/* * Block driver for Hyper-V VHDX Images * * Copyright (c) 2013 Red Hat, Inc., * * Authors: * Jeff Cody <jcody@redhat.com> * * This is based on the "VHDX Format Specification v1.00", published 8/25/2012 * by Microsoft: * https://www.microsoft.com/en-us/download/details.aspx?id=34750 * * This file covers the functionality of the metadata log writing, parsing, and * replay. * * This work is licensed under the terms of the GNU LGPL, version 2 or later. * See the COPYING.LIB file in the top-level directory. * */ #include "qemu/osdep.h" #include "qapi/error.h" #include "block/block_int.h" #include "qemu/error-report.h" #include "qemu/bswap.h" #include "vhdx.h" typedef struct VHDXLogSequence { bool valid; uint32_t count; VHDXLogEntries log; VHDXLogEntryHeader hdr; } VHDXLogSequence; typedef struct VHDXLogDescEntries { VHDXLogEntryHeader hdr; VHDXLogDescriptor desc[]; } VHDXLogDescEntries; static const MSGUID zero_guid = { 0 }; /* The log located on the disk is circular buffer containing * sectors of 4096 bytes each. * * It is assumed for the read/write functions below that the * circular buffer scheme uses a 'one sector open' to indicate * the buffer is full. Given the validation methods used for each * sector, this method should be compatible with other methods that * do not waste a sector. */ /* Allow peeking at the hdr entry at the beginning of the current * read index, without advancing the read index */ static int vhdx_log_peek_hdr(BlockDriverState *bs, VHDXLogEntries *log, VHDXLogEntryHeader *hdr) { int ret = 0; uint64_t offset; uint32_t read; assert(hdr != NULL); /* peek is only supported on sector boundaries */ if (log->read % VHDX_LOG_SECTOR_SIZE) { ret = -EFAULT; goto exit; } read = log->read; /* we are guaranteed that a) log sectors are 4096 bytes, * and b) the log length is a multiple of 1MB. So, there * is always a round number of sectors in the buffer */ if ((read + sizeof(VHDXLogEntryHeader)) > log->length) { read = 0; } if (read == log->write) { ret = -EINVAL; goto exit; } offset = log->offset + read; ret = bdrv_pread(bs->file, offset, hdr, sizeof(VHDXLogEntryHeader)); if (ret < 0) { goto exit; } vhdx_log_entry_hdr_le_import(hdr); exit: return ret; } /* Index increment for log, based on sector boundaries */ static int vhdx_log_inc_idx(uint32_t idx, uint64_t length) { idx += VHDX_LOG_SECTOR_SIZE; /* we are guaranteed that a) log sectors are 4096 bytes, * and b) the log length is a multiple of 1MB. So, there * is always a round number of sectors in the buffer */ return idx >= length ? 0 : idx; } /* Reset the log to empty */ static void vhdx_log_reset(BlockDriverState *bs, BDRVVHDXState *s) { MSGUID guid = { 0 }; s->log.read = s->log.write = 0; /* a log guid of 0 indicates an empty log to any parser of v0 * VHDX logs */ vhdx_update_headers(bs, s, false, &guid); } /* Reads num_sectors from the log (all log sectors are 4096 bytes), * into buffer 'buffer'. Upon return, *sectors_read will contain * the number of sectors successfully read. * * It is assumed that 'buffer' is already allocated, and of sufficient * size (i.e. >= 4096*num_sectors). * * If 'peek' is true, then the tail (read) pointer for the circular buffer is * not modified. * * 0 is returned on success, -errno otherwise. */ static int vhdx_log_read_sectors(BlockDriverState *bs, VHDXLogEntries *log, uint32_t *sectors_read, void *buffer, uint32_t num_sectors, bool peek) { int ret = 0; uint64_t offset; uint32_t read; read = log->read; *sectors_read = 0; while (num_sectors) { if (read == log->write) { /* empty */ break; } offset = log->offset + read; ret = bdrv_pread(bs->file, offset, buffer, VHDX_LOG_SECTOR_SIZE); if (ret < 0) { goto exit; } read = vhdx_log_inc_idx(read, log->length); *sectors_read = *sectors_read + 1; num_sectors--; } exit: if (!peek) { log->read = read; } return ret; } /* Writes num_sectors to the log (all log sectors are 4096 bytes), * from buffer 'buffer'. Upon return, *sectors_written will contain * the number of sectors successfully written. * * It is assumed that 'buffer' is at least 4096*num_sectors large. * * 0 is returned on success, -errno otherwise */ static int vhdx_log_write_sectors(BlockDriverState *bs, VHDXLogEntries *log, uint32_t *sectors_written, void *buffer, uint32_t num_sectors) { int ret = 0; uint64_t offset; uint32_t write; void *buffer_tmp; BDRVVHDXState *s = bs->opaque; ret = vhdx_user_visible_write(bs, s); if (ret < 0) { goto exit; } write = log->write; buffer_tmp = buffer; while (num_sectors) { offset = log->offset + write; write = vhdx_log_inc_idx(write, log->length); if (write == log->read) { /* full */ break; } ret = bdrv_pwrite(bs->file, offset, buffer_tmp, VHDX_LOG_SECTOR_SIZE); if (ret < 0) { goto exit; } buffer_tmp += VHDX_LOG_SECTOR_SIZE; log->write = write; *sectors_written = *sectors_written + 1; num_sectors--; } exit: return ret; } /* Validates a log entry header */ static bool vhdx_log_hdr_is_valid(VHDXLogEntries *log, VHDXLogEntryHeader *hdr, BDRVVHDXState *s) { int valid = false; if (hdr->signature != VHDX_LOG_SIGNATURE) { goto exit; } /* if the individual entry length is larger than the whole log * buffer, that is obviously invalid */ if (log->length < hdr->entry_length) { goto exit; } /* length of entire entry must be in units of 4KB (log sector size) */ if (hdr->entry_length % (VHDX_LOG_SECTOR_SIZE)) { goto exit; } /* per spec, sequence # must be > 0 */ if (hdr->sequence_number == 0) { goto exit; } /* log entries are only valid if they match the file-wide log guid * found in the active header */ if (!guid_eq(hdr->log_guid, s->headers[s->curr_header]->log_guid)) { goto exit; } if (hdr->descriptor_count * sizeof(VHDXLogDescriptor) > hdr->entry_length) { goto exit; } valid = true; exit: return valid; } /* * Given a log header, this will validate that the descriptors and the * corresponding data sectors (if applicable) * * Validation consists of: * 1. Making sure the sequence numbers matches the entry header * 2. Verifying a valid signature ('zero' or 'desc' for descriptors) * 3. File offset field is a multiple of 4KB * 4. If a data descriptor, the corresponding data sector * has its signature ('data') and matching sequence number * * @desc: the data buffer containing the descriptor * @hdr: the log entry header * * Returns true if valid */ static bool vhdx_log_desc_is_valid(VHDXLogDescriptor *desc, VHDXLogEntryHeader *hdr) { bool ret = false; if (desc->sequence_number != hdr->sequence_number) { goto exit; } if (desc->file_offset % VHDX_LOG_SECTOR_SIZE) { goto exit; } if (desc->signature == VHDX_LOG_ZERO_SIGNATURE) { if (desc->zero_length % VHDX_LOG_SECTOR_SIZE == 0) { /* valid */ ret = true; } } else if (desc->signature == VHDX_LOG_DESC_SIGNATURE) { /* valid */ ret = true; } exit: return ret; } /* Prior to sector data for a log entry, there is the header * and the descriptors referenced in the header: * * [] = 4KB sector * * [ hdr, desc ][ desc ][ ... ][ data ][ ... ] * * The first sector in a log entry has a 64 byte header, and * up to 126 32-byte descriptors. If more descriptors than * 126 are required, then subsequent sectors can have up to 128 * descriptors. Each sector is 4KB. Data follows the descriptor * sectors. * * This will return the number of sectors needed to encompass * the passed number of descriptors in desc_cnt. * * This will never return 0, even if desc_cnt is 0. */ static int vhdx_compute_desc_sectors(uint32_t desc_cnt) { uint32_t desc_sectors; desc_cnt += 2; /* account for header in first sector */ desc_sectors = desc_cnt / 128; if (desc_cnt % 128) { desc_sectors++; } return desc_sectors; } /* Reads the log header, and subsequent descriptors (if any). This * will allocate all the space for buffer, which must be NULL when * passed into this function. Each descriptor will also be validated, * and error returned if any are invalid. */ static int vhdx_log_read_desc(BlockDriverState *bs, BDRVVHDXState *s, VHDXLogEntries *log, VHDXLogDescEntries **buffer, bool convert_endian) { int ret = 0; uint32_t desc_sectors; uint32_t sectors_read; VHDXLogEntryHeader hdr; VHDXLogDescEntries *desc_entries = NULL; VHDXLogDescriptor desc; int i; assert(*buffer == NULL); ret = vhdx_log_peek_hdr(bs, log, &hdr); if (ret < 0) { goto exit; } if (vhdx_log_hdr_is_valid(log, &hdr, s) == false) { ret = -EINVAL; goto exit; } desc_sectors = vhdx_compute_desc_sectors(hdr.descriptor_count); desc_entries = qemu_try_blockalign(bs->file->bs, desc_sectors * VHDX_LOG_SECTOR_SIZE); if (desc_entries == NULL) { ret = -ENOMEM; goto exit; } ret = vhdx_log_read_sectors(bs, log, §ors_read, desc_entries, desc_sectors, false); if (ret < 0) { goto free_and_exit; } if (sectors_read != desc_sectors) { ret = -EINVAL; goto free_and_exit; } /* put in proper endianness, and validate each desc */ for (i = 0; i < hdr.descriptor_count; i++) { desc = desc_entries->desc[i]; vhdx_log_desc_le_import(&desc); if (convert_endian) { desc_entries->desc[i] = desc; } if (vhdx_log_desc_is_valid(&desc, &hdr) == false) { ret = -EINVAL; goto free_and_exit; } } if (convert_endian) { desc_entries->hdr = hdr; } *buffer = desc_entries; goto exit; free_and_exit: qemu_vfree(desc_entries); exit: return ret; } /* Flushes the descriptor described by desc to the VHDX image file. * If the descriptor is a data descriptor, than 'data' must be non-NULL, * and >= 4096 bytes (VHDX_LOG_SECTOR_SIZE), containing the data to be * written. * * Verification is performed to make sure the sequence numbers of a data * descriptor match the sequence number in the desc. * * For a zero descriptor, it may describe multiple sectors to fill with zeroes. * In this case, it should be noted that zeroes are written to disk, and the * image file is not extended as a sparse file. */ static int vhdx_log_flush_desc(BlockDriverState *bs, VHDXLogDescriptor *desc, VHDXLogDataSector *data) { int ret = 0; uint64_t seq, file_offset; uint32_t offset = 0; void *buffer = NULL; uint64_t count = 1; int i; buffer = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE); if (desc->signature == VHDX_LOG_DESC_SIGNATURE) { /* data sector */ if (data == NULL) { ret = -EFAULT; goto exit; } /* The sequence number of the data sector must match that * in the descriptor */ seq = data->sequence_high; seq <<= 32; seq |= data->sequence_low & 0xffffffff; if (seq != desc->sequence_number) { ret = -EINVAL; goto exit; } /* Each data sector is in total 4096 bytes, however the first * 8 bytes, and last 4 bytes, are located in the descriptor */ memcpy(buffer, &desc->leading_bytes, 8); offset += 8; memcpy(buffer+offset, data->data, 4084); offset += 4084; memcpy(buffer+offset, &desc->trailing_bytes, 4); } else if (desc->signature == VHDX_LOG_ZERO_SIGNATURE) { /* write 'count' sectors of sector */ memset(buffer, 0, VHDX_LOG_SECTOR_SIZE); count = desc->zero_length / VHDX_LOG_SECTOR_SIZE; } else { error_report("Invalid VHDX log descriptor entry signature 0x%" PRIx32, desc->signature); ret = -EINVAL; goto exit; } file_offset = desc->file_offset; /* count is only > 1 if we are writing zeroes */ for (i = 0; i < count; i++) { ret = bdrv_pwrite_sync(bs->file, file_offset, buffer, VHDX_LOG_SECTOR_SIZE); if (ret < 0) { goto exit; } file_offset += VHDX_LOG_SECTOR_SIZE; } exit: qemu_vfree(buffer); return ret; } /* Flush the entire log (as described by 'logs') to the VHDX image * file, and then set the log to 'empty' status once complete. * * The log entries should be validate prior to flushing */ static int vhdx_log_flush(BlockDriverState *bs, BDRVVHDXState *s, VHDXLogSequence *logs) { int ret = 0; int i; uint32_t cnt, sectors_read; uint64_t new_file_size; void *data = NULL; int64_t file_length; VHDXLogDescEntries *desc_entries = NULL; VHDXLogEntryHeader hdr_tmp = { 0 }; cnt = logs->count; data = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE); ret = vhdx_user_visible_write(bs, s); if (ret < 0) { goto exit; } /* each iteration represents one log sequence, which may span multiple * sectors */ while (cnt--) { ret = vhdx_log_peek_hdr(bs, &logs->log, &hdr_tmp); if (ret < 0) { goto exit; } file_length = bdrv_getlength(bs->file->bs); if (file_length < 0) { ret = file_length; goto exit; } /* if the log shows a FlushedFileOffset larger than our current file * size, then that means the file has been truncated / corrupted, and * we must refused to open it / use it */ if (hdr_tmp.flushed_file_offset > file_length) { ret = -EINVAL; goto exit; } ret = vhdx_log_read_desc(bs, s, &logs->log, &desc_entries, true); if (ret < 0) { goto exit; } for (i = 0; i < desc_entries->hdr.descriptor_count; i++) { if (desc_entries->desc[i].signature == VHDX_LOG_DESC_SIGNATURE) { /* data sector, so read a sector to flush */ ret = vhdx_log_read_sectors(bs, &logs->log, §ors_read, data, 1, false); if (ret < 0) { goto exit; } if (sectors_read != 1) { ret = -EINVAL; goto exit; } vhdx_log_data_le_import(data); } ret = vhdx_log_flush_desc(bs, &desc_entries->desc[i], data); if (ret < 0) { goto exit; } } if (file_length < desc_entries->hdr.last_file_offset) { new_file_size = desc_entries->hdr.last_file_offset; if (new_file_size % (1 * MiB)) { /* round up to nearest 1MB boundary */ new_file_size = QEMU_ALIGN_UP(new_file_size, MiB); if (new_file_size > INT64_MAX) { ret = -EINVAL; goto exit; } ret = bdrv_truncate(bs->file, new_file_size, false, PREALLOC_MODE_OFF, NULL); if (ret < 0) { goto exit; } } } qemu_vfree(desc_entries); desc_entries = NULL; } ret = bdrv_flush(bs); if (ret < 0) { goto exit; } /* once the log is fully flushed, indicate that we have an empty log * now. This also sets the log guid to 0, to indicate an empty log */ vhdx_log_reset(bs, s); exit: qemu_vfree(data); qemu_vfree(desc_entries); return ret; } static int vhdx_validate_log_entry(BlockDriverState *bs, BDRVVHDXState *s, VHDXLogEntries *log, uint64_t seq, bool *valid, VHDXLogEntryHeader *entry) { int ret = 0; VHDXLogEntryHeader hdr; void *buffer = NULL; uint32_t i, desc_sectors, total_sectors, crc; uint32_t sectors_read = 0; VHDXLogDescEntries *desc_buffer = NULL; *valid = false; ret = vhdx_log_peek_hdr(bs, log, &hdr); if (ret < 0) { goto inc_and_exit; } if (vhdx_log_hdr_is_valid(log, &hdr, s) == false) { goto inc_and_exit; } if (seq > 0) { if (hdr.sequence_number != seq + 1) { goto inc_and_exit; } } desc_sectors = vhdx_compute_desc_sectors(hdr.descriptor_count); /* Read all log sectors, and calculate log checksum */ total_sectors = hdr.entry_length / VHDX_LOG_SECTOR_SIZE; /* read_desc() will increment the read idx */ ret = vhdx_log_read_desc(bs, s, log, &desc_buffer, false); if (ret < 0) { goto free_and_exit; } crc = vhdx_checksum_calc(0xffffffff, (void *)desc_buffer, desc_sectors * VHDX_LOG_SECTOR_SIZE, 4); crc ^= 0xffffffff; buffer = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE); if (total_sectors > desc_sectors) { for (i = 0; i < total_sectors - desc_sectors; i++) { sectors_read = 0; ret = vhdx_log_read_sectors(bs, log, §ors_read, buffer, 1, false); if (ret < 0 || sectors_read != 1) { goto free_and_exit; } crc = vhdx_checksum_calc(crc, buffer, VHDX_LOG_SECTOR_SIZE, -1); crc ^= 0xffffffff; } } crc ^= 0xffffffff; if (crc != hdr.checksum) { goto free_and_exit; } *valid = true; *entry = hdr; goto free_and_exit; inc_and_exit: log->read = vhdx_log_inc_idx(log->read, log->length); free_and_exit: qemu_vfree(buffer); qemu_vfree(desc_buffer); return ret; } /* Search through the log circular buffer, and find the valid, active * log sequence, if any exists * */ static int vhdx_log_search(BlockDriverState *bs, BDRVVHDXState *s, VHDXLogSequence *logs) { int ret = 0; uint32_t tail; bool seq_valid = false; VHDXLogSequence candidate = { 0 }; VHDXLogEntryHeader hdr = { 0 }; VHDXLogEntries curr_log; memcpy(&curr_log, &s->log, sizeof(VHDXLogEntries)); curr_log.write = curr_log.length; /* assume log is full */ curr_log.read = 0; /* now we will go through the whole log sector by sector, until * we find a valid, active log sequence, or reach the end of the * log buffer */ for (;;) { uint64_t curr_seq = 0; VHDXLogSequence current = { 0 }; tail = curr_log.read; ret = vhdx_validate_log_entry(bs, s, &curr_log, curr_seq, &seq_valid, &hdr); if (ret < 0) { goto exit; } if (seq_valid) { current.valid = true; current.log = curr_log; current.log.read = tail; current.log.write = curr_log.read; current.count = 1; current.hdr = hdr; for (;;) { ret = vhdx_validate_log_entry(bs, s, &curr_log, curr_seq, &seq_valid, &hdr); if (ret < 0) { goto exit; } if (seq_valid == false) { break; } current.log.write = curr_log.read; current.count++; curr_seq = hdr.sequence_number; } } if (current.valid) { if (candidate.valid == false || current.hdr.sequence_number > candidate.hdr.sequence_number) { candidate = current; } } if (curr_log.read < tail) { break; } } *logs = candidate; if (candidate.valid) { /* this is the next sequence number, for writes */ s->log.sequence = candidate.hdr.sequence_number + 1; } exit: return ret; } /* Parse the replay log. Per the VHDX spec, if the log is present * it must be replayed prior to opening the file, even read-only. * * If read-only, we must replay the log in RAM (or refuse to open * a dirty VHDX file read-only) */ int vhdx_parse_log(BlockDriverState *bs, BDRVVHDXState *s, bool *flushed, Error **errp) { int ret = 0; VHDXHeader *hdr; VHDXLogSequence logs = { 0 }; hdr = s->headers[s->curr_header]; *flushed = false; /* s->log.hdr is freed in vhdx_close() */ if (s->log.hdr == NULL) { s->log.hdr = qemu_blockalign(bs, sizeof(VHDXLogEntryHeader)); } s->log.offset = hdr->log_offset; s->log.length = hdr->log_length; if (s->log.offset < VHDX_LOG_MIN_SIZE || s->log.offset % VHDX_LOG_MIN_SIZE) { ret = -EINVAL; goto exit; } /* per spec, only log version of 0 is supported */ if (hdr->log_version != 0) { ret = -EINVAL; goto exit; } /* If either the log guid, or log length is zero, * then a replay log is not present */ if (guid_eq(hdr->log_guid, zero_guid)) { goto exit; } if (hdr->log_length == 0) { goto exit; } if (hdr->log_length % VHDX_LOG_MIN_SIZE) { ret = -EINVAL; goto exit; } /* The log is present, we need to find if and where there is an active * sequence of valid entries present in the log. */ ret = vhdx_log_search(bs, s, &logs); if (ret < 0) { goto exit; } if (logs.valid) { if (bs->read_only) { bdrv_refresh_filename(bs); ret = -EPERM; error_setg(errp, "VHDX image file '%s' opened read-only, but " "contains a log that needs to be replayed", bs->filename); error_append_hint(errp, "To replay the log, run:\n" "qemu-img check -r all '%s'\n", bs->filename); goto exit; } /* now flush the log */ ret = vhdx_log_flush(bs, s, &logs); if (ret < 0) { goto exit; } *flushed = true; } exit: return ret; } static void vhdx_log_raw_to_le_sector(VHDXLogDescriptor *desc, VHDXLogDataSector *sector, void *data, uint64_t seq) { /* 8 + 4084 + 4 = 4096, 1 log sector */ memcpy(&desc->leading_bytes, data, 8); data += 8; desc->leading_bytes = cpu_to_le64(desc->leading_bytes); memcpy(sector->data, data, 4084); data += 4084; memcpy(&desc->trailing_bytes, data, 4); desc->trailing_bytes = cpu_to_le32(desc->trailing_bytes); data += 4; sector->sequence_high = (uint32_t) (seq >> 32); sector->sequence_low = (uint32_t) (seq & 0xffffffff); sector->data_signature = VHDX_LOG_DATA_SIGNATURE; vhdx_log_desc_le_export(desc); vhdx_log_data_le_export(sector); } static int vhdx_log_write(BlockDriverState *bs, BDRVVHDXState *s, void *data, uint32_t length, uint64_t offset) { int ret = 0; void *buffer = NULL; void *merged_sector = NULL; void *data_tmp, *sector_write; unsigned int i; int sector_offset; uint32_t desc_sectors, sectors, total_length; uint32_t sectors_written = 0; uint32_t aligned_length; uint32_t leading_length = 0; uint32_t trailing_length = 0; uint32_t partial_sectors = 0; uint32_t bytes_written = 0; uint64_t file_offset; int64_t file_length; VHDXHeader *header; VHDXLogEntryHeader new_hdr; VHDXLogDescriptor *new_desc = NULL; VHDXLogDataSector *data_sector = NULL; MSGUID new_guid = { 0 }; header = s->headers[s->curr_header]; /* need to have offset read data, and be on 4096 byte boundary */ if (length > header->log_length) { /* no log present. we could create a log here instead of failing */ ret = -EINVAL; goto exit; } if (guid_eq(header->log_guid, zero_guid)) { vhdx_guid_generate(&new_guid); vhdx_update_headers(bs, s, false, &new_guid); } else { /* currently, we require that the log be flushed after * every write. */ ret = -ENOTSUP; goto exit; } /* 0 is an invalid sequence number, but may also represent the first * log write (or a wrapped seq) */ if (s->log.sequence == 0) { s->log.sequence = 1; } sector_offset = offset % VHDX_LOG_SECTOR_SIZE; file_offset = QEMU_ALIGN_DOWN(offset, VHDX_LOG_SECTOR_SIZE); aligned_length = length; /* add in the unaligned head and tail bytes */ if (sector_offset) { leading_length = (VHDX_LOG_SECTOR_SIZE - sector_offset); leading_length = leading_length > length ? length : leading_length; aligned_length -= leading_length; partial_sectors++; } sectors = aligned_length / VHDX_LOG_SECTOR_SIZE; trailing_length = aligned_length - (sectors * VHDX_LOG_SECTOR_SIZE); if (trailing_length) { partial_sectors++; } sectors += partial_sectors; file_length = bdrv_getlength(bs->file->bs); if (file_length < 0) { ret = file_length; goto exit; } /* sectors is now how many sectors the data itself takes, not * including the header and descriptor metadata */ new_hdr = (VHDXLogEntryHeader) { .signature = VHDX_LOG_SIGNATURE, .tail = s->log.tail, .sequence_number = s->log.sequence, .descriptor_count = sectors, .reserved = 0, .flushed_file_offset = file_length, .last_file_offset = file_length, .log_guid = header->log_guid, }; desc_sectors = vhdx_compute_desc_sectors(new_hdr.descriptor_count); total_length = (desc_sectors + sectors) * VHDX_LOG_SECTOR_SIZE; new_hdr.entry_length = total_length; vhdx_log_entry_hdr_le_export(&new_hdr); buffer = qemu_blockalign(bs, total_length); memcpy(buffer, &new_hdr, sizeof(new_hdr)); new_desc = buffer + sizeof(new_hdr); data_sector = buffer + (desc_sectors * VHDX_LOG_SECTOR_SIZE); data_tmp = data; /* All log sectors are 4KB, so for any partial sectors we must * merge the data with preexisting data from the final file * destination */ merged_sector = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE); for (i = 0; i < sectors; i++) { new_desc->signature = VHDX_LOG_DESC_SIGNATURE; new_desc->sequence_number = s->log.sequence; new_desc->file_offset = file_offset; if (i == 0 && leading_length) { /* partial sector at the front of the buffer */ ret = bdrv_pread(bs->file, file_offset, merged_sector, VHDX_LOG_SECTOR_SIZE); if (ret < 0) { goto exit; } memcpy(merged_sector + sector_offset, data_tmp, leading_length); bytes_written = leading_length; sector_write = merged_sector; } else if (i == sectors - 1 && trailing_length) { /* partial sector at the end of the buffer */ ret = bdrv_pread(bs->file, file_offset, merged_sector + trailing_length, VHDX_LOG_SECTOR_SIZE - trailing_length); if (ret < 0) { goto exit; } memcpy(merged_sector, data_tmp, trailing_length); bytes_written = trailing_length; sector_write = merged_sector; } else { bytes_written = VHDX_LOG_SECTOR_SIZE; sector_write = data_tmp; } /* populate the raw sector data into the proper structures, * as well as update the descriptor, and convert to proper * endianness */ vhdx_log_raw_to_le_sector(new_desc, data_sector, sector_write, s->log.sequence); data_tmp += bytes_written; data_sector++; new_desc++; file_offset += VHDX_LOG_SECTOR_SIZE; } /* checksum covers entire entry, from the log header through the * last data sector */ vhdx_update_checksum(buffer, total_length, offsetof(VHDXLogEntryHeader, checksum)); /* now write to the log */ ret = vhdx_log_write_sectors(bs, &s->log, §ors_written, buffer, desc_sectors + sectors); if (ret < 0) { goto exit; } if (sectors_written != desc_sectors + sectors) { /* instead of failing, we could flush the log here */ ret = -EINVAL; goto exit; } s->log.sequence++; /* write new tail */ s->log.tail = s->log.write; exit: qemu_vfree(buffer); qemu_vfree(merged_sector); return ret; } /* Perform a log write, and then immediately flush the entire log */ int vhdx_log_write_and_flush(BlockDriverState *bs, BDRVVHDXState *s, void *data, uint32_t length, uint64_t offset) { int ret = 0; VHDXLogSequence logs = { .valid = true, .count = 1, .hdr = { 0 } }; /* Make sure data written (new and/or changed blocks) is stable * on disk, before creating log entry */ ret = bdrv_flush(bs); if (ret < 0) { goto exit; } ret = vhdx_log_write(bs, s, data, length, offset); if (ret < 0) { goto exit; } logs.log = s->log; /* Make sure log is stable on disk */ ret = bdrv_flush(bs); if (ret < 0) { goto exit; } ret = vhdx_log_flush(bs, s, &logs); if (ret < 0) { goto exit; } s->log = logs.log; exit: return ret; }