xref: /titanic_41/usr/src/uts/common/fs/ufs/ufs_snap.c (revision 7c478bd95313f5f23a4c958a745db2134aa03244)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License, Version 1.0 only
6  * (the "License").  You may not use this file except in compliance
7  * 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 2004 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 #pragma ident	"%Z%%M%	%I%	%E% SMI"
28 
29 #include <sys/systm.h>
30 #include <sys/types.h>
31 #include <sys/vnode.h>
32 #include <sys/file.h>
33 #include <sys/buf.h>
34 #include <sys/ddi.h>
35 #include <sys/errno.h>
36 #include <sys/cmn_err.h>
37 #include <sys/fs/ufs_inode.h>
38 #include <sys/fs/ufs_filio.h>
39 #include <sys/fs/ufs_snap.h>
40 #include <sys/fssnap_if.h>
41 #include <sys/sysmacros.h>
42 #include <sys/modctl.h>
43 #include <sys/fs/ufs_bio.h>
44 #include <sys/debug.h>
45 #include <sys/kmem.h>
46 #include <sys/inttypes.h>
47 #include <sys/vfs.h>
48 #include <sys/disp.h>
49 #include <sys/atomic.h>
50 #include <sys/conf.h>
51 #include <sys/param.h>
52 #include <sys/policy.h>
53 
54 static int ufs_snap_init_backfile(int  *, int, vnode_t ***, struct ufsvfs *);
55 static void release_backing_vnodes(vnode_t ***, int);
56 static int ufs_snap_find_candidates(void *, struct ufsvfs *, int);
57 
58 /*
59  * Create a snapshot on a file system
60  */
61 int
ufs_snap_create(struct vnode * vp,struct fiosnapcreate_multi * fiosnapp,cred_t * cr)62 ufs_snap_create(struct vnode *vp, struct fiosnapcreate_multi *fiosnapp,
63     cred_t *cr)
64 {
65 	int		error = 0;
66 	struct ufsvfs	*ufsvfsp = VTOI(vp)->i_ufsvfs;
67 	struct fs	*fs = ufsvfsp->vfs_fs;
68 	vnode_t		**bfvpp = NULL;
69 	struct lockfs	lf;
70 	void		*snapid = NULL;
71 
72 	u_offset_t	nchunks;
73 	uint_t		chunksize, fragsperchunk;
74 
75 	/*
76 	 * Only privilege processes can create a snapshot for now.  This
77 	 * would be better if it was based on the permissions of the device
78 	 * file.
79 	 */
80 	if (secpolicy_fs_config(cr, ufsvfsp->vfs_vfs) != 0)
81 		return (EPERM);
82 
83 	/*
84 	 * There is no reason to make a snapshot of a read-only file system
85 	 */
86 	if (fs->fs_ronly) {
87 		fiosnapp->error = FIOCOW_EREADONLY;
88 		return (EROFS);
89 	}
90 
91 	/*
92 	 * Initialize the backing files to store old data.  This assumes any
93 	 * preallocation and setup has been done already.
94 	 * ufs_snap_init_backfile() allocates and returns a pointer to
95 	 * a null-terminated array of vnodes in bfvpp.
96 	 */
97 	error = ufs_snap_init_backfile(fiosnapp->backfiledesc,
98 	    fiosnapp->backfilecount, &bfvpp, ufsvfsp);
99 	if (error) {
100 		fiosnapp->error = FIOCOW_EBACKFILE;
101 		return (error);
102 	}
103 
104 	/*
105 	 * File system must be write locked to prevent updates while
106 	 * the snapshot is being established.
107 	 */
108 	if ((error = ufs_fiolfss(vp, &lf)) != 0) {
109 		release_backing_vnodes(&bfvpp, fiosnapp->backfilecount);
110 		return (error);
111 	}
112 
113 	if (!LOCKFS_IS_ULOCK(&lf)) {
114 		release_backing_vnodes(&bfvpp, fiosnapp->backfilecount);
115 		fiosnapp->error = FIOCOW_EULOCK;
116 		return (EINVAL);
117 	}
118 
119 	lf.lf_lock = LOCKFS_WLOCK;
120 	lf.lf_flags = 0;
121 	lf.lf_comment = NULL;
122 	if ((error = ufs_fiolfs(vp, &lf, 1)) != 0) {
123 		release_backing_vnodes(&bfvpp, fiosnapp->backfilecount);
124 		fiosnapp->error = FIOCOW_EWLOCK;
125 		return (EINVAL);
126 	}
127 
128 	/*
129 	 * File system must be fairly consistent to enable snapshots
130 	 */
131 	if (fs->fs_clean != FSACTIVE &&
132 	    fs->fs_clean != FSSTABLE &&
133 	    fs->fs_clean != FSCLEAN &&
134 	    fs->fs_clean != FSLOG) {
135 		fiosnapp->error = FIOCOW_ECLEAN;
136 		error = EINVAL;
137 		goto unlockout;
138 	}
139 
140 	/*
141 	 * Only one snapshot is allowed per file system, so error if
142 	 * a snapshot is already enabled.
143 	 */
144 	if (ufsvfsp->vfs_snapshot) {
145 		fiosnapp->error = FIOCOW_EBUSY;
146 		error = EBUSY;
147 		goto unlockout;
148 	}
149 
150 	/* Tell bio.c how to call our strategy routine.  XXX ugly hack */
151 	if (bio_snapshot_strategy == NULL)
152 		bio_snapshot_strategy =
153 		    (void (*) (void *, buf_t *))fssnap_strategy;
154 
155 	/*
156 	 * use chunk size that is passed in, or the file system
157 	 * block size if it is zero.  For most cases, the file system
158 	 * block size will be reasonably efficient.  A larger
159 	 * chunksize uses less memory but may potentially induce more
160 	 * I/O copying the larger chunks aside.
161 	 */
162 	if (fiosnapp->chunksize != 0)
163 		chunksize = fiosnapp->chunksize;
164 	else
165 		chunksize = fs->fs_bsize * 4;
166 
167 
168 	/*
169 	 * compute the number of chunks in this whole file system.  Since
170 	 * the UFS allocation bitmaps are in units of fragments, we first
171 	 * compute the number of fragments per chunk.  Things work out
172 	 * nicer if the chunk size is a power-of-two multiple of the
173 	 * fragment size.
174 	 */
175 	if ((chunksize < fs->fs_fsize) || (chunksize % fs->fs_fsize != 0)) {
176 		fiosnapp->error = FIOCOW_ECHUNKSZ;
177 		error = EINVAL;
178 		goto unlockout;
179 	}
180 	fragsperchunk = chunksize >> fs->fs_fshift;
181 	nchunks = (fs->fs_size + fragsperchunk) / fragsperchunk;
182 
183 	/*
184 	 * Create and initialize snapshot state and allocate/initialize
185 	 * translation table.  This does the real work of taking the snapshot.
186 	 */
187 	snapid = fssnap_create(nchunks, chunksize, fiosnapp->maxsize, vp,
188 	    fiosnapp->backfilecount, bfvpp, fiosnapp->backfilename,
189 	    fiosnapp->backfilesize);
190 	if (snapid == NULL) {
191 		fiosnapp->error = FIOCOW_ECREATE;
192 		error = EINVAL;
193 		goto unlockout;
194 	}
195 
196 	error = ufs_snap_find_candidates(snapid, ufsvfsp, chunksize);
197 	fiosnapp->snapshotnumber = fssnap_create_done(snapid);
198 
199 	if (error) {
200 		cmn_err(CE_WARN, "ufs_snap_create: failed scanning bitmaps, "
201 		    "error = %d.", error);
202 		fiosnapp->error = FIOCOW_EBITMAP;
203 		goto unlockout;
204 	}
205 
206 	ufsvfsp->vfs_snapshot = snapid;
207 
208 unlockout:
209 	/*
210 	 * Unlock the file system
211 	 */
212 	lf.lf_lock = LOCKFS_ULOCK;
213 	lf.lf_flags = 0;
214 	if ((ufs_fiolfs(vp, &lf, 1) != 0) && !error) {
215 		fiosnapp->error = FIOCOW_ENOULOCK;
216 		error = EINVAL;
217 	} else {
218 		fiosnapp->error = 0;
219 	}
220 
221 	/* clean up the snapshot if an error occurred. */
222 	if (error && snapid != NULL)
223 		(void) fssnap_delete(&snapid);
224 	else if (error && bfvpp != NULL)
225 		release_backing_vnodes(&bfvpp, fiosnapp->backfilecount);
226 
227 	return (error);
228 }
229 
230 static int
ufs_snap_init_backfile(int * filedesc,int count,vnode_t *** vppp,struct ufsvfs * ufsvfsp)231 ufs_snap_init_backfile(int *filedesc, int count, vnode_t ***vppp,
232     struct ufsvfs *ufsvfsp)
233 {
234 	file_t *fp;
235 	vnode_t **vpp;
236 	int i;
237 
238 	vpp = (vnode_t **)kmem_zalloc((count  + 1) * sizeof (vnode_t *),
239 	    KM_SLEEP);
240 	*vppp = vpp;
241 	for (i = 0; i < count; i++) {
242 		if ((fp = getf(*filedesc)) == NULL) {
243 			release_backing_vnodes(vppp, count);
244 			*vppp = NULL;
245 			return (EBADF);
246 		}
247 
248 		ASSERT(fp->f_vnode != NULL);
249 		VN_HOLD(fp->f_vnode);
250 
251 		*vpp = fp->f_vnode;
252 		releasef(*filedesc);
253 		filedesc++;
254 
255 		/* make sure the backing file is on a different file system */
256 		if ((*vpp)->v_vfsp == ufsvfsp->vfs_vfs) {
257 			release_backing_vnodes(vppp, count);
258 			*vppp = NULL;
259 			return (EINVAL);
260 		}
261 		vpp++;
262 	}
263 	return (0);
264 }
265 
266 static void
release_backing_vnodes(vnode_t *** bvppp,int count)267 release_backing_vnodes(vnode_t ***bvppp, int count)
268 {
269 	vnode_t **vpp;
270 
271 	vpp = *bvppp;
272 	while (*vpp) {
273 		VN_RELE(*vpp);
274 		*vpp++ = NULL;
275 	}
276 	kmem_free(*bvppp, (count + 1) * sizeof (vnode_t *));
277 	*bvppp = NULL;
278 }
279 
280 static int
ufs_snap_find_candidates(void * snapid,struct ufsvfs * ufsvfsp,int chunksize)281 ufs_snap_find_candidates(void *snapid, struct ufsvfs *ufsvfsp, int chunksize)
282 {
283 	struct fs	*fs = ufsvfsp->vfs_fs;
284 	struct buf	*cgbp;	/* cylinder group buffer */
285 	struct cg	*cgp;	/* cylinder group data */
286 	ulong_t		cg;
287 	ulong_t		cgbase;
288 	ulong_t		chunk;
289 	uchar_t		*blksfree;
290 
291 	ulong_t		curfrag;
292 	int		error = 0;
293 
294 	/*
295 	 * read through each ufs cylinder group and fetch the fragment
296 	 * allocation bitmap.  UFS indicates a fragment is allocated by
297 	 * a zero bit (not a one bit) in the fragment offset.
298 	 */
299 	cgbase = 0LL;
300 	for (cg = 0; cg < fs->fs_ncg; cg++) {
301 		/* read the cylinder group in */
302 		cgbp = BREAD(ufsvfsp->vfs_dev,
303 		    (daddr_t)fsbtodb(fs, cgtod(fs, cg)), (int)fs->fs_cgsize);
304 		if ((error = geterror(cgbp)) != 0) {
305 			brelse(cgbp);
306 			goto errout;
307 		}
308 		cgp = cgbp->b_un.b_cg;
309 
310 		/* check the magic number */
311 		if (cgp->cg_magic != CG_MAGIC) {
312 			cmn_err(CE_WARN, "ufs_snap_find_candidates: cg %lu "
313 			    "magic number (0x%x) does not match expected "
314 			    "magic number (0x%x)", cg, cgp->cg_magic, CG_MAGIC);
315 			error = EIO;
316 			goto errout;
317 		}
318 
319 		blksfree = cg_blksfree(cgp);
320 
321 		/*
322 		 * go through the allocation bitmap and set the
323 		 * corresponding bit in the candidate map.
324 		 */
325 		for (curfrag = 0; curfrag < cgp->cg_ndblk; curfrag++) {
326 			if (isclr(blksfree, curfrag)) {
327 				/*
328 				 * this assumes chunksize is a multiple of
329 				 * the fragment size
330 				 */
331 				chunk = (ulong_t)((cgbase + curfrag) /
332 				    (chunksize >> fs->fs_fshift));
333 
334 				fssnap_set_candidate(snapid, chunk);
335 				/*
336 				 * no need to scan the rest of this chunk since
337 				 * it is already marked, so skip to the next
338 				 */
339 				curfrag += ((chunksize >> fs->fs_fshift) -
340 				    ((cgbase + curfrag) %
341 				    (chunksize >> fs->fs_fshift))) - 1;
342 			}
343 		}
344 
345 		cgbase += cgp->cg_ndblk;
346 		ASSERT(cgbase <= fs->fs_size);
347 		brelse(cgbp);
348 	} /* cylinder group loop */
349 
350 	ASSERT(cgbase == fs->fs_size);
351 
352 errout:
353 	return (error);
354 }
355 
356 
357 int
ufs_snap_delete(struct vnode * vp,struct fiosnapdelete * fiosnapp,cred_t * cr)358 ufs_snap_delete(struct vnode *vp, struct fiosnapdelete *fiosnapp, cred_t *cr)
359 {
360 	struct ufsvfs	*ufsvfsp = VTOI(vp)->i_ufsvfs;
361 	struct fs	*fs = ufsvfsp->vfs_fs;
362 
363 	/*
364 	 * Initialize fields in the user's buffer
365 	 */
366 	fiosnapp->error = 0;
367 
368 	/*
369 	 * No snapshot exists, we're done.
370 	 */
371 	if (ufsvfsp->vfs_snapshot == NULL)
372 		return (ENOENT);
373 
374 	/*
375 	 * must have sufficient privileges.
376 	 */
377 	if (secpolicy_fs_config(cr, ufsvfsp->vfs_vfs) != 0)
378 		return (EPERM);
379 
380 	/*
381 	 * Readonly file system
382 	 */
383 	if (fs->fs_ronly) {
384 		fiosnapp->error = FIOCOW_EREADONLY;
385 		return (EROFS);
386 	}
387 
388 	/* free the data structures and clear the vfs_snapshot field. */
389 	fiosnapp->snapshotnumber = fssnap_delete(&ufsvfsp->vfs_snapshot);
390 
391 	if (fiosnapp->snapshotnumber == -1)
392 		return (EINVAL);
393 
394 	return (0);
395 }
396