target/arm: Require alignment for load exclusive
[qemu/ar7.git] / block / vhdx-log.c
blob14b724ef7bc4b9bbdc7e520b29dcfd0f78626e4e
1 /*
2 * Block driver for Hyper-V VHDX Images
4 * Copyright (c) 2013 Red Hat, Inc.,
6 * Authors:
7 * Jeff Cody <jcody@redhat.com>
9 * This is based on the "VHDX Format Specification v1.00", published 8/25/2012
10 * by Microsoft:
11 * https://www.microsoft.com/en-us/download/details.aspx?id=34750
13 * This file covers the functionality of the metadata log writing, parsing, and
14 * replay.
16 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
17 * See the COPYING.LIB file in the top-level directory.
20 #include "qemu/osdep.h"
21 #include "qapi/error.h"
22 #include "qemu-common.h"
23 #include "block/block_int.h"
24 #include "qemu/error-report.h"
25 #include "qemu/module.h"
26 #include "qemu/bswap.h"
27 #include "block/vhdx.h"
30 typedef struct VHDXLogSequence {
31 bool valid;
32 uint32_t count;
33 VHDXLogEntries log;
34 VHDXLogEntryHeader hdr;
35 } VHDXLogSequence;
37 typedef struct VHDXLogDescEntries {
38 VHDXLogEntryHeader hdr;
39 VHDXLogDescriptor desc[];
40 } VHDXLogDescEntries;
42 static const MSGUID zero_guid = { 0 };
44 /* The log located on the disk is circular buffer containing
45 * sectors of 4096 bytes each.
47 * It is assumed for the read/write functions below that the
48 * circular buffer scheme uses a 'one sector open' to indicate
49 * the buffer is full. Given the validation methods used for each
50 * sector, this method should be compatible with other methods that
51 * do not waste a sector.
55 /* Allow peeking at the hdr entry at the beginning of the current
56 * read index, without advancing the read index */
57 static int vhdx_log_peek_hdr(BlockDriverState *bs, VHDXLogEntries *log,
58 VHDXLogEntryHeader *hdr)
60 int ret = 0;
61 uint64_t offset;
62 uint32_t read;
64 assert(hdr != NULL);
66 /* peek is only supported on sector boundaries */
67 if (log->read % VHDX_LOG_SECTOR_SIZE) {
68 ret = -EFAULT;
69 goto exit;
72 read = log->read;
73 /* we are guaranteed that a) log sectors are 4096 bytes,
74 * and b) the log length is a multiple of 1MB. So, there
75 * is always a round number of sectors in the buffer */
76 if ((read + sizeof(VHDXLogEntryHeader)) > log->length) {
77 read = 0;
80 if (read == log->write) {
81 ret = -EINVAL;
82 goto exit;
85 offset = log->offset + read;
87 ret = bdrv_pread(bs->file, offset, hdr, sizeof(VHDXLogEntryHeader));
88 if (ret < 0) {
89 goto exit;
91 vhdx_log_entry_hdr_le_import(hdr);
93 exit:
94 return ret;
97 /* Index increment for log, based on sector boundaries */
98 static int vhdx_log_inc_idx(uint32_t idx, uint64_t length)
100 idx += VHDX_LOG_SECTOR_SIZE;
101 /* we are guaranteed that a) log sectors are 4096 bytes,
102 * and b) the log length is a multiple of 1MB. So, there
103 * is always a round number of sectors in the buffer */
104 return idx >= length ? 0 : idx;
108 /* Reset the log to empty */
109 static void vhdx_log_reset(BlockDriverState *bs, BDRVVHDXState *s)
111 MSGUID guid = { 0 };
112 s->log.read = s->log.write = 0;
113 /* a log guid of 0 indicates an empty log to any parser of v0
114 * VHDX logs */
115 vhdx_update_headers(bs, s, false, &guid);
118 /* Reads num_sectors from the log (all log sectors are 4096 bytes),
119 * into buffer 'buffer'. Upon return, *sectors_read will contain
120 * the number of sectors successfully read.
122 * It is assumed that 'buffer' is already allocated, and of sufficient
123 * size (i.e. >= 4096*num_sectors).
125 * If 'peek' is true, then the tail (read) pointer for the circular buffer is
126 * not modified.
128 * 0 is returned on success, -errno otherwise. */
129 static int vhdx_log_read_sectors(BlockDriverState *bs, VHDXLogEntries *log,
130 uint32_t *sectors_read, void *buffer,
131 uint32_t num_sectors, bool peek)
133 int ret = 0;
134 uint64_t offset;
135 uint32_t read;
137 read = log->read;
139 *sectors_read = 0;
140 while (num_sectors) {
141 if (read == log->write) {
142 /* empty */
143 break;
145 offset = log->offset + read;
147 ret = bdrv_pread(bs->file, offset, buffer, VHDX_LOG_SECTOR_SIZE);
148 if (ret < 0) {
149 goto exit;
151 read = vhdx_log_inc_idx(read, log->length);
153 *sectors_read = *sectors_read + 1;
154 num_sectors--;
157 exit:
158 if (!peek) {
159 log->read = read;
161 return ret;
164 /* Writes num_sectors to the log (all log sectors are 4096 bytes),
165 * from buffer 'buffer'. Upon return, *sectors_written will contain
166 * the number of sectors successfully written.
168 * It is assumed that 'buffer' is at least 4096*num_sectors large.
170 * 0 is returned on success, -errno otherwise */
171 static int vhdx_log_write_sectors(BlockDriverState *bs, VHDXLogEntries *log,
172 uint32_t *sectors_written, void *buffer,
173 uint32_t num_sectors)
175 int ret = 0;
176 uint64_t offset;
177 uint32_t write;
178 void *buffer_tmp;
179 BDRVVHDXState *s = bs->opaque;
181 ret = vhdx_user_visible_write(bs, s);
182 if (ret < 0) {
183 goto exit;
186 write = log->write;
188 buffer_tmp = buffer;
189 while (num_sectors) {
191 offset = log->offset + write;
192 write = vhdx_log_inc_idx(write, log->length);
193 if (write == log->read) {
194 /* full */
195 break;
197 ret = bdrv_pwrite(bs->file, offset, buffer_tmp,
198 VHDX_LOG_SECTOR_SIZE);
199 if (ret < 0) {
200 goto exit;
202 buffer_tmp += VHDX_LOG_SECTOR_SIZE;
204 log->write = write;
205 *sectors_written = *sectors_written + 1;
206 num_sectors--;
209 exit:
210 return ret;
214 /* Validates a log entry header */
215 static bool vhdx_log_hdr_is_valid(VHDXLogEntries *log, VHDXLogEntryHeader *hdr,
216 BDRVVHDXState *s)
218 int valid = false;
220 if (hdr->signature != VHDX_LOG_SIGNATURE) {
221 goto exit;
224 /* if the individual entry length is larger than the whole log
225 * buffer, that is obviously invalid */
226 if (log->length < hdr->entry_length) {
227 goto exit;
230 /* length of entire entry must be in units of 4KB (log sector size) */
231 if (hdr->entry_length % (VHDX_LOG_SECTOR_SIZE)) {
232 goto exit;
235 /* per spec, sequence # must be > 0 */
236 if (hdr->sequence_number == 0) {
237 goto exit;
240 /* log entries are only valid if they match the file-wide log guid
241 * found in the active header */
242 if (!guid_eq(hdr->log_guid, s->headers[s->curr_header]->log_guid)) {
243 goto exit;
246 if (hdr->descriptor_count * sizeof(VHDXLogDescriptor) > hdr->entry_length) {
247 goto exit;
250 valid = true;
252 exit:
253 return valid;
257 * Given a log header, this will validate that the descriptors and the
258 * corresponding data sectors (if applicable)
260 * Validation consists of:
261 * 1. Making sure the sequence numbers matches the entry header
262 * 2. Verifying a valid signature ('zero' or 'desc' for descriptors)
263 * 3. File offset field is a multiple of 4KB
264 * 4. If a data descriptor, the corresponding data sector
265 * has its signature ('data') and matching sequence number
267 * @desc: the data buffer containing the descriptor
268 * @hdr: the log entry header
270 * Returns true if valid
272 static bool vhdx_log_desc_is_valid(VHDXLogDescriptor *desc,
273 VHDXLogEntryHeader *hdr)
275 bool ret = false;
277 if (desc->sequence_number != hdr->sequence_number) {
278 goto exit;
280 if (desc->file_offset % VHDX_LOG_SECTOR_SIZE) {
281 goto exit;
284 if (desc->signature == VHDX_LOG_ZERO_SIGNATURE) {
285 if (desc->zero_length % VHDX_LOG_SECTOR_SIZE == 0) {
286 /* valid */
287 ret = true;
289 } else if (desc->signature == VHDX_LOG_DESC_SIGNATURE) {
290 /* valid */
291 ret = true;
294 exit:
295 return ret;
299 /* Prior to sector data for a log entry, there is the header
300 * and the descriptors referenced in the header:
302 * [] = 4KB sector
304 * [ hdr, desc ][ desc ][ ... ][ data ][ ... ]
306 * The first sector in a log entry has a 64 byte header, and
307 * up to 126 32-byte descriptors. If more descriptors than
308 * 126 are required, then subsequent sectors can have up to 128
309 * descriptors. Each sector is 4KB. Data follows the descriptor
310 * sectors.
312 * This will return the number of sectors needed to encompass
313 * the passed number of descriptors in desc_cnt.
315 * This will never return 0, even if desc_cnt is 0.
317 static int vhdx_compute_desc_sectors(uint32_t desc_cnt)
319 uint32_t desc_sectors;
321 desc_cnt += 2; /* account for header in first sector */
322 desc_sectors = desc_cnt / 128;
323 if (desc_cnt % 128) {
324 desc_sectors++;
327 return desc_sectors;
331 /* Reads the log header, and subsequent descriptors (if any). This
332 * will allocate all the space for buffer, which must be NULL when
333 * passed into this function. Each descriptor will also be validated,
334 * and error returned if any are invalid. */
335 static int vhdx_log_read_desc(BlockDriverState *bs, BDRVVHDXState *s,
336 VHDXLogEntries *log, VHDXLogDescEntries **buffer,
337 bool convert_endian)
339 int ret = 0;
340 uint32_t desc_sectors;
341 uint32_t sectors_read;
342 VHDXLogEntryHeader hdr;
343 VHDXLogDescEntries *desc_entries = NULL;
344 VHDXLogDescriptor desc;
345 int i;
347 assert(*buffer == NULL);
349 ret = vhdx_log_peek_hdr(bs, log, &hdr);
350 if (ret < 0) {
351 goto exit;
354 if (vhdx_log_hdr_is_valid(log, &hdr, s) == false) {
355 ret = -EINVAL;
356 goto exit;
359 desc_sectors = vhdx_compute_desc_sectors(hdr.descriptor_count);
360 desc_entries = qemu_try_blockalign(bs->file->bs,
361 desc_sectors * VHDX_LOG_SECTOR_SIZE);
362 if (desc_entries == NULL) {
363 ret = -ENOMEM;
364 goto exit;
367 ret = vhdx_log_read_sectors(bs, log, &sectors_read, desc_entries,
368 desc_sectors, false);
369 if (ret < 0) {
370 goto free_and_exit;
372 if (sectors_read != desc_sectors) {
373 ret = -EINVAL;
374 goto free_and_exit;
377 /* put in proper endianness, and validate each desc */
378 for (i = 0; i < hdr.descriptor_count; i++) {
379 desc = desc_entries->desc[i];
380 vhdx_log_desc_le_import(&desc);
381 if (convert_endian) {
382 desc_entries->desc[i] = desc;
384 if (vhdx_log_desc_is_valid(&desc, &hdr) == false) {
385 ret = -EINVAL;
386 goto free_and_exit;
389 if (convert_endian) {
390 desc_entries->hdr = hdr;
393 *buffer = desc_entries;
394 goto exit;
396 free_and_exit:
397 qemu_vfree(desc_entries);
398 exit:
399 return ret;
403 /* Flushes the descriptor described by desc to the VHDX image file.
404 * If the descriptor is a data descriptor, than 'data' must be non-NULL,
405 * and >= 4096 bytes (VHDX_LOG_SECTOR_SIZE), containing the data to be
406 * written.
408 * Verification is performed to make sure the sequence numbers of a data
409 * descriptor match the sequence number in the desc.
411 * For a zero descriptor, it may describe multiple sectors to fill with zeroes.
412 * In this case, it should be noted that zeroes are written to disk, and the
413 * image file is not extended as a sparse file. */
414 static int vhdx_log_flush_desc(BlockDriverState *bs, VHDXLogDescriptor *desc,
415 VHDXLogDataSector *data)
417 int ret = 0;
418 uint64_t seq, file_offset;
419 uint32_t offset = 0;
420 void *buffer = NULL;
421 uint64_t count = 1;
422 int i;
424 buffer = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE);
426 if (desc->signature == VHDX_LOG_DESC_SIGNATURE) {
427 /* data sector */
428 if (data == NULL) {
429 ret = -EFAULT;
430 goto exit;
433 /* The sequence number of the data sector must match that
434 * in the descriptor */
435 seq = data->sequence_high;
436 seq <<= 32;
437 seq |= data->sequence_low & 0xffffffff;
439 if (seq != desc->sequence_number) {
440 ret = -EINVAL;
441 goto exit;
444 /* Each data sector is in total 4096 bytes, however the first
445 * 8 bytes, and last 4 bytes, are located in the descriptor */
446 memcpy(buffer, &desc->leading_bytes, 8);
447 offset += 8;
449 memcpy(buffer+offset, data->data, 4084);
450 offset += 4084;
452 memcpy(buffer+offset, &desc->trailing_bytes, 4);
454 } else if (desc->signature == VHDX_LOG_ZERO_SIGNATURE) {
455 /* write 'count' sectors of sector */
456 memset(buffer, 0, VHDX_LOG_SECTOR_SIZE);
457 count = desc->zero_length / VHDX_LOG_SECTOR_SIZE;
458 } else {
459 error_report("Invalid VHDX log descriptor entry signature 0x%" PRIx32,
460 desc->signature);
461 ret = -EINVAL;
462 goto exit;
465 file_offset = desc->file_offset;
467 /* count is only > 1 if we are writing zeroes */
468 for (i = 0; i < count; i++) {
469 ret = bdrv_pwrite_sync(bs->file, file_offset, buffer,
470 VHDX_LOG_SECTOR_SIZE);
471 if (ret < 0) {
472 goto exit;
474 file_offset += VHDX_LOG_SECTOR_SIZE;
477 exit:
478 qemu_vfree(buffer);
479 return ret;
482 /* Flush the entire log (as described by 'logs') to the VHDX image
483 * file, and then set the log to 'empty' status once complete.
485 * The log entries should be validate prior to flushing */
486 static int vhdx_log_flush(BlockDriverState *bs, BDRVVHDXState *s,
487 VHDXLogSequence *logs)
489 int ret = 0;
490 int i;
491 uint32_t cnt, sectors_read;
492 uint64_t new_file_size;
493 void *data = NULL;
494 int64_t file_length;
495 VHDXLogDescEntries *desc_entries = NULL;
496 VHDXLogEntryHeader hdr_tmp = { 0 };
498 cnt = logs->count;
500 data = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE);
502 ret = vhdx_user_visible_write(bs, s);
503 if (ret < 0) {
504 goto exit;
507 /* each iteration represents one log sequence, which may span multiple
508 * sectors */
509 while (cnt--) {
510 ret = vhdx_log_peek_hdr(bs, &logs->log, &hdr_tmp);
511 if (ret < 0) {
512 goto exit;
514 file_length = bdrv_getlength(bs->file->bs);
515 if (file_length < 0) {
516 ret = file_length;
517 goto exit;
519 /* if the log shows a FlushedFileOffset larger than our current file
520 * size, then that means the file has been truncated / corrupted, and
521 * we must refused to open it / use it */
522 if (hdr_tmp.flushed_file_offset > file_length) {
523 ret = -EINVAL;
524 goto exit;
527 ret = vhdx_log_read_desc(bs, s, &logs->log, &desc_entries, true);
528 if (ret < 0) {
529 goto exit;
532 for (i = 0; i < desc_entries->hdr.descriptor_count; i++) {
533 if (desc_entries->desc[i].signature == VHDX_LOG_DESC_SIGNATURE) {
534 /* data sector, so read a sector to flush */
535 ret = vhdx_log_read_sectors(bs, &logs->log, &sectors_read,
536 data, 1, false);
537 if (ret < 0) {
538 goto exit;
540 if (sectors_read != 1) {
541 ret = -EINVAL;
542 goto exit;
544 vhdx_log_data_le_import(data);
547 ret = vhdx_log_flush_desc(bs, &desc_entries->desc[i], data);
548 if (ret < 0) {
549 goto exit;
552 if (file_length < desc_entries->hdr.last_file_offset) {
553 new_file_size = desc_entries->hdr.last_file_offset;
554 if (new_file_size % (1024*1024)) {
555 /* round up to nearest 1MB boundary */
556 new_file_size = QEMU_ALIGN_UP(new_file_size, MiB);
557 if (new_file_size > INT64_MAX) {
558 ret = -EINVAL;
559 goto exit;
561 ret = bdrv_truncate(bs->file, new_file_size, PREALLOC_MODE_OFF,
562 NULL);
563 if (ret < 0) {
564 goto exit;
568 qemu_vfree(desc_entries);
569 desc_entries = NULL;
572 ret = bdrv_flush(bs);
573 if (ret < 0) {
574 goto exit;
576 /* once the log is fully flushed, indicate that we have an empty log
577 * now. This also sets the log guid to 0, to indicate an empty log */
578 vhdx_log_reset(bs, s);
580 exit:
581 qemu_vfree(data);
582 qemu_vfree(desc_entries);
583 return ret;
586 static int vhdx_validate_log_entry(BlockDriverState *bs, BDRVVHDXState *s,
587 VHDXLogEntries *log, uint64_t seq,
588 bool *valid, VHDXLogEntryHeader *entry)
590 int ret = 0;
591 VHDXLogEntryHeader hdr;
592 void *buffer = NULL;
593 uint32_t i, desc_sectors, total_sectors, crc;
594 uint32_t sectors_read = 0;
595 VHDXLogDescEntries *desc_buffer = NULL;
597 *valid = false;
599 ret = vhdx_log_peek_hdr(bs, log, &hdr);
600 if (ret < 0) {
601 goto inc_and_exit;
604 if (vhdx_log_hdr_is_valid(log, &hdr, s) == false) {
605 goto inc_and_exit;
608 if (seq > 0) {
609 if (hdr.sequence_number != seq + 1) {
610 goto inc_and_exit;
614 desc_sectors = vhdx_compute_desc_sectors(hdr.descriptor_count);
616 /* Read all log sectors, and calculate log checksum */
618 total_sectors = hdr.entry_length / VHDX_LOG_SECTOR_SIZE;
621 /* read_desc() will increment the read idx */
622 ret = vhdx_log_read_desc(bs, s, log, &desc_buffer, false);
623 if (ret < 0) {
624 goto free_and_exit;
627 crc = vhdx_checksum_calc(0xffffffff, (void *)desc_buffer,
628 desc_sectors * VHDX_LOG_SECTOR_SIZE, 4);
629 crc ^= 0xffffffff;
631 buffer = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE);
632 if (total_sectors > desc_sectors) {
633 for (i = 0; i < total_sectors - desc_sectors; i++) {
634 sectors_read = 0;
635 ret = vhdx_log_read_sectors(bs, log, &sectors_read, buffer,
636 1, false);
637 if (ret < 0 || sectors_read != 1) {
638 goto free_and_exit;
640 crc = vhdx_checksum_calc(crc, buffer, VHDX_LOG_SECTOR_SIZE, -1);
641 crc ^= 0xffffffff;
644 crc ^= 0xffffffff;
645 if (crc != hdr.checksum) {
646 goto free_and_exit;
649 *valid = true;
650 *entry = hdr;
651 goto free_and_exit;
653 inc_and_exit:
654 log->read = vhdx_log_inc_idx(log->read, log->length);
656 free_and_exit:
657 qemu_vfree(buffer);
658 qemu_vfree(desc_buffer);
659 return ret;
662 /* Search through the log circular buffer, and find the valid, active
663 * log sequence, if any exists
664 * */
665 static int vhdx_log_search(BlockDriverState *bs, BDRVVHDXState *s,
666 VHDXLogSequence *logs)
668 int ret = 0;
669 uint32_t tail;
670 bool seq_valid = false;
671 VHDXLogSequence candidate = { 0 };
672 VHDXLogEntryHeader hdr = { 0 };
673 VHDXLogEntries curr_log;
675 memcpy(&curr_log, &s->log, sizeof(VHDXLogEntries));
676 curr_log.write = curr_log.length; /* assume log is full */
677 curr_log.read = 0;
680 /* now we will go through the whole log sector by sector, until
681 * we find a valid, active log sequence, or reach the end of the
682 * log buffer */
683 for (;;) {
684 uint64_t curr_seq = 0;
685 VHDXLogSequence current = { 0 };
687 tail = curr_log.read;
689 ret = vhdx_validate_log_entry(bs, s, &curr_log, curr_seq,
690 &seq_valid, &hdr);
691 if (ret < 0) {
692 goto exit;
695 if (seq_valid) {
696 current.valid = true;
697 current.log = curr_log;
698 current.log.read = tail;
699 current.log.write = curr_log.read;
700 current.count = 1;
701 current.hdr = hdr;
704 for (;;) {
705 ret = vhdx_validate_log_entry(bs, s, &curr_log, curr_seq,
706 &seq_valid, &hdr);
707 if (ret < 0) {
708 goto exit;
710 if (seq_valid == false) {
711 break;
713 current.log.write = curr_log.read;
714 current.count++;
716 curr_seq = hdr.sequence_number;
720 if (current.valid) {
721 if (candidate.valid == false ||
722 current.hdr.sequence_number > candidate.hdr.sequence_number) {
723 candidate = current;
727 if (curr_log.read < tail) {
728 break;
732 *logs = candidate;
734 if (candidate.valid) {
735 /* this is the next sequence number, for writes */
736 s->log.sequence = candidate.hdr.sequence_number + 1;
740 exit:
741 return ret;
744 /* Parse the replay log. Per the VHDX spec, if the log is present
745 * it must be replayed prior to opening the file, even read-only.
747 * If read-only, we must replay the log in RAM (or refuse to open
748 * a dirty VHDX file read-only) */
749 int vhdx_parse_log(BlockDriverState *bs, BDRVVHDXState *s, bool *flushed,
750 Error **errp)
752 int ret = 0;
753 VHDXHeader *hdr;
754 VHDXLogSequence logs = { 0 };
756 hdr = s->headers[s->curr_header];
758 *flushed = false;
760 /* s->log.hdr is freed in vhdx_close() */
761 if (s->log.hdr == NULL) {
762 s->log.hdr = qemu_blockalign(bs, sizeof(VHDXLogEntryHeader));
765 s->log.offset = hdr->log_offset;
766 s->log.length = hdr->log_length;
768 if (s->log.offset < VHDX_LOG_MIN_SIZE ||
769 s->log.offset % VHDX_LOG_MIN_SIZE) {
770 ret = -EINVAL;
771 goto exit;
774 /* per spec, only log version of 0 is supported */
775 if (hdr->log_version != 0) {
776 ret = -EINVAL;
777 goto exit;
780 /* If either the log guid, or log length is zero,
781 * then a replay log is not present */
782 if (guid_eq(hdr->log_guid, zero_guid)) {
783 goto exit;
786 if (hdr->log_length == 0) {
787 goto exit;
790 if (hdr->log_length % VHDX_LOG_MIN_SIZE) {
791 ret = -EINVAL;
792 goto exit;
796 /* The log is present, we need to find if and where there is an active
797 * sequence of valid entries present in the log. */
799 ret = vhdx_log_search(bs, s, &logs);
800 if (ret < 0) {
801 goto exit;
804 if (logs.valid) {
805 if (bs->read_only) {
806 ret = -EPERM;
807 error_setg(errp,
808 "VHDX image file '%s' opened read-only, but "
809 "contains a log that needs to be replayed",
810 bs->filename);
811 error_append_hint(errp, "To replay the log, run:\n"
812 "qemu-img check -r all '%s'\n",
813 bs->filename);
814 goto exit;
816 /* now flush the log */
817 ret = vhdx_log_flush(bs, s, &logs);
818 if (ret < 0) {
819 goto exit;
821 *flushed = true;
825 exit:
826 return ret;
831 static void vhdx_log_raw_to_le_sector(VHDXLogDescriptor *desc,
832 VHDXLogDataSector *sector, void *data,
833 uint64_t seq)
835 /* 8 + 4084 + 4 = 4096, 1 log sector */
836 memcpy(&desc->leading_bytes, data, 8);
837 data += 8;
838 cpu_to_le64s(&desc->leading_bytes);
839 memcpy(sector->data, data, 4084);
840 data += 4084;
841 memcpy(&desc->trailing_bytes, data, 4);
842 cpu_to_le32s(&desc->trailing_bytes);
843 data += 4;
845 sector->sequence_high = (uint32_t) (seq >> 32);
846 sector->sequence_low = (uint32_t) (seq & 0xffffffff);
847 sector->data_signature = VHDX_LOG_DATA_SIGNATURE;
849 vhdx_log_desc_le_export(desc);
850 vhdx_log_data_le_export(sector);
854 static int vhdx_log_write(BlockDriverState *bs, BDRVVHDXState *s,
855 void *data, uint32_t length, uint64_t offset)
857 int ret = 0;
858 void *buffer = NULL;
859 void *merged_sector = NULL;
860 void *data_tmp, *sector_write;
861 unsigned int i;
862 int sector_offset;
863 uint32_t desc_sectors, sectors, total_length;
864 uint32_t sectors_written = 0;
865 uint32_t aligned_length;
866 uint32_t leading_length = 0;
867 uint32_t trailing_length = 0;
868 uint32_t partial_sectors = 0;
869 uint32_t bytes_written = 0;
870 uint64_t file_offset;
871 int64_t file_length;
872 VHDXHeader *header;
873 VHDXLogEntryHeader new_hdr;
874 VHDXLogDescriptor *new_desc = NULL;
875 VHDXLogDataSector *data_sector = NULL;
876 MSGUID new_guid = { 0 };
878 header = s->headers[s->curr_header];
880 /* need to have offset read data, and be on 4096 byte boundary */
882 if (length > header->log_length) {
883 /* no log present. we could create a log here instead of failing */
884 ret = -EINVAL;
885 goto exit;
888 if (guid_eq(header->log_guid, zero_guid)) {
889 vhdx_guid_generate(&new_guid);
890 vhdx_update_headers(bs, s, false, &new_guid);
891 } else {
892 /* currently, we require that the log be flushed after
893 * every write. */
894 ret = -ENOTSUP;
895 goto exit;
898 /* 0 is an invalid sequence number, but may also represent the first
899 * log write (or a wrapped seq) */
900 if (s->log.sequence == 0) {
901 s->log.sequence = 1;
904 sector_offset = offset % VHDX_LOG_SECTOR_SIZE;
905 file_offset = (offset / VHDX_LOG_SECTOR_SIZE) * VHDX_LOG_SECTOR_SIZE;
907 aligned_length = length;
909 /* add in the unaligned head and tail bytes */
910 if (sector_offset) {
911 leading_length = (VHDX_LOG_SECTOR_SIZE - sector_offset);
912 leading_length = leading_length > length ? length : leading_length;
913 aligned_length -= leading_length;
914 partial_sectors++;
917 sectors = aligned_length / VHDX_LOG_SECTOR_SIZE;
918 trailing_length = aligned_length - (sectors * VHDX_LOG_SECTOR_SIZE);
919 if (trailing_length) {
920 partial_sectors++;
923 sectors += partial_sectors;
925 file_length = bdrv_getlength(bs->file->bs);
926 if (file_length < 0) {
927 ret = file_length;
928 goto exit;
931 /* sectors is now how many sectors the data itself takes, not
932 * including the header and descriptor metadata */
934 new_hdr = (VHDXLogEntryHeader) {
935 .signature = VHDX_LOG_SIGNATURE,
936 .tail = s->log.tail,
937 .sequence_number = s->log.sequence,
938 .descriptor_count = sectors,
939 .reserved = 0,
940 .flushed_file_offset = file_length,
941 .last_file_offset = file_length,
942 .log_guid = header->log_guid,
946 desc_sectors = vhdx_compute_desc_sectors(new_hdr.descriptor_count);
948 total_length = (desc_sectors + sectors) * VHDX_LOG_SECTOR_SIZE;
949 new_hdr.entry_length = total_length;
951 vhdx_log_entry_hdr_le_export(&new_hdr);
953 buffer = qemu_blockalign(bs, total_length);
954 memcpy(buffer, &new_hdr, sizeof(new_hdr));
956 new_desc = buffer + sizeof(new_hdr);
957 data_sector = buffer + (desc_sectors * VHDX_LOG_SECTOR_SIZE);
958 data_tmp = data;
960 /* All log sectors are 4KB, so for any partial sectors we must
961 * merge the data with preexisting data from the final file
962 * destination */
963 merged_sector = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE);
965 for (i = 0; i < sectors; i++) {
966 new_desc->signature = VHDX_LOG_DESC_SIGNATURE;
967 new_desc->sequence_number = s->log.sequence;
968 new_desc->file_offset = file_offset;
970 if (i == 0 && leading_length) {
971 /* partial sector at the front of the buffer */
972 ret = bdrv_pread(bs->file, file_offset, merged_sector,
973 VHDX_LOG_SECTOR_SIZE);
974 if (ret < 0) {
975 goto exit;
977 memcpy(merged_sector + sector_offset, data_tmp, leading_length);
978 bytes_written = leading_length;
979 sector_write = merged_sector;
980 } else if (i == sectors - 1 && trailing_length) {
981 /* partial sector at the end of the buffer */
982 ret = bdrv_pread(bs->file,
983 file_offset,
984 merged_sector + trailing_length,
985 VHDX_LOG_SECTOR_SIZE - trailing_length);
986 if (ret < 0) {
987 goto exit;
989 memcpy(merged_sector, data_tmp, trailing_length);
990 bytes_written = trailing_length;
991 sector_write = merged_sector;
992 } else {
993 bytes_written = VHDX_LOG_SECTOR_SIZE;
994 sector_write = data_tmp;
997 /* populate the raw sector data into the proper structures,
998 * as well as update the descriptor, and convert to proper
999 * endianness */
1000 vhdx_log_raw_to_le_sector(new_desc, data_sector, sector_write,
1001 s->log.sequence);
1003 data_tmp += bytes_written;
1004 data_sector++;
1005 new_desc++;
1006 file_offset += VHDX_LOG_SECTOR_SIZE;
1009 /* checksum covers entire entry, from the log header through the
1010 * last data sector */
1011 vhdx_update_checksum(buffer, total_length,
1012 offsetof(VHDXLogEntryHeader, checksum));
1014 /* now write to the log */
1015 ret = vhdx_log_write_sectors(bs, &s->log, &sectors_written, buffer,
1016 desc_sectors + sectors);
1017 if (ret < 0) {
1018 goto exit;
1021 if (sectors_written != desc_sectors + sectors) {
1022 /* instead of failing, we could flush the log here */
1023 ret = -EINVAL;
1024 goto exit;
1027 s->log.sequence++;
1028 /* write new tail */
1029 s->log.tail = s->log.write;
1031 exit:
1032 qemu_vfree(buffer);
1033 qemu_vfree(merged_sector);
1034 return ret;
1037 /* Perform a log write, and then immediately flush the entire log */
1038 int vhdx_log_write_and_flush(BlockDriverState *bs, BDRVVHDXState *s,
1039 void *data, uint32_t length, uint64_t offset)
1041 int ret = 0;
1042 VHDXLogSequence logs = { .valid = true,
1043 .count = 1,
1044 .hdr = { 0 } };
1047 /* Make sure data written (new and/or changed blocks) is stable
1048 * on disk, before creating log entry */
1049 ret = bdrv_flush(bs);
1050 if (ret < 0) {
1051 goto exit;
1054 ret = vhdx_log_write(bs, s, data, length, offset);
1055 if (ret < 0) {
1056 goto exit;
1058 logs.log = s->log;
1060 /* Make sure log is stable on disk */
1061 ret = bdrv_flush(bs);
1062 if (ret < 0) {
1063 goto exit;
1066 ret = vhdx_log_flush(bs, s, &logs);
1067 if (ret < 0) {
1068 goto exit;
1071 s->log = logs.log;
1073 exit:
1074 return ret;