
919 /*
920  * Return shadow vnode with the given vp as its subordinate
921  */
922 struct vnode *
923 decompvp(struct vnode *vp, cred_t *cred, caller_context_t *ctp)
924 {
925 	struct dcnode *dp, *ndp;
926 	struct comphdr thdr, *hdr;
927 	struct kmem_cache **cpp;
928 	struct vattr vattr;
929 	size_t hdrsize, bsize;
930 	int error;
931 
932 	/*
933 	 * See if we have an existing shadow
934 	 * If none, we have to manufacture one
935 	 */
936 	mutex_enter(&dctable_lock);
937 	dp = dcfind(vp);
938 	mutex_exit(&dctable_lock);
939 	if (dp != NULL)
940 		return (DCTOV(dp));
941 
942 	/*
943 	 * Make sure it's a valid compressed file
944 	 */
945 	hdr = &thdr;
946 	error = vn_rdwr(UIO_READ, vp, (caddr_t)hdr, sizeof (struct comphdr), 0,
947 	    UIO_SYSSPACE, 0, 0, cred, NULL);
948 	if (error || hdr->ch_magic != CH_MAGIC_ZLIB ||
949 	    hdr->ch_version != CH_VERSION || hdr->ch_algorithm != CH_ALG_ZLIB ||
950 	    hdr->ch_fsize == 0 || hdr->ch_blksize < PAGESIZE ||
951 	    hdr->ch_blksize > ptob(DCCACHESIZE) ||
952 	    (hdr->ch_blksize & (hdr->ch_blksize - 1)) != 0)
953 		return (NULL);
954 
955 	/* get underlying file size */
956 	if (VOP_GETATTR(vp, &vattr, 0, cred, ctp) != 0)
957 		return (NULL);
958 
959 	/*
960 	 * Re-read entire header
961 	 */
962 	hdrsize = hdr->ch_blkmap[0] + sizeof (uint64_t);
963 	hdr = kmem_alloc(hdrsize, KM_SLEEP);
964 	error = vn_rdwr(UIO_READ, vp, (caddr_t)hdr, hdrsize, 0, UIO_SYSSPACE,
965 	    0, 0, cred, NULL);
966 	if (error) {
967 		kmem_free(hdr, hdrsize);
968 		return (NULL);
969 	}
970 
971 	/*
972 	 * add extra blkmap entry to make dc_getblock()'s
973 	 * life easier
974 	 */
975 	bsize = hdr->ch_blksize;
976 	hdr->ch_blkmap[((hdr->ch_fsize-1) / bsize) + 1] = vattr.va_size;
977 
978 	ndp = dcnode_alloc();
979 	ndp->dc_subvp = vp;
980 	VN_HOLD(vp);
981 	ndp->dc_hdr = hdr;
982 	ndp->dc_hdrsize = hdrsize;
983 
984 	/*
985 	 * Allocate kmem cache if none there already
986 	 */
987 	ndp->dc_zmax = ZMAXBUF(bsize);
988 	cpp = &dcbuf_cache[btop(bsize)];
989 	mutex_enter(&dccache_lock);
990 	if (*cpp == NULL)
991 		*cpp = kmem_cache_create("dcbuf_cache", ndp->dc_zmax, 0, NULL,
992 		    NULL, NULL, NULL, NULL, 0);
993 	mutex_exit(&dccache_lock);
994 	ndp->dc_bufcache = *cpp;
995 
996 	/*
997 	 * Recheck table in case someone else created shadow
998 	 * while we were blocked above.
999 	 */
1000 	mutex_enter(&dctable_lock);
1001 	dp = dcfind(vp);
1002 	if (dp != NULL) {
1003 		mutex_exit(&dctable_lock);
1004 		dcnode_recycle(ndp);
1005 		kmem_cache_free(dcnode_cache, ndp);
1006 		return (DCTOV(dp));
1007 	}
1008 	dcinsert(ndp);
1009 	mutex_exit(&dctable_lock);
1010 
1011 	return (DCTOV(ndp));
1012 }
1013 
1014 
1015 /*
1016  * dcnode lookup table
1017  * These routines maintain a table of dcnodes hashed by their
1018  * subordinate vnode so that they can be found if they already
1019  * exist in the vnode cache
1020  */
1021 
1022 /*
1023  * Put a dcnode in the table.
1024  */
1025 static void
1026 dcinsert(struct dcnode *newdp)
1027 {
1028 	int idx = DCHASH(newdp->dc_subvp);
1029 
1030 	ASSERT(MUTEX_HELD(&dctable_lock));
1031 	newdp->dc_hash = dctable[idx];
1032 	dctable[idx] = newdp;
1033 }
1034 
1035 /*
1036  * Remove a dcnode from the hash table.
1037  */
1038 void
1039 dcdelete(struct dcnode *deldp)
1040 {
1041 	int idx = DCHASH(deldp->dc_subvp);
1042 	struct dcnode *dp, *prevdp;
1043 
1044 	ASSERT(MUTEX_HELD(&dctable_lock));
1045 	dp = dctable[idx];
1046 	if (dp == deldp)
1047 		dctable[idx] = dp->dc_hash;
1048 	else {
1049 		for (prevdp = dp, dp = dp->dc_hash; dp != NULL;
1050 		    prevdp = dp, dp = dp->dc_hash) {
1051 			if (dp == deldp) {
1052 				prevdp->dc_hash = dp->dc_hash;
1053 				break;
1054 			}
1055 		}
1056 	}
1057 	ASSERT(dp != NULL);
1058 }
1059 
1060 /*
1061  * Find a shadow vnode in the dctable hash list.
1062  */
1063 static struct dcnode *
1064 dcfind(struct vnode *vp)
1065 {
1066 	struct dcnode *dp;
1067 
1068 	ASSERT(MUTEX_HELD(&dctable_lock));
1069 	for (dp = dctable[DCHASH(vp)]; dp != NULL; dp = dp->dc_hash)
1070 		if (dp->dc_subvp == vp) {
1071 			VN_HOLD(DCTOV(dp));
1072 			if (dp->dc_lrunext)
1073 				dclru_sub(dp);
1074 			return (dp);
1075 		}
1076 	return (NULL);
1077 }
1078 
1079 #ifdef	DEBUG
1080 static int
1081 dclru_count(void)
1082 {
1083 	struct dcnode *dp;
1084 	int i = 0;
1085 
1086 	if (dclru == NULL)
1087 		return (0);
1088 	for (dp = dclru; dp->dc_lrunext != dclru; dp = dp->dc_lrunext)
1089 		i++;
1090 	return (i + 1);
1091 }
1092 #endif
1093 
1094 static void
1095 dclru_add(struct dcnode *dp)
1096 {
1097 	/*
1098 	 * Add to dclru as double-link chain
1099 	 */
1100 	ASSERT(MUTEX_HELD(&dctable_lock));
1101 	if (dclru == NULL) {
1102 		dclru = dp;
1103 		dp->dc_lruprev = dp->dc_lrunext = dp;
1104 	} else {
1105 		struct dcnode *last = dclru->dc_lruprev;
1106 
1107 		dclru->dc_lruprev = dp;
1108 		last->dc_lrunext = dp;
1109 		dp->dc_lruprev = last;
1110 		dp->dc_lrunext = dclru;
1111 	}
1112 	dclru_len++;
1113 	ASSERT(dclru_len == dclru_count());
1114 }
1115 
1116 static void
1117 dclru_sub(struct dcnode *dp)
1118 {
1119 	ASSERT(MUTEX_HELD(&dctable_lock));
1120 	dp->dc_lrunext->dc_lruprev = dp->dc_lruprev;
1121 	dp->dc_lruprev->dc_lrunext = dp->dc_lrunext;
1122 	if (dp == dclru)
1123 		dclru = dp->dc_lrunext == dp ? NULL : dp->dc_lrunext;
1124 	dp->dc_lrunext = dp->dc_lruprev = NULL;
1125 	dclru_len--;
1126 	ASSERT(dclru_len == dclru_count());
1127 }
1128