xref: /illumos-kvm-cmd/block/qcow2-cluster.c (revision 68396ea9)
1 /*
2  * Block driver for the QCOW version 2 format
3  *
4  * Copyright (c) 2004-2006 Fabrice Bellard
5  *
6  * Permission is hereby granted, free of charge, to any person obtaining a copy
7  * of this software and associated documentation files (the "Software"), to deal
8  * in the Software without restriction, including without limitation the rights
9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10  * copies of the Software, and to permit persons to whom the Software is
11  * furnished to do so, subject to the following conditions:
12  *
13  * The above copyright notice and this permission notice shall be included in
14  * all copies or substantial portions of the Software.
15  *
16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22  * THE SOFTWARE.
23  */
24 
25 #include <zlib.h>
26 
27 #include "qemu-common.h"
28 #include "block_int.h"
29 #include "block/qcow2.h"
30 
qcow2_grow_l1_table(BlockDriverState * bs,int min_size,bool exact_size)31 int qcow2_grow_l1_table(BlockDriverState *bs, int min_size, bool exact_size)
32 {
33     BDRVQcowState *s = bs->opaque;
34     int new_l1_size, new_l1_size2, ret, i;
35     uint64_t *new_l1_table;
36     int64_t new_l1_table_offset;
37     uint8_t data[12];
38 
39     if (min_size <= s->l1_size)
40         return 0;
41 
42     if (exact_size) {
43         new_l1_size = min_size;
44     } else {
45         /* Bump size up to reduce the number of times we have to grow */
46         new_l1_size = s->l1_size;
47         if (new_l1_size == 0) {
48             new_l1_size = 1;
49         }
50         while (min_size > new_l1_size) {
51             new_l1_size = (new_l1_size * 3 + 1) / 2;
52         }
53     }
54 
55 #ifdef DEBUG_ALLOC2
56     printf("grow l1_table from %d to %d\n", s->l1_size, new_l1_size);
57 #endif
58 
59     new_l1_size2 = sizeof(uint64_t) * new_l1_size;
60     new_l1_table = qemu_mallocz(align_offset(new_l1_size2, 512));
61     memcpy(new_l1_table, s->l1_table, s->l1_size * sizeof(uint64_t));
62 
63     /* write new table (align to cluster) */
64     BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ALLOC_TABLE);
65     new_l1_table_offset = qcow2_alloc_clusters(bs, new_l1_size2);
66     if (new_l1_table_offset < 0) {
67         qemu_free(new_l1_table);
68         return new_l1_table_offset;
69     }
70 
71     ret = qcow2_cache_flush(bs, s->refcount_block_cache);
72     if (ret < 0) {
73         return ret;
74     }
75 
76     BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_WRITE_TABLE);
77     for(i = 0; i < s->l1_size; i++)
78         new_l1_table[i] = cpu_to_be64(new_l1_table[i]);
79     ret = bdrv_pwrite_sync(bs->file, new_l1_table_offset, new_l1_table, new_l1_size2);
80     if (ret < 0)
81         goto fail;
82     for(i = 0; i < s->l1_size; i++)
83         new_l1_table[i] = be64_to_cpu(new_l1_table[i]);
84 
85     /* set new table */
86     BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ACTIVATE_TABLE);
87     cpu_to_be32w((uint32_t*)data, new_l1_size);
88     cpu_to_be64wu((uint64_t*)(data + 4), new_l1_table_offset);
89     ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, l1_size), data,sizeof(data));
90     if (ret < 0) {
91         goto fail;
92     }
93     qemu_free(s->l1_table);
94     qcow2_free_clusters(bs, s->l1_table_offset, s->l1_size * sizeof(uint64_t));
95     s->l1_table_offset = new_l1_table_offset;
96     s->l1_table = new_l1_table;
97     s->l1_size = new_l1_size;
98     return 0;
99  fail:
100     qemu_free(new_l1_table);
101     qcow2_free_clusters(bs, new_l1_table_offset, new_l1_size2);
102     return ret;
103 }
104 
105 /*
106  * l2_load
107  *
108  * Loads a L2 table into memory. If the table is in the cache, the cache
109  * is used; otherwise the L2 table is loaded from the image file.
110  *
111  * Returns a pointer to the L2 table on success, or NULL if the read from
112  * the image file failed.
113  */
114 
l2_load(BlockDriverState * bs,uint64_t l2_offset,uint64_t ** l2_table)115 static int l2_load(BlockDriverState *bs, uint64_t l2_offset,
116     uint64_t **l2_table)
117 {
118     BDRVQcowState *s = bs->opaque;
119     int ret;
120 
121     ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset, (void**) l2_table);
122 
123     return ret;
124 }
125 
126 /*
127  * Writes one sector of the L1 table to the disk (can't update single entries
128  * and we really don't want bdrv_pread to perform a read-modify-write)
129  */
130 #define L1_ENTRIES_PER_SECTOR (512 / 8)
write_l1_entry(BlockDriverState * bs,int l1_index)131 static int write_l1_entry(BlockDriverState *bs, int l1_index)
132 {
133     BDRVQcowState *s = bs->opaque;
134     uint64_t buf[L1_ENTRIES_PER_SECTOR];
135     int l1_start_index;
136     int i, ret;
137 
138     l1_start_index = l1_index & ~(L1_ENTRIES_PER_SECTOR - 1);
139     for (i = 0; i < L1_ENTRIES_PER_SECTOR; i++) {
140         buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]);
141     }
142 
143     BLKDBG_EVENT(bs->file, BLKDBG_L1_UPDATE);
144     ret = bdrv_pwrite_sync(bs->file, s->l1_table_offset + 8 * l1_start_index,
145         buf, sizeof(buf));
146     if (ret < 0) {
147         return ret;
148     }
149 
150     return 0;
151 }
152 
153 /*
154  * l2_allocate
155  *
156  * Allocate a new l2 entry in the file. If l1_index points to an already
157  * used entry in the L2 table (i.e. we are doing a copy on write for the L2
158  * table) copy the contents of the old L2 table into the newly allocated one.
159  * Otherwise the new table is initialized with zeros.
160  *
161  */
162 
l2_allocate(BlockDriverState * bs,int l1_index,uint64_t ** table)163 static int l2_allocate(BlockDriverState *bs, int l1_index, uint64_t **table)
164 {
165     BDRVQcowState *s = bs->opaque;
166     uint64_t old_l2_offset;
167     uint64_t *l2_table;
168     int64_t l2_offset;
169     int ret;
170 
171     old_l2_offset = s->l1_table[l1_index];
172 
173     /* allocate a new l2 entry */
174 
175     l2_offset = qcow2_alloc_clusters(bs, s->l2_size * sizeof(uint64_t));
176     if (l2_offset < 0) {
177         return l2_offset;
178     }
179 
180     ret = qcow2_cache_flush(bs, s->refcount_block_cache);
181     if (ret < 0) {
182         goto fail;
183     }
184 
185     /* allocate a new entry in the l2 cache */
186 
187     ret = qcow2_cache_get_empty(bs, s->l2_table_cache, l2_offset, (void**) table);
188     if (ret < 0) {
189         return ret;
190     }
191 
192     l2_table = *table;
193 
194     if (old_l2_offset == 0) {
195         /* if there was no old l2 table, clear the new table */
196         memset(l2_table, 0, s->l2_size * sizeof(uint64_t));
197     } else {
198         uint64_t* old_table;
199 
200         /* if there was an old l2 table, read it from the disk */
201         BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_COW_READ);
202         ret = qcow2_cache_get(bs, s->l2_table_cache, old_l2_offset,
203             (void**) &old_table);
204         if (ret < 0) {
205             goto fail;
206         }
207 
208         memcpy(l2_table, old_table, s->cluster_size);
209 
210         ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &old_table);
211         if (ret < 0) {
212             goto fail;
213         }
214     }
215 
216     /* write the l2 table to the file */
217     BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_WRITE);
218 
219     qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
220     ret = qcow2_cache_flush(bs, s->l2_table_cache);
221     if (ret < 0) {
222         goto fail;
223     }
224 
225     /* update the L1 entry */
226     s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED;
227     ret = write_l1_entry(bs, l1_index);
228     if (ret < 0) {
229         goto fail;
230     }
231 
232     *table = l2_table;
233     return 0;
234 
235 fail:
236     qcow2_cache_put(bs, s->l2_table_cache, (void**) table);
237     s->l1_table[l1_index] = old_l2_offset;
238     return ret;
239 }
240 
count_contiguous_clusters(uint64_t nb_clusters,int cluster_size,uint64_t * l2_table,uint64_t start,uint64_t mask)241 static int count_contiguous_clusters(uint64_t nb_clusters, int cluster_size,
242         uint64_t *l2_table, uint64_t start, uint64_t mask)
243 {
244     int i;
245     uint64_t offset = be64_to_cpu(l2_table[0]) & ~mask;
246 
247     if (!offset)
248         return 0;
249 
250     for (i = start; i < start + nb_clusters; i++)
251         if (offset + (uint64_t) i * cluster_size != (be64_to_cpu(l2_table[i]) & ~mask))
252             break;
253 
254 	return (i - start);
255 }
256 
count_contiguous_free_clusters(uint64_t nb_clusters,uint64_t * l2_table)257 static int count_contiguous_free_clusters(uint64_t nb_clusters, uint64_t *l2_table)
258 {
259     int i = 0;
260 
261     while(nb_clusters-- && l2_table[i] == 0)
262         i++;
263 
264     return i;
265 }
266 
267 /* The crypt function is compatible with the linux cryptoloop
268    algorithm for < 4 GB images. NOTE: out_buf == in_buf is
269    supported */
qcow2_encrypt_sectors(BDRVQcowState * s,int64_t sector_num,uint8_t * out_buf,const uint8_t * in_buf,int nb_sectors,int enc,const AES_KEY * key)270 void qcow2_encrypt_sectors(BDRVQcowState *s, int64_t sector_num,
271                            uint8_t *out_buf, const uint8_t *in_buf,
272                            int nb_sectors, int enc,
273                            const AES_KEY *key)
274 {
275     union {
276         uint64_t ll[2];
277         uint8_t b[16];
278     } ivec;
279     int i;
280 
281     for(i = 0; i < nb_sectors; i++) {
282         ivec.ll[0] = cpu_to_le64(sector_num);
283         ivec.ll[1] = 0;
284         AES_cbc_encrypt(in_buf, out_buf, 512, key,
285                         ivec.b, enc);
286         sector_num++;
287         in_buf += 512;
288         out_buf += 512;
289     }
290 }
291 
292 
qcow2_read(BlockDriverState * bs,int64_t sector_num,uint8_t * buf,int nb_sectors)293 static int qcow2_read(BlockDriverState *bs, int64_t sector_num,
294                       uint8_t *buf, int nb_sectors)
295 {
296     BDRVQcowState *s = bs->opaque;
297     int ret, index_in_cluster, n, n1;
298     uint64_t cluster_offset;
299     struct iovec iov;
300     QEMUIOVector qiov;
301 
302     while (nb_sectors > 0) {
303         n = nb_sectors;
304 
305         ret = qcow2_get_cluster_offset(bs, sector_num << 9, &n,
306             &cluster_offset);
307         if (ret < 0) {
308             return ret;
309         }
310 
311         index_in_cluster = sector_num & (s->cluster_sectors - 1);
312         if (!cluster_offset) {
313             if (bs->backing_hd) {
314                 /* read from the base image */
315                 iov.iov_base = buf;
316                 iov.iov_len = n * 512;
317                 qemu_iovec_init_external(&qiov, &iov, 1);
318 
319                 n1 = qcow2_backing_read1(bs->backing_hd, &qiov, sector_num, n);
320                 if (n1 > 0) {
321                     BLKDBG_EVENT(bs->file, BLKDBG_READ_BACKING);
322                     ret = bdrv_read(bs->backing_hd, sector_num, buf, n1);
323                     if (ret < 0)
324                         return -1;
325                 }
326             } else {
327                 memset(buf, 0, 512 * n);
328             }
329         } else if (cluster_offset & QCOW_OFLAG_COMPRESSED) {
330             if (qcow2_decompress_cluster(bs, cluster_offset) < 0)
331                 return -1;
332             memcpy(buf, s->cluster_cache + index_in_cluster * 512, 512 * n);
333         } else {
334             BLKDBG_EVENT(bs->file, BLKDBG_READ);
335             ret = bdrv_pread(bs->file, cluster_offset + index_in_cluster * 512, buf, n * 512);
336             if (ret != n * 512)
337                 return -1;
338             if (s->crypt_method) {
339                 qcow2_encrypt_sectors(s, sector_num, buf, buf, n, 0,
340                                 &s->aes_decrypt_key);
341             }
342         }
343         nb_sectors -= n;
344         sector_num += n;
345         buf += n * 512;
346     }
347     return 0;
348 }
349 
copy_sectors(BlockDriverState * bs,uint64_t start_sect,uint64_t cluster_offset,int n_start,int n_end)350 static int copy_sectors(BlockDriverState *bs, uint64_t start_sect,
351                         uint64_t cluster_offset, int n_start, int n_end)
352 {
353     BDRVQcowState *s = bs->opaque;
354     int n, ret;
355 
356     n = n_end - n_start;
357     if (n <= 0)
358         return 0;
359     BLKDBG_EVENT(bs->file, BLKDBG_COW_READ);
360     ret = qcow2_read(bs, start_sect + n_start, s->cluster_data, n);
361     if (ret < 0)
362         return ret;
363     if (s->crypt_method) {
364         qcow2_encrypt_sectors(s, start_sect + n_start,
365                         s->cluster_data,
366                         s->cluster_data, n, 1,
367                         &s->aes_encrypt_key);
368     }
369     BLKDBG_EVENT(bs->file, BLKDBG_COW_WRITE);
370     ret = bdrv_write(bs->file, (cluster_offset >> 9) + n_start,
371         s->cluster_data, n);
372     if (ret < 0)
373         return ret;
374     return 0;
375 }
376 
377 
378 /*
379  * get_cluster_offset
380  *
381  * For a given offset of the disk image, find the cluster offset in
382  * qcow2 file. The offset is stored in *cluster_offset.
383  *
384  * on entry, *num is the number of contiguous clusters we'd like to
385  * access following offset.
386  *
387  * on exit, *num is the number of contiguous clusters we can read.
388  *
389  * Return 0, if the offset is found
390  * Return -errno, otherwise.
391  *
392  */
393 
qcow2_get_cluster_offset(BlockDriverState * bs,uint64_t offset,int * num,uint64_t * cluster_offset)394 int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
395     int *num, uint64_t *cluster_offset)
396 {
397     BDRVQcowState *s = bs->opaque;
398     unsigned int l1_index, l2_index;
399     uint64_t l2_offset, *l2_table;
400     int l1_bits, c;
401     unsigned int index_in_cluster, nb_clusters;
402     uint64_t nb_available, nb_needed;
403     int ret;
404 
405     index_in_cluster = (offset >> 9) & (s->cluster_sectors - 1);
406     nb_needed = *num + index_in_cluster;
407 
408     l1_bits = s->l2_bits + s->cluster_bits;
409 
410     /* compute how many bytes there are between the offset and
411      * the end of the l1 entry
412      */
413 
414     nb_available = (1ULL << l1_bits) - (offset & ((1ULL << l1_bits) - 1));
415 
416     /* compute the number of available sectors */
417 
418     nb_available = (nb_available >> 9) + index_in_cluster;
419 
420     if (nb_needed > nb_available) {
421         nb_needed = nb_available;
422     }
423 
424     *cluster_offset = 0;
425 
426     /* seek the the l2 offset in the l1 table */
427 
428     l1_index = offset >> l1_bits;
429     if (l1_index >= s->l1_size)
430         goto out;
431 
432     l2_offset = s->l1_table[l1_index];
433 
434     /* seek the l2 table of the given l2 offset */
435 
436     if (!l2_offset)
437         goto out;
438 
439     /* load the l2 table in memory */
440 
441     l2_offset &= ~QCOW_OFLAG_COPIED;
442     ret = l2_load(bs, l2_offset, &l2_table);
443     if (ret < 0) {
444         return ret;
445     }
446 
447     /* find the cluster offset for the given disk offset */
448 
449     l2_index = (offset >> s->cluster_bits) & (s->l2_size - 1);
450     *cluster_offset = be64_to_cpu(l2_table[l2_index]);
451     nb_clusters = size_to_clusters(s, nb_needed << 9);
452 
453     if (!*cluster_offset) {
454         /* how many empty clusters ? */
455         c = count_contiguous_free_clusters(nb_clusters, &l2_table[l2_index]);
456     } else {
457         /* how many allocated clusters ? */
458         c = count_contiguous_clusters(nb_clusters, s->cluster_size,
459                 &l2_table[l2_index], 0, QCOW_OFLAG_COPIED);
460     }
461 
462     qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
463 
464    nb_available = (c * s->cluster_sectors);
465 out:
466     if (nb_available > nb_needed)
467         nb_available = nb_needed;
468 
469     *num = nb_available - index_in_cluster;
470 
471     *cluster_offset &=~QCOW_OFLAG_COPIED;
472     return 0;
473 }
474 
475 /*
476  * get_cluster_table
477  *
478  * for a given disk offset, load (and allocate if needed)
479  * the l2 table.
480  *
481  * the l2 table offset in the qcow2 file and the cluster index
482  * in the l2 table are given to the caller.
483  *
484  * Returns 0 on success, -errno in failure case
485  */
get_cluster_table(BlockDriverState * bs,uint64_t offset,uint64_t ** new_l2_table,uint64_t * new_l2_offset,int * new_l2_index)486 static int get_cluster_table(BlockDriverState *bs, uint64_t offset,
487                              uint64_t **new_l2_table,
488                              uint64_t *new_l2_offset,
489                              int *new_l2_index)
490 {
491     BDRVQcowState *s = bs->opaque;
492     unsigned int l1_index, l2_index;
493     uint64_t l2_offset;
494     uint64_t *l2_table = NULL;
495     int ret;
496 
497     /* seek the the l2 offset in the l1 table */
498 
499     l1_index = offset >> (s->l2_bits + s->cluster_bits);
500     if (l1_index >= s->l1_size) {
501         ret = qcow2_grow_l1_table(bs, l1_index + 1, false);
502         if (ret < 0) {
503             return ret;
504         }
505     }
506     l2_offset = s->l1_table[l1_index];
507 
508     /* seek the l2 table of the given l2 offset */
509 
510     if (l2_offset & QCOW_OFLAG_COPIED) {
511         /* load the l2 table in memory */
512         l2_offset &= ~QCOW_OFLAG_COPIED;
513         ret = l2_load(bs, l2_offset, &l2_table);
514         if (ret < 0) {
515             return ret;
516         }
517     } else {
518         /* First allocate a new L2 table (and do COW if needed) */
519         ret = l2_allocate(bs, l1_index, &l2_table);
520         if (ret < 0) {
521             return ret;
522         }
523 
524         /* Then decrease the refcount of the old table */
525         if (l2_offset) {
526             qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t));
527         }
528         l2_offset = s->l1_table[l1_index] & ~QCOW_OFLAG_COPIED;
529     }
530 
531     /* find the cluster offset for the given disk offset */
532 
533     l2_index = (offset >> s->cluster_bits) & (s->l2_size - 1);
534 
535     *new_l2_table = l2_table;
536     *new_l2_offset = l2_offset;
537     *new_l2_index = l2_index;
538 
539     return 0;
540 }
541 
542 /*
543  * alloc_compressed_cluster_offset
544  *
545  * For a given offset of the disk image, return cluster offset in
546  * qcow2 file.
547  *
548  * If the offset is not found, allocate a new compressed cluster.
549  *
550  * Return the cluster offset if successful,
551  * Return 0, otherwise.
552  *
553  */
554 
qcow2_alloc_compressed_cluster_offset(BlockDriverState * bs,uint64_t offset,int compressed_size)555 uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
556                                                uint64_t offset,
557                                                int compressed_size)
558 {
559     BDRVQcowState *s = bs->opaque;
560     int l2_index, ret;
561     uint64_t l2_offset, *l2_table;
562     int64_t cluster_offset;
563     int nb_csectors;
564 
565     ret = get_cluster_table(bs, offset, &l2_table, &l2_offset, &l2_index);
566     if (ret < 0) {
567         return 0;
568     }
569 
570     cluster_offset = be64_to_cpu(l2_table[l2_index]);
571     if (cluster_offset & QCOW_OFLAG_COPIED)
572         return cluster_offset & ~QCOW_OFLAG_COPIED;
573 
574     if (cluster_offset)
575         qcow2_free_any_clusters(bs, cluster_offset, 1);
576 
577     cluster_offset = qcow2_alloc_bytes(bs, compressed_size);
578     if (cluster_offset < 0) {
579         qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
580         return 0;
581     }
582 
583     nb_csectors = ((cluster_offset + compressed_size - 1) >> 9) -
584                   (cluster_offset >> 9);
585 
586     cluster_offset |= QCOW_OFLAG_COMPRESSED |
587                       ((uint64_t)nb_csectors << s->csize_shift);
588 
589     /* update L2 table */
590 
591     /* compressed clusters never have the copied flag */
592 
593     BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE_COMPRESSED);
594     qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
595     l2_table[l2_index] = cpu_to_be64(cluster_offset);
596     ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
597     if (ret < 0) {
598         return 0;
599     }
600 
601     return cluster_offset;
602 }
603 
qcow2_alloc_cluster_link_l2(BlockDriverState * bs,QCowL2Meta * m)604 int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
605 {
606     BDRVQcowState *s = bs->opaque;
607     int i, j = 0, l2_index, ret;
608     uint64_t *old_cluster, start_sect, l2_offset, *l2_table;
609     uint64_t cluster_offset = m->cluster_offset;
610     bool cow = false;
611 
612     if (m->nb_clusters == 0)
613         return 0;
614 
615     old_cluster = qemu_malloc(m->nb_clusters * sizeof(uint64_t));
616 
617     /* copy content of unmodified sectors */
618     start_sect = (m->offset & ~(s->cluster_size - 1)) >> 9;
619     if (m->n_start) {
620         cow = true;
621         ret = copy_sectors(bs, start_sect, cluster_offset, 0, m->n_start);
622         if (ret < 0)
623             goto err;
624     }
625 
626     if (m->nb_available & (s->cluster_sectors - 1)) {
627         uint64_t end = m->nb_available & ~(uint64_t)(s->cluster_sectors - 1);
628         cow = true;
629         ret = copy_sectors(bs, start_sect + end, cluster_offset + (end << 9),
630                 m->nb_available - end, s->cluster_sectors);
631         if (ret < 0)
632             goto err;
633     }
634 
635     /*
636      * Update L2 table.
637      *
638      * Before we update the L2 table to actually point to the new cluster, we
639      * need to be sure that the refcounts have been increased and COW was
640      * handled.
641      */
642     if (cow) {
643         qcow2_cache_depends_on_flush(s->l2_table_cache);
644     }
645 
646     qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache);
647     ret = get_cluster_table(bs, m->offset, &l2_table, &l2_offset, &l2_index);
648     if (ret < 0) {
649         goto err;
650     }
651     qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
652 
653     for (i = 0; i < m->nb_clusters; i++) {
654         /* if two concurrent writes happen to the same unallocated cluster
655 	 * each write allocates separate cluster and writes data concurrently.
656 	 * The first one to complete updates l2 table with pointer to its
657 	 * cluster the second one has to do RMW (which is done above by
658 	 * copy_sectors()), update l2 table with its cluster pointer and free
659 	 * old cluster. This is what this loop does */
660         if(l2_table[l2_index + i] != 0)
661             old_cluster[j++] = l2_table[l2_index + i];
662 
663         l2_table[l2_index + i] = cpu_to_be64((cluster_offset +
664                     (i << s->cluster_bits)) | QCOW_OFLAG_COPIED);
665      }
666 
667 
668     ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
669     if (ret < 0) {
670         goto err;
671     }
672 
673     /*
674      * If this was a COW, we need to decrease the refcount of the old cluster.
675      * Also flush bs->file to get the right order for L2 and refcount update.
676      */
677     if (j != 0) {
678         for (i = 0; i < j; i++) {
679             qcow2_free_any_clusters(bs,
680                 be64_to_cpu(old_cluster[i]) & ~QCOW_OFLAG_COPIED, 1);
681         }
682     }
683 
684     ret = 0;
685 err:
686     qemu_free(old_cluster);
687     return ret;
688  }
689 
690 /*
691  * alloc_cluster_offset
692  *
693  * For a given offset of the disk image, return cluster offset in qcow2 file.
694  * If the offset is not found, allocate a new cluster.
695  *
696  * If the cluster was already allocated, m->nb_clusters is set to 0,
697  * m->depends_on is set to NULL and the other fields in m are meaningless.
698  *
699  * If the cluster is newly allocated, m->nb_clusters is set to the number of
700  * contiguous clusters that have been allocated. This may be 0 if the request
701  * conflict with another write request in flight; in this case, m->depends_on
702  * is set and the remaining fields of m are meaningless.
703  *
704  * If m->nb_clusters is non-zero, the other fields of m are valid and contain
705  * information about the first allocated cluster.
706  *
707  * Return 0 on success and -errno in error cases
708  */
qcow2_alloc_cluster_offset(BlockDriverState * bs,uint64_t offset,int n_start,int n_end,int * num,QCowL2Meta * m)709 int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
710     int n_start, int n_end, int *num, QCowL2Meta *m)
711 {
712     BDRVQcowState *s = bs->opaque;
713     int l2_index, ret;
714     uint64_t l2_offset, *l2_table;
715     int64_t cluster_offset;
716     unsigned int nb_clusters, i = 0;
717     QCowL2Meta *old_alloc;
718 
719     ret = get_cluster_table(bs, offset, &l2_table, &l2_offset, &l2_index);
720     if (ret < 0) {
721         return ret;
722     }
723 
724     nb_clusters = size_to_clusters(s, n_end << 9);
725 
726     nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);
727 
728     cluster_offset = be64_to_cpu(l2_table[l2_index]);
729 
730     /* We keep all QCOW_OFLAG_COPIED clusters */
731 
732     if (cluster_offset & QCOW_OFLAG_COPIED) {
733         nb_clusters = count_contiguous_clusters(nb_clusters, s->cluster_size,
734                 &l2_table[l2_index], 0, 0);
735 
736         cluster_offset &= ~QCOW_OFLAG_COPIED;
737         m->nb_clusters = 0;
738         m->depends_on = NULL;
739 
740         goto out;
741     }
742 
743     /* for the moment, multiple compressed clusters are not managed */
744 
745     if (cluster_offset & QCOW_OFLAG_COMPRESSED)
746         nb_clusters = 1;
747 
748     /* how many available clusters ? */
749 
750     while (i < nb_clusters) {
751         i += count_contiguous_clusters(nb_clusters - i, s->cluster_size,
752                 &l2_table[l2_index], i, 0);
753         if ((i >= nb_clusters) || be64_to_cpu(l2_table[l2_index + i])) {
754             break;
755         }
756 
757         i += count_contiguous_free_clusters(nb_clusters - i,
758                 &l2_table[l2_index + i]);
759         if (i >= nb_clusters) {
760             break;
761         }
762 
763         cluster_offset = be64_to_cpu(l2_table[l2_index + i]);
764 
765         if ((cluster_offset & QCOW_OFLAG_COPIED) ||
766                 (cluster_offset & QCOW_OFLAG_COMPRESSED))
767             break;
768     }
769     assert(i <= nb_clusters);
770     nb_clusters = i;
771 
772     /*
773      * Check if there already is an AIO write request in flight which allocates
774      * the same cluster. In this case we need to wait until the previous
775      * request has completed and updated the L2 table accordingly.
776      */
777     QLIST_FOREACH(old_alloc, &s->cluster_allocs, next_in_flight) {
778 
779         uint64_t end_offset = offset + nb_clusters * s->cluster_size;
780         uint64_t old_offset = old_alloc->offset;
781         uint64_t old_end_offset = old_alloc->offset +
782             old_alloc->nb_clusters * s->cluster_size;
783 
784         if (end_offset < old_offset || offset > old_end_offset) {
785             /* No intersection */
786         } else {
787             if (offset < old_offset) {
788                 /* Stop at the start of a running allocation */
789                 nb_clusters = (old_offset - offset) >> s->cluster_bits;
790             } else {
791                 nb_clusters = 0;
792             }
793 
794             if (nb_clusters == 0) {
795                 /* Set dependency and wait for a callback */
796                 m->depends_on = old_alloc;
797                 m->nb_clusters = 0;
798                 *num = 0;
799                 ret = 0;
800                 goto fail;
801             }
802         }
803     }
804 
805     if (!nb_clusters) {
806         abort();
807     }
808 
809     QLIST_INSERT_HEAD(&s->cluster_allocs, m, next_in_flight);
810 
811     /* allocate a new cluster */
812 
813     cluster_offset = qcow2_alloc_clusters(bs, nb_clusters * s->cluster_size);
814     if (cluster_offset < 0) {
815         QLIST_REMOVE(m, next_in_flight);
816         ret = cluster_offset;
817         goto fail;
818     }
819 
820     /* save info needed for meta data update */
821     m->offset = offset;
822     m->n_start = n_start;
823     m->nb_clusters = nb_clusters;
824 
825 out:
826     ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
827     if (ret < 0) {
828         return ret;
829     }
830 
831     m->nb_available = MIN(nb_clusters << (s->cluster_bits - 9), n_end);
832     m->cluster_offset = cluster_offset;
833 
834     *num = m->nb_available - n_start;
835 
836     return 0;
837 
838 fail:
839     qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
840     return ret;
841 }
842 
decompress_buffer(uint8_t * out_buf,int out_buf_size,const uint8_t * buf,int buf_size)843 static int decompress_buffer(uint8_t *out_buf, int out_buf_size,
844                              const uint8_t *buf, int buf_size)
845 {
846     z_stream strm1, *strm = &strm1;
847     int ret, out_len;
848 
849     memset(strm, 0, sizeof(*strm));
850 
851     strm->next_in = (uint8_t *)buf;
852     strm->avail_in = buf_size;
853     strm->next_out = out_buf;
854     strm->avail_out = out_buf_size;
855 
856     ret = inflateInit2(strm, -12);
857     if (ret != Z_OK)
858         return -1;
859     ret = inflate(strm, Z_FINISH);
860     out_len = strm->next_out - out_buf;
861     if ((ret != Z_STREAM_END && ret != Z_BUF_ERROR) ||
862         out_len != out_buf_size) {
863         inflateEnd(strm);
864         return -1;
865     }
866     inflateEnd(strm);
867     return 0;
868 }
869 
qcow2_decompress_cluster(BlockDriverState * bs,uint64_t cluster_offset)870 int qcow2_decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset)
871 {
872     BDRVQcowState *s = bs->opaque;
873     int ret, csize, nb_csectors, sector_offset;
874     uint64_t coffset;
875 
876     coffset = cluster_offset & s->cluster_offset_mask;
877     if (s->cluster_cache_offset != coffset) {
878         nb_csectors = ((cluster_offset >> s->csize_shift) & s->csize_mask) + 1;
879         sector_offset = coffset & 511;
880         csize = nb_csectors * 512 - sector_offset;
881         BLKDBG_EVENT(bs->file, BLKDBG_READ_COMPRESSED);
882         ret = bdrv_read(bs->file, coffset >> 9, s->cluster_data, nb_csectors);
883         if (ret < 0) {
884             return ret;
885         }
886         if (decompress_buffer(s->cluster_cache, s->cluster_size,
887                               s->cluster_data + sector_offset, csize) < 0) {
888             return -EIO;
889         }
890         s->cluster_cache_offset = coffset;
891     }
892     return 0;
893 }
894 
895 /*
896  * This discards as many clusters of nb_clusters as possible at once (i.e.
897  * all clusters in the same L2 table) and returns the number of discarded
898  * clusters.
899  */
discard_single_l2(BlockDriverState * bs,uint64_t offset,unsigned int nb_clusters)900 static int discard_single_l2(BlockDriverState *bs, uint64_t offset,
901     unsigned int nb_clusters)
902 {
903     BDRVQcowState *s = bs->opaque;
904     uint64_t l2_offset, *l2_table;
905     int l2_index;
906     int ret;
907     int i;
908 
909     ret = get_cluster_table(bs, offset, &l2_table, &l2_offset, &l2_index);
910     if (ret < 0) {
911         return ret;
912     }
913 
914     /* Limit nb_clusters to one L2 table */
915     nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);
916 
917     for (i = 0; i < nb_clusters; i++) {
918         uint64_t old_offset;
919 
920         old_offset = be64_to_cpu(l2_table[l2_index + i]);
921         old_offset &= ~QCOW_OFLAG_COPIED;
922 
923         if (old_offset == 0) {
924             continue;
925         }
926 
927         /* First remove L2 entries */
928         qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
929         l2_table[l2_index + i] = cpu_to_be64(0);
930 
931         /* Then decrease the refcount */
932         qcow2_free_any_clusters(bs, old_offset, 1);
933     }
934 
935     ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
936     if (ret < 0) {
937         return ret;
938     }
939 
940     return nb_clusters;
941 }
942 
qcow2_discard_clusters(BlockDriverState * bs,uint64_t offset,int nb_sectors)943 int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
944     int nb_sectors)
945 {
946     BDRVQcowState *s = bs->opaque;
947     uint64_t end_offset;
948     unsigned int nb_clusters;
949     int ret;
950 
951     end_offset = offset + (nb_sectors << BDRV_SECTOR_BITS);
952 
953     /* Round start up and end down */
954     offset = align_offset(offset, s->cluster_size);
955     end_offset &= ~(s->cluster_size - 1);
956 
957     if (offset > end_offset) {
958         return 0;
959     }
960 
961     nb_clusters = size_to_clusters(s, end_offset - offset);
962 
963     /* Each L2 table is handled by its own loop iteration */
964     while (nb_clusters > 0) {
965         ret = discard_single_l2(bs, offset, nb_clusters);
966         if (ret < 0) {
967             return ret;
968         }
969 
970         nb_clusters -= ret;
971         offset += (ret * s->cluster_size);
972     }
973 
974     return 0;
975 }
976