diff options
Diffstat (limited to 'src/block/vhdx-log.c')
| -rw-r--r-- | src/block/vhdx-log.c | 1040 |
1 files changed, 1040 insertions, 0 deletions
diff --git a/src/block/vhdx-log.c b/src/block/vhdx-log.c new file mode 100644 index 0000000..47ae4b1 --- /dev/null +++ b/src/block/vhdx-log.c @@ -0,0 +1,1040 @@ +/* + * 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-common.h" +#include "block/block_int.h" +#include "qemu/error-report.h" +#include "qemu/module.h" +#include "block/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->bs, 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->bs, 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->bs, 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->bs, 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; + 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; + } + /* 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 > bdrv_getlength(bs->file->bs)) { + 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 (bdrv_getlength(bs->file->bs) < desc_entries->hdr.last_file_offset) { + new_file_size = desc_entries->hdr.last_file_offset; + if (new_file_size % (1024*1024)) { + /* round up to nearest 1MB boundary */ + new_file_size = ((new_file_size >> 20) + 1) << 20; + bdrv_truncate(bs->file->bs, new_file_size); + } + } + qemu_vfree(desc_entries); + desc_entries = NULL; + } + + bdrv_flush(bs); + /* 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) { + ret = -EPERM; + error_setg_errno(errp, EPERM, + "VHDX image file '%s' opened read-only, but " + "contains a log that needs to be replayed. To " + "replay the log, execute:\n qemu-img check -r " + "all '%s'", + bs->filename, 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; + cpu_to_le64s(&desc->leading_bytes); + memcpy(sector->data, data, 4084); + data += 4084; + memcpy(&desc->trailing_bytes, data, 4); + cpu_to_le32s(&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; + 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 = (offset / VHDX_LOG_SECTOR_SIZE) * 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; + + /* 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 = bdrv_getlength(bs->file->bs), + .last_file_offset = bdrv_getlength(bs->file->bs), + }; + + new_hdr.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->bs, 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->bs, + 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 */ + bdrv_flush(bs); + 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 */ + bdrv_flush(bs); + ret = vhdx_log_flush(bs, s, &logs); + if (ret < 0) { + goto exit; + } + + s->log = logs.log; + +exit: + return ret; +} + |
