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qemu/block/vhdx-log.c
Jeff Cody 8adc52336d block: vhdx - add log write support 
This adds support for writing to the VHDX log.

For spec details, see VHDX Specification Format v1.00:
https://www.microsoft.com/en-us/download/details.aspx?id=34750

There are a few limitations to this log support:
1.) There is no caching yet
2.) The log is flushed after each entry

The primary write interface, vhdx_log_write_and_flush(), performs a log
write followed by an immediate flush of the log.

As each log entry sector is a minimum of 4KB, partial sector writes are
filled in with data from the disk write destination.

If the current file log GUID is 0, a new GUID is generated and updated
in the header.

Signed-off-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-07 13:58:59 +01:00

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/*
* 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/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, offset, hdr, sizeof(VHDXLogEntryHeader));
if (ret < 0) {
goto exit;
}
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 (memcmp(&hdr->signature, "loge", 4)) {
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 (!memcmp(&desc->signature, "zero", 4)) {
if (desc->zero_length % VHDX_LOG_SECTOR_SIZE == 0) {
/* valid */
ret = true;
}
} else if (!memcmp(&desc->signature, "desc", 4)) {
/* 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)
{
int ret = 0;
uint32_t desc_sectors;
uint32_t sectors_read;
VHDXLogEntryHeader hdr;
VHDXLogDescEntries *desc_entries = NULL;
int i;
assert(*buffer == NULL);
ret = vhdx_log_peek_hdr(bs, log, &hdr);
if (ret < 0) {
goto exit;
}
vhdx_log_entry_hdr_le_import(&hdr);
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_blockalign(bs, desc_sectors * VHDX_LOG_SECTOR_SIZE);
ret = vhdx_log_read_sectors(bs, log, &sectors_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++) {
vhdx_log_desc_le_import(&desc_entries->desc[i]);
if (vhdx_log_desc_is_valid(&desc_entries->desc[i], &hdr) == false) {
ret = -EINVAL;
goto free_and_exit;
}
}
*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 (!memcmp(&desc->signature, "desc", 4)) {
/* 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 (!memcmp(&desc->signature, "zero", 4)) {
/* write 'count' sectors of sector */
memset(buffer, 0, VHDX_LOG_SECTOR_SIZE);
count = desc->zero_length / VHDX_LOG_SECTOR_SIZE;
}
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;
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)) {
ret = -EINVAL;
goto exit;
}
ret = vhdx_log_read_desc(bs, s, &logs->log, &desc_entries);
if (ret < 0) {
goto exit;
}
for (i = 0; i < desc_entries->hdr.descriptor_count; i++) {
if (!memcmp(&desc_entries->desc[i].signature, "desc", 4)) {
/* data sector, so read a sector to flush */
ret = vhdx_log_read_sectors(bs, &logs->log, &sectors_read,
data, 1, false);
if (ret < 0) {
goto exit;
}
if (sectors_read != 1) {
ret = -EINVAL;
goto exit;
}
}
ret = vhdx_log_flush_desc(bs, &desc_entries->desc[i], data);
if (ret < 0) {
goto exit;
}
}
if (bdrv_getlength(bs->file) < 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, 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;
}
vhdx_log_entry_hdr_le_import(&hdr);
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 desc sectors, and calculate log checksum */
total_sectors = hdr.entry_length / VHDX_LOG_SECTOR_SIZE;
/* read_desc() will incrememnt the read idx */
ret = vhdx_log_read_desc(bs, s, log, &desc_buffer);
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, &sectors_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 != desc_buffer->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)
{
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) {
/* 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),
.last_file_offset = bdrv_getlength(bs->file),
};
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 = (VHDXLogDescriptor *) (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));
cpu_to_le32s((uint32_t *)(buffer + 4));
/* now write to the log */
vhdx_log_write_sectors(bs, &s->log, &sectors_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;
}
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